Patent Publication Number: US-2011067750-A1

Title: Tracking solar photovoltaic power generation system, and tracking control method and tracking shift correction method for tracking solar photovoltaic power generation system

Description:
TECHNICAL FIELD 
     The present invention relates to a tracking solar photovoltaic power generation system for causing a photovoltaic panel to track the solar trajectory, and a tracking control method and a tracking shift correction method for the tracking solar photovoltaic power generation system. 
     BACKGROUND ART 
     Various types of solar photovoltaic power generators for converting solar energy into electric power have been put to practical use, and tracking drive solar photovoltaic power generators of the type that track the motion of the sun (solar trajectory) and provide a rotation (tracking drive) of a photovoltaic panel have been developed in order to increase the power generating capacity and accordingly obtain large amounts of electric power. 
     In particular, concentrating solar photovoltaic power generators, in which electric power is generated by concentrating sunlight with a concentrating lens, have the advantage of considerably improved power generation efficiency because their sun-tracking drive (tracking and concentrating) allows sunlight to be perpendicularly concentrated and applied onto the light receiving surfaces of solar cell elements. With such advantageous features, tracking drive (tracking and concentrating) solar photovoltaic power generators using concentrating lenses are used for power supply and power stations in such areas as where a large area is available for installation. 
     As one example of conventional tracking drive solar photovoltaic power generators, a device that enables a tracking drive of a photovoltaic panel attached to a column has been proposed (see Patent Document 1, for example). 
     Also, various proposals have been made for an alignment control method (tracking control method) for causing a photovoltaic panel to be opposed to (directly face) the solar trajectory (see Patent Documents 2 to 4, for example). 
     In the case of tracking sunlight with a sensor (pyrheliometer), there are concerns that additional sensor installation is needed and the accuracy of sensors needs to be ensured. In addition, when some of solar cells are used as sensors, a problem arises that generated electric power is wasted. 
     Also, in the case of using no sensor, another problem arises that high-level installation work is required in order to improve installation accuracy. In other words, as a precondition for a photovoltaic panel to directly face the solar trajectory, the photovoltaic panel needs to be positioned and installed with high precision on a driving portion including a column (supporting portion). 
       FIG. 27  is a perspective view illustrating an overview of a conventional tracking drive solar photovoltaic power generator. 
     The tracking drive solar photovoltaic power generator shown in the drawing includes a photovoltaic panel  110  that can be driven during tracking. The photovoltaic panel  110  is held by a column  111 , and its turning direction Roth (turning coordinate φ) and tilt direction Rotv (tilt coordinate θ) are controlled by a driving portion  112  provided on the top of the column  111 . 
     The driving portion  112  includes a turning drive portion (not shown) and a tilt drive portion (not shown) and is configured to track the solar trajectory based on the turning coordinate φ (turning direction Roth) and the tilt coordinate θ (tilt direction Rotv) transmitted from a tracking control portion  113  via a control line  113   c.    
     Although the column  111  is installed vertically relative to the ground, it is difficult in practice to install the column  111  completely vertically, and therefore the column  111  has a tilt to some extent. In addition, the driving portion  112  needs to be positioned with high precision in advance relative to a reference (the ground) since it controls the turning direction Roth and the tilt direction Rotv of the photovoltaic panel  110 . 
     In order to position the driving portion  112  with high precision relative to the reference, the positioning of the driving portion  112  is implemented by applying a declinometer, a clinometer, or a GPS, for example (see Patent Document 4, for example). The positioning of the driving portion  112  thus takes enormous effort and time. In other words, there are problems in that, even in the case of installing only a single tracking drive solar photovoltaic power generator, installation work requires excessive effort and cost. In addition, in the case of building up a system with a large number of photovoltaic panels  110 , a situation may arise in which installation itself is difficult. 
     That is, conventional tracking drive solar photovoltaic power generators necessitate highly reliable sensors that operate with high precision, or conventional tracking drive solar photovoltaic power generators have problems in terms of installation, such as requiring installation work with high-precision positioning. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         [Patent Document 1] JP 11-284217A 
         [Patent Document 2] JP 8-241125A 
         [Patent Document 3] JP 2002-202817A 
         [Patent Document 4] JP 2007-19331A 
       
    
     SUMMARY OF INVENTION 
     Problem to be Solved by the Invention 
     The present invention has been conceived in view of such circumstances, and it is an object of the present invention to provide a tracking control method for a tracking solar photovoltaic power generation system, in which a shift in the position of the turning coordinate relative to the solar azimuth angle is detected with use of the turning coordinate at which the panel output reaches its maximum value, and a shift in the position of the tilt coordinate relative to the solar altitude is detected with use of the tilt coordinate at which the panel output reaches its maximum value, and therefore the turning position and the tilt position of a photovoltaic panel can be adjusted with ease and high precision so that the photovoltaic panel can directly face the solar trajectory (solar azimuth and altitude). 
     It is also another object of the present invention to provide a highly reliable and productive tracking shift correction method for a tracking solar photovoltaic power generation system, the method eliminating the need to stop the tracking solar photovoltaic power generation system associated with tracking shift correction and causing no loss in the amount of generated electric power, by detecting a tracking shift of a photovoltaic panel that is targeted for tracking shift correction in a state in which a tracking drive solar photovoltaic power generator is connected to a power conversion portion in the tracking solar photovoltaic power generation system. 
     It is still another object of the present invention to provide a highly reliable and productive tracking solar photovoltaic power generation system that eliminates the need to be stopped associated with tracking shift correction and causes no loss in the amount of generated electric power, by adopting a configuration in which the system comprises a power conversion portion that converts direct-current electric power generated by a plurality of tracking drive solar photovoltaic power generators, which are arranged in parallel connection, into alternating-current electric power and supplies the alternating-current electric power to an interconnection load, and a tracking shift of a photovoltaic panel targeted for tracking shift correction is detected in a state in which the photovoltaic panel is running by being connected to the power conversion portion. 
     Means for Solving the Problems 
     The present invention provides a tracking control method for a tracking solar photovoltaic power generation system for causing a photovoltaic panel to track the solar trajectory, in which a tracking drive solar photovoltaic power generator includes a photovoltaic panel that converts sunlight into electric power, and a tracking control portion that provides tracking control over the turning position and the tilt position of the photovoltaic panel so that the photovoltaic panel can directly face the solar trajectory based on control coordinates, namely a turning coordinate and a tilt coordinate, that have been set corresponding to the solar azimuth angle and the solar altitude. The method comprises a first directly-facing turning coordinate detection process for detecting a first directly-facing turning coordinate at which a panel output reaches its maximum value, by moving the turning position of the photovoltaic panel while sequentially changing the turning coordinate in a first turning detection range that is defined in connection with a first turning coordinate corresponding to the solar azimuth angle, and a first directly-facing tilt coordinate detection process for detecting a first directly-facing tilt coordinate at which the panel output reaches its maximum value, by moving the tilt position of the photovoltaic panel while sequentially changing the tilt coordinate in a first tilt detection range that is defined in connection with a first tilt coordinate corresponding to the solar altitude. 
     This configuration makes it possible to detect a shift in the position of the turning coordinate (first turning coordinate) relative to the solar azimuth angle with use of the first directly-facing turning coordinate and to detect a shift in the position of the tilt coordinate (first tilt coordinate) relative to the solar altitude with use of the first directly-facing tilt coordinate. By correcting both the shift in the position of the turning coordinate (first directly-facing turning coordinate) relative to the solar azimuth angle and the shift in the position of the tilt coordinate (first directly-facing tilt coordinate) relative to the solar altitude to be corrected together, it is possible to adjust the turning position and tilt position of a photovoltaic panel with ease and high precision so that the photovoltaic panel can directly face the solar trajectory (solar azimuth angle and solar altitude). 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, the first turning detection range is defined from a first turning detection start coordinate to a first turning detection end coordinate by using the first turning coordinate as a first turning detection reference coordinate and applying a predetermined first turning displacement angle in both positive and negative directions of the first turning detection reference coordinate, and the first tilt detection range is defined from a first tilt detection start coordinate to a first tilt detection end coordinate by using either the first tilt coordinate or a first time-dependent corrected tilt coordinate obtained through time-dependent correction of the first tilt coordinate as a first tilt detection reference coordinate and applying a predetermined first tilt displacement angle in both positive and negative directions of the first tilt detection reference coordinate. 
     This configuration makes it possible to define the first turning detection range and the first tilt detection range with ease and high precision, thus enabling the first directly-facing turning coordinate and the first directly-facing tilt coordinate to be detected with ease and high precision. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, the first directly-facing tilt coordinate detection process is performed after execution of a first directly-facing turning coordinate alignment process in which the turning coordinate is aligned with the first directly-facing turning coordinate detected in the first directly-facing turning coordinate detection process. 
     This configuration makes it possible to detect a shift in the position of the tilt coordinate (first tilt coordinate) in a state in which the photovoltaic panel directly faces the solar trajectory in the turning direction, thus enabling precise detection of the first directly-facing tilt coordinate. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, before execution of the first directly-facing tilt coordinate detection process, the first time-dependent corrected tilt coordinate is calculated through time-dependent correction of the first tilt coordinate that reflects an amount of change in the solar altitude over time, and the first tilt detection reference coordinate is displaced in advance from the first tilt coordinate to the first time-dependent corrected tilt coordinate. 
     This configuration makes it possible to perform the first directly-facing tilt coordinate detection process by applying the first time-dependent corrected tilt coordinate that has been calculated with the amount of change in the solar altitude over time being reflected in the tilt coordinate, thus enabling the first directly-facing tilt coordinate to be detected in a short time with high precision. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, a photovoltaic panel is driven by applying a corrected target turning coordinate and a corrected target tilt coordinate that have been defined by specifying a targeted solar azimuth angle as a target solar azimuth angle and a targeted solar altitude as a target solar altitude, performing coordinate transformation using preset equations from the target solar azimuth angle and the target solar altitude to a target turning coordinate and a target tilt coordinate for the turning coordinate and the tilt coordinate, and correcting the target turning coordinate and the target tilt coordinate based on the first directly-facing turning coordinate and the first directly-facing tilt coordinate. 
     With this configuration, since a photovoltaic panel is driven by applying the corrected target turning coordinate and the corrected target tilt coordinate that have been defined through the correction based on the first directly-facing turning coordinate and the first directly-facing tilt coordinate, it is possible to correct a shift in position with ease and high precision before driving a photovoltaic panel. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, voltage is used to detect the panel output in the first directly-facing turning coordinate detection process and the first directly-facing tilt coordinate detection process. 
     This configuration makes it possible to detect the panel output with ease and a simple structure even if a shift in position is relatively large. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, current is used to detect the panel output in the first directly-facing turning coordinate detection process and the first directly-facing tilt coordinate detection process. 
     This configuration makes it possible to detect the panel output with high precision and a simple structure. 
     Moreover, the tracking control method for the tracking solar photovoltaic power generation system according to the present invention comprises a second directly-facing turning coordinate detection process for detecting a second directly-facing turning coordinate at which the panel output reaches its maximum value, by moving the turning position of the photovoltaic panel while sequentially changing the turning coordinate in a second turning detection range that is defined in connection with the first directly-facing turning coordinate, and a second directly-facing tilt coordinate detection process for detecting a second directly-facing tilt coordinate at which the panel output reaches its maximum value, by moving the tilt position of the photovoltaic panel while sequentially changing the tilt coordinate in a second tilt detection range that is defined in connection with the first directly-facing tilt coordinate. 
     This configuration makes it possible to detect a shift in the position of the first directly-facing turning coordinate relative to the solar azimuth angle with high precision with use of the second directly-facing turning coordinate detected in the second turning detection range that is smaller than the first turning detection range and to detect a shift in the position of the first directly-facing tilt coordinate relative to the solar altitude with high precision with use of the second directly-facing tilt coordinate detected in the second tilt detection range that is smaller than the first tilt detection range. By correcting together the shift in the position of the turning coordinate (second directly-facing turning coordinate) relative to the solar azimuth angle and the shift in the position of the tilt coordinate (second directly-facing tilt coordinate) relative to the solar altitude, it is thus possible to adjust the turning position and tilt position of the photovoltaic panel with ease and high precision so that the photovoltaic panel can directly face the solar trajectory. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, the second turning detection range is defined from a second turning detection start coordinate to a second turning detection end coordinate by using either the first directly-facing turning coordinate or a first time-dependent corrected turning coordinate obtained through time-dependent correction of the first directly-facing turning coordinate as a second turning detection reference coordinate and applying a predetermined second turning displacement angle smaller than the first turning displacement angle in both positive and negative directions of the second turning detection reference coordinate, and the second tilt detection range is defined from a second tilt detection start coordinate to a second tilt detection end coordinate by using either the first directly-facing tilt coordinate or a second time-dependent corrected tilt coordinate obtained through time-dependent correction of the first directly-facing tilt coordinate as a second tilt detection reference coordinate and applying a predetermined second tilt displacement angle smaller than the first tilt displacement angle in both positive and negative directions of the second tilt detection reference coordinate. 
     This configuration makes it possible to define the second turning detection range and the second tilt detection range to be smaller than the first turning detection range and the first tilt detection range, thus enabling the second directly-facing turning coordinate and the second directly-facing tilt coordinate to be detected with higher precision than the first directly-facing turning coordinate and the first directly-facing tilt coordinate. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, before execution of the second directly-facing turning coordinate detection process, the first time-dependent corrected turning coordinate is calculated through time-dependent correction of the first directly-facing turning coordinate that reflects an amount of change in the solar azimuth angle over time, and the second turning detection reference coordinate is displaced in advance from the first directly-facing turning coordinate to the first time-dependent corrected turning coordinate. 
     This configuration makes it possible to perform subsequent processing (second operation pattern) by applying the first time-dependent corrected turning coordinate that has been calculated with the amount of change in the solar azimuth angle over time being reflected in the first directly-facing turning coordinate, thus enabling the second directly-facing turning coordinate to be detected in a short time with high precision. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, the second directly-facing tilt coordinate detection process is performed after execution of a second directly-facing turning coordinate alignment process in which the turning coordinate is aligned with the second directly-facing turning coordinate detected in the second directly-facing turning coordinate detection process. 
     This configuration makes it possible to detect a shift in the position of the tile coordinate in a state in which a photovoltaic panel directly faces the solar trajectory in the turning direction, thus enabling precise detection of the second directly-facing tilt coordinate. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, before execution of the second directly-facing tilt coordinate detection process, the second time-dependent corrected tilt coordinate is calculated through time-dependent correction of the first directly-facing tilt coordinate that reflects an amount of change in the solar altitude over time, and the second tilt detection reference coordinate is displaced in advance from the first directly-facing tilt coordinate to the second time-dependent corrected tilt coordinate. 
     This configuration makes it possible to perform the second directly-facing tilt coordinate detection process by applying the second time-dependent corrected tilt coordinate that has been calculated with the amount of change in the solar altitude θ over time being reflected in the first directly-facing tilt coordinate, thus enabling the second directly-facing tilt coordinate to be detected in a short time with high precision. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, a photovoltaic panel is driven by applying a corrected target turning coordinate and a corrected target tilt coordinate that have been defined by specifying a targeted solar azimuth angle as a target solar azimuth angle and a targeted solar altitude as a target solar altitude, performing coordinate transformation using preset equations from the target solar azimuth angle and the target solar altitude to a target turning coordinate and a target tilt coordinate for the turning coordinate and the tilt coordinate, and correcting the target turning coordinate and the target tilt coordinate based on the second directly-facing turning coordinate and the second directly-facing tilt coordinate. 
     With this configuration, since a photovoltaic panel is driven by applying the corrected target turning coordinate and the corrected target tilt coordinate that are defined by the correction based on the second directly-facing turning coordinate and the second directly-facing tilt coordinate, it is possible to correct a shift in position with ease and high precision before driving the photovoltaic panel. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, voltage is used to detect the panel output in the first directly-facing turning coordinate detection process and the first directly-facing tilt coordinate detection process, and current is used to detect the panel output in the second directly-facing turning coordinate detection process and the second directly-facing tilt coordinate detection process. 
     This configuration makes it possible to detect the panel output with ease with use of voltage in previous processes (first directly-facing turning coordinate detection process and first directly-facing tilt coordinate detection process) and to detect the panel output with high precision with use of current in subsequent processes (second directly-facing turning coordinate detection process and second directly-facing tilt coordinate detection process), thus enabling a shift in the position of the turning coordinate relative to the solar azimuth angle and a shift in the position of the tilt coordinate to be detected with ease and high precision. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, current is used to detect the panel output in the first directly-facing turning coordinate detection process and the first directly-facing tilt coordinate detection process as well as to detect the panel output in the second directly-facing turning coordinate detection process and the second directly-facing tilt coordinate detection process. 
     This configuration makes it possible to detect the panel output with high precision with use of current in both previous (first directly-facing turning coordinate detection process and first directly-facing tilt coordinate detection process) and subsequent (second directly-facing turning coordinate detection process and second directly-facing tilt coordinate detection process) processes, thus enabling a shift in the position of the turning coordinate relative to the solar azimuth angle and a shift in the position of the tilt coordinate to be detected with ease and high precision. 
     Moreover, the tracking control method for the tracking solar photovoltaic power generation system according to the present invention comprises a third directly-facing turning coordinate detection process for detecting a third directly-facing turning coordinate at which the panel output reaches its maximum value by controlling the turning position of the photovoltaic panel while sequentially changing the turning coordinate in a third turning detection range that is defined in connection with the second directly-facing turning coordinate, and a third directly-facing tilt coordinate detection process for detecting a third directly-facing tilt coordinate at which the panel output reaches its maximum value, by controlling the tilt coordinate in a third tilt detection range that is defined in connection with the second directly-facing tilt coordinate. The third turning detection range is defined from a third turning detection start coordinate to a third turning detection end coordinate by using either the second directly-facing turning coordinate or a second time-dependent corrected turning coordinate obtained through time-dependent correction of the second directly-facing turning coordinate as a third turning detection reference coordinate and applying a predetermined third turning displacement angle smaller than the second turning displacement angle in both positive and negative directions of the third turning detection reference coordinate, and the third tilt detection range is defined from a third tilt detection start coordinate to a third tilt detection end coordinate by using either the second directly-facing tilt coordinate or a third time-dependent corrected tilt coordinate obtained through time-dependent correction of the second directly-facing tilt coordinate as a third tilt detection reference coordinate and applying a predetermined third tilt displacement angle smaller than the second tilt displacement angle in both positive and negative directions of the third tilt detection reference coordinate. 
     This configuration makes it possible to define the third turning detection range to be smaller than the second turning detection range and define the third tilt detection range to be smaller than the second tilt detection range, thus enabling the third directly-facing turning coordinate and the third directly-facing tilt coordinate to be detected with higher precision than the second directly-facing turning coordinate and the second directly-facing tilt coordinate. Furthermore, by correcting a shift in the position of the turning coordinate (third directly-facing turning coordinate) relative to the solar azimuth angle and a shift in the position of the tilt coordinate (third directly-facing tilt coordinate) relative to the solar altitude with high precision, it is possible to adjust the turning position and the tilt position of the photovoltaic panel with ease and higher precision so that the photovoltaic panel can directly face the solar trajectory. 
     Moreover, in the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, current is used to detect the panel output in the third directly-facing turning coordinate detection process and the third directly-facing tilt coordinate detection process. 
     This configuration it possible to detect the maximum panel output multiple times with use of current, thus enabling the panel output to be detected with ease and high precision in a state in which the positions of the turning coordinate and the tilt coordinate are slightly shifted relative to the solar azimuth angle. 
     Moreover, the present invention provides a tracking shift correction method for a tracking solar photovoltaic power generation system for causing a photovoltaic panel to track a solar trajectory, the system comprising a plurality of tracking drive solar photovoltaic power generators that are arranged in parallel connection and a power conversion portion that converts direct-current electric power generated by the tracking drive solar photovoltaic power generators into alternating-current electric power and supplies the alternating-current electric power to an interconnection load, each of the tracking drive solar photovoltaic power generators comprising a photovoltaic panel that converts sunlight into direct-current electric power, and a driving portion that drives the photovoltaic panel based on tracking information causing the photovoltaic panel to track the solar trajectory, wherein a tracking shift of the one of the photovoltaic panels that is targeted for tracking shift correction is detected in a state in which the corresponding tracking drive solar photovoltaic power generator is running by being connected to the power conversion portion. 
     With this configuration, since a tracking shift of a photovoltaic panel is detected with the photovoltaic panel being connected to the power conversion portion, the tracking shift of the photovoltaic panel can be corrected while maintaining system interconnection by continuing electric power generation by the tracking drive solar photovoltaic power generators and electric power supply from the power conversion portion to the interconnection load. It is thus possible to provide a highly reliable and productive tracking shift correction method for the tracking solar photovoltaic power generation system, which eliminates the need to stop the tracking solar photovoltaic power generation system associated with tracking shift correction and causes no loss in the amount of generated electric power. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, each of the tracking drive solar photovoltaic power generators comprises a tracking control portion that outputs the tracking information, in which a tracking shift is detected by the tracking control portion, and the driving portion is configured to correct a tracking shift of the photovoltaic panel in accordance with the tracking shift detected by the tracking control portion. 
     This configuration makes it possible to detect and correct a tracking shift individually for each of the tracking drive solar photovoltaic power generators, thus enabling the tracking control portions to be dispersed in the tracking solar photovoltaic power generation system. It is thus possible to provide a highly reliable tracking solar photovoltaic power generation system at low cost, which simplifies wiring structure of a control system and accordingly simplifies installation work. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, each of the tracking drive solar photovoltaic power generators comprises a detection circuit that detects the output of the photovoltaic panel, and the tracking control portion detects a tracking shift based on the output of the photovoltaic panel detected by the detection circuit. 
     This configuration makes it possible to detect the output of the photovoltaic panel with ease and high precision, thus enabling a tracking shift of the photovoltaic panel to be detected and corrected with ease and high precision. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, the detection circuit includes a current detecting portion that detects output current of the photovoltaic panel. 
     This configuration makes it possible to detect the output current of the photovoltaic panel to be detected with ease and high precision, thus enabling a tracking shift of the photovoltaic panel to be corrected with ease and high precision. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, a directly-facing position in which the photovoltaic panel directly faces the solar trajectory is determined based on the output current detected by the current detecting portion, and the photovoltaic panel is moved to the directly-facing position so as to correct a shift in position. 
     This configuration makes it possible to correct a tracking shift by applying variations in the output current that is sensitive to a tracking shift, thus enabling the directly-facing position in which the photovoltaic panel directly faces the solar trajectory to be determined with ease and high precision and accordingly a tracking shift to be corrected with ease and high precision. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, the detection circuit includes a voltage detecting portion that detects output voltage of the photovoltaic panel. 
     This configuration makes it possible to detect the output voltage of the photovoltaic panel with ease and high precision, thus enabling a tracking shift of the photovoltaic panel to be corrected with ease and high precision. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, a directly-facing position in which the photovoltaic panel directly faces the solar trajectory is determined based on the output voltage detected by the voltage detecting portion, and the photovoltaic panel is moved to the directly-facing position so as to correct a shift in position. 
     This configuration makes it possible to correct a tracking shift by applying variations in the output voltage that is responsive to a wide range of tracking shifts, thus enabling the directly-facing position in which the photovoltaic panel directly faces the solar trajectory to be determined with ease and high precision and accordingly a tracking shift to be corrected with ease and high precision. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, the directly-facing position is determined as a directly-facing turning position that is a directly-facing position in a turning direction. 
     This configuration makes it possible to correct a tracking shift in the turning direction with ease and high precision. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, the directly-facing position is determined as a directly-facing tilt position that is a directly-facing position in a tilt direction. 
     This configuration makes it possible to correct a tracking shift in the tilt direction with ease and high precision. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, the power conversion portion comprises a common inverter that is connected so as to convert direct-current electric power that is output from each of the photovoltaic panels collectively into alternating-current electric power and supply the resultant alternating-current electric power to the interconnection load. 
     With this configuration, a plurality of tracking drive solar photovoltaic power generators are run by being connected to a single common inverter. It is thus possible to simplify the configuration of the power conversion portion and to stabilize the operating voltage at the direct-current electric power, thus enabling a tracking shift to be detected with ease and high precision. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, the power conversion portion comprises a plurality of individual inverters that are connected so as to each convert direct-current electric power that is output from each of the photovoltaic panels individually into alternating-current electric power and supply the resultant alternating-current electric power collectively to the interconnection load. 
     With this configuration, the individual inverters each having a capacity corresponding to the capacity of each tracking drive solar photovoltaic power generator (photovoltaic panel) are arranged in direct correspondence with the photovoltaic panels. It is thus possible to stabilize the operating voltage by adjusting the outputs of the photovoltaic panels and to thereby detect a tracking shift with ease and high precision. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, the common inverter is configured to cause output operating points of the photovoltaic panels to follow an optimum operating point under maximum power point tracking control. 
     This configuration makes it possible to correct a tracking shift in a state in which the photovoltaic panels are operated at the optimum operating point (optimum output voltage), thus enabling a tracking shift to be corrected with ease and high precision under stable operating conditions. 
     Moreover, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, the common inverter or the individual inverters operate under constant voltage control and hold output operating points of the photovoltaic panels at a constant voltage. 
     This configuration makes it possible to correct a tracking shift in a state in which the photovoltaic panels are operated at a constant voltage, thus enabling a tracking shift to be corrected with ease and high precision under stable operating conditions. 
     Moreover, the present invention provides a tracking solar photovoltaic power generation system for causing a photovoltaic panel to track a solar trajectory, the system comprising a plurality of tracking drive solar photovoltaic power generators that are arranged in parallel connection, and a power conversion portion that converts direct-current electric power generated by the tracking drive solar photovoltaic power generators into alternating-current electric power and supply the alternating-current electric power to an interconnection load, each of the tracking drive solar photovoltaic power generators comprising a photovoltaic panel that converts sunlight into direct-current electric power, and a driving portion that drives the photovoltaic panel based on tracking information causing the photovoltaic panel to track the solar trajectory, wherein a tracking shift of the one of the photovoltaic panels that is targeted for tracking shift correction is detected in a state in which the corresponding tracking drive solar photovoltaic power generator is running by being connected to the power conversion portion. 
     This configuration makes it possible to detect a tracking shift of a photovoltaic panel in a state in which the corresponding tracking drive solar photovoltaic power generator is running by being connected to the power conversion portion, thus providing a highly reliable and productive tracking solar photovoltaic power generation system that eliminates the need to be stopped associated with tracking shift correction and causes no loss in the amount of generated electric power. 
     Moreover, in the tracking solar photovoltaic power generation system according to the present invention, the power conversion portion comprises a common inverter that is connected so as to convert direct-current electric power that is output from each of the photovoltaic panels collectively into alternating-current electric power and supply the resultant alternating-current electric power to the interconnection load. 
