Patent Description:
A power generation device using wind power or hydraulic power is known. For example, <CIT> (<CIT> (PTL <NUM>)) discloses a wind power generation device that converts rotational energy of a windmill into electric energy by a generator connected to a main shaft of the windmill, performs power conversion to an output power of the generator, and outputs the power to a power supply target such as a grid. This wind power generation device is adapted to have a map indicating a relationship between a number of rotations of the windmill (generator) and output characteristics, and control the generator on the basis of a predetermined torque command pattern to thereby obtain a desired output power. From <CIT> (PTL <NUM>) a power generating system and its control method are known. A power controller calculates an induced voltage or rotor magnetic flux from an output voltage and an output current of a generator, estimates a shaft speed of the generator from a phase of the induced voltage or the phase of the rotor magnetic flux, and calculates the output of a windmill from the estimated value of the shaft speed and the output of the generator. In <CIT> an over speed control circuit for a wind turbine generator is disclosed. The over speed control circuit forms a closed feedback loop which periodically measures the output voltage of the wind turbine generator in order to regulate its speed by electronically controlling a load on the generator. The over speed control circuit in accordance with the present invention is adapted to work in conjunction with known over speed protection lock out relays. More particularly, the over speed control circuit causes a short circuit to be placed the generator terminals when the generator voltage reaches a threshold value, relatively less than the threshold value used to trigger the over speed lockout relay.

The output characteristics of the wind power generation device may vary, depending on an environment of a location where the wind power generation device is installed. Therefore, in a case where maximum efficiency is to be exhibited by the wind power generation device by the control according to the map, there is a possibility that in some location where the wind power generation device is installed, the wind power generation device does not exhibit the maximum efficiency. In the wind power generation device disclosed in PTL <NUM>, no consideration is given to variation in output characteristics depending on the environment of the installation location of the wind power generation device. A hydraulic power generation device structurally similar to the wind power generation device may also have the same problem as described above.

The present invention has been made to solve the above problem, and an object of the present invention is to provide a control device capable of controlling a power generation device to exhibit maximum efficiency in accordance with an environment of an installation location of the power generation device including a generator that converts rotational energy of a rotating body configured of a windmill or a waterwheel into electric energy.

According to the control device according to the present invention, there can be provided a control device capable of controlling a power generation device to exhibit maximum efficiency in accordance with an environment of an installation location of the power generation device including a generator that converts rotational energy of a rotating body configured of a windmill or a waterwheel into electric energy.

Hereinafter, referring to the drawings, embodiments of the present invention will be described in detail. Note that in figures, the same or corresponding parts are denoted by the same reference signs, and description thereof will not be repeated.

<FIG> is a block diagram illustrating a configuration example of a power generation system <NUM> according to a first embodiment. Power generation system <NUM> includes a wind power generation device <NUM> and a control device <NUM>. In power generation system <NUM> according to the first embodiment, control device <NUM> performs power conversion to a power generated by wind power generation device <NUM>, and supplies the converted power to a power supply target <NUM>.

Wind power generation device <NUM> includes a windmill <NUM>, a main shaft <NUM>, a speed increasing gear <NUM>, a generator <NUM>, and a first sensor group <NUM>. Windmill <NUM> is, for example, a horizontal axis windmill. Windmill <NUM> is provided at a tip of main shaft <NUM> and converts wind energy into rotational energy. Specifically, windmill <NUM> converts a wind power into a rotational torque and transmits the rotational torque to main shaft <NUM>. Note that windmill <NUM> may be a vertical axis windmill.

Main shaft <NUM> is connected to an input shaft of the speed increasing gear and is rotatably supported by a main bearing not illustrated. Main shaft <NUM> transmits the rotational torque from windmill <NUM> to the input shaft of speed increasing gear <NUM>.

Speed increasing gear <NUM> is provided between main shaft <NUM> and generator <NUM>. Speed increasing gear <NUM> increases a rotational speed of main shaft <NUM> and outputs the increased rotational speed to generator <NUM>. As an example, speed increasing gear <NUM> is configured of a gear speed increasing mechanism including a planetary gear, an intermediate shaft, a high-speed shaft, and the like.

Generator <NUM> is connected to an output shaft of speed increasing gear <NUM>. Generator <NUM> is configured of, for example, an induction generator, and generates an electric power by the rotational torque received from speed increasing gear <NUM>. That is, generator <NUM> converts the rotational energy of windmill <NUM> into electric energy.

First sensor group <NUM> includes a wind speed sensor <NUM> and a rotational speed sensor <NUM>. Wind speed sensor <NUM> detects a wind speed at a location where wind power generation device <NUM> is installed. Rotational speed sensor <NUM> detects the rotational speed of windmill <NUM> (rotational speed of main shaft <NUM>). Each sensor of first sensor group <NUM> outputs a detection result to control device <NUM>.

Control device <NUM> includes a power conversion device <NUM>, a second sensor group <NUM>, a storage device <NUM>, and a central processing unit (CPU) <NUM>.

Power conversion device <NUM> performs power conversion to the power output from generator <NUM> of wind power generation device <NUM> and outputs the power to power supply target <NUM>. Power supply target <NUM> includes a grid <NUM> and a battery <NUM>. That is, the power input from wind power generation device <NUM> to control device <NUM> is converted into a power corresponding to each of grid <NUM> and battery <NUM> by power conversion device <NUM>, and is supplied to grid <NUM> and battery <NUM>.

Battery <NUM> includes a plurality of stacked batteries. The battery is, for example, a secondary battery such as a nickel hydrogen battery or a lithium ion battery. Moreover, the battery may be a battery having a liquid electrolyte between a positive electrode and a negative electrode, or may be a battery having a solid electrolyte (all-solid battery). In addition, battery <NUM> includes a charger that converts the power supplied from control device <NUM> into a charging power for charging the battery.

