Abstract:
A method for determining a bearing of a wind turbine comprising, receiving a signal from a satellite at a first antenna disposed on a wind turbine, receiving the signal from the satellite at a second antenna disposed on the wind turbine, determining a position of the first antenna responsive to receiving the signal, determining a position of the second antenna responsive to receiving the signal, calculating a line of bearing intersecting the position of the first antenna and the position of the second antenna, determining an angle of the line of bearing relative to a reference bearing, and defining the bearing of the wind turbine as the angle of the line of bearing relative to the reference bearing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to wind turbines and methods and systems for determining a bearing direction of wind turbines. 
         [0002]    Wind turbines are often used to generate electrical power. Wind turbines are most effective when they face the direction of the wind and the wind is unobstructed. Since wind direction varies, wind turbines are designed to rotate to face the wind as the wind direction varies. Wind turbines are disposed in grid patterns that are designed to efficiently utilize the prevailing winds in a given location. As the direction of the wind changes, the wind turbine rotates, however some wind directions may result in obstructions (e.g., natural, man made, or other wind turbines in the array) causing undesirable wind turbulence (wake effect) to particular turbines in an array. If the direction of a wind turbine is accurately known, the operation of the array may be adjusted to compensate for a given wind direction, allowing the entire array to operate more efficiently. 
         [0003]    Previous methods of determining a direction that a wind turbine faces (bearing) are inaccurate with a degree of error of up to ±10 degrees. Accurately determining and controlling the bearing of wind turbines increases the efficiency of the wind turbines. A system and method that economically and effectively determines a bearing of a wind turbine is desired. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of the invention, method for determining a bearing of a wind turbine comprising, receiving a signal from a satellite at a first antenna disposed on a wind turbine, receiving the signal from the satellite at a second antenna disposed on the wind turbine, determining a position of the first antenna responsive to receiving the signal, determining a position of the second antenna responsive to receiving the signal, calculating a line of bearing intersecting the position of the first antenna and the position of the second antenna, determining an angle of the line of bearing relative to a reference bearing, and defining the bearing of the wind turbine as the angle of the line of bearing relative to the reference bearing. 
         [0005]    According to another aspect of the invention, A wind turbine system comprising, a wind turbine, a controller operative to control an operation of the wind turbine, a first antenna disposed on the wind turbine operative to receive a signal from a satellite, a second antenna disposed on the wind turbine operative to receive the signal from the satellite, and a processor communicatively connected to the controller, the first antenna, and the second antenna, operative to process the signal received from the first antenna and determine a position of the first antenna, process the signal received from the second antenna and determine a position of the second antenna, calculate a line of bearing intersecting the position of the first antenna and the position of the second antenna, determine an angle of the line of bearing relative to a reference bearing, define the bearing of the wind turbine as the angle of the line of bearing relative to the reference bearing, and send the defined bearing of the wind turbine to the controller. 
         [0006]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0008]      FIG. 1  illustrates an example of a wind turbine array. 
           [0009]      FIG. 2  illustrates a side view of exemplary embodiment of a wind turbine system. 
           [0010]      FIG. 3  illustrates a top view of the wind turbine system of  FIG. 2 . 
       
    
    
       [0011]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Wind turbines generate electrical power for electrical systems. Often, a number of wind turbines are arranged in an array over a geographical space to more efficiently harness wind power. Wind turbines are more efficient when they directly face a direction of the wind (wind bearing). Because the direction of the wind changes, the wind turbines may rotate the bearing of the wind turbine (turbine bearing) to face the wind bearing. Accurately determining the turbine bearing relative to a known reference bearing, for example true North is desirable to increase the efficiency of wind turbines and wind turbine arrays. 
         [0013]      FIG. 1  illustrates an example of a wind turbine array  100 . The array  100  includes a row of wind turbines  102 . Line  104  illustrates a line of bearing that corresponds to the turbine bearing. The upper illustration depicts an example of an orientation of the array  100  when the wind direction is perpendicular to the array. When the wind direction is perpendicular to the array, there are no obstructions to the wind that turns the wind turbines  102 . The lower illustration depicts an example of the orientation of the array  100  when the wind direction has shifted to being parallel to the array  100 . In the lower illustration, the right most wind turbine  102  obstructs the flow of wind. The obstruction may cause undesirable turbulence in the other wind turbines  102  of the array  100 . To more efficiently produce electrical power, control systems may be used to disable particular wind turbines  102  that are subjected to (or cause) turbulent wind flow when the wind is prevailing from a particular wind bearing. 
         [0014]    In general operation, a controller determines a wind bearing and directs the wind turbines to rotate such that the turbine bearing is reciprocal to the wind bearing. The controller may compare the wind bearing to a data base to determine if at a given wind bearing a particular wind turbine should be disabled to mitigate the effects of turbulent wind on the array. Disabling particular wind turbines for a given wind bearing may reduce the overall effects of turbulent wind on the array and increase the net power output of the array. 