     This configuration simplifies the configuration of the power conversion portion and stabilizes the operating voltage with direct-current electric power, thus enabling a tracking shift to be detected with ease and high precision. 
     Moreover, in the tracking solar photovoltaic power generation system according to the present invention, the power conversion portion comprises a plurality of individual inverters that are connected so as to each convert direct-current electric power that is output from each of the photovoltaic panels individually into alternating-current electric power and supply the resultant alternating-current electric power collectively to the interconnection load. 
     This configuration makes it possible to use individual inverters each having a capacity corresponding to the capacity of each tracking drive solar photovoltaic power generator, thus enabling a tracking solar photovoltaic power generation system to be easily constructed at low cost by applying small-capacity, low-cost individual inverters. In addition, since the photovoltaic panels and the individual inverters are in direct correspondence with one another, it becomes easy to optimize the outputs of the photovoltaic panels and simplify output wiring. This makes the tracking solar photovoltaic power generation system rational and economical. 
     EFFECTS OF THE INVENTION 
     In accordance with the tracking control method for the tracking solar photovoltaic power generation system according to the present invention, the method comprises the first directly-facing turning coordinate detection process for detecting the first directly-facing turning coordinate at which the panel output reaches its maximum value, by moving the turning position of the photovoltaic panel while sequentially changing the turning coordinate in the first turning detection range that is defined in connection with the first turning coordinate corresponding to the solar azimuth angle, and the first directly-facing tilt coordinate detection process for detecting the first directly-facing tilt coordinate at which the panel output reaches its maximum value, by moving the tilt position of the photovoltaic panel while sequentially changing the tilt coordinate in the first tilt detection range that is defined in connection with the first tilt coordinate corresponding to the solar altitude. Therefore, a shift in the position of the turning coordinate (first turning coordinate) relative to the solar azimuth angle is detected with use of the first directly-facing turning coordinate, and a shift in the position of the tilt coordinate (first tilt coordinate) relative to the solar altitude is detected with use of the first directly-facing tilt coordinate. 
     Correcting together a shift in the position of the turning coordinate (first directly-facing turning coordinate) relative to the solar azimuth angle and a shift in the position of the tilt coordinate θ (first directly-facing tilt coordinate) relative to the solar altitude brings about the effect of enabling easy and high-precision adjustment of the turning position and the tilt position of a photovoltaic panel so that the photovoltaic panel can directly face the solar trajectory (solar azimuth angle and solar altitude). 
     Moreover, in accordance with the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present invention, each of the tracking drive solar photovoltaic power generators comprises a photovoltaic panel that converts sunlight into direct-current electric power and a driving portion that drives the photovoltaic panel based on tracking information causing the photovoltaic panel to track the solar trajectory, and a configuration is adopted in which a tracking shift of the one of the photovoltaic panels that is targeted for tracking shift correction is detected in a state in which the corresponding tracking drive solar photovoltaic power generator is running while being connected to the power conversion portion. It is thus possible to detect a tracking shift of a photovoltaic panel while connecting the photovoltaic panel to the power conversion portion and to thereby correct a tracking shift of the photovoltaic panel while maintaining the system interconnection by continuing electric power generation by the tracking drive solar photovoltaic power generators and electric power supply from the power conversion portion to the interconnection load. This brings about the effect of providing a highly reliable and productive tracking shift correction method for the tracking solar photovoltaic power generation system, which eliminates the need to stop the tracking solar photovoltaic power generation system associated with tracking shift correction and causes no loss in the amount of generated electric power. 
     Moreover, in accordance with the tracking solar photovoltaic power generation system according to the present invention, the system comprises a plurality of tracking drive solar photovoltaic power generators that are arranged in parallel connection, and a power conversion portion that converts direct-current electric power generated by the tracking drive solar photovoltaic power generators into alternating-current electric power and supplies the alternating-current electric power to an interconnection load, wherein each of the tracking drive solar photovoltaic power generator comprises a photovoltaic panel that converts sunlight into direct-current electric power and a driving portion that drives the photovoltaic panel based on tracking information causing the photovoltaic panel to track the solar trajectory, and a tracking shift of the one of the photovoltaic panels that is targeted for tracking shift correction is detected in a state in which the corresponding tracking drive solar photovoltaic power generator is running by being connected to the power conversion portion. This configuration makes it possible to detect a tracking shift of a photovoltaic panel in a state in which the corresponding tracking drive solar photovoltaic power generator is running by being connected to the power conversion portion, thus providing a highly reliable and productive tracking solar photovoltaic power generation system that eliminates the need to be stopped associated with tracking shift correction and causes no loss in the amount of generated electric power. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a schematic configuration of a tracking drive solar photovoltaic power generator during operation, according to Embodiment 1 of the present invention. 
         FIG. 2  is a block diagram illustrating a schematic configuration of a tracking solar photovoltaic power generation system when performing a tracking control method, according to Embodiment 1 of the present invention. 
         FIG. 3  is a block diagram illustrating a schematic configuration of a personal computer applied to perform the tracking control method for the tracking solar photovoltaic power generation system according to Embodiment 1 of the present invention. 
         FIG. 4  is a flowchart showing the procedure performed according to a first operation pattern when detecting and correcting a shift in the position of a tracking drive solar photovoltaic power generator according to Embodiment 2 of the present invention. 
         FIG. 5A  is a reference chart containing detailed information about the transition of control coordinates according to the first operation pattern shown in  FIG. 4 . 
         FIG. 5B  is an explanatory chart containing footnotes to  FIG. 5A . 
         FIG. 6  is a coordinate diagram plotting the transition of the control coordinates according to the first operation pattern shown in  FIG. 4 . 
         FIG. 7  is a flowchart showing the procedure performed according to a second operation pattern when detecting and correcting a shift in the position of a tracking drive solar photovoltaic power generator according to Embodiment 3 of the present invention. 
         FIG. 8A  is a reference chart containing detailed information about the transition of the control coordinates according to the second operation pattern shown in  FIG. 7 . 
         FIG. 8B  is an explanatory chart containing footnotes to  FIG. 8A . 
         FIG. 9  is a coordinate diagram plotting the transition of the control coordinates according to the second operation pattern shown in  FIG. 7 . 
         FIG. 10  is a flowchart showing the procedure performed according to a third operation pattern when detecting and correcting a shift in the position of a tracking drive solar photovoltaic power generator according to Embodiment 4 of the present invention. 
         FIG. 11A  is a reference chart containing detailed information about the transition of the control coordinates according to the third operation pattern shown in  FIG. 10 . 
         FIG. 11B  is an explanatory chart containing footnotes to  FIG. 11A . 
         FIG. 12  is a coordinate diagram plotting the transition of the control coordinates according to the third operation pattern shown in  FIG. 10 . 
         FIG. 13  shows a coordinate graphic illustrating the correlation between a coordinate system applied to a tracking drive solar photovoltaic power generator and control parameters, according to Embodiment 5 of the present invention. 
         FIG. 14  is a flowchart showing the procedure of computation processing performed based on the coordinate graphic shown in  FIG. 13  when correcting a shift in the positions of the control coordinates and driving a photovoltaic panel. 
         FIG. 15  is a block diagram illustrating a schematic configuration of a tracking solar photovoltaic power generation system during operation, according to Embodiment 6 of the present invention. 
         FIG. 16  is a block diagram illustrating a schematic configuration of a tracking solar photovoltaic power generation system when performing a tracking control method, according to Embodiment 6 of the present invention. 
         FIG. 17  is a block diagram illustrating a schematic configuration of a tracking solar photovoltaic power generation system according to Embodiment 7 of the present invention. 
         FIG. 18  is a block diagram illustrating a schematic configuration of a tracking drive solar photovoltaic power generator constituting the tracking solar photovoltaic power generation system shown in  FIG. 17 . 
         FIG. 19  is a characteristic graph showing a VI characteristic curve representative of the output state of a photovoltaic panel in the tracking solar photovoltaic power generation system shown in  FIG. 17 . 
         FIG. 20  is a flowchart showing the procedure for correcting a tracking shift in a tracking shift correction method for a tracking solar photovoltaic power generation system, according to Embodiment 8 of the present invention. 
         FIGS. 21(A) and 21(B)  are explanatory drawings for explaining the procedure for detecting a tracking shift in the turning direction in accordance with the flowchart shown in  FIG. 20 ,  FIG. 21(A)  being a graph showing the relationship between the turning position and the output current, and  FIG. 21(B)  being a flowchart showing the procedure. 
         FIGS. 22(A) and 22(B)  are explanatory drawings for explaining the procedure for correcting a tracking shift in the tilt direction in accordance with the flowchart shown in  FIG. 20 ,  FIG. 22(A)  being a graph showing the relationship between the tilt position and the output current, and  FIG. 22(B)  being a flowchart showing the procedure. 
         FIG. 23  is a block diagram illustrating a schematic configuration of a tracking solar photovoltaic power generation system according to Embodiment 10 of the present invention. 
         FIGS. 24(A) to 24(C)  are graphs showing VI characteristic curves of a photovoltaic panel in a tracking solar photovoltaic power generation system according to Embodiment 11 of the present invention,  FIG. 24(A)  showing normal characteristics of a photovoltaic panel that is not targeted for correction,  FIG. 24(B)  showing normal characteristics of a photovoltaic panel that is targeted for correction, and  FIG. 24(C)  showing combined characteristics of the photovoltaic panel that is not targeted for correction and the photovoltaic panel that is targeted for correction. 
         FIGS. 25(A) to 25(C)  are graphs showing VI characteristic curves of a photovoltaic panel in the tracking solar photovoltaic power generation system under MPPT control, according to Embodiment 11 of the present invention,  FIG. 25(A)  showing normal characteristics of a photovoltaic panel that is not targeted for correction,  FIG. 25(B)  showing characteristics in a state in which a tracking position is moved in order to detect a shift in the position of a photovoltaic panel that is targeted for correction, and  FIG. 25(C)  showing combined characteristics of the photovoltaic panel that is not targeted for correction and a photovoltaic panel that is targeted for correction. 
         FIGS. 26(A) to 26(C)  are graphs showing VI characteristic curves of a photovoltaic panel in the tracking solar photovoltaic power generation system under constant voltage control, according to Embodiment 11 of the present invention,  FIG. 26(A)  showing normal characteristics of a photovoltaic panel that is not targeted for correction,  FIG. 26(B)  showing characteristics in a state in which the tracking position is moved in order to detect a shift in the position of a photovoltaic panel that is targeted for correction, and  FIG. 26(C)  showing combined characteristics of the photovoltaic panel that is not targeted for correction and the photovoltaic panel that is targeted for correction. 
         FIG. 27  is a perspective view illustrating an overview of a conventional tracking drive solar photovoltaic power generator. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, a tracking solar photovoltaic power generation system and a tracking control method and a tracking shift correction method for the tracking solar photovoltaic power generation system according to embodiments of the present invention will be described in orderly sequence with reference to the drawings. 
     Tracking Control Method for Tracking Solar Photovoltaic Power Generation System 
     Embodiment 1 
     First is a description of a tracking control method for a tracking solar photovoltaic power generation system according to Embodiment 1, given with reference to  FIGS. 1 to 3 . 
       FIG. 1  is a block diagram illustrating a schematic configuration of the tracking solar photovoltaic power generation system according to Embodiment 1. 
     In the tracking control method for the tracking solar photovoltaic power generation system according to the present embodiment, a tracking drive solar photovoltaic power generator  1  includes a photovoltaic panel  10  that converts sunlight into electric power, and a tracking control portion  13  that provides tracking control over the turning position and tilt position of the photovoltaic panel  10  so that the photovoltaic panel  10  can track the solar trajectory based on a turning coordinate φ (turning direction Roth) and a tilt coordinate θ (tilt direction Rotv) that have been set corresponding to a solar azimuth angle φs and a solar altitude θs. 
     Also, the photovoltaic panel  10  is held by a column  11 , and its turning direction Roth (turning coordinate φ) and tilt direction Rotv (tilt coordinate θ) are controlled by a driving portion  12  provided on the top of the column  11 . The driving portion  12  includes a turning drive portion (not shown) and a tilt drive portion (not shown) and is capable of tracking the solar trajectory based on the turning coordinate φ (turning direction Roth) and the tilt coordinate θ (tilt direction Rotv) transmitted from the tracking control portion  13  via a control line  13   c.    
     The tracking control portion  13  supplies the turning coordinate φ (turning direction Roth) and the tilt coordinate θ (tilt direction Rotv) to the driving portion  12  in accordance with data supplied from a personal computer (PC)  30  via a communication line  13   b . In other words, the PC  30  is configured to hold data about solar coordinates (solar azimuth angle φs and solar altitude θs) and generate control coordinates (turning coordinate φ and tilt coordinate θ) corresponding to the solar coordinates. 
     Electric power generated on the photovoltaic panel  10  is input to an electric power monitoring board  20  via an electric power line  20   b  and is output from the electric power monitoring board  20  via an electric power line  20   c  to an inverter  40  as a load. The electric power monitoring board  20  includes a switch  21  that is installed in the middle of the electric power line  20   b  and used to control the closing and opening of connection to the photovoltaic panel  10 , a detection circuit  22  that detects the condition of generated electric power, and an output side circuit breaker  25  that is installed in the middle of the electric power line  20   c  and is used to control the closing and opening of connection to the inverter  40 . 
     The detection circuit  22  includes a current detecting resistor  23  for detecting the magnitude of generated electric power by current and a voltage detection resistor  24  for detecting the magnitude of generated electric power by voltage. The current (analog value) detected by the current detecting resistor  23  and the voltage (analog value) detected by the voltage detection resistor  24  are transmitted to an A/D conversion portion  26  in which analog-to-digital conversion is performed, and are converted into digital values in a form that can be handled by the PC  30 . 
     Such current data and voltage data converted into digital values are transmitted to the PC  30  via a detection line  22   b , so that the PC  30  can monitor the status of generation of electric power. In other words, the PC  30  is configured to perform operation management during operation. For example, a configuration is also possible in which, in the event of a data error (power generation malfunction) during monitoring, a warning is output according to a pre-installed computer program. 
     It should be noted that, although the present embodiment will be described with the case where a single electric power monitoring board  20  is arranged for a single photovoltaic panel  10 , the electric power monitoring board  20  may be configured with multiple photovoltaic panels  10  being connected thereto (see  FIGS. 15 and 16 ). 
     Alternatively, in the case where a single or several photovoltaic panels  10  are operated by being directly connected to the inverter  40 , a configuration is also possible in which the detection circuit  22  is connected individually to each of the photovoltaic panels  10  so that the photovoltaic panels  10  can operate without applying the electric power monitoring board  20 . 
       FIG. 2  is a block diagram illustrating a schematic configuration of the tracking drive solar photovoltaic power generator  1  when performing the tracking control method, according to Embodiment 1 of the present invention. 
       FIG. 2  illustrates a connection state of constituent blocks in the case where a shift in the position of the turning coordinate φ relative to the solar azimuth angle φs and a shift in the position of the tilt coordinate θ relative to the solar altitude θs are detected and corrected. The basic configuration is similar to that during operation shown in  FIG. 1 , and therefore descriptions are primarily given regarding different points. 
     In the tracking control method (detection and correction of shifts in positions) for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, a simulated load  41  is connected instead of the inverter  40 . The simulated load  41  can provide stable load conditions if constituted as, for example, a resistor, and therefore it is possible to stably detect and correct a shift in position. 
     The switching between the inverter  40  and the simulated load  41  can be performed safely in a state in which the supply of electric power from the photovoltaic panel is eliminated with both the switch  21  and the output side circuit breaker  25  being set to an open state (OFF). It should be noted that, although the switching between the open (OFF) and closed (ON) states of the switch  21  and the output side circuit breaker  25  can be performed by transmitting instructions from the PC  30  to the switch  21  and the output side circuit breaker  25  via control lines (not shown), the switching may be performed manually. 
     Moreover, it is also possible to install an operation program (computer program used in the operating state in  FIG. 1 ) and a correction program (computer program used in the correction state in  FIG. 2 ) together on the PC  30 . Accordingly, the same apparatus can be applied as the PC  30  used during operation and the PC  30  used during correction. 
     It should be noted that it is also possible, instead of applying the same apparatus, to apply different PCs for operation and correction. Also, the connection of the tracking control portion  13  and the A/D conversion portion  26  to the PC  30  can be established by appropriate switching using, for example, a USB terminal, and therefore detailed descriptions thereof have been omitted. 
     In the connection state in  FIG. 2 , a computer program for detecting a shift in position and a computer program for correcting a shift in position based on the detected shift in position are executed. It should be noted that a configuration is possible in which those computer programs are pre-installed on the PC  30  and their menus are displayed on the display screen of the PC  30  so that the computer programs can be executed by selecting a corresponding instruction button from the menus (menu buttons). 
     A configuration is also possible in which the PC  30  is defined as a dedicated device and equipped with special-purpose operation buttons corresponding to instructions. 
     The contents of the tracking control method (detection and correction of a shift in position) performed by the tracking drive solar photovoltaic power generator  1  in the connection state shown in  FIG. 2  will be described in detail in Embodiment 2. 
       FIG. 3  is a block diagram illustrating a schematic configuration of the PC applied to perform the tracking control method for the tracking solar photovoltaic power generation system according to Embodiment 1. 
     The PC  30  applied to the tracking drive solar photovoltaic power generator  1  according to the present embodiment includes a CPU (central processing unit)  31  that serves as, for example, a controller for executing an instruction selected from the menu and to which a program memory  32 , a data memory  33 , an RTC (real time clock)  34 , a display portion  35 , a detected data input portion  36 , and a control data output portion  37  are connected via a bus  31   b.    
     The program memory  32  has pre-installed thereon an operation program for performing the tracking control method for operating the tracking drive solar photovoltaic power generator  1 , and a positional shift detection/correction program for detecting and correcting a shift in the position of the tracking drive solar photovoltaic power generator  1 . 
     The data memory  33  stores data, such as position information corresponding to the latitude and the longitude, data indicating the solar coordinates (solar azimuth angle φs and solar altitude θs) corresponding to the solar trajectory determined based on the position information and time information, and the amount of a shift in position. 
     The RTC (real time clock)  34  is an electronic component that generates the current time and day, year, month, and date. Providing time data enables the solar coordinates corresponding to time to be provided with high precision. 
     The display portion  35  is configured to, for example, display a menu screen and allow selection of operations, such as an operation performed in the operating state in the tracking control method and an operation performed in a state in which a shift in position is detected or corrected in the tracking control method. 
     The detected data input portion  36  receives inputs of the current data detected by the current detecting resistor  23  and the voltage data detected by the voltage detection resistor  24  as digital data via the A/D conversion portion  26 . The CPU  31  is thus capable of determining the control coordinates (turning coordinate φ and tilt coordinate θ) at which the photovoltaic panel can directly face the sun, based on the input current data and voltage data. 
     The current data and the voltage data can be acquired by, for example, sampling the panel output (current data and voltage data input that are input to the CPU  31 ) per second, accumulating the sampled data in the data memory  33 , and performing computations in the PC  30 . 
     It should be noted that the photovoltaic panel  10  (solar cell) has characteristics that, when the amount of sunlight irradiation varies, the output voltage varies little, but the output current varies greatly. Therefore, in the case where detection is performed by voltage, the coordinates (turning coordinate φ and tilt coordinate θ) at the middle of the duration, during which the measured voltage was, for example, 95% or more of the detected maximum value, may be obtained as detection results. Also, in the case where detection is performed by current, the coordinates (turning coordinate φ and tilt coordinate θ) at, for example, a position corresponding to a maximum value may be obtained as detection results. That is, a configuration is possible in which the voltage data and the current data are detected while limiting the influence of variations in sunlight. 
     The control data output portion  37  is capable of outputting, to the tracking control portion  13 , new control coordinates (turning coordinate φ and tilt coordinate θ) that are obtained through correction based on the difference (shifts in the positions of the control coordinates that produce a shift in the position of the photovoltaic panel  10 ) between the obtained control coordinates (turning coordinate φ and tilt coordinate θ; e.g., later-described first directly-facing turning coordinate φ 1   m  and first directly-facing tilt coordinate θ 1   m ) at which the photovoltaic panel directly faces the sun, and the solar coordinates (solar azimuth angle φs and solar altitude θs). 
     Second Embodiment 
     Next is a description of a tracking control method (tracking control method adopting a positional shift detection/correction program) for a tracking solar photovoltaic power generation system according to Embodiment 2 of the present invention, given with reference to  FIGS. 4 to 6 . 
       FIG. 4  is a flowchart showing the procedure performed according to a first operation pattern when detecting and correcting a shift in the position of a tracking drive solar photovoltaic power generator in accordance with the tracking control method for the tracking solar photovoltaic power generation system according to Embodiment 2.  FIG. 5A  is a reference chart containing detailed information about the transition of the control coordinates according to the first operation pattern shown in  FIG. 4 , and  FIG. 5B  is an explanatory chart containing footnotes to  FIG. 5A .  FIG. 6  is a coordinate diagram plotting the transition of the control coordinates according to the first operation pattern shown in  FIG. 4 . 
     The tracking control method (tracking control method adopting a positional shift detection/correction program) for the tracking solar photovoltaic power generation system according to Embodiment 2 is performed in accordance with a procedure (first operation pattern) including, for example, steps S 1  to S 10 . It should be noted that the following steps S 1  to S 10  are performed according to a computer program installed on the PC  30  as described above. 
     Step S 1  (Process S 1 ): 
     Solar coordinates (solar azimuth angle φs and solar altitude θs) are specified at time T 1  when the tracking control method adopting the positional shift detection/correction program is executed (started). 
     For example, when the program is started at time T 1 , e.g., 10:00:00 a.m. (hereinafter, hour, minute, and second are simply indicated in the format of time “10:00:00”), the solar azimuth angle φs@T 1  as −30° and the solar altitude θs@T 1  as 50°, for example, are specified corresponding to the solar trajectory. It should be noted that the turning coordinate φ and the solar azimuth angle φs are 0° at the meridian (due south). 
     The values of the solar coordinates are set (applied) as is to the control coordinates (turning coordinate φ and tilt coordinate θ) that are to be set corresponding to the solar coordinates, because it is prior to correction of a shift in position. That is, the turning coordinate φ and the tilt coordinate θ are changed respectively into a first turning coordinate φ 1  (φ 1 =−30°) that corresponds to the solar azimuth angle φs and a first tilt coordinate θ 1  (θ 1 =50°) that corresponds to the solar altitude θs. 
     Accordingly, the control coordinates are arranged in position P 1  at time T 1 . Meanwhile, the turning position of the photovoltaic panel  10  is moved in accordance with the turning coordinate φ, whereas the tilt position of the photovoltaic panel  10  is moved in accordance with the tilt coordinate θ. That is, the orientation of the photovoltaic panel  10  is controlled by changing the control coordinates. 
     Step S 2  (Process S 2 ): 
     With the tilt coordinate θ fixed at the first tilt coordinate θ 1  (θ 1 =50°), the turning coordinate φ is moved from the first turning coordinate φ 1  (φ 1 =−30°) in a negative direction by a first turning displacement angle dφ 1  (dφ 1 =15°) and changed into a the first turning detection start coordinate (φ 1 −dφ 1 ) (φ 1 −dφ 1 =−30−15=−45). 
     Specifically, the turning coordinate φ is moved from position P 1  (first turning coordinate φ 1 ) to position P 2  (first turning detection start coordinate (φ 1 −dφ 1 )). Here, time T 2  when the turning coordinate has moved to position P 2  is 10:00:30, for example. The time required for the movement varies depending on the drive speed of the driving portion  12  (drive speed when moving the photovoltaic panel  10 ), and the drive speed of the driving portion  12  is preset corresponding to the functions required. 
     Step S 3  (Process S 3 ): 
     With the first tilt coordinate φ 1  (φ 1 =50°) fixed, the turning coordinate φ is sequentially changed from the first turning detection start coordinate (φ 1 −dφ 1 ) (φ 1 −dφ 1 =−45°) to a first turning detection end coordinate (φ 1 +dφ 1 ) (φ 1 +dφ 1 =−30+15=−15°). 
     Specifically, the turning coordinate φ is moved from position P 2  (first turning detection start coordinate (φ 1 −dφ 1 )) to position P 3  (first turning detection end coordinate (φ 1 +dφ 1 )). Here, time T 3  when the turning coordinate has moved to position P 3  is 10:01:30, for example. 
     In this step, a first directly-facing turning coordinate φ 1   m  at which the panel output (the output of the photovoltaic panel  10 ) transmitted from the A/D conversion portion  26  reaches its maximum value is also detected concurrently with changes in the turning coordinate φ (first directly-facing turning coordinate detection process). For example, it is assumed that the first directly-facing turning coordinate φ 1   m  is detected as −25°. 
     It should be noted that the maximum value of the panel output can be detected in the form of either voltage or current. In other words, the first directly-facing turning coordinate φ 1   m  at which the panel output reaches its maximum value can be determined by, for example, the turning coordinate φ at which the voltage detected by the voltage detection resistor  24  reaches its maximum value. Alternatively, the turning coordinate φ at which the current detected by the current detecting resistor  23  reaches its maximum value may be used. 
     In this step, the first directly-facing turning coordinate φ 1   m  at which the panel output reaches its maximum value is detected by moving the turning position of the photovoltaic panel while sequentially changing the turning coordinate φ in a first turning detection range (e.g., (φ 1 −dφ 1 ) to (φ 1 +dφ 1 )) that is defined in connection with the first turning coordinate φ 1  corresponding to the solar azimuth angle φs. 
     It should be noted that the first turning detection range is defined from the first turning detection start coordinate (e.g., (φ 1 −dφ 1 ), i.e., position P 2 ) to the first turning detection end coordinate (e.g., (φ 1 +dφ 1 ), i.e., position P 3 ) that are set by using the first turning coordinate φ 1  (=−30°) as a first turning detection reference coordinate and applying a predetermined first turning displacement angle dφ 1  (=15°) in both positive and negative directions of the first turning detection reference coordinate. 
     Step S 4  (Process S 4 ): 
     With the first tilt coordinate θ 1  (θ 1 =50°) fixed, the turning coordinate φ is aligned with the first directly-facing turning coordinate φ 1   m  (φ 1   m =−25°) at which the panel output reaches its maximum value and that was detected in the first directly-facing turning coordinate detection process S 3  (first directly-facing turning coordinate alignment process). 
     Specifically, the turning coordinate φ is moved from position P 3  to position P 4  (first directly-facing turning coordinate φ 1   m ). Here, time T 4  (first directly-facing turning coordinate setting time) when the turning coordinate φ has moved to position P 4  is 10:01:55, for example. 
     It should be noted that step S 5  may also be performed without moving the turning coordinate φ to position P 4 , i.e., with the turning coordinate φ unchanged (position P 3 ). Specifically, in the case where the turning coordinate φ is not aligned with the coordinate (first directly-facing turning coordinate φ 1   m ) at which the panel output reaches its maximum value, the first directly-facing tilt coordinate θ 1   m  will be detected in the direction of the tilt coordinate θ in position P 3 , using the turning coordinate φ=φ 1 +dφ 1  (see step S 7 ). 
     Step S 5  (Process S 5 ): 
     A first time-dependent corrected tilt coordinate θ 1   t  (θ 1   t =52°) is calculated by performing time-dependent correction on the first tilt coordinate θ 1  (θ 1 =50°). Then, with the first directly-facing turning coordinate φ 1   m  (φ 1   m =−25°) fixed, the tilt coordinate θ is changed from the first tilt coordinate θ 1  to the first time-dependent corrected tilt coordinate θ 1   t  (first time-dependent tilt correction process). 
     Specifically, with the turning coordinate φ fixed at the first directly-facing turning coordinate φ 1   m , the tilt coordinate θ is changed from position P 4  to position P 5 . Here, time T 5  when the tilt coordinate θ has moved to position P 5  is 10:02:00, for example. 
     That is, elapsed-time-dependent correction is performed on the first tilt coordinate θ 1 , taking into consideration a change in the solar altitude θs over time from time T 1  (10:00:00) when the tilt coordinate θ has been set to the first tilt coordinate θ 1  to time T 4  (10:01:55) when the turning coordinate φ has been aligned with φ=φ 1   m  (see Footnote  2  in  FIG. 5B ). 
     Accordingly, the tilt coordinate θ 1  is changed into the first time-dependent corrected tilt coordinate θ 1   t  (position P 5  at time T 5 ), taking into consideration the amount of change dθs in the solar altitude θs@T 4  (e.g., 52°) relative to the solar altitude θs@T 1  (e.g., 50°). It should be noted that the first time-dependent corrected tilt coordinate θ 1   t  to which the tilt coordinate θ is to be changed is calculated by determining the amount of altitude change dθs as dθs=θs@T 4 −θs@T 1 =52−50=2° and adding the amount of altitude change dθs to the first tilt coordinate θ 1  (θ 1   t =θ 1 +dθs=50+2=52°). 
     As described above, in this step, before execution of a later-described first directly-facing tilt coordinate detection process S 7 , the first time-dependent corrected tilt coordinate θ 1   t  is calculated through the time-dependent correction of the first tilt coordinate θ 1  that reflects the amount of change dθs (=2°) in the solar altitude θs over time, and a first tilt detection reference coordinate (see step S 7 ) is displaced in advance from the first tilt coordinate θ 1  to the first time-dependent corrected tilt coordinate θ 1   t.    
     This configuration makes it possible to perform the first directly-facing tilt coordinate detection process S 7  by applying the first time-dependent corrected tilt coordinate θ 1   t  that has been calculated with the amount of change dθs in the solar altitude θs over time being reflected in the tilt coordinate θ 1 , thus enabling the first directly-facing tilt coordinate θ 1   m  to be detected in a short time with high precision. 
     When the time-dependent correction is performed on the tilt coordinate θ in this step, the first tilt detection reference coordinate is displaced from the first tilt coordinate θ 1  (e.g., position P 4 ) to the first time-dependent corrected tilt coordinate θ 1   t  (e.g., position P 5 ), so that the first tilt detection start coordinate is changed from the tilt coordinate (θ 1 −dθ 1 ) to a tilt coordinate (θ 1   t −dθ 1 ) (position P 6 ) and the first tilt detection end coordinate is changed from the tilt coordinate (θ 1 +dθ 1 ) to a tilt coordinate (θ 1   t +dθ 1 ) (position P 7 ). 
     In other words, when the time-dependent correction is not performed on the first tilt coordinate θ 1  (tilt coordinate θ) in this step, subsequent processing is performed with the first time-dependent corrected tilt coordinate θ 1   t  replaced by the first tilt coordinate θ 1  (i.e., using the first tilt coordinate θ 1  before changed by the time-dependent correction into the first time-dependent corrected tilt coordinate θ 1   t ). 
     It should be noted that, in the case of not performing this step (first time-dependent tilt correction process), the first time-dependent corrected tilt coordinate θ 1   t  is not set and therefore the tilt coordinate θ remains unchanged as the first tilt coordinate θ 1 . Accordingly, the first tilt detection start coordinate is the tilt coordinate (θ 1 −dθ 1 ), instead of the tilt coordinate (θ 1   t −dθ 1 ) (position P 6 ), and the first tilt detection end coordinate is the tilt coordinate (θ 1 +dθ 1 ), instead of the tilt coordinate (θ 1   t +dθ 1 ) (position P 7 ). 
     Step S 6  (Process S 6 ): 
     With the first directly-facing turning coordinate φ 1   m  (φ 1   m =−25°) fixed, the tilt coordinate θ is moved from the first time-dependent corrected tilt coordinate θ 1   t  (θ 1   t =52°) in the negative direction by a first tilt displacement angle dθ 1  (dθ 1 =5°) and changed into the first tilt detection start coordinate (θ 1   t −dθ 1 ))(=52−5=47°). 
     Specifically, the tilt coordinate θ is moved from position P 5  (first time-dependent corrected tilt coordinate θ 1   t ) to position P 6  (first tilt detection start coordinate (θ 1   t −dθ 1 )). Here, time T 6  when the tilt coordinate θ has moved to position P 6  is 10:02:30, for example. 
     Step S 7  (Process S 7 ): 
     With the first directly-facing turning coordinate φ 1   m  (φ 1   m =−25°) fixed, the tilt coordinate θ is sequentially changed from the first tilt detection start coordinate (θ 1   t −dθ 1 ) (=52−5=47°) to the first tilt detection end coordinate (θ 1   t +dθ 1 ) (=52+5=57°). 
     Specifically, the tilt coordinate θ is moved from position P 6  (first tilt detection start coordinate (θ 1   t −dθ 1 )) to position P 7  (first tilt detection end coordinate (θ 1   t +dθ 1 )). Here, time T 7  when the tilt coordinate θ has moved to position P 7  is 10:03:30, for example. 
     In this step, a first directly-facing tilt coordinate θ 1   m  at which the panel output (the output of the photovoltaic panel  10 ) transmitted from the A/D conversion portion  26  reaches its maximum value is also detected concurrently with changes in the tilt coordinate θ (first directly-facing tilt coordinate detection process). For example, it is assumed that the first directly-facing tilt coordinate θ 1   m  is detected as 53°. 
     It should be noted that the first directly-facing tilt coordinate θ 1   m  at which the panel output reaches its maximum value can be determined by, for example, the turning coordinate φ at which the voltage detected by the voltage detection resistor  24  reaches its maximum value. Alternatively, it may be determined by the turning coordinate φ at which the current detected by the current detecting resistor  23  reaches its maximum value. The method for detecting voltage or current is similar to that in the case of step S 3 , and therefore descriptions thereof have been omitted (the same applies for the following descriptions). 
     In this step, the first directly-facing tilt coordinate θ 1   m  at which the panel output reaches its maximum value is detected by moving the tilt position of the photovoltaic panel while sequentially changing the tilt coordinate θ in a first tilt detection range (e.g., from (θ 1   t −dθ 1 ) to (θ 1   t +dθ 1 )) that is defined in connection with the first tilt coordinate θ 1  corresponding to the solar altitude θs. 
     It should be noted that, when the time-dependent correction (step S 5 ) is not performed on the tilt coordinate θ, processing is performed with the tilt coordinate θ 1   t  replaced by the tilt coordinate θ 1  (i.e., using the tilt coordinate θ 1  before changed by the time-dependent correction into the first time-dependent corrected tilt coordinate θ 1   t ) as described in step S 5 . In other words, the first tilt detection range in which the tilt coordinate θ is moved is from a first tilt detection start coordinate (θ 1 −dθ 1 ) to a first tilt detection end coordinate (θ 1 +dθ 1 ). 
     Accordingly, the first tilt detection range is defined from the first tilt detection start coordinate (e.g., position P 6  (θ 1   t −dθ 1 ) or a position (θ 1 −dθ 1 ) (not shown) corresponding to position P 6 ) to the first tilt detection end coordinate (e.g., position P 7  (θ 1   t +dθ 1 ) or a position (θ 1 +dθ 1 ) (not shown) corresponding to position P 7 ) by using either the first tilt coordinate θ 1  (=50°) or the first time-dependent corrected tilt coordinate θ 1   t  (=52°) obtained through the time-dependent correction of the first tilt coordinate θ 1  as a first tilt detection reference coordinate and applying a predetermined first tilt displacement angle dθ 1  (=5°) in both positive and negative directions of the first tilt detection reference coordinate. This step (first directly-facing tilt coordinate detection process) is performed after execution of the first directly-facing turning coordinate alignment process S 4  in which the turning coordinate φ is aligned with the first directly-facing turning coordinate φ 1   m  detected in the first directly-facing turning coordinate detection process S 3 . 
     This configuration makes it possible to detect a shift in the position of the tilt coordinate θ (first tilt coordinate θ 1 ) in a state in which the photovoltaic panel directly faces the solar trajectory in the turning direction, thus enabling precise detection of the first directly-facing tilt coordinate θ 1   m.    
     Step S 8  (Process S 8 ): 
     With the first directly-facing turning coordinate φ 1   m  (φ 1   m =−25°) fixed, the tilt coordinate θ is aligned with the first directly-facing tilt coordinate θ 1   m  (θ 1   m= 53°) at which the panel output reaches its maximum value and that was detected in the first directly-facing tilt coordinate detection process (first directly-facing tilt coordinate alignment process). Specifically, the tilt coordinate θ is moved from position P 7  to position P 8  (first directly-facing tilt coordinate θ 1   m ). Here, time T 8  (first directly-facing tilt coordinate setting time) when the tilt coordinate θ has moved to position P 8  is 10:04:00, for example. 
     Step S 9  (Process S 9 ): 
     A first time-dependent corrected turning coordinate φ 1   mt  (φ 1   mt =−23°) is calculated by performing time-dependent correction on the first directly-facing turning coordinate φ 1   m  (φ 1   m =−25°). Then, with the first directly-facing tilt coordinate θ 1   m  (θ 1   m =53°) fixed, the turning coordinate φ is changed from the first directly-facing turning coordinate φ 1   m  into the first time-dependent corrected turning coordinate φ 1   mt  (first time-dependent turning correction process). 
     Specifically, with the tilt coordinate θ fixed at the first directly-facing tilt coordinate θ 1   m , the turning coordinate φ is changed and moved from position P 8  to position P 9 . Here, time T 9  when the turning coordinate φ has moved to position P 9  is 10:04:05, for example. 
     That is, elapsed-time-dependent correction is performed on the first directly-facing turning coordinate φ 1   m , taking into consideration a change in the solar azimuth angle φs over time from time T 1  (10:00:00) when the turning coordinate φ has been set to the first tilt coordinate φ 1  to time T 8  (10:04:00) when the tilt coordinate θ has been aligned with the first directly-facing tilt coordinate θ 1   m  (see Footnote  3  in  FIG. 5B ). 
     Accordingly, the first directly-facing turning coordinate φ 1   m  is changed into the first time-dependent corrected turning coordinate φ 1   mt  (position P 9  at time T 9 ), taking into consideration the amount of change dφs in the solar azimuth angle φs@T 8  (e.g., −28°) relative to the solar azimuth angle φs@T 1  (e.g., −30°). It should be noted that the first time-dependent corrected turning coordinate φ 1   mt  to which the turning coordinate is to be changed is calculated by determining the amount of solar azimuth angle change dφs as dφs=φs@T 8 −φs@T 1 =−28−(−30)=2° and adding the amount of solar azimuth angle change clips to the first directly-facing turning coordinate φ 1   m  (φ 1   mt =φ 1   m +dφs=−25+2=−23°). 
     As described above, in this step, before execution of a later-described second directly-facing turning coordinate detection process S 22 , the first time-dependent corrected turning coordinate φ 1   mt  is calculated by performing the time-dependent correction of the first directly-facing turning coordinate φ 1   m  that reflects the amount of change dφs (=2°) in the solar azimuth angle φs over time, and a second turning detection reference coordinate (see step S 22 ) is displaced in advance from the first directly-facing turning coordinate φ 1   m  to the first time-dependent corrected turning coordinate φ 1   mt.    
     This configuration makes it possible to perform subsequent processing (second operation pattern) by applying the first time-dependent corrected turning coordinate φ 1   mt  that has been calculated with the amount of change dφs in the solar azimuth angle φs over time being reflected in the first directly-facing turning coordinate φ 1   m , thus enabling the second directly-facing turning coordinate φ 2   m  to be detected in a short time with high precision. 
     When the time-dependent correction is performed on the turning coordinate φ in this step, the second turning detection reference coordinate is displaced from the first directly-facing turning coordinate φ 1   m  (corresponding to position P 8 ) to the first time-dependent corrected turning coordinate φ 1   mt  (corresponding to position P 9 ), so that a second turning detection start coordinate is changed from the turning coordinate (φ 1   m −dφ 2 ) to a turning coordinate (φ 1   mt −dφ 2 ) (position P 21 ) and a second turning detection end coordinate is changed from a turning coordinate (φ 1   m +dφ 2 ) to a turning coordinate (φ 1   mt +dφ 2 ) (position P 22 ). 
     In other words, when the time-dependent correction is not performed on the first directly-facing turning coordinate φ 1   m  (turning coordinate φ) in this step, subsequent processing is performed with the first time-dependent corrected turning coordinate φ 1   mt  replaced by the first directly-facing turning coordinate φ 1   m  (i.e., using the first directly-facing turning coordinate φ 1   m  before changed by the time-dependent correction into the first time-dependent corrected turning coordinate φ 1   mt ). 
     It should be noted that, when this step (first time-dependent turning correction process) is not performed, the first time-dependent corrected turning coordinate φ 1   mt  is not set and therefore the turning coordinate φ remains unchanged as the first directly-facing turning coordinate φ 1   m . Accordingly, the second turning detection start coordinate is the turning coordinate (φ 1   m −dφ 2 ), instead of the turning coordinate (φ 1   mt −dφ 2 ) (position P 21 ), and the second turning detection end coordinate is the turning coordinate (φ 1   m +dφ 2 ), instead of the turning coordinate (φ 1   mt +dφ 2 ) (position P 22 ). 
     It is possible through the steps S 1  to S 9  described above to detect the first directly-facing turning coordinate φ 1   m  and the first directly-facing tilt coordinate θ 1   m  and associate the turning coordinate φ and the tilt coordinate θ respectively with the first directly-facing turning coordinate φ 1   m  and the first directly-facing tilt coordinate θ 1   m . After step S 9 , if the detection of a shift in position is ended and the system is to be placed in the operating state, the processing proceeds to step S 10 . 
     In the case of detecting a shift in position with higher precision, on the other hand, the processing proceeds to a procedure including steps S 21  to S 29  (see a second operation pattern in  FIGS. 7 to 9 ). Such a mode of performing the second operation pattern following the first operation pattern can be implemented as appropriate by a menu selection method. 
     Step S 10  (Process S 10 ): 
     The photovoltaic panel  10  is driven after correcting a shift in the position of the turning coordinate φ relative to the solar azimuth angle φs and correcting a shift in the position of the tilt coordinate θ relative to the solar altitude θs (correction and drive process). Since correction is performed based on the first directly-facing turning coordinate φ 1   m  and the first directly-facing tilt coordinate θ 1   m  before driving the photovoltaic panel  10 , it is possible to correct the shifts in positions with ease and high precision before driving the photovoltaic panel  10 . 
     Note that a specific computation process will be described in Embodiment 5. 
     When time-dependent correction is not performed on the first directly-facing turning coordinate φ 1   m  (turning coordinate φ) in step S 9 , processing is performed with the first time-dependent corrected turning coordinate φ 1   mt  replaced by the first directly-facing turning coordinate φ 1   m . That is, a shift in the position of the turning coordinate φ is corrected based on a difference between the solar azimuth angle φs at time T 8  and the first directly-facing turning coordinate φ 1   m.    
     It should be noted that the first operation pattern, if performed during installation or maintenance control, can provide high-precision alignment with the photovoltaic panel  10  with ease and at low cost. In the case where the first operation pattern is applied during installation, installation work can be simplified considerably, which results in a considerable reduction in the cost of the installation process. 
     A configuration is also possible in which the first operation pattern is performed repeatedly at fixed intervals, not only during installation or maintenance control. In the case where the first operation pattern is performed repeatedly at fixed intervals, it is possible to easily detect the occurrence of abnormalities and accordingly provide higher precision control, thus increasing the reliability of the tracking drive solar photovoltaic power generator  1 . 
     A computer program for executing the first operation pattern (positional shift detection/correction program) may be installed in combination with an operation program in advance. By combining that program with the operation program in advance, a selection menu method that provides interconnection between the operation program and the first operation pattern interconnected becomes available, and therefore it is possible to perform the first operation pattern by simple instructions and to easily place the system in the operating state after the first operation pattern is completed. 
     According to the present embodiment, the first directly-facing tilt coordinate θ 1   m  is set to position P 8  at time T 8  (=10:04:05), and the first time-dependent corrected turning coordinate φ 1   mt  is set to position P 9  at time T 9  (=10:04:05). That is, the control coordinates can be aligned in a very short time to the tilt position and the turning position at which the panel output reaches its maximum value. Accordingly, extremely high-precision alignment can be accomplished in a short time with ease. 
     Moreover, in the present embodiment, the duration of time from time T 1  (10:00:00) in step S 1  to time T 9  (10:04:05) in step S 9  is 4:05. That is, the detection and further correction of a shift in position can be performed in a short time on the order of four minutes. 
     As described above, the tracking control method (first operation pattern) for the tracking drive solar photovoltaic power generator  1  according to the present embodiment is a tracking control method for the tracking drive solar photovoltaic power generator  1  that includes the photovoltaic panel  10  that converts sunlight into electric power, and the tracking control portion  13  that provides tracking control over the turning and tilt positions of the photovoltaic panel  10  so that the photovoltaic panel can track the solar trajectory based on the turning coordinate φ and the tilt coordinate θ that have been set corresponding to the solar azimuth angle φs and the solar altitude θs. 
     The tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment includes the first directly-facing turning coordinate detection process S 3  in which the first directly-facing turning coordinate φ 1   m  at which the panel output reaches its maximum value is detected by moving the turning position of the photovoltaic panel while sequentially changing the turning coordinate φ in the first turning detection range (e.g., from (φ 1 −dφ 1 ) to (φ 1 +dφ 1 )) that is defined in connection with the first turning coordinate φ 1  corresponding to the solar azimuth angle φs, and the first directly-facing tilt coordinate detection process S 7  in which the first directly-facing tilt coordinate θ 1   m  at which the panel output reaches its maximum value is detected by moving the tilt position of the photovoltaic panel while sequentially changing the tilt coordinate θ in the first tilt detection range (e.g., from (θ 1   t −dθ 1 ) to (θ 1   t +dθ 1 )) that is defined in connection with the first tilt coordinate θ 1  corresponding to the solar altitude θs. 
     This configuration makes it possible to detect a shift in the position of the turning coordinate φ (first turning coordinate φ 1 ) relative to the solar azimuth angle φs with use of the first directly-facing turning coordinate φ 1   m  and a shift in the position of the tilt coordinate θ (first tilt coordinate θ 1 ) relative to the solar altitude θs with use of the first directly-facing tilt coordinate θ 1   m  and to thereby correct a shift in the position of the turning coordinate φ (first directly-facing turning coordinate φ 1   m ) relative to the solar azimuth angle φs and a shift in the position of the tilt coordinate θ (first directly-facing tilt coordinate θ 1   m ) relative to the solar altitude θs, thus enabling the turning position and the tilt position of the photovoltaic panel  10  to be adjusted with ease and high precision so that the photovoltaic panel directly faces the solar trajectory (solar azimuth angle φs and solar altitude θs). 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, the first turning detection range is defined from the first turning detection start coordinate (e.g., position P 2  (φ 1 −dφ 1 )) to the first turning detection end coordinate (e.g., position P 3  (φ 1 +dφ 1 )) by using the first turning coordinate φ 1  (=−30°) as a first turning detection reference coordinate and applying a predetermined first turning displacement angle dφ 1  (=15°) in both positive and negative directions of the first turning detection reference coordinate. Also, the first tilt detection range is defined from the first tilt detection start coordinate (e.g., position P 6  (θ 1   t −dθ 1 ) or a position (θ 1 −dθ 1 ) (not shown) corresponding to position P 6 ) to the first tilt detection end coordinate (e.g., position P 7  (θ 1   t +dθ 1 ) or a position (θ 1 +dθ 1 ) (not shown) corresponding to position P 7 ) by using either the first tilt coordinate θ 1  (=50°) or the first time-dependent corrected tilt coordinate θ 1   t  (=52°) obtained through the time-dependent correction of the first tilt coordinate θ 1  as a first tilt detection reference coordinate and applying a predetermined first tilt displacement angle dθ 1  (=5°) in both positive and negative directions of the first tilt detection reference coordinate. 
     This configuration makes it possible to define the first turning detection range (=30°) and the first tilt detection range (=10°) with ease and high precision, thus enabling the first directly-facing turning coordinate φ 1   m  and the first directly-facing tilt coordinate θ 1   m  to be detected with ease and high precision. 
     In addition, it is possible in the first operation pattern to set the first turning displacement angle φ 1  and the first tilt displacement angle θ 1  to relatively large angles, such as ±15° and ±5° respectively, and it is sufficient that the accuracy in installing the photovoltaic panel  10  via the column  11  and the driving portion  12  is to such an extent as to allow detection of the first directly-facing turning coordinate φ 1   m  in the first turning detection range defined by the first turning displacement angle φ 1  and detection of the first directly-facing tilt coordinate θ 1   m  in the first tilt detection range defined by the first tilt displacement angle θ 1 . It is thus possible to significantly reduce time and manpower required for installation work. In other words, even if alignment accuracy is low during installation, high-precision alignment can be achieved, which significantly simplifies installation work and significantly reduces installation cost. 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, the first directly-facing tilt coordinate detection process S 7  is performed after execution of the first directly-facing turning coordinate alignment process S 4  in which the turning coordinate φ is aligned with the first directly-facing turning coordinate φ 1   m  detected in the first directly-facing turning coordinate detection process S 3 . 
     This configuration makes it possible to detect a shift in the position of the tilt coordinate θ (first tilt coordinate θ 1 ) in a state in which the photovoltaic panel  10  directly faces the solar trajectory in the turning direction, thus enabling precise detection of the first directly-facing tilt coordinate θ 1   m.    
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, before execution of the first directly-facing tilt coordinate detection process S 7 , the first time-dependent corrected tilt coordinate θ 1   t  is calculated through the time-dependent correction of the first tilt coordinate θ 1  that reflects the amount of change dθs in the solar altitude θs over time (=2°), and the first tilt detection reference coordinate is displaced in advance from the first tilt coordinate θ 1  to the first time-dependent corrected tilt coordinate θ 1   t  (first time-dependent tilt correction process S 5 ). 
     This configuration makes it possible to perform the first directly-facing tilt coordinate detection process S 7  by applying the first time-dependent corrected tilt coordinate θ 1   t  that has been calculated with the amount of change dθs in the solar altitude θs over time being reflected in the tilt coordinate θ 1 , thus enabling the first directly-facing tilt coordinate θ 1   m  to be detected in a short time with high precision. 
     The tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment includes the correction and drive process S 10  in which the photovoltaic panel  10  is driven after correcting a shift in the position of the turning coordinate φ relative to the solar azimuth angle φs and correcting a shift in the position of the tilt coordinate θ relative to the solar altitude θs. Since the correction is performed based on the first directly-facing turning coordinate φ 1   m  and the first directly-facing tilt coordinate θ 1   m  before driving the photovoltaic panel  10 , it is possible to correct the shifts in positions with ease and high precision before driving the photovoltaic panel  10 . 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, a configuration may be adopted in which voltage is used to detect the panel output in the first directly-facing turning coordinate detection process S 3  and the first directly-facing tilt coordinate detection process S 7 . Accordingly, even if a tracking shift is relatively large, the panel output can be detected easily with a simple structure. 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, a configuration may be adopted in which current is used to detect the panel output in the first directly-facing turning coordinate detection process S 3  and the first directly-facing tilt coordinate detection process S 7 . Accordingly, the panel output can be detected with high precision with a simple structure. 
     Third Embodiment 
     Next is a description of a tracking control method for a tracking solar photovoltaic power generation system (tracking control method adopting a positional shift detection/correction program) according to Embodiment 3 of the present invention, given with reference to  FIGS. 7 to 9 . 
       FIG. 7  is a flowchart showing the procedure performed according to the second operation pattern when detecting and correcting a shift in the position of a tracking drive solar photovoltaic power generator in accordance with the tracking control method for the tracking solar photovoltaic power generation system according to Embodiment 3.  FIG. 8A  is a reference chart containing detailed information about the transition of the control coordinates according to the second operation pattern shown in  FIG. 7 , and  FIG. 8B  is an explanatory chart containing footnotes to  FIG. 8A .  FIG. 9  is a coordinate diagram plotting the transition of the control coordinates according to the second operation pattern shown in  FIG. 7 . 
     The tracking control method for the tracking solar photovoltaic power generation system (tracking control method adopting a positional shift detection/correction program) according to the present embodiment is configured to be implemented, for example according to a procedure including steps S 21  to S 29  (second operation pattern). Note that the following steps S 21  to S 29  are executed in accordance with a computer program installed on the PC  30  as described above. 
     It should be noted that the second operation pattern is performed following step S 9  (position P 9  at time T 9 ) in the first operation pattern of Embodiment 2. Such a form of performing the second operation pattern following the first operation pattern can be implemented as appropriate by a menu selection method. Furthermore, the basic configuration as well as the functions and effects of the second operation pattern are similar to those of the first operation pattern, and therefore descriptions are primarily given regarding different points. 
     Step S 21  (Process S 21 ): 
     With the first directly-facing tilt coordinate θ 1   m  (θ 1   m =53°) fixed, the turning coordinate φ is moved from the first time-dependent corrected turning coordinate φ 1   mt  (φ 1   mt =−23°) in the negative direction by a second turning displacement angle dφ 2  (dφ 2 =5°) and changed into a second turning detection start coordinate (φ 1   mt −dφ 2 ) (φ 1   mt −dφ 2 =−23−5=−28°). 
     Specifically, the turning coordinate φ is moved from position P 9  (first time-dependent corrected turning coordinate φ 1   mt ) to position P 21  (second turning detection start coordinate (φ 1   mt −dφ 2 )). Here, time T 21  when the turning coordinate φ has moved to position P 21  is 10:04:20, for example. 
     Step S 22  (Process S 22 ): 
     With the first directly-facing tilt coordinate θ 1   m  (θ 1   m =53°) fixed, the turning coordinate φ is sequentially changed from the second turning detection start coordinate (φ 1   mt −dφ 2 ) (φ 1   mt −dφ 2 =−28°) to a second turning detection end coordinate (φ 1   mt +dφ 2 ) (φ 1   mt +dφ 2 =−23+5=−18°). 