         [0015]    Accurate determination of the wind bearing and the turbine bearing of each wind turbine in an array increases the efficiency of the array. Previous methods of determining turbine bearing relied on a position sensor in the wind turbine that was used to determine a bearing of the wind turbine relative to a fixed reference bearing of a base of the wind turbine. The position sensor was calibrated by a technician using a hand held magnetic compass and a visual reference. Usually the calibration procedure is performed while the technician is standing at the base of a tower of the wind turbine up to 100 meters from the rotating turbine. The laborious method resulted in inaccuracies due to human error and inaccurate measuring procedures that approached ±10 degrees. Thus, a manually calibrated wind turbine may send inaccurate turbine bearing measurements that result in a loss of array efficiency. 
         [0016]      FIG. 2  illustrates a side view of exemplary embodiment of a wind turbine system  200 . The wind turbine system  200  includes a nacelle portion  202  that houses a generator (not shown) connected to a rotor assembly  204 . The nacelle portion  202  is connected to a tower  206 . The nacelle portion  202  is operative to rotate relative to the tower  206 . The operations of the wind turbine system may be controlled with a controller  201  that may include a processor. The controller  201  is communicatively linked to the electrical and mechanical systems in the nacelle portion  202  and may be used, for example, to control the rotation of the nacelle portion  202  relative to the tower  206 . 
         [0017]    Though a magnetic compass system may be placed in the nacelle portion  202  to directly measure the wind turbine bearing, the use of a magnetic compass system presents a few drawbacks. The performance of a magnetic compass system depends on the magnetic fields measured by the magnetic compass system. The fields from the electrical generator in the nacelle, the rotating rotor assembly, and the metal structure of the wind turbine all affect the magnetic fields measured by the magnetic compass system. Additionally, magnetic compasses determine magnetic North, which is not the same as true North (located at the North Pole). The magnetic fields of the Earth are variable depending on geographical location and further change over time. Thus, to accurately determine magnetic North, a magnetic compass is calibrated to correct for geographical location. To determine true North from a magnetic North determination, calculations are performed to correct for a change in the position of magnetic North over time. 
         [0018]    Referring to  FIG. 2 , the wind turbine system  200  further includes a first antenna  208  and a second antenna  210  the first antenna  208  and the second antenna  210  are communicatively linked to the controller  201  that is operative to process signals received from the first antenna  208  and the second antenna  210 . Satellites  203  are shown that send signals  205  used to determine a geographical position. The satellites  203  may be, for example, Global Positioning System (GPS) satellites. In the illustrated embodiment, the first antenna  208 , the second antenna  210 , and the controller  201  are compatible with the GPS system. 
         [0019]      FIG. 3  illustrates a top view of the wind turbine system  200 . In operation, the first antenna  208  and the second antenna  210  receive signals from the satellites  203 . The signals are sent to the controller  201  (of  FIG. 2 ) that processes the signals and determines a geographical position of the first antenna  208  and a geographical position of the second antenna  210 . Once the geographical positions of each of the antennas are known, a line of bearing  304  may be calculated that intersects the geographical position of the first antenna  208  and a geographical position of the second antenna  210 . In the illustrated embodiment, the first antenna  208  and the second antenna  210  are positioned in a line that is parallel to an axis of rotation of the rotor assembly  204 . Thus, the line of bearing  302  corresponds to the axis of rotation of the rotor assembly  204 . Once the line of bearing  302  is calculated, an angle (b) of the line of bearing relative to a reference bearing  304  may be calculated. Once b is calculated, the bearing of the axis of rotation of the rotor assembly  204  has been accurately determined. 
         [0020]    In the illustrated embodiment, the reference bearing  304  is true north; however other embodiments may use an alternative reference bearing. When true North defines the reference bearing, the line of bearing  302  is a true bearing. 
         [0021]    Other embodiments may include antennas that are not parallel to the axis of rotation of the rotor assembly  204 . If the antennas are not parallel to the axis of rotation of the rotor assembly  204 , the controller  201  may process an algorithm that adjusts for the location of the antennas relative to the axis of rotation of the rotor assembly  204  resulting in a second line of bearing that corresponds to the axis of rotation of the rotor assembly  204 . The second line of bearing is then used to calculate the angle (b). 
         [0022]    Once the bearing of the axis of rotation of the rotor assembly  204  has been accurately determined, the controller  201  (of  FIG. 2 ) may be used to control the wind turbine system  200  to more efficiently operate in an array. If the wind direction is known, the controller may direct the wind turbine to rotate the axis of rotation of the rotor assembly  204  (via rotating the nacelle portion  202 ) to face the wind direction. The controller  201  may also determine that for a given wind bearing threshold, the wake effect on wind turbine array may be reduced if the wind turbine system  200  is halted or operated power curtailed, reducing the net wake effect on the array and increasing the electrical power output of the array. 
         [0023]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.