     Specifically, the turning coordinate φ is moved from position P 21  (second turning detection start coordinate (φ 1   mt −dφ 2 )) to position P 22  (second turning detection end coordinate (φ 1   mt +dφ 2 )). Here, time T 22  when the turning coordinate φ has moved to position P 22  is 10:05:00, for example. 
     In this step, a second directly-facing turning coordinate φ 2   m  at which the panel output (the output of the photovoltaic panel  10 ) transmitted from the A/D conversion portion  26  reaches its maximum value is also detected concurrently (second directly-facing turning coordinate detection process). 
     For example, it is assumed that the second directly-facing turning coordinate φ 2   m  is detected as −26°. It should be noted that the second directly-facing turning coordinate φ 2   m  at which the panel output reaches its maximum value can be determined by, for example, the turning coordinate φ at which the current detected by the current detecting resistor  23  reaches its maximum value. Since the turning coordinate φ is obtained at a maximum value of current that is sensitive to a shift in the position of the photovoltaic panel  10  relative to sunlight, the turning coordinate φ can be determined with high precision. 
     Specifically, in this step, the second directly-facing turning coordinate φ 2   m  at which the panel output reaches its maximum value is detected by moving the turning position of the photovoltaic panel while sequentially changing the turning coordinate φ in a second turning detection range (e.g., from (φ 1   mt −dφ 2 ) to (φ 1   mt +dφ 2 )) that is defined in connection with the first directly-facing turning coordinate φ 1   m.    
     It should be noted that the second turning detection range is defined from the second turning detection start coordinate (e.g., position P 21  (φ 1   mt −dφ 2 ) or a position (φ 1   m −dφ 2 ) (not shown) corresponding to position P 21 ) to the second turning detection end coordinate (e.g., position P 22  (φ 1   mt +dφ 2 ) or a position (φ 1   m +dφ 2 ) (not shown) corresponding to position P 22 ) by using either the first directly-facing turning coordinate φ 1   m  (=−25°) or the first time-dependent corrected turning coordinate φ 1   mt  (=−23°) obtained through the time-dependent correction of the first directly-facing turning coordinate φ 1   m  as a second turning detection reference coordinate and applying a predetermined second turning displacement angle dφ 2  (=5°) that is smaller than the first turning displacement angle dφ 1  (=15°), in both positive and negative directions of the second turning detection reference coordinate. 
     When time-dependent correction is not performed on the first directly-facing turning coordinate φ 1   m  (turning coordinate φ) in step S 9 , processing is performed with the first time-dependent corrected turning coordinate φ 1   mt  replaced by the first directly-facing turning coordinate φ 1   m  as described above. 
     Step S 23  (Process S 23 ): 
     With the second directly-facing tilt coordinate θ 2   m  (θ 1   m =53°) fixed, the turning coordinate φ is aligned with the second directly-facing turning coordinate φ 2   m  (φ 2   m =−26°) detected in the second directly-facing turning coordinate detection process S 22  (second directly-facing turning coordinate alignment process). 
     Specifically, the turning coordinate φ is moved from position P 22  to position P 23  (second directly-facing turning coordinate φ 2   m ). Here, time T 23  (second directly-facing turning coordinate setting time) when the turning coordinate φ has moved to position P 23  is 10:05:20, for example. 
     It should be noted that step S 24  may be performed without moving the turning coordinate φ to position P 23 , i.e., with the turning coordinate φ unchanged (position P 22 ). In other words, when the turning coordinate φ is not aligned with the coordinate (second directly-facing turning coordinate φ 2   m ) at which the panel output reaches its maximum value, a second directly-facing tilt coordinate θ 2   m  (see step S 26 ) will be detected in the direction of the tilt coordinate θ in position P 22 , using the turning coordinate φ=φ 1   mt +dφ 2 . 
     Step S 24  (Process S 24 ): 
     A second time-dependent corrected tilt coordinate θ 1   mt  (θ 1   mt =54°) is calculated by performing time-dependent correction on the first directly-facing tilt coordinate θ 1   m  (θ 1   m =53°). Then, with the second directly-facing turning coordinate φ 2   m  (φ 2   m =−26°) fixed, the tilt coordinate θ is changed from the first directly-facing tilt coordinate θ 1   m  to the second time-dependent corrected tilt coordinate θ 1   mt  (second time-dependent tilt correction process). 
     Specifically, with the turning coordinate φ fixed at the second directly-facing turning coordinate φ 2   m , the tilt coordinate θ is changed and moved from position P 23  to position P 24 . Here, time T 24  when the tilt coordinate θ has moved to position P 24  is 10:05:25, for example. 
     That is, elapsed-time-dependent correction is performed on the first directly-facing tilt coordinate θ 1   m , taking into consideration a change in the solar altitude θs over time from time T 8  (10:04:00) when the tilt coordinate θ has been set to the first directly-facing tilt coordinate θ 1   m  to time T 23  (10:05:20) when the turning coordinate φ has been aligned with φ=φ 2   m  (see Footnote  2  in  FIG. 8B ). 
     Accordingly, the first directly-facing tilt coordinate θ 1   m  is changed into the second time-dependent corrected tilt coordinate θ 1   mt  (position P 24  at time T 24 ), taking into consideration the amount of change dθs in the solar altitude θs@T 23  (e.g., 55°) relative to the solar altitude θs@T 8  (e.g., 54°). It should be noted that the second time-dependent corrected tilt coordinate θ 1   mt  to which the tilt coordinate is to be changed is calculated by determining the amount of altitude change dθs as dθs=θs@T 23 −θs@T 8 =55−54=1° and adding the amount of altitude change dθs to the first directly-facing tilt coordinate θ 1   m  (θ 1   mt =θ 1   m +dθs=53+1=54°). 
     As described above, in this step, before execution of a later-described second directly-facing tilt coordinate detection process S 26 , the second time-dependent corrected tilt coordinate θ 1   mt  is calculated through the time-dependent correction of the first directly-facing tilt coordinate θ 1   m  that reflects the amount of change dθs (=1°) in the solar altitude θs over time, and a second tilt detection reference coordinate (see step S 26 ) is displaced in advance from the first directly-facing tilt coordinate θ 1   m  to the second time-dependent corrected tilt coordinate θ 1   mt.    
     This configuration makes it possible to perform the second directly-facing tilt coordinate detection process S 26  by applying the second time-dependent corrected tilt coordinate θ 1   mt  that has been calculated with the amount of change dθs in the solar altitude θ over time being reflected in the first directly-facing tilt coordinate θ 1   m , thus enabling the second directly-facing tilt coordinate θ 2   m  to be detected in a short time with high precision. 
     When time-dependent correction is performed on the tilt coordinate θ in this step, the second tilt detection reference coordinate is displaced from the first directly-facing tilt coordinate θ 1   m  (e.g., position P 23 ) to the second time-dependent corrected tilt coordinate θ 1   mt  (e.g., position P 24 ), so that a second tilt detection start coordinate is changed from the tilt coordinate (θ 1   m −dθ 2 ) to a tilt coordinate (θ 1   mt −dθ 2 ) (position P 25 ) and a second tilt detection end coordinate is changed from the tilt coordinate (θ 1   m +dθ 2 ) to a tilt coordinate (θ 1   mt +dθ 2 ) (position P 26 ). 
     In other words, when time-dependent correction is not performed on the first directly-facing tilt coordinate θ 1   m  (tilt coordinate θ) in this step, subsequent processing is performed with the second time-dependent corrected tilt coordinate θ 1   mt  replaced by the first directly-facing tilt coordinate θ 1   m  (i.e., using the first directly-facing tilt coordinate θ 1   m  before changed by the time-dependent correction into the second time-dependent corrected tilt coordinate θ 1   mt ). 
     It should be noted that, when this step (second time-dependent tilt correction process) is not performed, the second time-dependent corrected tilt coordinate θ 1   mt  is not set and therefore the tilt coordinate θ remains unchanged as the first directly-facing tilt coordinate θ 1   m . Accordingly, the second tilt detection start coordinate is the tilt coordinate (θ 1   m −dθ 2 ), instead of the tilt coordinate (θ 1   mt −dθ 2 ) (position P 25 ), and the second tilt detection end coordinate is the tilt coordinate (θ 1   m +dθ 2 ), instead of the tilt coordinate (θ 1   mt +dθ 2 ) (position P 26 ). 
     Step S 25  (Process S 25 ): 
     With the second directly-facing turning coordinate φ 2   m  (φ 2   m =−26°) fixed, the tilt coordinate θ is moved from the second time-dependent corrected tilt coordinate θ 1   mt  (θ 1   mt =54°) in the negative direction by a second tilt displacement angle dθ 2  (dθ 2 =2°) and changed into the second tilt detection start coordinate (θ 1   mt −dθ 2 ) (θ 1   mt −dθ 2 =54−2=52). 
     Specifically, the tilt coordinate θ is moved from position P 24  (second time-dependent corrected tilt coordinate θ 1   mt ) to position P 25  (second tilt detection start coordinate (θ 1   mt −dθ 2 )). Here, time T 25  when the tilt coordinate θ has moved to position P 25  is 10:05:40, for example. 
     Step S 26  (Process S 26 ): 
     With the second directly-facing turning coordinate φ 2   m  (φ 2   m =−26°) fixed, the tilt coordinate θ is sequentially changed from the second tilt detection start coordinate (θ 1   mt −dθ 2 ) (=54−2=52°) to the second tilt detection end coordinate (θ 1   mt +dθ 2 ) (θ 1   mt +dθ 2 =54+2=56). 
     Specifically, the tilt coordinate θ is moved from position P 25  (second tilt detection start coordinate (θ 1   mt −dθ 2 )) to position P 26  (second tilt detection end coordinate (θ 1   mt +dθ 2 )). Here, time T 26  when the tilt coordinate θ has moved to position P 26  is 10:06:20, for example. 
     In this step, a second directly-facing tilt coordinate θ 2   m  at which the panel output (the output of the photovoltaic panel  10 ) transmitted from the A/D conversion portion  26  reaches its maximum value is also detected concurrently with changes in the tilt coordinate θ (second directly-facing tilt coordinate detection process). For example, it is assumed that the second directly-facing tilt coordinate θ 2   m  is detected as 54.5°. 
     It should be noted that the second directly-facing tilt coordinate θ 2   m  at which the panel output reaches its maximum value can be determined by, for example, the turning coordinate φ at which the current detected by the current detecting resistor  23  reaches its maximum value. By detecting current that is sensitive to a shift in position, the accuracy of detection can be increased as compared with the case of detecting voltage. 
     In this step, the second directly-facing tilt coordinate θ 2   m  at which the panel output reaches its maximum value is detected by moving the tilt position of the photovoltaic panel while sequentially changing the tilt coordinate θ in a second tilt detection range (e.g., from (θ 1   mt −dθ 2 ) to (θ 1   mt +dθ 2 )) that is defined in connection with the first directly-facing tilt coordinate θ 1   m  corresponding to the solar altitude θs. 
     It should be noted that, when the time-dependent correction (step S 24 ) is not performed on the tilt coordinate θ, processing is performed with the tilt coordinate θ 1   mt  replaced by the first directly-facing tilt coordinate θ 1   m  (i.e., using the first directly-facing tilt coordinate θ 1   m  before changed by the time-dependent correction into the second time-dependent corrected tilt coordinate θ 1   mt ) as described in step S 24 . That is, the second tilt detection range in the second directly-facing tilt coordinate detection process, in which the tilt coordinate θ is moved, is from the second tilt detection start coordinate (θ 1   m −dθ 2 ) to the second tilt detection end coordinate (θ 1   m +dθ 2 ). 
     Accordingly, the second tilt detection range is defined from the second tilt detection start coordinate (e.g., position P 25  (θ 1   mt −dθ 2 ) or a position (θ 1   m −dθ 2 ) (not shown) corresponding to position P 25 ) to the second tilt detection end coordinate (e.g., position P 26  (θ 1   mt +dθ 2 ) or a position (θ 1   m +dθ 2 ) (not shown) corresponding to position P 26 ) by using either the first directly-facing tilt coordinate θ 1   m  (=53°) or the second time-dependent corrected tilt coordinate θ 1   mt  (=54°) obtained through the time-dependent correction of the first directly-facing tilt coordinate θ 1   m  as a second tilt detection reference coordinate and applying a predetermined second tilt displacement angle dθ 2  (=2°) that is smaller than the first tilt displacement angle dθ 1  (=5°), in both positive and negative directions of the second tilt detection reference coordinate. 
     This step (second directly-facing tilt coordinate detection process) is performed after execution of the second directly-facing turning coordinate alignment process S 23  in which the turning coordinate φ is aligned with the second directly-facing turning coordinate φ 2   m  detected in the second directly-facing turning coordinate detection process S 22 . 
     This configuration makes it possible to detect a shift in the position of the tilt coordinate θ in a state in which the photovoltaic panel directly faces the solar trajectory in the turning direction, thus enabling precise detection of the second directly-facing tilt coordinate θ 2   m.    
     Step S 27  (Process S 27 ): 
     With the second directly-facing turning coordinate φ 2   m  (φ 2   m =−26°) fixed, the tilt coordinate θ is aligned with the second directly-facing tilt coordinate θ 2   m  (θ 2   m= 54.5°) at which the panel output reaches its maximum value and that was detected in the second directly-facing tilt coordinate detection process S 26  (second directly-facing tilt coordinate alignment process). Specifically, the tilt coordinate θ is moved from position P 26  to position P 27  (second directly-facing tilt coordinate θ 2   m ). Here, time T 27  (second directly-facing tilt coordinate setting time) when the tilt coordinate θ has moved to position P 27  is 10:06:30, for example. 
     Step S 28  (Process S 28 ): 
     A second time-dependent corrected turning coordinate φ 2   mt  (φ 2   mt =−23°) is calculated by performing time-dependent correction on the second directly-facing turning coordinate φ 2   m  (φ 2   m =−26°). Then, with the second directly-facing tilt coordinate θ 2   m  (θ 2   m =54.5°) fixed, the turning coordinate φ is changed from the second directly-facing turning coordinate φ 2   m  to the second time-dependent corrected turning coordinate φ 2   mt  (second time-dependent turning correction process). 
     Specifically, with the tilt coordinate θ fixed at the second directly-facing tilt coordinate θ 2   m , the turning coordinate φ is changed and moved from position P 27  to position P 28 . Here, time T 28  when the turning coordinate φ has moved to position P 28  is 10:06:35, for example. 
     That is, elapsed-time-dependent correction is performed on the second directly-facing turning coordinate φ 2   m , taking into consideration a change in the solar azimuth angle φs over time from time T 23  (10:05:20) when the turning coordinate φ has been set to the second directly-facing turning coordinate φ 2   m  to time T 27  (10:06:30) when the tilt coordinate θ has been aligned with the second directly-facing tilt coordinate θ 2   m  (see Footnote  3  in  FIG. 8B ). 
     Accordingly, the second directly-facing turning coordinate φ 2   m  is changed into the second time-dependent corrected turning coordinate φ 2   mt  (position P 28  at time T 28 ), taking into consideration the amount of change dφs in the solar azimuth angle φs@T 27  (e.g., −21°) relative to the solar azimuth angle φs@T 23  (e.g., −24°). It should be noted that the second time-dependent corrected turning coordinate φ 2   mt  to which the turning coordinate is to be changed is calculated by determining the amount of solar azimuth angle change dφs as dφs=φs@T 27 −φs@T 23 =−21−(−24)=3° and adding the amount of solar azimuth angle change dφs to the second directly-facing turning coordinate φ 2   m  (φ 2   mt =φ 2   m +dφs=−26+3=−23°). 
     As described above, in this step, before execution of a later described third directly-facing turning coordinate detection process S 32 , the second time-dependent corrected turning coordinate φ 2   mt  is calculated through the time-dependent correction of the second directly-facing turning coordinate φ 2   m  that reflects the amount of change dφs (=3°) in the solar azimuth angle φs over time, and a third turning detection reference coordinate (see step S 32 ) is displaced in advance from the second directly-facing turning coordinate φ 1   m  to the second time-dependent corrected turning coordinate φ 2   mt.    
     This configuration makes it possible to perform subsequent processing (third operation pattern) by applying the second time-dependent corrected turning coordinate φ 2   mt  that has been calculated with the amount of change dφs in the solar azimuth angle φs over time being reflected in the second directly-facing turning coordinate φ 2   m , thus enabling the third directly-facing turning coordinate φ 3   m  to be detected in a short time with high precision. 
     When time-dependent correction is performed on the turning coordinate φ in this step, the third turning detection reference coordinate is displaced from the second directly-facing turning coordinate φ 2   m  (corresponding to position P 27 ) to the second time-dependent corrected turning coordinate φ 2   mt  (corresponding to position P 28 ), so that the third turning detection start coordinate is changed from the turning coordinate (φ 2   m −dφ 3 ) to a turning coordinate (φ 2   mt −dφ 3 ) (position P 31 ) and the third turning detection end coordinate is changed from the turning coordinate (φ 2   m +dφ 3 ) to a turning coordinate (φ 2   mt +dφ 3 ) (position P 32 ). 
     In other words, when time-dependent correction is not performed on the second directly-facing turning coordinate φ 2   m  (turning coordinate φ) in this step, subsequent processing is performed with the second time-dependent corrected turning coordinate φ 2   mt  replaced by the second directly-facing turning coordinate φ 2   m  (i.e., using the second directly-facing turning coordinate φ 2   m  before changed by the time-dependent correction into the second time-dependent corrected turning coordinate φ 2   mt ). 
     It should be noted that, when this step (second time-dependent turning correction process) is not performed, the second time-dependent corrected turning coordinate φ 2   mt  is not set and therefore the turning coordinate φ remains unchanged as the second directly-facing turning coordinate φ 2   m . Accordingly, a third turning detection start coordinate is the turning coordinate (φ 2   m −dφ 3 ), instead of the turning coordinate (φ 2   mt −dφ 3 ) (position P 31 ), and the third turning detection end coordinate is the turning coordinate (φ 2   m +dφ 3 ), instead of the turning coordinate (φ 2   mt +dφ 3 ) (position P 32 ). 
     It is possible through the steps S 21  to S 28  described above to detect the second directly-facing turning coordinate φ 2   m  and the second directly-facing tilt coordinate θ 2   m  and associate the turning coordinate φ and the tilt coordinate θ respectively with the second directly-facing turning coordinate φ 2   m  and the second directly-facing tilt coordinate θ 2   m . After step S 28 , if the detection of a shift in position is ended and the system is placed in the operating state, the processing proceeds to step S 29 . 
     In the case of detecting a shift in position with higher precision, on the other hand, the processing proceeds to a procedure including steps S 31  to S 39  (see a third operation pattern in  FIGS. 10 to 12 ). Such a form of performing the third operation pattern following the second operation pattern can be implemented as appropriate by a menu selection method. 
     Step S 29  (Process S 29 ): 
     The photovoltaic panel  10  is driven after correcting a shift in the position of the turning coordinate φ relative to the solar azimuth angle φs and correcting a shift in the position of the tilt coordinate θ relative to the solar altitude θs (correction and drive process). Since the correction is performed based on the second directly-facing turning coordinate φ 2   m  and the second directly-facing tilt coordinate θ 2   m  before driving the photovoltaic panel  10 , it is possible to correct the shifts in positions with ease and high precision before driving the photovoltaic panel  10 . 
     Note that a specific computation process will be described in Embodiment 5. 
     When time-dependent correction is not performed on the second directly-facing turning coordinate φ 2   m  (turning coordinate φ) in step S 28 , processing is performed with the second time-dependent corrected turning coordinate φ 2   mt  replaced by the second directly-facing turning coordinate φ 2   m . Specifically, a shift in the position of the turning coordinate φ is corrected based on a difference between the solar azimuth angle φs at time T 27  and the second directly-facing turning coordinate φ 2   m.    
     According to the present embodiment, the second directly-facing tilt coordinate θ 2   m  is set to position P 27  at time T 27  (=10:06:30) and the second time-dependent corrected turning coordinate φ 2   mt  is set to position P 28  at time T 28  (=10:06:35). That is, the control coordinates can be aligned in a very short time to the tilt position and the turning position at which the panel output reaches its maximum value. Accordingly, extremely high-precision alignment can be accomplished in a short time with ease. 
     Moreover, in the present embodiment, the duration of time from time T 9  (10:04:05) in step S 9  to time T 28  (10:06:35) in step S 28  is 2:30. That is, the detection and further correction of a shift in position can be performed in a short time of the order of 2:30, which enables higher precision alignment to be accomplished in a shorter time than in Embodiment 1. 
     As described above, the tracking control method (second operation pattern) for the tracking drive solar photovoltaic power generator  1  according to the present embodiment is performed following Embodiment 2 (first operation pattern), and includes the second directly-facing turning coordinate detection process S 22  in which the second directly-facing turning coordinate φ 2   m  at which the panel output reaches its maximum value is detected by moving the turning position of the photovoltaic panel while sequentially changing the turning coordinate φ in the second turning detection range (e.g., from (φ 1   mt −dφ 2 ) to (φ 1   mt +dφ 2 )) that is defined in connection with the first directly-facing turning coordinate φ 1   m , and the second directly-facing tilt coordinate detection process S 26  in which the second directly-facing tilt coordinate θ 2   m  at which the panel output reaches its maximum value is detected by moving the tilt position of the photovoltaic panel while sequentially changing the tilt coordinate θ in the second tilt detection range (e.g., from (θ 1   mt −dθ 2 ) to (θ 1   mt +dθ 2 )) that is defined in connection with the first directly-facing tilt coordinate θ 1   m.    
     This configuration makes it possible to detect a shift in the position of the first directly-facing turning coordinate φ 1   m  relative to the solar azimuth angle φs with high precision with use of the second directly-facing turning coordinate φ 2   m , which has been detected in the second turning detection range (e.g., from (φ 1   mt −dφ 2 ) to (φ 1   mt +dφ 2 )=10°) smaller than the first turning detection range (e.g., from (φ 1 −dφ 1 ) to (φ 1 +dφ 1 )=30°), and a shift in the position of the first directly-facing tilt coordinate θ 1   m  relative to the solar altitude θs with high precision with use of the second directly-facing tilt coordinate θ 2   m , which has been detected in the second tilt detection range (e.g., from (θ 1   mt −dθ 2 ) to (θ 1   mt +dθ 2 )=4°) smaller than the first tilt detection range (e.g., from (θ 1   t −dθ 1 ) to (θ 1   t +dθ 1 )=10°), and thereby to correct a shift in the position of the turning coordinate φ (second directly-facing turning coordinate φ 2   m ) relative to the solar azimuth angle φs and a shift in the position of the tilt coordinate θ (second directly-facing tilt coordinate θ 2   m ) relative to the solar altitude θs, thus enabling the turning position and the tilt position of the photovoltaic panel to be adjusted with ease and high precision so that the photovoltaic panel can directly face the solar trajectory. 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, the second turning detection range is defined from the second turning detection start coordinate (e.g., position P 21  (φ 1   mt −dφ 2 ) or a position (φ 1   m −dφ 2 ) (not shown) corresponding to position P 21 ) to the second turning detection end coordinate (e.g., position P 22  (φ 1   mt +dφ 2 ) or a position (φ 1   m +dφ 2 ) (not shown) corresponding to position P 22 ) by using either the first directly-facing turning coordinate φ 1   m  (=−25°) or the first time-dependent corrected turning coordinate φ 1   mt  (=−23°) obtained through the time-dependent correction of the first directly-facing turning coordinate φ 1   m  as a second turning detection reference coordinate and applying a predetermined second turning displacement angle dφ 2  (=5°) that is smaller than the first turning displacement angle dφ 1  (=15°), in both positive and negative directions of the second turning detection reference coordinate. Also, the second tilt detection range is defined from the second tilt detection start coordinate (e.g., position P 25  (θ 1   mt −dθ 2 ) or a position (θ 1   m −dθ 2 ) (not shown) corresponding to position P 25 ) to the second tilt detection end coordinate (e.g., position P 26  (θ 1   mt +dθ 2 ) or a position (θ 1   m +dθ 2 ) (not shown) corresponding to position P 26 ) by using either the first directly-facing tilt coordinate θ 1   m  (=53°) or the second time-dependent corrected tilt coordinate θ 1   mt  (=54°) obtained through the time-dependent correction of the first directly-facing tilt coordinate θ 1   m  as a second tilt detection reference coordinate and applying a predetermined second tilt displacement angle dθ 2  (=2°) that is smaller than the first tilt displacement angle dθ 1  (=5°), in both positive and negative directions of the second tilt detection reference coordinate. 
     This configuration makes it possible to set the second turning detection range (=10°) and the second tilt detection range (=4°) to be smaller than the first turning detection range (=30°) and the first tilt detection range (=10°), thus enabling the second directly-facing turning coordinate φ 2   m  and the second directly-facing tilt coordinate θ 2   m  to be detected with higher precision than the first directly-facing turning coordinate φ 1   m  and the first directly-facing tilt coordinate θ 1   m.    
     Note that although descriptions have been given regarding the tracking solar photovoltaic power generation system in which the photovoltaic panel tracks the solar trajectory in both the turning direction Roth and in the tilt direction Rotv, the contents of the present invention may be applied to a method for controlling either one of the turning direction Roth and the tilt direction Rotv. Alternatively, similar effects can of course be achieved with a tracking solar photovoltaic power generation system of such a type that the photovoltaic panel can track the sun in only either the turning direction Roth or the tilt direction Rotv. 
     In addition, the range of a shift in position can sequentially be narrowed down because, according to the second operation pattern (subsequent operation pattern), a shift in position is detected in a narrower range than the first operation pattern (previous operation pattern), and therefore efficient alignment is possible. In other words, the accuracy in detecting a shift in position can be improved with reliability by repeating operation patterns depending on the degree of light gathering accuracy (light gathering magnification). Therefore, even if the method is applied to a high-magnification solar photovoltaic power generator, alignment according to high magnifications can be accomplished. 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, before execution of the second directly-facing turning coordinate detection process S 22 , the first time-dependent corrected turning coordinate φ 1   mt  is calculated through time-dependent correction of the first directly-facing turning coordinate φ 1   m  that reflects the amount of change dφs (=2°) in the solar azimuth angle φs over time, and the second turning detection reference coordinate is displaced in advance from the first directly-facing turning coordinate φ 1   m  to the first time-dependent corrected turning coordinate φ 1   mt  (first time-dependent turning correction process S 9 ). 
     This configuration makes it possible to perform subsequent processing (second operation pattern) by applying the first time-dependent corrected turning coordinate φ 1   mt  that has been calculated with the amount of change dφs in the solar azimuth angle φs over time being reflected in the first directly-facing turning coordinate φ 1   m , thus enabling the second directly-facing turning coordinate φ 2   m  to be detected in a short time with high precision. 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, the second directly-facing tilt coordinate detection process S 26  is performed after execution of the second directly-facing turning coordinate alignment process S 23  in which the turning coordinate φ is aligned with the second directly-facing turning coordinate φ 2   m  detected in the second directly-facing turning coordinate detection process S 22 . 
     This configuration makes it possible to detect a shift in the position of the tilt coordinate θ in a state in which the photovoltaic panel  10  directly faces the solar trajectory in the turning direction, thus enabling precise detection of the second directly-facing tilt coordinate θ 2   m.    
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, before execution of the second directly-facing tilt coordinate detection process S 26 , the second time-dependent corrected tilt coordinate θ 1   mt  is calculated through time-dependent correction of the first directly-facing tilt coordinate θ 1   m  that reflects the amount of change dθs (=1°) in the solar altitude θs over time, and the second tilt detection reference coordinate is displaced in advance from the first directly-facing tilt coordinate θ 1   m  to the second time-dependent corrected tilt coordinate θ 1   mt  (second time-dependent tilt correction process S 24 ). 
     This configuration makes it possible to perform the second directly-facing tilt coordinate detection process S 26  by applying the second time-dependent corrected tilt coordinate θ 1   mt  that has been calculated with the amount of change dθs in the solar altitude θ over time being reflected in the first directly-facing tilt coordinate θ 1   m , thus enabling the second directly-facing tilt coordinate θ 2   m  to be detected in a short time with high precision. 
     The tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment includes the correction and drive process S 29  in which the photovoltaic panel  10  is driven after correcting a shift in the position of the turning coordinate φ relative to the solar azimuth angle φs and correcting a shift in the position of the tilt coordinate θ relative to the solar altitude θs. Since the correction is performed based on the second directly-facing turning coordinate φ 2   m  and the second directly-facing tilt coordinate θ 2   m  before driving the photovoltaic panel  10 , it is possible to correct the shifts in positions with ease and high precision before driving the photovoltaic panel  10 . 
     The tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment may adopt a configuration in which voltage is used to detect the panel output in the first directly-facing turning coordinate detection process S 3  and the first directly-facing tilt coordinate detection process S 7 , and current is used to detect the panel output in the second directly-facing turning coordinate detection process S 22  and the second directly-facing tilt coordinate detection process S 26 . 
     This configuration makes it possible to detect the panel output with ease by voltage in the previous process (first directly-facing turning coordinate detection process S 3  and first directly-facing tilt coordinate detection process S 7 ) and detect the panel output with high precision by current in the subsequent process (second directly-facing turning coordinate detection process S 22  and second directly-facing tilt coordinate detection process S 26 ), thus enabling a shift in the position of the turning coordinate relative to the solar azimuth angle and a shift in the position of the tilt coordinate to be detected with ease and high precision. 
     The tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment may adopt a configuration in which current is used to detect the panel output in the first directly-facing turning coordinate detection process S 3  and the first directly-facing tilt coordinate detection process S 7  and to detect the panel output in the second directly-facing turning coordinate detection process S 22  and the second directly-facing tilt coordinate detection process S 26 . 
     This configuration makes it possible to detect the panel output with high precision by current in both of the previous process (first directly-facing turning coordinate detection process S 3  and first directly-facing tilt coordinate detection process S 7 ) and the subsequent process (second directly-facing turning coordinate detection process S 22  and second directly-facing tilt coordinate detection process S 26 ), thus enabling a shift in the position of the turning coordinate relative to the solar azimuth angle and a shift in the position of the tilt coordinate relative to the solar altitude to be detected with ease and high precision. 
     Fourth Embodiment 
     Next is a description of a tracking control method for a tracking solar photovoltaic power generation system (tracking control method adopting a positional shift detection/correction program) according to Embodiment 4 of the present invention, given with reference to  FIGS. 10 to 12 . 
       FIG. 10  is a flowchart showing the procedure performed according to the third operation pattern when detecting and correcting a shift in the position of a tracking drive solar photovoltaic power generator in accordance with the tracking control method for the tracking solar photovoltaic power generation system according to Embodiment 4. 
       FIG. 11A  is a reference chart containing detailed information about the transition of the control coordinates according to the third operation pattern shown in  FIG. 10 , and  FIG. 11B  is an explanatory chart containing footnotes to  FIG. 11A .  FIG. 12  is a coordinate diagram plotting the transition of the control coordinates according to the third operation pattern shown in  FIG. 10 . 
     The tracking control method (tracking control method adopting a program for detecting and correcting a shift in position) for the tracking solar photovoltaic power generation system according to the present embodiment is implemented according to, for example, a procedure including steps S 31  to S 39  (third operation pattern). Note that the following steps S 31  to S 39  are performed in accordance with a computer program installed on the PC  30  as described above. 
     It should be noted that the third operation pattern is performed following step S 28  (position P 28  at time T 28 ) in the second operation pattern of Embodiment 3. Such a form of performing the third operation pattern following the second operation pattern can be implemented as appropriate by a menu selection method. Furthermore, the basic configuration as well as the functions and effects of the third operation pattern are similar to those of the first operation pattern and the second operation pattern, and therefore descriptions are primarily given regarding different points. 
     According to the third operation pattern, a third directly-facing turning coordinate φ 3   m  and a third directly-facing tilt coordinate θ 3   m  are detected in ranges smaller than the second turning detection range and the second tilt detection range by applying a third displacement angle dφ 3  and a third tilt displacement angle dθ 3  that are smaller than the second turning displacement angle dφ 2  and the second tilt displacement angle dθ 2  of the second operation pattern. It is thus possible to detect shifts in the positions of the turning coordinate φ and the tilt coordinate θ with higher precision than in the second operation pattern. That is, the third operation pattern is applied to make finer adjustments than the second operation pattern by repeating processing similar to that of the second operation pattern. 
     Step S 31  (Process S 31 ): 
     With the second directly-facing tilt coordinate θ 2   m  (θ 2   m =54.5°) fixed, the turning coordinate φ is moved from the second time-dependent corrected turning coordinate φ 2   mt  (φ 2   mt =−23°) in the negative direction by the second turning displacement angle dφ 3  (dφ 3 =2°) and changed into a third turning detection start coordinate (φ 2   mt −dφ 3 ) (φ 2   mt −dφ 3 =−23−2=−25°). 
     Specifically, the turning coordinate φ is moved from position P 28  (second time-dependent corrected turning coordinate φ 2   mt ) to position P 31  (third turning detection start coordinate (φ 2   mt −dφ 3 )). Here, time T 31  when the turning coordinate φ has moved to position P 31  is 10:07:45, for example. 
     Step S 32  (Process S 32 ): 
     With the second directly-facing tilt coordinate θ 2   m  (θ 2   m =54.5°) fixed, the turning coordinate φ is sequentially changed from the third turning detection start coordinate (φ 2   mt −dφ 3 ) (φ 2   m −dφ 3 =−25°) to the third turning detection end coordinate (φ 2   mt +dφ 3 ) (φ 2   mt +dφ 3 =−23+2=−21°). 
     Specifically, the turning coordinate φ is moved from position P 31  (third turning detection start coordinate (φ 2   mt −dφ 3 )) to position P 32  (third turning detection end coordinate (φ 2   mt +dφ 3 )). Here, time T 32  when the turning coordinate φ has moved to position P 32  is 10:07:20, for example. 
     In this step, a third directly-facing turning coordinate φ 3   m  at which the panel output (the output of the photovoltaic panel  10 ) transmitted from the A/D conversion portion  26  reaches its maximum value is also detected concurrently (third directly-facing turning coordinate detection process). 
     For example, it is assumed that the third directly-facing turning coordinate φ 3   m  is detected as −22.5°. It should be noted that, as in the case of the second operation pattern, the third directly-facing turning coordinate φ 3   m  at which the panel output reaches its maximum value can be determined by, for example, the turning coordinate φ at which the current detected by the current detecting resistor  23  reaches its maximum value. Since the turning coordinate φ is obtained at a maximum value of current that is sensitive to a shift in the position of the photovoltaic panel  10  relative to sunlight, the turning coordinate φ can be determined with high precision. 
     That is, in this step, the third directly-facing turning coordinate φ 3   m  at which the panel output reaches its maximum value is detected by moving the turning position of the photovoltaic panel while sequentially changing the turning coordinate φ in the third turning detection range (e.g., from (φ 2   mt −dφ 3 ) to (φ 2   mt +dφ 3 )) that is defined in connection with the second directly-facing turning coordinate φ 2   m.    
     It should be noted that the third turning detection range is defined from the third turning detection start coordinate (e.g., position P 31  (φ 2   mt −dφ 3 ) or a position (φ 2   m −dφ 3 ) (not shown) corresponding to position P 31 ) to the third turning detection end coordinate (e.g., position P 32  (φ 2   mt +dφ 3 ) or a position (φ 2   m +dφ 3 ) (not shown) corresponding to position P 32 ) by using either the second directly-facing turning coordinate φ 2   m  (=−26°) or the second time-dependent corrected turning coordinate φ 2   mt  (=−23°) obtained through time-dependent correction of the second directly-facing turning coordinate φ 2   m  as a third turning detection reference coordinate and applying a predetermined third turning displacement angle dφ 3  (=2°) that is smaller than the second turning displacement angle dφ 2  (=5°), in both positive and negative directions of the third turning detection reference coordinate. 
     When time-dependent correction is not performed on the first directly-facing turning coordinate φ 2   m  (turning coordinate φ) in step S 28 , processing is performed with the second time-dependent corrected turning coordinate φ 2   mt  replaced by the second directly-facing turning coordinate φ 2   m  as described above. 
     Step S 33  (Process S 33 ): 
     With the second directly-facing tilt coordinate θ 2   m  (θ 2   m =54.5°) fixed, the turning coordinate φ is aligned with the third directly-facing turning coordinate φ 3   m  (φ 3   m =−22.5°) at which the panel output reaches its maximum value and that was detected in the third directly-facing turning coordinate detection process S 32  (third directly-facing turning coordinate alignment process). 
     Specifically, the turning coordinate φ is moved from position P 32  to position P 33  (third directly-facing turning coordinate φ 3   m ). Here, time T 33  (third directly-facing turning coordinate setting time) when the turning coordinate φ has moved to position P 33  is 10:07:30, for example. 
     It should be noted that step S 34  may be performed without moving the turning coordinate φ to position P 33 , i.e., with the turning coordinate φ unchanged (position P 32 ). That is, when the turning coordinate φ is not aligned with the coordinate (third directly-facing turning coordinate φ 3   m ) at which the panel output reaches its maximum value, a third directly-facing tilt coordinate θ 3   m  (see step S 36 ) is detected in the direction of the tilt coordinate θ in position P 32 , using turning coordinate φ=φ 2   mt +dφ 3 . 
     Step S 34  (Process S 34 ): 
     A third time-dependent corrected tilt coordinate θ 2   mt  (θ 2   mt =54.7°) is calculated by performing time-dependent correction on the second directly-facing tilt coordinate θ 2   m  (θ 2   m =54.5°). Also, with the third directly-facing turning coordinate φ 3   m  (φ 3   m =−22.5°) fixed, the tilt coordinate θ is changed from the second directly-facing tilt coordinate θ 2   m  into the third time-dependent corrected tilt coordinate θ 2   mt  (third time-dependent tilt correction process). 
     Specifically, with the turning coordinate φ fixed at the third directly-facing turning coordinate φ 3   m , the tilt coordinate θ is changed and moved from position P 33  to position P 34 . Here, time T 34  when the tilt coordinate θ has moved to position P 34  is 10:07:35, for example. 
     That is, elapsed-time-dependent correction is performed on the second directly-facing tilt coordinate θ 2   m , taking into consideration a change in the solar altitude θs over time, from time T 27  (10:06:30) when the tilt coordinate θ has been set to the second directly-facing tilt coordinate θ 2   m  to time T 33  (10:07:30) when the turning coordinate φ has been aligned with φ=φ 3   m  (see Footnote  2  in  FIG. 11B ). 
     Accordingly, the second directly-facing tilt coordinate θ 2   m  is changed into the third time-dependent corrected tilt coordinate θ 2   mt  (position P 34  at time T 34 ), taking into consideration the amount of change dθs in the solar altitude θs@T 33  (e.g., 23.0°) relative to the solar altitude θs@T 27  (e.g., 22.8°). Note that the third time-dependent corrected tilt coordinate θ 2   mt  to which the tilt coordinate is to be changed is calculated by determining the amount of altitude change dθs as dθs=θs@T 33 −θs@T 27 =23.0−22.8=0.2° and adding the amount of altitude change dθs to the second directly-facing tilt coordinate θ 2   m  (θ 2   mt =θ 2   m +dθs=54.5+0.2=54.7°). 
     As described above, in this step, before execution of a later-described third directly-facing tilt coordinate detection process S 36 , the third time-dependent corrected tilt coordinate θ 2   mt  is calculated through the time-dependent correction of the second directly-facing tilt coordinate θ 2   m  that reflects the amount of change dθs in the solar altitude θs over time (=0.2°), and a third tilt detection reference coordinate (see step S 36 ) is displaced in advance from the second directly-facing tilt coordinate θ 2   m  to the third time-dependent corrected tilt coordinate θ 2   mt.    
     This configuration makes it possible to perform the third directly-facing tilt coordinate detection process S 36  by applying the third time-dependent corrected tilt coordinate θ 2   mt  that has been calculated with the amount of change dθs in the solar altitude θ over time being reflected in the second directly-facing tilt coordinate θ 2   m , thus enabling the third directly-facing tilt coordinate θ 3   m  to be detected in a short time with high precision. 
     When time-dependent correction is performed on the tilt coordinate θ in this step, the third tilt detection reference coordinate is displaced from the second directly-facing tilt coordinate θ 2   m  (e.g., position P 33 ) to the third time-dependent corrected tilt coordinate θ 2   mt  (e.g., position P 34 ), so that the third tilt detection start coordinate is changed from a tilt coordinate (θ 2   m −dθ 3 ) to a tilt coordinate (θ 2   mt −dθ 3 ) (position P 35 ) and the third tilt detection end coordinate is changed from a tilt coordinate (θ 2   m +dθ 3 ) to a tilt coordinate (θ 2   mt +dθ 3 ) (position P 36 ). 
     In other words, when time-dependent correction is not performed on the second directly-facing tilt coordinate θ 2   m  (tilt coordinate θ) in this step, subsequent processing is performed with the third time-dependent corrected tilt coordinate θ 2   mt  replaced by the second directly-facing tilt coordinate θ 2   m  (i.e., using the second directly-facing tilt coordinate θ 2   m  before changed by the time-dependent correction into the third time-dependent corrected tilt coordinate θ 2   mt ). 
     It should be noted that, when this step (third time-dependent tilt correction process) is not performed, the third time-dependent corrected tilt coordinate θ 2   mt  is not set and therefore the tilt coordinate θ remains unchanged as the second directly-facing tilt coordinate θ 2   m . Thus, the third tilt detection start coordinate is the tilt coordinate (θ 2   m −dθ 3 ), instead of the tilt coordinate (θ 2   mt −dθ 3 ) (position P 35 ), and the third tilt detection end coordinate is the tilt coordinate (θ 2   m +dθ 3 ), instead of the tilt coordinate (θ 2   mt +dθ 3 ) (position P 36 ). 
     Step S 35  (Process S 35 ): 
     With the third directly-facing turning coordinate φ 3   m  (φ 3   m =−22.5°) fixed, the tilt coordinate θ is moved from the third time-dependent corrected tilt coordinate θ 2   mt  (θ 2   mt =54.7°) in the negative direction by a third tilt displacement angle dθ 3  (dθ 3 =0.5°) and changed into the third tilt detection start coordinate (θ 2   mt −dθ 3 ) (θ 2   mt −dθ 3 =54.7−0.5=54.2°). 
     Specifically, the tilt coordinate θ is moved from position P 34  (third time-dependent corrected tilt coordinate θ 2   mt ) to position P 35  (third tilt detection start coordinate (θ 2   mt −dθ 3 )). Here, time T 35  when the tilt coordinate θ has moved to position P 35  is 10:07:40, for example. 
     Step S 36  (Process S 36 ): 
     With the third directly-facing turning coordinate φ 3   m  (φ 3   m =−22.5°) fixed, the tilt coordinate θ is sequentially changed from the third tilt detection start coordinate (θ 2   mt −dθ 3 ) (θ 2   mt −dθ 3 =54.2°) to the third tilt detection end coordinate (θ 2   mt +dθ 3 ) (θ 2   mt +dθ 3 =54.7+0.5=55.2°). 
     Specifically, the tilt coordinate θ is moved from position P 35  (third tilt detection start coordinate (θ 2   mt −dθ 3 )) to position P 36  (third tilt detection end coordinate (θ 2   mt +dθ 3 )). Here, time T 36  when the tilt coordinate θ has moved to position P 36  is 10:08:00, for example. 
     In this step, a third directly-facing tilt coordinate θ 3   m  at which the panel output (the output of the photovoltaic panel  10 ) transmitted from the A/D conversion portion  26  reaches its maximum value is also detected concurrently with changes in the tilt coordinate θ (third directly-facing tilt coordinate detection process). For example, it is assumed that the third directly-facing tilt coordinate θ 3   m  is detected as 55.0°. 
     It should be noted that the third directly-facing tilt coordinate θ 3   m  at which the panel output reaches its maximum value can be determined by, for example, the turning coordinate φ at which the current detected by the current detecting resistor  23  reaches its maximum value. 
     In this step, the third directly-facing tilt coordinate θ 3   m  at which the panel output reaches its maximum value is detected by moving the tilt position of the photovoltaic panel while sequentially changing the tilt coordinate θ in a third tilt detection range (e.g., from (θ 2   mt −dθ 3 ) to (θ 2   mt +dθ 3 )) that is defined in connection with the second directly-facing tilt coordinate θ 2   m  corresponding to the solar altitude θs. 
     It should be noted that, when the time-dependent correction (step S 34 ) is not performed on the tilt coordinate θ, processing is performed with the tilt coordinate θ 2   mt  replaced by the second directly-facing tilt coordinate θ 2   m  (i.e., using the second directly-facing tilt coordinate θ 2   m  before changed by the time-dependent correction into the third time-dependent corrected tilt coordinate θ 2   mt ) as described in step S 34 . That is, the third tilt detection range in the third directly-facing tilt coordinate detection process, in which the tilt coordinate θ is moved, is from a third tilt detection start coordinate (θ 2   m −dθ 3 ) to a third tilt detection end coordinate (θ 2   m +dθ 3 ). 
     Accordingly, the third tilt detection range is defined from the third tilt detection start coordinate (e.g., position P 35  (θ 2   mt −dθ 3 ) or a position (θ 2   m −dθ 3 ) (not shown) corresponding to position P 35 ) to the third tilt detection end coordinate (e.g., position P 36  (θ 2   mt +dθ 3 ) or a position (θ 2   m +dθ 3 ) (not shown) corresponding to position P 36 ) by using either the second directly-facing tilt coordinate θ 2   m  (=54.5°) or the third time-dependent corrected tilt coordinate θ 2   mt  (=54.7°) obtained through the time-dependent correction of the second directly-facing tilt coordinate θ 2   m  as a third tilt detection reference coordinate and applying the predetermined third tilt displacement angle dθ 3  (=0.5°) that is smaller than the second tilt displacement angle dθ 2  (=2°), in both positive and negative directions of the third tilt detection reference coordinate. 
     This step (third directly-facing tilt coordinate detection process) is performed after execution of the third directly-facing turning coordinate alignment process S 33  in which the turning coordinate φ is aligned with the third directly-facing turning coordinate φ 3   m  detected in the third directly-facing turning coordinate detection process S 32 . 
     This configuration makes it possible to detect a shift in the position of the tilt coordinate θ in a state in which the photovoltaic panel directly faces the solar trajectory in the turning direction, thus enabling precise detection of the third directly-facing tilt coordinate θ 3   m.    
     Step S 37  (Process S 37 ): 
     With the third directly-facing turning coordinate φ 3   m  (φ 3   m =−22.5°) fixed, the tilt coordinate θ is aligned with the third directly-facing tilt coordinate θ 3   m  (θ 3   m =55.0°) at which the panel output reaches its maximum value and that was detected in the third directly-facing tilt coordinate detection process S 36  (third directly-facing tilt coordinate alignment process). Specifically, the tilt coordinate θ is moved from position P 36  to position P 37  (third directly-facing tilt coordinate θ 3   m ). Here, time T 37  (third directly-facing tilt coordinate setting time) when the tilt coordinate θ has moved to position P 37  is 10:08:10, for example. 
     Step S 38  (Process S 38 ): 
     A third time-dependent corrected turning coordinate φ 3   mt  (φ 3   mt =−22°) is calculated by performing time-dependent correction on the third directly-facing turning coordinate φ 3   m  (φ 3   m =−22.5°). Also, with the third directly-facing tilt coordinate θ 3   m  (θ 3   m =55.0°) fixed, the turning coordinate φ is changed from the third directly-facing turning coordinate φ 3   m  to the third time-dependent corrected turning coordinate φ 3   mt  (third time-dependent turning correction process). 
     Specifically, with the tilt coordinate θ fixed at the third directly-facing tilt coordinate θ 3   m , the turning coordinate φ is changed and moved from position P 37  to position P 38 . Here, time T 38  when the turning coordinate φ has moved to position P 38  is 10:08:15, for example. 
     That is, elapsed-time-dependent correction is performed on the third directly-facing turning coordinate φ 3   m , taking into consideration a change in the solar azimuth angle φs over time from time T 33  (10:05:20) when the turning coordinate φ has been set to the third tilt coordinate φ 3   m  to time T 37  (10:08:10) when the tilt coordinate θ has been aligned with the third directly-facing tilt coordinate θ 3   m  (see Footnote  3  in  FIG. 11B ). 
     Accordingly, the third directly-facing turning coordinate φ 3   m  is changed into the third time-dependent corrected turning coordinate φ 3   mt  (position P 38  at time T 38 ), taking into consideration the amount of change dφs in the solar azimuth angle φs@T 37  (e.g., −20.0°) relative to the solar azimuth angle φs@T 33  (e.g., −20.5°). It should be noted that the third time-dependent corrected turning coordinate φ 3   mt  to which the turning coordinate φ is to be changed is calculated by determining the amount of solar azimuth angle change dφs as dφs=φs@T 37 −φs@T 33 =−20.0−(−20.5)=0.5° and adding the amount of solar azimuth angle change dφs to the third directly-facing turning coordinate φ 3   m  (φ 3   mt =φ 3   m +dφs=−22.5+0.5=−22.0°). 
     When time-dependent correction is not performed on the third directly-facing turning coordinate φ 3   m  (turning coordinate φ) in this step, subsequent processing is performed with the third time-dependent corrected turning coordinate φ 3   mt  replaced by third directly-facing turning coordinate φ 3   m  (i.e., using the third directly-facing turning coordinate φ 3   m  before changed by the time-dependent correction into the third time-dependent corrected turning coordinate φ 3   mt ). 
     In the case of detecting a shift in position with higher precision, a similar procedure may further be repeated. If the detection of a shift in position is ended and the system is placed in the operating state, the processing proceeds to step S 39 . 
     According to the present embodiment, the third directly-facing tilt coordinate θ 3   m  is set to position P 37  at 10:08:10 and the third time-dependent corrected turning coordinate φ 3   mt  is set to position P 38  at 10:08:15. That is, the tilt position and the turning position can be aligned in an extremely short time to those at which the panel output reaches its maximum value. Accordingly, extremely high precision alignment can be accomplished with ease by repeating procedures such as the first to third operation patterns. 
     Step S 39  (Process S 39 ): 
     The photovoltaic panel  10  is driven after correcting a shift in the position of the turning coordinate φ relative to the solar azimuth angle φs and correcting a shift in the position of the tilt coordinate θ relative to the solar altitude θs (correction and drive process). Since the correction is performed based on the third directly-facing turning coordinate φ 3   m  and the third directly-facing tilt coordinate θ 3   m  before driving the photovoltaic panel  10 , it is possible to correct the shifts in positions with ease and high precision before driving the photovoltaic panel  10 . 
     Note that a specific computation process will be described in Embodiment 5. 
     Also, when time-dependent correction is not performed on the third directly-facing turning coordinate φ 3   m  (turning coordinate φ) in step S 38 , processing is performed with the third time-dependent corrected turning coordinate φ 3   mt  replaced by the third directly-facing turning coordinate φ 3   m . That is, a shift in the position of the turning coordinate φ is corrected based on a difference between the solar azimuth angle φs at time T 37  and the third directly-facing turning coordinate φ 3   m.    
     According to the present embodiment, the third directly-facing tilt coordinate θ 3   m  is set to position P 37  at time T 37  (=10:08:10), and the third time-dependent corrected turning coordinate φ 3   mt  is set to position P 38  at time T 38  (=10:08:15). That is, the control coordinates can be aligned in an extremely short time to the tilt position and the turning position at which the panel output reaches its maximum value. Accordingly, extremely high-precision alignment can be accomplished with ease in a short time. 
     In the present embodiment, the duration of time from time T 28  (10:06:35) in step S 28  to time T 38  (10:08:15) in step S 38  is 1:40. That is, the detection and further correction of a shift in position can be performed in a short time on the order of 1:40, which enables higher-precision alignment to be accomplished in a shorter time than in Embodiment 2. 
     As described above, the tracking control method (third operation pattern) for the tracking drive solar photovoltaic power generator  1  according to the present embodiment is performed following Embodiment 3 (second operation pattern), and includes the third directly-facing turning coordinate detection process S 32  in which the third directly-facing turning coordinate φ 3   m  at which the panel output reaches its maximum value is detected by moving the turning position of the photovoltaic panel while sequentially changing the turning coordinate φ in the third turning detection range (e.g., from (φ 2   mt −dφ 3 ) to (φ 2   mt +dφ 3 )) that is defined in connection with the second directly-facing turning coordinate φ 2   m , and the third directly-facing tilt coordinate detection process S 36  in which the third directly-facing tilt coordinate θ 3   m  at which the panel output reaches its maximum value is detected by moving the tilt position of the photovoltaic panel while sequentially changing the tilt coordinate θ in the third tilt detection range (e.g., from (θ 2   mt −dθ 3 ) to (θ 2   mt +dθ 3 )) that is defined in connection with the second directly-facing tilt coordinate θ 2   m.    
     This configuration makes it possible to detect a shift in the position of the turning coordinate φ (second directly-facing turning coordinate φ 2   m ) relative to the solar azimuth angle φs with high precision with use of the third directly-facing turning coordinate φ 3   m , which has been detected in the third turning detection range (e.g., from (φ 2   mt −dφ 3 ) to (φ 2   mt +dφ 3 )=4°) smaller than the second turning detection range (e.g., from (φ 1   mt −dφ 2 ) to (φ 1   mt +dφ 2 )=10°), and a shift in the position of the second directly-facing tilt coordinate θ 2   m  relative to the solar altitude θs with high precision with use of the third directly-facing tilt coordinate θ 3   m , which has been detected in the third tilt detection range (e.g., from (θ 2   mt −dθ 3 ) to (θ 2   mt +dθ 3 )=1°) smaller than the second tilt detection range (e.g., from (θ 1   mt −dθ 2 ) to (θ 1   mt +dθ 2 )=4°), and to thereby correct a shift in the position of the turning coordinate φ relative to the solar azimuth angle φs and a shift in the position of the tilt coordinate θ relative to the solar altitude θs with high precision, thus enabling the turning position and the tilt position of the photovoltaic panel  10  to be adjusted with ease and high precision so that the photovoltaic panel can directly face the solar trajectory. 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, the third turning detection range is defined from the third turning detection start coordinate (e.g., position P 31  (φ 2   mt −dφ 3 ) or a position (φ 2   m −dφ 3 ) (not shown) corresponding to position P 31 ) to the third turning detection end coordinate (e.g., position P 32  (φ 2   mt +dφ 3 ) or a position (φ 2   m +dφ 3 ) (not shown) corresponding to position P 32 ) by using either the second directly-facing turning coordinate φ 2   m  (=−26°) or the second time-dependent corrected turning coordinate φ 2   mt  (=−23°) obtained through the time-dependent correction of the second directly-facing turning coordinate φ 2   m  as a third turning detection reference coordinate and applying a predetermined third turning displacement angle dφ 3  (=2°) that is smaller than the second turning displacement angle dφ 2  (=5°), in both positive and negative directions of the third turning detection reference coordinate. Also, the third tilt detection range is defined from the third tilt detection start coordinate (e.g., position P 35  (θ 2   mt −dθ 3 ) or a position (θ 2   m −dθ 3 ) (not shown) corresponding to position P 35 ) to the third tilt detection end coordinate (e.g., position P 36  (θ 2   mt +dθ 3 ) or a position (θ 2   m +dθ 3 ) (not shown) corresponding to position P 36 ) by using either the second directly-facing tilt coordinate θ 2   m  (=54.5°) or the third time-dependent corrected tilt coordinate θ 2   mt  (=54.7°) obtained through the time-dependent correction of the second directly-facing tilt coordinate θ 2   m  as a third tilt detection reference coordinate and applying a predetermined third tilt displacement angle dθ 3  (=0.5°) that is smaller than the second tilt displacement angle dθ 2  (=2°), in both positive and negative directions of the third tilt detection reference coordinate. 
     This configuration makes it possible to set the third turning detection range (=4°) and the third tilt detection range (=1°) to be smaller than the second turning detection range (=10°) and the second tilt detection range (=4°), thus enabling the third directly-facing turning coordinate φ 3   m  and the third directly-facing tilt coordinate θ 3   m  to be detected with higher precision than the second directly-facing turning coordinate φ 2   m  and the second directly-facing tilt coordinate θ 2   m.    
     Accordingly, it is possible to correct a shift in the position of the turning coordinate φ (third directly-facing turning coordinate φ 3   m ) relative to the solar azimuth angle φs and a shift in the position of the tilt coordinate θ (third directly-facing tilt coordinate θ 3   m ) relative to the solar altitude θs with high precision, which enables the turning position and the tilt position of the photovoltaic panel  10  to be adjusted with ease and high precision so that the photovoltaic panel can directly face the solar trajectory. 
     In addition, the range of a shift in position can sequentially be narrowed down because, according to the third operation pattern (subsequent operation pattern) a shift in position is detected in a narrower range than in the second operation pattern (previous operation pattern), and therefore efficient alignment is possible. That is, it is possible to further improve the accuracy in detecting a shift in position depending on the degree of light gathering accuracy (light gathering magnification). 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, before execution of the third directly-facing turning coordinate detection process S 32 , the second time-dependent corrected turning coordinate φ 2   mt  is calculated through the time-dependent correction of the second directly-facing turning coordinate φ 2   m  that reflects the amount of change dφs (3°) in the solar azimuth angle φs over time, and the third turning detection reference coordinate is displaced in advance from the second directly-facing turning coordinate φ 2   m  to the second time-dependent corrected turning coordinate φ 2   mt  (second time-dependent turning correction process S 28 ). 
     This configuration makes it possible to perform subsequent processing (third operation pattern) by applying the second time-dependent corrected turning coordinate φ 2   mt  that has been calculated with the amount of change in the solar azimuth angle φ over time being reflected in the second directly-facing turning coordinate φ 2   m , thus enabling the third directly-facing turning coordinate φ 3   m  to be detected in a short time with high precision. 
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, the third directly-facing tilt coordinate detection process S 36  is performed after execution of the third directly-facing turning coordinate alignment process S 33  in which the turning coordinate φ is aligned with the third directly-facing turning coordinate φ 3   m  detected in the third directly-facing turning coordinate detection process S 32 . 
     This configuration makes it possible to detect a shift in the position of the tilt coordinate θ in a state in which the photovoltaic panel  10  directly faces the solar trajectory in the turning direction, thus enabling precise detection of the third directly-facing tilt coordinate θ 3   m.    
     In the tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment, before execution of the third directly-facing tilt coordinate detection process S 36 , the third time-dependent corrected tilt coordinate θ 2   mt  is calculated through the time-dependent correction of the second directly-facing tilt coordinate θ 2   m  that reflects the amount of change dθs in the solar altitude θs over time (=0.2°), and the third tilt detection reference coordinate is displaced in advance from the second directly-facing tilt coordinate θ 2   m  to the third time-dependent corrected tilt coordinate θ 2   mt  (third time-dependent tilt correction process S 34 ). 
     This configuration makes it possible to perform the third directly-facing tilt coordinate detection process S 36  by applying the third time-dependent corrected tilt coordinate θ 2   mt  that has been calculated with the amount of change dθs in the solar altitude θ over time being reflected in the second directly-facing tilt coordinate θ 2   m , thus enabling the third directly-facing tilt coordinate θ 3   m  to be detected in a short time with high precision. 
     The tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment includes the correction and drive process S 39  in which the photovoltaic panel  10  is driven after correcting a shift in the position of the turning coordinate φ relative to the solar azimuth angle φs and correcting a shift in the position of the tilt coordinate θ relative to the solar altitude θs. Since the correction is performed based on the third directly-facing turning coordinate φ 3   m  and the third directly-facing tilt coordinate θ 3   m  before driving the photovoltaic panel  10 , it is possible to correct the shifts in positions with ease and high precision before driving the photovoltaic panel  10 . 
     The tracking control method for the tracking drive solar photovoltaic power generator  1  according to the present embodiment adopts a configuration in which current is used to detect the panel output in the third directly-facing turning coordinate detection process S 32  and the third directly-facing tilt coordinate detection process S 36 . It is thus possible, by means of current that is sensitive to a shift in the position of the photovoltaic panel  10  relative to sunlight, to detect, multiple times, the turning coordinate φ and the tilt coordinate θ at which the panel output reaches its maximum value, and therefore the panel output can be detected with ease and high precision even in a state in which there is only a slight shift in the position of the turning coordinate relative to the solar azimuth angle and a slight shift in the position of the tilt coordinate relative to the solar altitude. 
     As can be seen from the comparisons of the operation patterns described in Embodiments 2 to 4, a shift in position can be detected in a shorter time as the precision increases according to the present invention, which enables a shift in position to be detected and corrected with efficiency and effectiveness. 
     Fifth Embodiment 
     Next is a description of a tracking control method for a tracking solar photovoltaic power generation system according to Embodiment 5, given with reference to  FIGS. 13 and 14 . In the present embodiment, a correction and drive process is described in which a photovoltaic panel is driven after correcting a shift in the position of the panel (i.e., detailed descriptions of step S 10  in Embodiment 2, step S 29  in Embodiment 3, and step S 39  in Embodiment 4). 
       FIG. 13  shows a coordinate graphic showing the correlation between a coordinate system applied to a tracking drive solar photovoltaic power generator and control parameters, in the tracking control method for the tracking solar photovoltaic power generation system according to Embodiment 5. 
     Solar coordinates (solar azimuth angle φs and solar altitude θs) that indicate the position of the sun targeted for tracking are represented by target solar coordinates (target solar azimuth angle φsg and target solar altitude θsg). Orthogonal coordinates obtained by coordinate transformation from the target solar coordinates are represented by target orthogonal solar coordinates (x, y, z). 
     The target orthogonal solar coordinates (x, y, z) are transformed into target orthogonal control coordinates (X, Y, Z) that are orthogonal coordinates corresponding to the control coordinates (turning coordinate φ and tilt coordinate θ). Coordinate transformation parameters used at this time are denoted by α for the x axis, β for the y axis, and γ for the z axis. 
     The target orthogonal control coordinates (X, Y, Z) are transformed into target control coordinates (target turning coordinate φg and target tilt coordinate θg) for the control coordinates (turning coordinate φ and tilt coordinate θ). Then, an offset (shift in position) of the target control coordinates (target turning coordinate φg and target tilt coordinate θg) is corrected. 
     An offset is set as follows. An offset ε of the turning coordinate φ is determined based on a difference between the solar azimuth angle φs and a detected Nth directly-facing turning coordinate φNm, and an offset δ of the tilt coordinate θ is determined based on a difference between the solar altitude and a detected Nth directly-facing tilt coordinate θNm. 
     Note that N denotes the final number of times each coordinate is detected. For example, in the case of the first operation pattern of Embodiment 2, the Nth directly-facing turning coordinate φNm is the first time-dependent corrected turning coordinate φ 1   mt  (or the first directly-facing turning coordinate φ 1   m ), and the Nth directly-facing tilt coordinate θNm is the first directly-facing tilt coordinate θ 1   m . In the case of the second operation pattern of Embodiment 3, the Nth directly-facing turning coordinate φNm is the second time-dependent corrected turning coordinate φ 2   mt  (or the second directly-facing turning coordinate φ 2   m ), and the Nth directly-facing tilt coordinate θNm is the second directly-facing tilt coordinate θ 2   m . In the case of the third operation pattern of Embodiment 4, the Nth directly-facing turning coordinate φNm is the third time-dependent corrected turning coordinate φ 3   mt  (or the third directly-facing turning coordinate φ 3   m ), and the Nth directly-facing tilt coordinate θNm is the third directly-facing tilt coordinate θ 3   m.    
     Moreover, in the present embodiment, the driving portion  12  is constituted by, for example, a turntable turning drive mechanism or a jack cylinder tilt drive mechanism. Therefore, an offset τ of a cylinder length L is taken into consideration. 
     Specifically, values obtained by correcting the target control coordinates (target turning coordinate φg and target tilt coordinate θg) in consideration of offsets are determined as corrected target control values (corrected target turning coordinate φgc, corrected target tilt coordinate θgc, and corrected target cylinder length Lgc (not shown), which are calculated by computation processing of step S 54  in  FIG. 14 ). 
     It should be noted that various modifications in the form of offsets are conceivable depending on the configuration of the driving portion  12 . 
       FIG. 14  is a flowchart showing the procedure of computation processing that is performed based on the coordinate graphic shown in  FIG. 13  when correcting shifts in the positions of the control coordinates and driving a photovoltaic panel. 
     Correction processing for correcting shifts in the positions of the control coordinates (turning coordinate φ and tilt coordinate θ) and driving the photovoltaic panel  10 , according to the present embodiment, can be implemented, for example according to a procedure including steps S 50  to S 55 . Note that, like other procedures, the procedure of steps S 50  to S 55  is performed by a computer program installed on the PC  30 . 
     Step S 50 : 
     Targeted solar coordinates (solar azimuth angle φs and solar altitude θs) are specified as target solar coordinates (target solar azimuth angle φsg and target solar altitude θsg). 
     Step S 51 : 
     Coordinate transformation from the solar coordinates to orthogonal coordinates is performed. Specifically, the target solar coordinates are transformed into orthogonal coordinates so as to obtain target orthogonal solar coordinates (x, y, z). The details thereof are as given by Equation  1  ( FIG. 14 ). 
     Step S 52 : 
     The target orthogonal solar coordinates (x, y, z) are transformed into orthogonal coordinates that correspond to the control coordinates (turning coordinate φ and the tilt coordinate θ), so as to obtain target orthogonal control coordinates (X, Y, Z). The details thereof are as given by Equation  2  ( FIG. 14 ). Note that α, β, and γ are applied respectively to the x, y, and z axes as coordinate transformation parameters for the coordinate transformation. 
     Step S 53 : 
     The target orthogonal control coordinates (X, Y, Z) are transformed into control coordinates (turning coordinate φ and the tilt coordinate θ) so as to obtain target control coordinates (target turning coordinate φg and target tilt coordinate θg). The details thereof are as given by Equations  3   a ,  3   b , and  3   c  ( FIG. 14 ). 
     Step S 54 : 
     The target control coordinates (target turning coordinate φg and target tilt coordinate θg) are corrected in consideration of the offsets of the turning coordinate φ and the tilt coordinate θ (i.e., shifts in positions, the offset ε of the turning coordinate φ being defined based on a difference between the solar azimuth angle φs and the Nth directly-facing turning coordinate φNm, and the offset δ of the tilt coordinate θ being defined based on a difference between the solar altitude θs and the Nth directly-facing tilt coordinate θNm, where N denotes the final number of times each coordinate is detected), so as to obtain corrected target control values (corrected target turning coordinate φgc and corrected target tilt coordinate θgc). The details thereof are as given by Equations  4   a  and  4   b  ( FIG. 14 ). 
     It should be noted that, since a jack-cylinder tilt drive mechanism is used in the present embodiment, a target cylinder length L (θgc) is corrected in consideration of the offset τ of the cylinder length L, so as to obtain a corrected target cylinder length Lgc. The details thereof are as given by Equation  4   c  ( FIG. 14 ). 
     That is, in the present embodiment, the values obtained by adding the corrected target cylinder length Lgc to the corrected target turning coordinate φgc and the corrected target tilt coordinate θgc are defined as corrected target control values. 
     As described above, in the present embodiment, the corrected target turning coordinate φgc, the corrected target tilt coordinate θgc, and the corrected target cylinder length Lgc are defined as corrected target control values by applying six correction parameters (target turning coordinate φg, target tilt coordinate θg, target cylinder length L(θgc), offset ε of the turning coordinate φ, offset δ of the tilt coordinate θ, and offset τ of the cylinder length L). 
     The correction parameters are to be set as appropriate by a drive system constituting the driving portion  12 . In addition, it is desirable that multiple sets (data sets) of directly-facing coordinates (directly-facing turning coordinate and directly-facing tilt coordinate) and solar coordinates (solar azimuth angle and solar altitude) are obtained. Such multiple data sets are desirably obtained at appropriate time intervals. Specifically, the time interval is approximately two hours, for example. 
     The above-described six correction parameters can be derived by two operations. In order to derive the correction parameters with higher precision, the number of operations is desirably increased. 
     It should be noted that Equations  1  to  4   c  described above are preset equations. 
     Step S 55 : 
     The photovoltaic panel is driven via the driving portion  12  based on the corrected target control values (corrected target turning coordinate φgc, corrected target tilt coordinate θgc, and corrected target cylinder length Lgc). 
     The following is a description of the case where the present embodiment is applied to the first operation pattern (step S 10 ) of Embodiment 2. 
     The process for correcting a shift in the position of the photovoltaic panel  10  and driving the photovoltaic panel  10  (tracking control method for the tracking solar photovoltaic power generation system) according to Embodiment 2 is configured such that the photovoltaic panel  10  is driven by application of the corrected target turning coordinate φgc and the corrected target tilt coordinate θgc that have been set by specifying a targeted solar azimuth angle φs as a target solar azimuth angle φsg and a targeted solar altitude θs as a target solar altitude θsg, performing coordinate transformation using preset equations from the target solar azimuth angle φsg and the target solar altitude θsg to a target turning coordinate φg for the turning coordinate φ and a target tilt coordinate θg for the tilt coordinate θ, and correcting the target turning coordinate φg and the target tilt coordinate θg based on the first directly-facing turning coordinate φ 1   m  and the first directly-facing tilt coordinate θ 1   m.    
     With this configuration, since the photovoltaic panel  10  is driven by applying the corrected target turning coordinate φgc and the corrected target tilt coordinate θgc that have been set through the correction based on the first directly-facing turning coordinate φ 1   m  and the directly facing tilt coordinate θ 1   m , it is possible to correct a shift in position with ease and high precision before driving the photovoltaic panel  10 . 
     Also, the following is a description of the case where the present embodiment is applied to the second operation pattern (step S 29 ) of Embodiment 3. 
     The process for correcting a shift in the position of the photovoltaic panel  10  and driving the photovoltaic panel  10  (tracking control method for the tracking solar photovoltaic power generation system) according to Embodiment 3 is configured such that the photovoltaic panel  10  is driven by application of the corrected target turning coordinate φgc and the corrected target tilt coordinate θgc that have been set by specifying a targeted solar azimuth angle φs as a target solar azimuth angle φsg and a targeted solar altitude θs as a target solar altitude θsg, performing coordinate transformation using preset equations from the target solar azimuth angle φsg and the target solar altitude θsg to a target turning coordinate φg for the turning coordinate and a target tilt coordinate θg for the tilt coordinate, and correcting the target turning coordinate φg and the target tilt coordinate θg based on the second directly-facing turning coordinate φ 2   m  and the second directly-facing tilt coordinate θ 2   m.    
     With this configuration, since the photovoltaic panel  10  is driven by applying the corrected target turning coordinate φgc and the corrected target tilt coordinate θgc that have been set through the correction based on the second directly-facing turning coordinate φ 2   m  and the second directly-facing tilt coordinate θ 2   m , it is possible to correct a shift in position with ease and high precision before driving the photovoltaic panel  10 . 
     Also, the following is a description of the case where the present embodiment is applied to the third operation pattern (step S 39 ) of Embodiment 4. 
     The process for correcting a shift in the position of the photovoltaic panel  10  and driving the photovoltaic panel  10  (tracking control method for the tracking solar photovoltaic power generation system) according to Embodiment 4 is configured such that the photovoltaic panel  10  is driven by application of the corrected target turning coordinate φgc and the corrected target tilt coordinate θgc that have been set by specifying a targeted solar azimuth angle φs as a target solar azimuth angle φsg and a targeted solar altitude θs as a target solar altitude θsg, performing coordinate transformation using preset equations from the target solar azimuth angle φsg and the target solar altitude θsg into the target turning coordinate φg for the turning coordinate and the target tilt coordinate φg for the tilt coordinate, and correcting the target turning coordinate φg and the target tilt coordinate θg based on the third directly-facing turning coordinate φ 3   m  and the third directly-facing tilt coordinate θ 3   m.    
     With this configuration, since the photovoltaic panel  10  is driven by applying the corrected target turning coordinate φgc and the corrected target tilt coordinate θgc that have been set through the correction based on the third directly-facing turning coordinate φ 3   m  and the third directly-facing tilt coordinate θ 3   m , it is possible to correct a shift in position with ease and high precision before driving the photovoltaic panel  10 . 
     Sixth Embodiment 
     Next is a description of a tracking control method for a tracking solar photovoltaic power generation system according to Embodiment 6, given with reference to  FIGS. 15 and 16 . 
       FIG. 15  is a block diagram illustrating a schematic configuration of a tracking solar photovoltaic power generation system during operation, according to Embodiment 6. 
     A tracking solar photovoltaic power generation system is according to the present embodiment includes multiple tracking drive solar photovoltaic power generators  1  described in Embodiments 1 to 5. Specifically, the tracking solar photovoltaic power generation system is according to the present embodiment includes multiple tracking drive solar photovoltaic power generators  1 , each of which includes a photovoltaic panel  10  that converts sunlight into electric power and a tracking control portion  12  that provides tracking control over the turning position and the tilt position of the photovoltaic panel  10  so that the photovoltaic panel can track the solar trajectory based on the turning coordinate φ and the tilt coordinate θa that have been set corresponding to the solar azimuth angle φs and the solar altitude θs. 
     The details of the tracking drive solar photovoltaic power generators  1  are similar to those of Embodiment 1, and therefore descriptions are primarily given regarding different points. A configuration is adopted in which the outputs of the multiple tracking drive solar photovoltaic power generators  1  are collected before entering the output side circuit breaker  25 , and electric power is supplied via the electric power line  20   c  to the inverter  40 . Specifically, the electric power monitoring board  20  is configured to provide centralized control by collecting electric power generated by the multiple photovoltaic panels  10 . 
     A detection circuit  22  connected to each of the photovoltaic panels  10  is connected via the detection line  22   b  to the PC  30 . Also, the tracking control portion  13  is configured to control each of the photovoltaic panels  10 . 
       FIG. 16  is a block diagram illustrating a schematic configuration when performing the tracking control method for the tracking solar photovoltaic power generation system according to Embodiment 6. 
     The tracking control method for the tracking solar photovoltaic power generation system is according to the present embodiment is applied individually to each of the tracking drive solar photovoltaic power generators  1 . Specifically, a configuration is adopted in which switches  21  are controlled so that only a tracking drive solar photovoltaic power generator  1  that is targeted for execution of the tracking control method is connected, so that the tracking control method described in any one of Embodiments 1 to 5 is performed sequentially on each of the tracking drive solar photovoltaic power generators  1 . 
     The switches  21  can be controlled directly via the electric power monitoring board  20 . A configuration is also possible in which a computer program for controlling the switches  21  is pre-installed on the PC  30  and a menu is displayed on the display screen of the PC  30 , so that a targeted switch  21  can be selected from the menu (menu button). In addition, a simulated load  41  is connected via the output side circuit breaker  25 , instead of the inverter  40 . 
     That is, the tracking control method for the tracking solar photovoltaic power generation system is according to the present embodiment is configured such that the tracking control method for the tracking drive solar photovoltaic power generator  1  described in any one of Embodiments 1 to 5 is applied individually to each of the tracking drive solar photovoltaic power generators  1 . 
     This configuration makes it possible to adjust a shift in position for each of the tracking drive solar photovoltaic power generators  1  and accordingly provide optimum tracking control over each of the tracking drive solar photovoltaic power generators  1 , and therefore the overall tracking solar photovoltaic power generation system is can generate maximum electric power with high efficiency. 
     Moreover, in the case where the tracking control method for the tracking solar photovoltaic power generation system is according to the present embodiment is applied to each of the tracking drive solar photovoltaic power generators  1  (photovoltaic panels  10 ), no adverse effect is caused by the movement of the sun (sunlight conditions). Therefore, installation work for a tracking solar photovoltaic power generation system  1   s , in which a large number of tracking drive solar photovoltaic power generators  1  are arranged, can be performed with considerable ease and high precision. 
     Tracking Solar Photovoltaic Power Generation System and Tracking Shift Correction Method for Tracking Solar Photovoltaic Power Generation System 
     In the tracking solar photovoltaic power generation system, if an inverter operates under maximum power point tracking control (MPPT control), the output operating point of a photovoltaic panel  10  is caused to follow an optimum operating point. In the above-described embodiment illustrated in  FIG. 1 , the photovoltaic panel  10  is interconnected in one-to-one correspondence with the inverter, under which condition the output operating point is controlled. The inverter is configured to control output voltage Vp and output current Ip of the photovoltaic panel  10  in accordance with variations in the output of the photovoltaic panel  10 . However, if tracking shift correction is performed with such a configuration of  FIG. 1 , the output current Ip or the output voltage Vp will not follow the correction operation because of under MPPT control. Thus, in order to avoid such a phenomenon and correct a tracking shift, the configuration as illustrated in  FIG. 2  may be adopted. In the case of the above-described configuration in  FIG. 2 , however, since correction operations cannot be performed during interconnection, it is more preferable to adopt a configuration in which tracking shift correction can be performed while maintaining system interconnection without the need to use dedicated equipment such as a simulated load and eliminating the need to stop the tracking solar photovoltaic power generation system associated with tracking shift correction as well as causing no loss in the amount of generated electric power. 
     Accordingly, in the following embodiments, a tracking solar photovoltaic power generation system and a configuration for implementing a tracking shift correction method for that system will be described with reference to the drawings. 
     Seventh Embodiment 
       FIGS. 17 to 19  show a tracking solar photovoltaic power generation system according to Embodiment 7, and a tracking shift correction method for correcting a tracking shift occurring in a tracking drive solar photovoltaic power generator. 
       FIG. 17  is a block diagram illustrating a schematic configuration of the tracking solar photovoltaic power generation system according to Embodiment 7.  FIG. 18  is a block diagram illustrating a schematic configuration of a tracking drive solar photovoltaic power generator constituting the tracking solar photovoltaic power generation system shown in  FIG. 17 . 
     The tracking shift correction method for the tracking solar photovoltaic power generation system according to the present embodiment is a method for correcting a tracking shift (shift in position during tracking control) relative to the solar trajectory in a tracking drive solar photovoltaic power generator  1  in a tracking solar photovoltaic power generation system is that includes multiple tracking drive solar photovoltaic power generators  1  that are arranged in parallel connection and a power conversion portion  50  that converts direct-current electric power generated by the tracking drive solar photovoltaic power generators  1  into alternating-current electric power and supplies the alternating-current electric power to an interconnection load CLD. 
     It should be noted that, as the multiple tracking drive solar photovoltaic power generators  1 , tracking drive solar photovoltaic power generators  1 - 1 ,  1 - 2 , . . . , and  1 - n  are arranged in parallel connection. Hereinafter, the tracking drive solar photovoltaic power generators  1 - 1 ,  1 - 2 , . . . , and  1 - n  each may be simply referred to as a “tracking drive solar photovoltaic power generator  1 ” when there is no particular need to distinguish between those generators. 
     Each of the tracking drive solar photovoltaic power generators  1  (tracking drive solar photovoltaic power generators  1 - 1 ,  1 - 2 , . . . , and  1 - n ) includes a photovoltaic panel  10  that converts sunlight into direct-current electric power and a driving portion  14  that drives the photovoltaic panel  10  based on tracking information that causes the photovoltaic panel  10  to track the solar trajectory. 
     Each of the tracking drive solar photovoltaic power generators  1  also includes a tracking control portion  13  that outputs the tracking information. In a steady state, information is transmitted and received between a PC  30  and the tracking control portion  13 , based on indirect tracking information (e.g., indirect information about tracking, such as time information used as a reference and overall operation information) that has been pre-installed on the PC  30 . The tracking control portion  13  transmits the tracking information (e.g., turning information and tilt information about the photovoltaic panel  10  based on the time information) to the driving portion  14  based on the indirect tracking information from the PC  30 , and the driving portion  14  drives the photovoltaic panel  10  in the turning direction Roth and the tilt direction Rotv based on the tracking information (turning information and tilt information) so that the photovoltaic panel  10  can track the solar trajectory. 
     It should be noted that a photovoltaic panel  10 - 1  of the tracking drive solar photovoltaic power generator  1 - 1 , a photovoltaic panel  10 - 2  of the tracking drive solar photovoltaic power generator  1 - 2 , . . . , and a photovoltaic panel  10 - n  of the tracking drive solar photovoltaic power generator  1 - n  are arranged as photovoltaic panels  10 . Hereinafter, each of the photovoltaic panels  10 - 1 ,  10 - 2 , . . . , and  10 - n  may be simply referred to as a “photovoltaic panel  10 ” when there is no particular need to distinguish between those panels. 
     It should also be noted that a tracking control portion  13 - 1  of the tracking drive solar photovoltaic power generator  1 - 1 , a tracking control portion  13 - 2  of the tracking drive solar photovoltaic power generator  1 - 2 , . . . , and a tracking control portion  13 - n  of the tracking drive solar photovoltaic power generator  1 - n  are arranged as tracking control portions  13 . Hereinafter, each of the tracking control portions  13 - 1 ,  13 - 2 , . . . , and  13 - n  may be simply referred to as a “tracking control portion  13 ” when there is no particular need to distinguish between those portions. 
     Note that a configuration is also possible in which the tracking control portions  13 - 1 ,  13 - 2 , . . . , and  13 - n  are organized into appropriate groups and arranged as tracking control portions  13  outside the tracking drive solar photovoltaic power generators  1 . In this case, wiring needs to be provided as appropriate between the tracking drive solar photovoltaic power generators  1  and the appropriately organized tracking control portions  13 . It should be noted that the tracking information itself is, of course, generated corresponding to each of the tracking drive solar photovoltaic power generators  1  and transmitted via wiring to each of the tracking drive solar photovoltaic power generators  1 . 
     Moreover, a driving portion  14 - 1  of the tracking drive solar photovoltaic power generator  1 - 1 , a driving portion  14 - 2  of the tracking drive solar photovoltaic power generator  1 - 2 , . . . , and a driving portion  14 - n  of the tracking drive solar photovoltaic power generator  1 - n  are arranged as driving portions  14 . Hereinafter, each of the driving portions  14 - 1 ,  14 - 2 , . . . , and  14 - n  may be simply referred to as a “driving portion  14 ” when there is no particular need to distinguish between those driving portions. 
     In the present embodiment, a configuration is adopted in which a tracking shift of a photovoltaic panel  10  that is targeted for tracking shift correction is detected in a state in which the corresponding tracking drive solar photovoltaic power generator  1  is running by being connected to the power conversion portion  50 . 
     For example, a tracking control portion  13  (any one of the tracking control portions  13 - 1 ,  13 - 2 , . . . , and  13 - n  corresponding to the photovoltaic panels  10 - 1 ,  10 - 2 , . . . , and  10 - n ) corresponding to a photovoltaic panel  10  (any one of the photovoltaic panels  10 - 1 ,  10 - 2 , . . . , and  10 - n ) that is targeted for tracking shift correction is configured to detect a tracking shift of the photovoltaic panel  10  in a state in which the corresponding tracking drive solar photovoltaic power generator  1  (photovoltaic panel  10 ) is running by being connected to the power conversion portion  50  (which will be described in more detail in Embodiment 8). That is, a tracking shift is detected by a tracking control portion  13 . 
     In other words, since a tracking shift of a photovoltaic panel  10  can be detected with the photovoltaic panel  10  being connected to the power conversion portion  50 , a tracking shift of the photovoltaic panel  10  can be corrected in a state in which system interconnection is maintained while continuing electric power generation by the corresponding tracking drive solar photovoltaic power generator  1  and electric power supply from the power conversion portion  50  to the interconnection load CLD. It is thus possible to provide a highly reliable and productive tracking shift correction method that eliminates the need to stop the tracking solar photovoltaic power generation system is associated with tracking shift correction and causes no loss in the amount of generated electric power. 
     As described above, each of the tracking drive solar photovoltaic power generators  1  is provided with a tracking control portion  13  that outputs tracking information, and a tracking shift is detected by the tracking control portion  13 . 
     Accordingly, a tracking shift can be detected and corrected individually for each of the tracking drive solar photovoltaic power generators  1 . This enables the tracking control portions  13  to be dispersed in the tracking solar photovoltaic power generation system  1   s , thereby simplifying a wiring structure of a control system and accordingly simplifying installation work. It is thus possible to provide a highly reliable tracking solar photovoltaic power generation system is at low cost. 
     It should be noted that the driving portion  14  is configured to correct a tracking shift of the photovoltaic panel  10  in accordance with a tracking shift detected by the tracking control portion  13  (which will be described in more detail in Embodiment 8). 
     The output (direct-current electric power) of each photovoltaic panel  10  is supplied via an electric power line  20   b  and the detection circuit  22  to the power conversion portion  50 . Note that a detection circuit  22 - 1  that detects the output of the photovoltaic panel  10 - 1 , a detection circuit  22 - 2  that detects the output of the photovoltaic panel  10 - 2 , . . . , and a detection circuit  22 - n  that detects the output of the photovoltaic panel  10 - n  are arranged as detection circuits  22 . Hereinafter, each of the detection circuits  22 - 1 ,  22 - 2 , . . . , and  22 - n  may be simply referred to as a “detection circuit  22 ” when there is no particular need to distinguish between those circuits. 
     Each of the tracking drive solar photovoltaic power generators  1  includes the detection circuit  22  that detects the output (output current Ip, output voltage Vp) of the photovoltaic panel  10 , and the tracking control portion  13  is configured to detect a tracking shift based on the output of the photovoltaic panel  10  detected by the detection circuit  22 . This configuration makes it possible to detect the output of the photovoltaic panel  10  with ease and high precision, thus enabling a tracking shift of the photovoltaic panel  10  to be detected and corrected with ease and high precision. 
     In a steady state, the tracking control portion  13  controls the driving portion  14  by acquiring tracking information (indirect tracking information) from the PC  30  and transmitting the tracking information to the driving portion  14 . However, when correcting a tracking shift, the tracking control portion  13  has the function of detecting a tracking shift based on the output (output current Ip and output voltage Vp) detected by the detection circuit  22 . 
     The power conversion portion  50  according to the present embodiment includes an electric power line connection portion  50   j  that collects the outputs (direct-current electric power) of the multiple tracking drive solar photovoltaic power generators  1  by connecting them in parallel, and a common inverter  51  that converts the direct-current electric power received from the electric power line connection portion  50   j  collectively into alternating-current electric power. The common inverter  51  (power conversion portion  50 ) supplies the generated alternating-current electric power to the interconnection load CLD via an electric power line  20   c.    
     That is, the power conversion portion  50  includes the common inverter  51  that is connected so as to convert direct-current electric power that is output from each of the photovoltaic panels  10  collectively into alternating-current electric power and supply the resultant alternating-current electric power to the interconnection load CLD. 
     Accordingly, the multiple tracking drive solar photovoltaic power generators  1  are operated by being connected to the single common inverter  51 . This simplifies the configuration of the power conversion portion  50  and stabilizes the operating voltage with direct-current electric power, thus enabling a tracking shift to be detected with ease and high precision. 
     It should be noted that a backflow preventing component (not shown; e.g., an anti-backflow diode or a fuse) is connected between the output line detecting portion  22  of each photovoltaic panel  10  and the electric power line connection portion  50   j . It is thus possible to provide output at a common voltage (optimum output voltage Vpj), irrespective of variations in the output of the photovoltaic panel  10 . 
     The common inverter  51  includes an MPPT control portion  51   c  (not shown in  FIG. 18 ) that provides MPPT (maximum power point tracking) control over the photovoltaic panels  10 . It should be noted that the MPPT control portion  51   c  is configured to operate integrally with the common inverter  51 . 
     MPPT control is a control method in which the output electric power (output voltage Vp×output current Ip; see  FIG. 19  for the characteristics of the output electric power) of a photovoltaic panel  10  is measured at fixed time intervals and compared with the previous measured value, and the output voltage Vp is changed always in a direction toward greater output electric power, so that the operating point of the photovoltaic panel can follow a maximum power point (see optimum operating point WPj in  FIG. 19 ). In the present embodiment, conventionally known MPPT control can be applied as-is, and therefore detailed descriptions thereof have been omitted. 
     Specifically, the common inverter  51  is configured to cause the output operating points of the parallel-connected photovoltaic panels  10  (tracking drive solar photovoltaic power generators  1 ) to follow the optimum operating point WPj under maximum power point tracking control (MPPT control). This configuration makes it possible to correct a tracking shift at the optimum operating point WPj (optimum output voltage Vpj) in the tracking solar photovoltaic power generation system  1   s , thus enabling a tracking shift to be corrected with ease and high precision under stable operating conditions. 
     Each detection circuit  22  includes a current detecting portion  23  that detects the output current Ip of the photovoltaic panel  10 . This makes it possible to detect the output current Ip of the photovoltaic panel  10  with ease and high precision, thus enabling a tracking shift of the photovoltaic panel  10  to be corrected with ease and high precision. 
     Each detection circuit  22  also includes a voltage detecting portion that detects the output voltage of the photovoltaic panel  10 . This makes it possible to detect the output voltage Vp of the photovoltaic panel  10  with ease and high precision, thus enabling a tracking shift of the photovoltaic panel  10  to be corrected with ease and high precision. 
     It should be noted that, since the output current Ip detected by the current detecting portion  23  and the output voltage Vp detected by the voltage detecting portion  24  are analog data, they are converted by an A/D conversion portion  26  into digital data that can be handled in the computation processing performed by the tracking control portion  13  and transmitted via a detection line  22   b  to the tracking control portion  13 , in which data processing (computation processing) for correcting a tracking shift is then performed. 
     In the present embodiment, tracking drive and tracking shift correction are performed in a configuration in which a tracking control portion  13  is arranged corresponding to each of the tracking drive solar photovoltaic power generators  1  (photovoltaic panels  10 ), and tracking information (turning information and tilt information regarding a photovoltaic panel  10 ) generated by the tracking control portion  13  is transmitted to the driving portion  14 . In other words, centralized control by the PC  30  is eliminated and each of the tracking drive solar photovoltaic power generators  1  (tracking control portions  13 ) performs distributed processing. This simplifies communication wiring among the tracking control portions  13 , the detection circuits  22 , and the PC  30 , and reduces communication noise and the amount of communication data, thus enabling provision of highly reliable tracking control. 
       FIG. 19  is a characteristic graph showing a VI characteristic curve representative of the output state of a photovoltaic panel in the tracking solar photovoltaic power generation system shown in  FIG. 17 . 
     Note that the horizontal axis indicates the output voltage Vp of the photovoltaic panel  10 , whereas the vertical axis indicates the output current Ip of the photovoltaic panel  10 . Therefore, a VI characteristic curve CCs is specified in accordance with sunlight irradiation conditions on the photovoltaic panel  10 . 
     In a normal operating state, the output operating point of the photovoltaic panel  10  is on the VI characteristic curve CCs, and the operating point is caused to follow the optimum operating point WPj under the control of the MPPT control portion  51   c  (MPPT control). Note that the output voltage Vp=Vpo indicates an open-circuit voltage, and the output current Ip=Ips indicates a short-circuit current. 
     Specifically, the output operating point of the photovoltaic panel  10  during normal operation, under MPPT control by the common inverter  51 , is positioned at the optimum operating point WPj on the VI characteristic curve CCs that corresponds to the sunlight irradiation conditions at that time, and the output voltage Vp is controlled to be the optimum output voltage Vpj. 
     In the present embodiment, electric power is supplied to the common inverter  51  in a state in which multiple (e.g., 10 or more) tracking drive solar photovoltaic power generators  1  are connected in parallel. Therefore, the output voltages Vp of all tracking drive solar photovoltaic power generators  1  (photovoltaic panels  10 ) match the optimum output voltage Vpj under the control of the MPPT control portion  51   c.    
     For example, when a tracking shift occurs during tracking control over the tracking drive solar photovoltaic power generator  1 - 1  (photovoltaic panel  10 - 1 ), the output of the photovoltaic panel  10 - 1  is reduced and the VI characteristic curve is changed into a tracking shift VI characteristic curve CCd. That is, the short circuit current on the VI characteristic curve CCd is is reduced to less than Ips, whereas the open-circuit voltage on the VI characteristic curve CCd is reduced to less than Vpo. Even with such a change of the VI characteristic curve into the tracking shift VI characteristic curve CCd, the output voltage Vp is maintained at the optimum output voltage Vpj because the overall tracking solar photovoltaic power generation system is under MPPT control. 
     From the above, the photovoltaic panel  10 - 1  operates at a tracking shift operating point WPd (output voltage Vp=optimum output voltage Vpj) on the tracking shift VI characteristic curve CCd because its output is reduced, and so the output current Ip is reduced to a tracking shift output current Ipd. 
     In other words, even if a single tracking drive solar photovoltaic power generator  1 , out of 10 or more connected tracking drive solar photovoltaic power generators  1 , causes a tracking shift, there is a small influence on the output voltage Vp (in short, one tenth or less; the influence becomes smaller if the number of connected generators increases), so that it is easy to maintain the optimum output voltage Vpj. 
     At the occurrence of a tracking shift, the tracking control portion  13  is capable of detecting the tracking shift by the output of the detection circuit  22 . Since the common inverter  51  is under MPPT control, the output voltage Vp can be maintained at the optimum output voltage Vpj. Therefore, a tracking shift is usually detected from variations in the output current Ip. It should be noted that it is also possible to detect a tracking shift by detecting variations in the output voltage Vp, in the same way as detecting variations in the output current Ip. 
     The tracking control portion  13  performs computation processing on the output of the detection circuit  22  by using, for example, equations pre-installed on the PC  30 , and detects a tracking shift (magnitude of tracking shift) from the output of the detection circuit  22 . The driving portion  14  corrects a tracking shift of the photovoltaic panel  10  in accordance with the tracking shift obtained by the tracking control portion  13 . A specific tracking shift method will be described in more detail in Embodiment 8. 
     That is, in the tracking solar photovoltaic power generation system is according to the present embodiment, it is possible to detect a tracking shift of each photovoltaic panel  10  individually based on the output data (output current Ip, output voltage Vp) detected by each detection circuit  22  and to correct the tracking shift of each photovoltaic panel  10  individually based on the detection results. 
     After tracking shift correction is performed on the tracking drive solar photovoltaic power generator  1 - 1  (photovoltaic panel  10 - 1 ), the output of the photovoltaic panel  10 - 1  returns from the tracking shift VI characteristic curve CCd to the VI characteristic curve CCs. Accordingly, the output current Ip of the photovoltaic panel  10 - 1  is increased as indicated by the arrow dIp with the output voltage Vp at the optimum output voltage Vpj, and the operating point returns from the tracking shift operating point WPd (tracking shift VI characteristic curve CCd) to the optimum operating point WPj (VI characteristic curve CCs). 
     As described above, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present embodiment, a configuration is adopted in which the common inverter  51  (power conversion portion  50 ) and the tracking drive solar photovoltaic power generators  1  (photovoltaic panels  10 ) run, and a tracking shift of a photovoltaic panel  10  (e.g., photovoltaic panel  10 - 1 ) that is selected as a target for tracking shift correction is corrected while the photovoltaic panel kept connected to the common inverter  51 . 
     With this configuration, since a tracking shift of a photovoltaic panel  10  targeted for correction is corrected while the photovoltaic panel kept connected to the common inverter  51 , a tracking shift in the tracking solar photovoltaic power generation system  1   s  can be corrected in a state in which the system interconnection is maintained while continuing electric power generation by the tracking drive solar photovoltaic power generators  1  and electric power supply from the common inverter  51  to the interconnection load CLD. It is thus possible to provide a highly reliable and productive tracking shift correction method that eliminates the need to stop the system associated with tracking shift correction and causes no loss in the amount of generated electric power. 
     Moreover, as described above, the common inverter  51  is configured to cause the output operating points of the photovoltaic panels  10  to follow the optimum operating point WPj under MPPT control (maximum power point tracking control). This configuration makes it possible to correct a tracking shift in a state in which the tracking solar photovoltaic power generation system is (photovoltaic panels  10 ) is operated at the optimum operating point WPj (optimum output voltage Vpj corresponding to the optimum operating point WPj), thus enabling a tracking shift to be corrected with ease and high precision under stable operating conditions. 
     In other words, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present embodiment, a tracking shift is corrected in a state in which the output voltage Vp of each photovoltaic panel  10  is maintained at the optimum output voltage Vpj under MPPT control of the common inverter  51 . Since a tracking shift can be corrected in a state in which the output voltage Vp of each photovoltaic panel  10  is held at the optimum output voltage Vpj by the common inverter  51 , it is possible to correct a tracking shift with ease and high precision. 
     As described above, the tracking solar photovoltaic power generation system is according to the present embodiment includes multiple tracking drive solar photovoltaic power generators  1  that are arranged in parallel connection, and the power conversion portion  50  that converts direct-current electric power generated by the tracking drive solar photovoltaic power generators  1  into alternating-current electric power and supplies the alternating-current electric power to the interconnection load CLD. 
     Also in the tracking solar photovoltaic power generation system  1   s , each of the tracking drive solar photovoltaic power generators  1  includes the photovoltaic panel  10  that converts sunlight into direct-current electric power, and the driving portion  14  that drives the photovoltaic panel  10  based on the tracking information causing the photovoltaic panel  10  to track the solar trajectory, and a configuration is adopted in which a tracking shift of a photovoltaic panel  10  that is targeted for tracking shift correction is detected in a state in which the corresponding tracking drive solar photovoltaic power generator  1  is running by being connected to the power conversion portion  50 . 
     Since a tracking shift of a photovoltaic panel  10  is detected in a state in which the corresponding tracking drive solar photovoltaic power generator  1  is running by being connected to the power conversion portion  50 , it is possible to provide a highly reliable and productive tracking solar photovoltaic power generation system is that eliminates the need to be stopped associated with tracking shift correction and causes no loss in the amount of generated electric power. 
     Also, the power conversion portion  50  includes the common inverter  51  that is connected so as to convert direct-current electric power that is output from each of the photovoltaic panels  10  collectively into alternating-current electric power supply and supplies the resultant alternating-current electric power to the interconnection load CLD. 
     This simplifies the configuration of the power conversion portion  50  and stabilizes the operating voltage with direct-current electric power, thus enabling a tracking shift to be detected with ease and high precision. 
     Eighth Embodiment 
     Next, the details of the tracking correction step and the operations of the tracking control portion  13  and the driving portion  14  in the tracking solar photovoltaic power generation system is, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the Embodiment 7, will be described with reference to  FIGS. 20 to 22  as Embodiment 8 of the present invention. It should be noted that the procedure of the tracking correction step is not limited to the one described in the present embodiment and other procedures are also applicable. 
       FIG. 20  is a flowchart showing the procedure for correcting a tracking shift in a tracking shift correction method for a tracking solar photovoltaic power generation system according to Embodiment 8. 
     A tracking shift (shift in position during tracking control) of a tracking drive solar photovoltaic power generator  1  (photovoltaic panel  10 ) can be corrected through the following steps S 1  to S 5  in the tracking shift correction method according to the present embodiment. 
     Specifically, a tracking drive solar photovoltaic power generator  1  that is targeted for correction is selected in step S 1 . Next, a directly-facing turning position in the turning direction is detected (a tracking shift in a turning direction Roth is detected) in step S 2 , and the tracking shift in the turning direction is corrected (the turning position is moved to a directly-facing turning position Phj) in step S 3 . Thereafter, a directly-facing tilt position in the tilt direction is detected (a tracking shift in a tilt direction Rotv is detected) in step S 4 , and the tracking shift in the tilt direction is corrected (the tilt direction is moved to a directly-facing tilt position Phv) in step S 5 . 
     It should be noted that the directly-facing turning position indicates a position in which the photovoltaic panel  10  directly faces the solar trajectory in the turning direction Roth, and the directly-facing tilt position indicates a position in which the photovoltaic panel  10  directly faces the solar trajectory in the tilt direction Rotv. Hereinafter, each step will be described in more detail. 
     Step S 1 : 
     A tracking drive solar photovoltaic power generator  1  (photovoltaic panel  10 ) that is targeted for correction is specified and selected. For example, the output current Ip detected by a current detecting portion  23  is sampled at regular intervals and compared with the output current Ip detected by another current detecting portion  23 , and a tracking drive solar photovoltaic power generator  1  having a low current value can be selected as one with a tracking shift. 
     For example, a tracking shift on the order of 0.2° causes approximately a 10% drop in output, and such a drop in output appears intact as a reduction in the output current Ip because the output voltage Vp is adjusted at the optimum voltage Vpj under MPPT control. Therefore, the drop in output can be detected with ease and high precision by the current detecting portion  23 . 
     That is, a photovoltaic panel  10  with a tracking shift (e.g., the photovoltaic panel  10 - 1 , which is hereinafter simply referred to as a “photovoltaic panel  10 ”) can be detected with ease and high precision by inter-comparison of the output current Ip detected by a current detecting portion  23  with the output currents Ip detected by other multiple current detecting portions  23  of the tracking drive solar photovoltaic power generators  1 . 
     It should be noted that, although the following description gives the case where the output current Ip is targeted for detection, similar processing may also be possible using the output voltage Vp as a target for detection. It should also be noted that, since variations in the output voltage Vp are weak under MPPT control, it is desirable that a higher-precision voltage detection method be employed. 
     Step S 2 : 
     The directly-facing turning position Phj (see  FIG. 21(A) ) of the selected photovoltaic panel  10  is detected. Specifically, a tracking shift in the turning direction Roth is detected by detecting the directly-facing turning position Phj. 
     The tracking control portion  13  can detect a tracking shift (tracking shift amount, tracking shift direction) of the photovoltaic panel  10  by performing computation processing on the output current Ip detected by the current detecting portion  23 . 
     As a method for detecting a tracking shift, various methods are applicable and one example is shown in  FIGS. 21(A) and 21(B) , which will be described later. 
     Step S 3 : 
     The turning position of the photovoltaic panel  10  that is targeted for correction is moved to the detected directly-facing turning position Phj so as to correct a tracking shift (shift in position) in the turning direction Roth. Specifically, the driving portion  14  corrects a tracking shift of the photovoltaic panel  10  in accordance with the tracking shift (tracking shift amount, tracking shift direction) detected by the tracking control portion  13 . 
     It should be noted that, when the turning position of the photovoltaic panel  10  is moved to the detected directly-facing turning position Phj, the accuracy in correcting a tracking shift can further be increased if the amount of transition of the directly-facing turning position Phj over time since the directly-facing turning position Phj was detected is corrected in advance. 
     Step S 4 : 
     A directly-facing tilt position Pvj (see  FIG. 22(A) ) of the selected photovoltaic panel  10  is detected. Specifically, a tracking shift in the tilt direction Rotv is detected by detecting the directly-facing tilt position Pvj. 
     The tracking control portion  13  can detect a tracking shift of the photovoltaic panel  10  (tracking shift amount, tracking shift direction) by performing computation processing on the output current Ip detected by the current detecting portion  23 . 
     As a method for detecting a tracking shift, various methods are applicable and one example is shown in  FIGS. 22(A) and 22(B) , which will be described later. 
     Step S 5 : 
     The tilt position of the photovoltaic panel  10  that is targeted for correction is moved to the detected directly-facing tilt position Pvj so as to correct a tracking shift (shift in position) in the tilt direction Rotv. Specifically, the driving portion  14  corrects a tracking shift of the photovoltaic panel  10  in accordance with the tracking shift (tracking shift amount, tracking shift direction) detected by the tracking control portion  13 . 
     It should be noted that, when the tilt position of the photovoltaic panel  10  is moved to the detected directly-facing tilt position Pvj, the accuracy in correcting a tracking shift can further be increased if the amount of transition of the directly-facing tilt position Pvj over time since the directly-facing tilt position Pvj was detected is corrected in advance. 
     As described above, tracking shift correction is implemented by determining a directly-facing position Pjc (directly-facing turning position Phj and directly-facing tilt position Pvj which may be simply referred to as a “directly-facing position Pjc” when there is no particular need to distinguish between the directly-facing turning position Phj and the directly-facing tilt position Pvj) in which the photovoltaic panel  10  directly faces the solar trajectory, through detection of the output current Ip (or output voltage Vp) of the photovoltaic panel  10 , and causing the photovoltaic panel  10  to track and move to the determined directly-facing position Pjc. 
     Specifically, the tracking control portion  13  is configured to detect a tracking shift of the photovoltaic panel  10  based on the output current Ip (output voltage Vp) detected by the current detecting portion  23  (voltage detecting portion  24 ), and the driving portion  14  is configured to correct a tracking shift of the photovoltaic panel  10  in accordance with the tracking shift (shift in position relative to the directly-facing position Pjc) detected by the tracking control portion  13 . 
     In the case where a tracking shift is detected based on the output current Ip, the tracking shift is corrected by applying variations in the output current IP that is responsive to a tracking shift. It is thus possible to determine the directly-facing position Pjc, in which the photovoltaic panel  10  directly faces the solar trajectory, with ease and high precision and to thereby correct a tracking shift with ease and high precision. 
     In the case where a tracking shift is detected based on the output voltage Vp, the tracking shift is corrected by applying variations in the output voltage Vp that is responsive to a wide range of tracking shifts. It is thus possible to determine the directly-facing position Pjc, in which the photovoltaic panel  10  directly faces the solar trajectory, with ease and high precision and to thereby correct a tracking shift with ease and high precision. 
     In addition, the directly-facing position Pjc is adaptable to either of the turning direction Roth and the tilt direction Rotv, as described above. 
     That is, the directly-facing position Pjc may be determined as a directly-facing turning position Phj that is the directly-facing position in the turning direction Roth. It is thus possible to correct a tracking shift in the turning direction Roth with ease and high precision. 
     Also, the directly-facing position Pjc may be determined as a directly-facing tilt position Pvj that is the directly-facing position in the tilt direction Rotv. It is thus possible to correct a tracking shift in the tilt direction Rotv with ease and high precision. 
     As described above, a tracking shift of the photovoltaic panel  10  that may occur during tracking control includes a tracking shift in the turning direction Roth and a tracking shift in the tilt direction Rotv. However, a tracking shift in the turning direction Roth is more likely to occur in general practice. Specifically, at the time of construction, although alignment in the tilt direction Rotv can be accomplished with relatively high precision, alignment in the turning direction Roth is more difficult to be accomplished than the alignment in the tilt direction Rotv. Therefore, a tracking shift is more likely to occur in the turning direction Roth. 
     For this reason, in the present embodiment a configuration may also be adopted in which the processing for correcting a tracking shift of a photovoltaic panel  10  is ended with only steps S 1  to S 3 . Alternatively, steps S 2  to S 5  may be repeated for further improvement in accuracy. 
     It should be noted that a computer program for implementing the procedure of steps S 1  to S 5  may be pre-installed on the tracking control portion  13  and the PC  30  in order to ease the implementation. 
       FIG. 21  is a diagram for explaining the procedure for detecting a tracking shift in the turning direction, in the flowchart shown in  FIG. 20 ,  FIG. 21(A)  being a graph showing the relationship between the turning position and the output current,  FIG. 21(B)  being a flowchart showing the procedure. 
     In  FIG. 21(A) , the horizontal axis indicates the turning position Ph of the photovoltaic panel  10 , whereas the vertical axis indicates the output current Ip of the photovoltaic panel  10 . 
     The directly-facing turning position Phj (directly-facing position Pjc) described in step S 2  can be detected through steps S 21  to S 23 . It should be noted that the method for detecting the directly-facing turning position Phj is not limited to the method described with reference to steps S 21  to S 23 , and various methods are applicable as described in step S 2 . 
     Step S 21 : 
     The photovoltaic panel  10  is turned and moved retroactively to a past solar azimuth position (corrective retroactive turning position Phb) that corresponds to a position displaced by a predetermined first turning movement angle dφ 1  from a correction start turning position Phs.  FIG. 21(A)  shows the case where the output current Ip is reduced due to an increased tracking shift associated with the turning movement. 
     Step S 22 : 
     The photovoltaic panel  10  is turned and moved to a later solar azimuth position (corrective later turning position Phf) ahead by a second turning movement angle dφ 2  from the corrective retroactive turning position Phb relative to the transition of the solar azimuth, during which the output current Ip of the photovoltaic panel  10  is detected. 
     The output current Ip describes an angular curve having a maximum value in accordance with the turning movement. Specifically, a position having a maximum value is the solar azimuth angle at which the photovoltaic panel  10  directly faces the sun. 
     Step S 23 : 
     A turning position Ph in which the output current Ip of the photovoltaic panel  10  during the turning movement reaches its maximum value is detected as a directly-facing turning position Phj. Specifically, the turning position Ph in which the output current Ip reaches its maximum value is determined as the directly-facing turning position Phj (directly-facing position Pjc). 
     The tracking control portion  13  is capable of detecting a shift in position from the relationship between the output current Ip detected by the current detecting portion  23  and the turning position Ph. That is, a tracking shift (tracking shift amount, tracking shift direction) is detected based on a difference (difference in position) between the directly-facing turning position Phj and the turning position Ph (e.g., the correction start turning position Phs or the corrective later turning position Phf). 
     The tracking control portion  13  also supplies information (turning position information and tilt position information) for correcting the detected tracking shift to the driving portion  14 , and the driving portion  14  adjusts (drives) the turning position and tilt position of the photovoltaic panel  10  according to the information received from the tracking control portion  13 . 
     It should be noted that, although the case where a tracking shift in the turning direction Roth is detected by detecting variations in the output current Ip has been described in  FIG. 21 , detecting variations in the output voltage Vp in order to detect a tracking shift in the turning direction Roth is also possible as well. 
       FIG. 22  is a diagram for explaining the procedure for detecting a tracking shift in the tilt direction, in the flowchart shown in  FIG. 20 ,  FIG. 22(A)  being a graph showing the relationship between the tilt position and the output current,  FIG. 22(B)  being a flowchart showing the procedure. 
     In  FIG. 22(A) , the horizontal axis indicates the tilt position Pv of the photovoltaic panel  10 , whereas the vertical axis indicates the output current Ip of the photovoltaic panel  10 . 
     The directly-facing tilt position Pvj (directly-facing position Pjc) described in step S 4  can be detected through the following steps S 41  to S 43 . It should be noted that the method for detecting the directly-facing tilt position Pvj is not limited to the method including steps S 31  to S 43 , and various methods are also applicable as described in step S 4 . 
     Step S 41 : 
     The photovoltaic panel  10  is tilted and moved retroactively to a past solar altitude position (corrective retroactive tilt position Pvb) that corresponds to a position displaced by a predetermined first tilt movement angle dθ 1  from a correction start tilt position Pvs.  FIG. 22(A)  shows the case where the output current Ip is reduced due to an increased tracking shift associated with the tilt movement. 
     Step S 42 : 
     The photovoltaic panel  10  is tilted and moved to a later solar altitude position (corrective later tilt position Pvf) ahead by a second tilt movement angle dθ 2  from the corrective tilt retroactive position Pvb relative to the transition of the solar altitude, during which the output current Ip of the photovoltaic panel  10  is detected. 
     The output current Ip describes an angular curve having a maximum value in accordance with the tilt movement. Specifically, a position in which the output current reaches its maximum value is the solar altitude at which the photovoltaic panel  10  is to face directly the sun. 
     Step S 43 : 
     A tilt position Pv in which the output current Ip of the photovoltaic panel  10  reaches its maximum value during the tilt movement is detected as a directly-facing tilt position Pvj. That is, the tilt position Pv in which the output current Ip reaches its maximum value is determined as a directly-facing tilt position Pvj (directly-facing position Pjc). 
     The operations of the tracking control portion  13  and the driving portion  14  are similar to those in the case of  FIG. 21 . 
     It should be noted that, although the case where a tracking shift in the tilt direction Rotv is detected by detecting variations in the output current Ip has been described in  FIG. 22 , detecting variations in the output voltage Vp in order to detect a tracking shift in the tilt direction Rotv is also possible as well. 
     As described above, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present embodiment, a shift in position is corrected by determining the directly-facing position Pjc in which the photovoltaic panel  10  directly faces the solar trajectory, based on the output current Ip detected by the current detecting portion  23  (computation processing performed by the tracking control portion  13 ), and then moving the photovoltaic panel  10  to the directly-facing position Pjc (control over the tracking direction of the photovoltaic panel  10 , performed by the driving portion  14 ). 
     Thus, a tracking shift is corrected by applying variations in the output current Ip that is sensitively responsive to a tracking shift. It is thus possible to determine the directly-facing position Pjc, in which the photovoltaic panel  10  directly faces the solar trajectory, with ease and high precision and to thereby correct a tracking shift with ease and high precision. 
     Alternatively, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present embodiment, a shift in position may be corrected by determining the directly-facing position Pjc in which the photovoltaic panel  10  directly faces the solar trajectory, based on the output voltage Vp detected by the voltage detecting portion  24 , and then moving the photovoltaic panel  10  to the directly-facing position Pjc. 
     Thus, a tracking shift is corrected by applying variations in the output voltage that is responsive to a wide range of tracking shifts. It is thus possible to determine the directly-facing position Pjc, in which the photovoltaic panel  10  directly faces the solar trajectory, with ease and high precision and to thereby correct a tracking shift with ease and high precision. 
     Ninth Embodiment 
     In Embodiments 7 and 8 described above, the common inverter  51  is operated under MPPT control by the MPPT control portion  51   c . A tracking shift correction method for a tracking solar photovoltaic power generation system according to the present embodiment is a method for correcting a tracking shift regardless of the MPPT control portion  51   c . It should be noted that the basic configuration is similar to those described in Embodiments 7 and 8, and therefor the same reference numerals are used as appropriate. 
     In accordance with the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present embodiment, the common inverter  51  does not provide MPPT control. Specifically, the common inverter  51  is configured to be operated under constant voltage control, instead of under MPPT control by the MPPT control portion  51   c , and hold the output operating point of a photovoltaic panel  10  at a constant voltage. 
     This configuration makes it possible to correct a tracking shift in a state in which a tracking solar photovoltaic power generation system  1  (photovoltaic panel  10 ) is operated at a constant voltage, thus enabling the tracking shift to be corrected with ease and high precision under stable operating conditions. 
     It should be noted that constant-voltage mode settings may be performed either automatically or manually in the common inverter  51 . In addition, a known technique is applicable to the constant-voltage mode settings, and therefore detailed descriptions thereof have been omitted. 
     That is, in the tracking shift correction method for the tracking solar photovoltaic power generation system according to the present embodiment, a tracking shift can be corrected in the same manner as in Embodiments 7 and 8. Thus, in the case of correcting a tracking shift, a directly-facing position Pjc can be detected from variations in the output current Ip of a photovoltaic panel  10  as in step S 2  (steps S 21  to S 23 ) and step S 4  (steps S 41  to S 43 ), and a tracking shift can be corrected through turning or tilt movement of the photovoltaic panel  10  toward the detected directly-facing position Pjc. 
     According to the present embodiment, tracking shift correction can be implemented more easily because there is no need to use the MPPT control portion  51   c . In addition, even in a tracking drive solar photovoltaic power generator  1   s  that includes a small number of tracking drive solar photovoltaic power generators  1 , the operating voltage can be held at a constant voltage during tracking shift correction operations, and therefore it is possible to correct a tracking shift with ease and precision. 
     Tenth Embodiment 
     Next is a description of a tracking solar photovoltaic power generation system according to Embodiment 10 and a tracking shift correction method for the tracking solar photovoltaic power generation system in which a tracking shift of a tracking drive solar photovoltaic power generator is corrected, given with reference to  FIG. 23 . 
     It should be noted that the basic configuration is similar to those of the tracking drive solar photovoltaic power generators  1 , the tracking solar photovoltaic power generation system  1   s , and the tracking shift correction method described in Embodiments 7 to 9, and therefore descriptions are primarily given regarding different points. 
       FIG. 23  is a block diagram illustrating a schematic configuration of the tracking solar photovoltaic power generation system according to Embodiment 10. 
     The tracking shift correction method for the tracking solar photovoltaic power generation system according to the present embodiment is a method for correcting a tracking shift (shift in position during tracking control) of a tracking drive solar photovoltaic power generator  1  in the tracking solar photovoltaic power generation system is relative to the solar trajectory, the system is including multiple tracking drive solar photovoltaic power generators  1  that are arranged in parallel connection and a power conversion portion  50  that converts direct-current electric power generated by the tracking drive solar photovoltaic power generators  1  into alternating-current electric power and supplies the alternating-current electric power to an interconnection load CLD. 
     The tracking drive solar photovoltaic power generators  1  have a similar configuration (photovoltaic panel  10 , tracking control portion  13 , driving portion  14 , and detection circuit  22 ) to those described in Embodiments 7 to 9. 
     In the present embodiment, the tracking control portion  13  corresponding to a photovoltaic panel  10  that is targeted for tracking shift correction is configured to detect a tracking shift of the photovoltaic panel  10  in a state in which the corresponding tracking drive solar photovoltaic power generator  1  (photovoltaic panel  10 ) is running by being connected to the power conversion portion  50 . Also, the corresponding driving portion  14  is configured to correct a tracking shift of the photovoltaic panel  10  in accordance with the tracking shift detected by the tracking control portion  13 . A specific configuration may be similar to that in the case of Embodiment 8. 
     The power conversion portion  50  according to the present embodiment includes multiple individual inverters  53  that are connected so as to each convert direct-current electric power that is output from each of the photovoltaic panels  10  individually into alternating-current electric power and supply the resultant alternating-current electric power collectively to the interconnection load CLD. The individual inverters  53  (power conversion portion  50 ) are connected in parallel by an electric power line connection portion  50   j  and supply generated alternating-current electric power to the interconnection load CLD via an electric power line  20   c.    
     The power conversion portion  50  has arranged therein an individual inverter  53 - 1  that changes the output of a photovoltaic panel  10 - 1  into electric power, an individual inverter  53 - 2  that changes the output of a photovoltaic panel  10 - 2  into electric power, . . . , and an individual inverter  53 - n  that changes the output of a photovoltaic panel  10 - n  into electric power. Hereinafter, each of the inverters may be simply referred to as “individual inverters  53 ” when there is no particular need to distinguish between the individual inverters  53 - 1 ,  53 - 2 , . . . , and  53 - n.    
     That is, the power conversion portion  50  includes individual inverters  53  that are connected so as to each convert direct-current electric power that is output from each of the photovoltaic panels  10  individually into alternating-current electric power and supply the resultant alternating-current electric power collectively to the interconnection load CLD. It should be noted that the individual inverters  53  are operated under constant voltage control. 
     Thus, the photovoltaic panels  10  can be brought in direct correspondence with the individual inverters  53  each having a capacity corresponding to the capacity of each tracking drive solar photovoltaic power generator  1  (photovoltaic panel), and therefore it is possible to adjust the outputs of the photovoltaic panels  10  and stabilize the operating voltages, which enables a tracking shift to be detected with ease and high precision. 
     It should be noted that, since the output sides of the individual inverters  53  are connected in parallel by the electric power line connection portion  50   j , the alternating-current electric power from each of the individual inverters  53  is collectively supplied by the electric power line connection portion  50   j  to the interconnection load CLD. 
     As described above, the tracking solar photovoltaic power generation system is according to the present embodiment includes multiple tracking drive solar photovoltaic power generators  1  that are arranged in parallel connection, and the power conversion portion  50  that converts direct-current electric power generated by the tracking drive solar photovoltaic power generators  1  into alternating-current electric power and supplies the resultant alternating-current electric power to the interconnection load CLD. 
     Also, in the tracking solar photovoltaic power generation system  1   s , each of the tracking drive solar photovoltaic power generators  1  includes a photovoltaic panel  10  that converts sunlight into direct-current electric power, a tracking control portion  13  that outputs tracking information that causes the photovoltaic panel  10  to track the solar trajectory, and a driving portion  14  that drives the photovoltaic panel  10  based on the tracking information. In this system, a configuration is adopted in which the tracking control portion  13  corresponding to a photovoltaic panel  10  that is targeted for tracking shift correction is configured to detect a tracking shift of the photovoltaic panel  10  in a state in which the corresponding tracking drive solar photovoltaic power generator  1  is running by being connected to the power conversion portion  50 . 
     Therefore, a tracking shift of the photovoltaic panel  10  is detected in a state in which the corresponding tracking drive solar photovoltaic power generator  1  is running by being connected to the power conversion portion  50 . This enables providing a highly reliable and productive tracking solar photovoltaic power generation system  1   s  that eliminates the need to be stopped associated with tracking shift correction and causes no loss in the amount of generated electric power. 
     The tracking solar photovoltaic power generation system  1   s  according to the present embodiment enables the use of the individual inverters  53  each having a capacity corresponding to the capacity of each tracking drive solar photovoltaic power generator  1 , and therefore the tracking solar photovoltaic power generation system  1   s  can be constructed with ease at low cost by application of small-capacity, low-cost individual inverters  53 . Moreover, direct correspondence between the photovoltaic panels  10  and the individual inverters  53  makes it easy to adjust the outputs of the photovoltaic panels  10  and simplify output wiring, thus making the tracking solar photovoltaic power generation system  1   s  rational and economical. 
     As described above, the individual inverters  53  are configured to operate under constant voltage control and hold the output operating points of the photovoltaic panels  10  at a constant voltage. In other words, the individual inverters  53  function similarly to the common inverter  51  of Embodiment 9. 
     It is thus possible to correct a tracking shift in a state in which the photovoltaic panels  10  are operated at a constant voltage and to thereby correct a tracking shift with ease and high precision under stable operating conditions. 
     It should be noted that an inverter is generally configured to be able to observe direct input current and direct input voltage. In the tracking solar photovoltaic power generation system  1   s  according to the present embodiment, since the individual inverters  53  are connected corresponding individually to the photovoltaic panels  10 , a configuration is also possible in which the outputs of the photovoltaic panels  10  are detected by the individual inverters  53 , instead of being detected by the detection circuits  22 . This configuration makes it possible to eliminate the need for the detection circuits  22  and to thereby simplify the circuit configuration of the tracking drive solar photovoltaic power generators  1 . 
     Eleventh Embodiment 
     Next is a description of a tracking solar photovoltaic power generation system is (hereinafter which may be simply referred to as a “system”) as described in Embodiments 7 to 9, in which the photovoltaic panels  10  (tracking drive solar photovoltaic power generators  1 ) are connected in parallel, i.e., the output characteristics (VI characteristic curve) obtained when applying a common inverter  51 , given with reference to  FIGS. 24 to 26 , as Embodiment 11 of the present invention. 
       FIG. 24  shows the characteristics of a photovoltaic panel  10  during normal operation,  FIG. 24(A)  showing the case where the photovoltaic panel  10  is not targeted for correction,  FIG. 24(B)  showing the case where the photovoltaic panel  10  is targeted for correction, and  FIG. 24(C)  showing the combined case for the system.  FIG. 25  shows the characteristics of a photovoltaic panel  10  when a shift in position occurs under MPPT control,  FIG. 25(A)  showing the case where the photovoltaic panel  10  is not targeted for correction,  FIG. 25(B)  showing the case where the photovoltaic panel  10  is targeted for correction, and  FIG. 25(C)  show the combined case for the system.  FIG. 26  shows the characteristics of a photovoltaic panel  10  when a shift in position occurs under constant voltage control,  FIG. 26(A)  showing the case where the photovoltaic panel  10  is not targeted for correction,  FIG. 26(B)  showing the case where the photovoltaic panel  10  is targeted for correction, and  FIG. 26(C)  showing the combined case for the system. 
     It should be noted that the combined case for the system refers to, for example, a case where the characteristics of a total of two photovoltaic panels, namely a photovoltaic panel that is not targeted for correction (e.g., photovoltaic panel  10 - 1 ) and a photovoltaic panel that is targeted for correction (e.g., photovoltaic panel  10 - 2 ), are combined. 
       FIG. 24  is a graph showing the VI characteristic curve of a photovoltaic panel in the tracking solar photovoltaic power generation system according to Embodiment 11 of the present invention. As described above,  FIG. 24(A)  shows normal characteristics of a photovoltaic panel that is not targeted for correction,  FIG. 24(B)  shows normal characteristics of a photovoltaic panel that is targeted for correction, and  FIG. 24(C)  shows combined characteristics of a photovoltaic panel that is not targeted for correction and a photovoltaic panel that is targeted for correction. 
     It should be noted that the horizontal axis indicates the output voltage Vp of a photovoltaic panel  10 , whereas the vertical axis indicates the output current Ip of the photovoltaic panel  10 . Accordingly, a VI characteristic curve CCs is specified in accordance with sunlight irradiation conditions on the photovoltaic panel  10 . Note that the same applies to  FIGS. 25 and 26 . 
     During normal operation of a tracking drive solar photovoltaic power generator  1  (photovoltaic panel  10 ), the output operating point of the photovoltaic panel  10  is on the VI characteristic curve CCs and is caused to follow an optimum operating point WPj under MPPT control. 
     Therefore, the optimum operating point WPj and an optimum output voltage Vpj are determined on a combined VI characteristic curve (combined VI characteristic curve TCCs) as shown in  FIG. 24(C) . 
     Under the condition that the optimum operating point WPj and the optimum output voltage Vpj are determined, the VI characteristic curve CCs ( FIG. 24(A) ) of the photovoltaic panel  10  that is not targeted for correction (e.g., photovoltaic panel  10 - 1 ) shows normal characteristics in accordance with sunlight irradiation conditions. Thus, an optimum output voltage Vpj corresponding to the optimum operating point WPj on the characteristic curve of the entire system, and its corresponding optimum output current Ipj are detected as outputs from the curve. 
     Also, under the condition that the optimum operating point WPj and the optimum output voltage Vpj are determined, the VI characteristic curve CCs ( FIG. 24(B) ) of the photovoltaic panel  10  that is targeted for correction (e.g., photovoltaic panel  10 - 2 ) shows, since during normal operation, normal characteristics similar to those of the photovoltaic panel  10 - 1 . Thus, the optimum output voltage Vpj corresponding to the optimum operating point WPj on the characteristic curve, and its corresponding optimum output current Ipj are detectable as outputs from the curve. 
     The above outputs (output current Ip) are combined since the photovoltaic panel  10 - 1  and the photovoltaic panel  10 - 2  are in parallel connection, forming the combined VI characteristic curve TCCs ( FIG. 24(C) ) as described above. That is, a characteristic curve of an open-circuit voltage Vpo and a short circuit current 2Ips is obtained. 
     Because both the photovoltaic panel  10 - 1  and the photovoltaic panel  10 - 2  are combined under normal conditions, the output voltage Vp equals the optimum output voltage Vpj and the combined output current TIp equals 2Ipj at the optimum operating point WPj, i.e., those panels are run in parallel due to their parallel connection. 
       FIG. 25  is a graph showing the VI characteristic curve of a photovoltaic panel under MPPT control in the tracking solar photovoltaic power generation system according to Embodiment 11.  FIG. 25(A)  shows normal characteristics of a photovoltaic panel that is not targeted for correction,  FIG. 25(B)  shows characteristics under a condition in which a tracking position is moved in order to detect a shift in the position of a photovoltaic panel that is targeted for correction, and  FIG. 25(C)  shows combined characteristics of a photovoltaic panel that is not targeted for correction and a photovoltaic panel that is targeted for correction. 
     The VI characteristic curve CCs ( FIG. 25(A) ) of the photovoltaic panel  10 - 1  that is not targeted for correction is similar to that in  FIG. 24(A) . That is, it shows normal characteristics in correspondence with sunlight irradiation conditions, and an optimum output voltage Vpj corresponding to an optimum operating point WPj on the characteristic curve, and its corresponding optimum output current Ipj can be detected as outputs from the curve. 
     A photovoltaic panel  10 - 2  that is targeted for correction is shifted from a normal tracking state in order to detect a shift in position. Its characteristic curve thus corresponds to a detection VI characteristic curve CCc (FIG.  25 (B)), giving an open-circuit voltage Vp 1  (&lt;normal open-circuit voltage Vpo) and a short circuit current Ip 2  (&lt;normal short circuit current Ips). 
     Since the system is under MPPT control, an optimum operating point WPc (detection operating point WPc) and its corresponding optimum output voltage Vpj are determined on the curve in  FIG. 25(C) . That is, the output voltage Vp of the photovoltaic panel  10 - 2  equals the optimum output voltage Vpj. Accordingly, the operating point is determined as a detection operating point WPc corresponding to the optimum output voltage Vpj, and the output current Ip is detected as an output current Ip 3  (current detected by the current detecting portion  23 ) on the detection VI characteristic curve CCc. 
     It should be noted that, when a small number of photovoltaic panels  10  are in parallel connection, the output voltage Vp corresponding to the detection operating point WPc is affected by a shift in position and accordingly reduced from the optimum output voltage Vpj. In the present embodiment, however, the output voltage can be maintained at the optimum output voltage Vpj because, for example, 10 or more photovoltaic panels  10  are in connection. 
     A combined output of the photovoltaic panel  10 - 1  and the photovoltaic panel  10 - 2  forms a combined detection VI characteristic curve TCCc ( FIG. 25(C) ). Since the output of the photovoltaic panel  10 - 2  is lower than the output of the photovoltaic panel  10 - 1 , a combined output current TIp at the time of short circuiting equals Ips+Ip 2  (TIp&lt;2Ips). A combined output current TIp at the operating point WPc equals Ipj+Ip 3 . 
     Therefore, the optimum output voltage Vpj can be maintained even in the case of correcting a shift in position. It is thus possible to detect the output current Ip (output current Ip 3 ) with high precision and to thereby detect a shift in position with high precision. 
       FIG. 26  is a graph showing the VI characteristic curve of a photovoltaic panel under constant voltage control in the tracking solar photovoltaic power generation system according to Embodiment 11 of the present invention.  FIG. 26(A)  shows normal characteristics of a photovoltaic panel that is not targeted for correction,  FIG. 26(B)  shows characteristics under a condition in which a tracking position is moved in order to detect a shift in the position of a photovoltaic panel that is targeted for correction, (C) shows combined characteristics of a photovoltaic panel that is not targeted for correction and a photovoltaic panel that is targeted for correction. 
     The VI characteristic curve CCs ( FIG. 26(A) ) of the photovoltaic panel  10 - 1  that is not targeted for correction is similar to those in  FIGS. 24(A) and 25(A) , showing normal characteristics in accordance with sunlight irradiation conditions. Also, a fixed output voltage Vpf that is determined for the entire system, and an output current Ipf that corresponds to the fixed output voltage Vpf on the VI characteristic curve CCs of the photovoltaic panel  10 - 1  can be detected from the curve. 
     A photovoltaic panel  10 - 2  that is targeted for correction is shifted from a normal tracking state in order to detect a shift in position. Therefore, its characteristic curve corresponds to a detection VI characteristic curve CCc (FIG.  26 (B)), giving an open-circuit voltage Vp 1  (&lt;normal open-circuit voltage Vpo) and a short circuit current Ip 4  (&lt;normal short circuit current Ips). 
     Also, the output voltage Vp becomes the fixed output voltage Vpf because the photovoltaic panel  10 - 2  is operated under constant voltage control. Accordingly, the operating point becomes a detection operating point WPc corresponding to the fixed output voltage Vpf, and the output current Ip is detected as output current Ipc (current detected by the current detecting portion  23 ) on the detection VI characteristic curve CCc. 
     A combined output of the photovoltaic panel  10 - 1  and the photovoltaic panel  10 - 2  forms a combined detection VI characteristic curve TCCc ( FIG. 26(C) ). Since the output of the photovoltaic panel  10 - 2  is lower than that of the photovoltaic panel  10 - 1 , a combined output current TIp during short circuiting equals Ips+Ip 4  (TIp&lt;2Ips). The combined output current TIp at the detection operating point WPc equals Ip 6  (=Ipf+Ipc). 
     Therefore, the fixed output voltage Vpf can be maintained even in the case of correcting a shift in position. It is thus possible to detect the output current Ip (output current Ip 5 ) with high precision and to thereby detect a shift in position with high precision. It should be noted that, although the fixed output voltage Vpf may be determined arbitrarily, a shift in position can be detected with higher precision if the fixed output voltage is set to exactly the same or close enough to the optimum output voltage Vpj corresponding to the optimum operating point WPj on the VI characteristic curve CCs showing normal characteristics or on the combined detection VI characteristic curve TCCs. 
     It should be noted that the present invention may be embodied in various other forms without departing from the gist or essential characteristics thereof. Therefore, the embodiments described above are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all modifications or changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein. 
     INDUSTRIAL APPLICABILITY 
     The present invention is suitably applicable to a tracking solar photovoltaic power generation system that causes a photovoltaic panel to track the solar trajectory. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               1 ,  1 - 1 ,  1 - 2 ,  1 - n  Tracking drive solar photovoltaic power generator 
               1   s  Tracking solar photovoltaic power generation system 
               10 ,  10 - 1 ,  10 - 2 ,  10 - n  Photovoltaic panel 
               11  Column 
               12  Driving portion 
               13 ,  13 - 1 ,  13 - 2 ,  13 - n  Tracking control portion 
               13   b  Communication line 
               13   c  Control line 
               20  Electric power monitoring board 
               20   b ,  20   c  Electric power line 
               21  Switch 
               22 ,  22 - 1 ,  22 - 2 ,  22 - n  Detection circuit 
               22   b  Detection line 
               25  Output side circuit breaker 
               26  A/D conversion portion 
               30  PC 
               40  Inverter 
               41  Simulated load 
               50  Power conversion portion 
               50   j  Electric power line connection portion 
               51  Common inverter 
               51   c  MPPT control portion 
               53 ,  53 - 1 ,  53 - 2 ,  53 - n  Individual inverters