Power conversion device <NUM> includes, for example, a converter, an inverter (neither is illustrated), and the like. The converter converts an AC power output from generator <NUM> into a DC power and outputs the DC power to the inverter. The inverter converts the DC power received from the converter into an AC power of a predetermined voltage and a predetermined frequency, and outputs the AC power to power supply target <NUM>.

Second sensor group <NUM> includes a voltage sensor <NUM> and a current sensor <NUM>. Voltage sensor <NUM> is configured to be able to detect a voltage of the power received from generator <NUM>. Current sensor <NUM> is configured to be able to detect a current of the power received from generator <NUM>. Voltage sensor <NUM> and current sensor <NUM> output detection results to CPU <NUM>.

Storage device <NUM> includes, for example, a read only memory (ROM), a random access memory (RAM), and the like. Storage device <NUM> stores various programs <NUM> that are executed by CPU <NUM>.

Moreover, a reference map <NUM> is stored in storage device <NUM>. Reference map <NUM> is a map indicating a relationship between an input voltage to control device <NUM> (power conversion device <NUM>) and an output power from control device <NUM> (power conversion device <NUM>). Reference map <NUM> indicates a theoretical (experimental) maximum output power of control device <NUM> with respect to the input voltage to the control device. For example, reference map <NUM> is generated on the basis of a test result, simulation, or the like at an arbitrary observation point, and is stored in storage device <NUM>. Details of reference map <NUM> will be described later with reference to <FIG>.

CPU <NUM> controls each of the devices in control device <NUM> by executing various programs <NUM> stored in storage device <NUM>. When controlling each of the devices in control device <NUM>, CPU <NUM> uses, for example, inputs from first sensor group <NUM>, second sensor group <NUM>, and the like. Note that the control performed by CPU <NUM> is not limited to processing by software, and can be constructed and processed by dedicated hardware (electronic circuit).

CPU <NUM> functions as an acquisition unit <NUM>, a monitoring unit <NUM>, an output control unit <NUM>, and an input control unit <NUM> by executing various programs <NUM>.

Acquisition unit <NUM> acquires the detection results from first sensor group <NUM> and second sensor group <NUM>. Acquisition unit <NUM> outputs the acquired detection results to monitoring unit <NUM>.

Monitoring unit <NUM> monitors a state of power generation system <NUM> on the basis of the detection results received from acquisition unit <NUM>. Monitoring unit <NUM> monitors, for example, the wind speed and the rotational speed of windmill <NUM> on the basis of the detection results of first sensor group <NUM>. Monitoring unit <NUM> monitors, for example, a state of generator <NUM> on the basis of the detection results of second sensor group <NUM>. In addition, monitoring unit <NUM> monitors whether or not a start condition and an end condition described later are satisfied. Monitoring unit <NUM> outputs monitoring results to output control unit <NUM> and input control unit <NUM>.

Input control unit <NUM> controls the state of generator <NUM> by controlling power conversion device <NUM>. Specifically, input control unit <NUM> can control the state of generator <NUM> by controlling power conversion device <NUM> to increase or decrease a load applied to generator <NUM>.

Output control unit <NUM> controls power conversion device <NUM> to supply desired power to power supply target <NUM>. Output control unit <NUM>, for example, controls power conversion device <NUM> to convert the power from generator <NUM> into an AC power of a predetermined voltage and a predetermined frequency, and outputs the desired power to grid <NUM>. Reference map <NUM> described above is used to control power conversion device <NUM>. Output control unit <NUM> controls the output power of power conversion device <NUM> in accordance with an input voltage (detection value of voltage sensor <NUM>) and reference map <NUM> stored in storage device <NUM>. Note that, hereinafter, the control of power conversion device <NUM> according to reference map <NUM> is also referred to as "normal control". This will be specifically described with reference to <FIG> and <FIG>.

<FIG> is a diagram illustrating one example of reference map <NUM>. A horizontal axis of <FIG> indicates an output voltage of generator <NUM>, that is, the input voltage to control device <NUM>. Note that the output voltage of generator <NUM> can be regarded as the rotational speed of generator <NUM>. Output power P of control device <NUM> is illustrated on a vertical axis of <FIG>.

When the wind rotates windmill <NUM>, a voltage corresponding to the rotational speed is output from generator <NUM>. CPU <NUM> acquires the output voltage of generator <NUM>, that is, the input voltage to control device <NUM> from voltage sensor <NUM>. CPU <NUM> collates the input voltage acquired from voltage sensor <NUM> with reference map <NUM> to obtain output power P of control device <NUM>. CPU <NUM> controls power conversion device <NUM> to output output power P. More specifically, for example, assuming that the input voltage is Vx, CPU <NUM> collates an input voltage Vx with reference map <NUM> to obtain an output power Px. CPU <NUM> controls power conversion device <NUM> to output output power Px. As a result, power Px is supplied from control device <NUM> to power supply target <NUM>. Theoretically, power generation system <NUM> can be operated at maximum efficiency by controlling power conversion device <NUM> to output the output power according to predetermined reference map <NUM>. Note that the maximum efficiency means that the maximum output power can be taken out from power generation system <NUM> at a certain wind power.

However, the output characteristics of wind power generation system <NUM> may vary depending on an environment of a location where wind power generation device <NUM> is installed. <FIG> is a diagram illustrating one example of the output characteristics of power generation system <NUM>. A horizontal axis of <FIG> indicates the input voltage to control device <NUM>. A vertical axis of <FIG> indicates output power P of control device <NUM>.

<FIG> illustrates the output characteristics of power generation system <NUM> at six wind speeds W1 to W6. Wind speeds W1 to W6 are wind speeds representing wind speed bands WB1 to WB6, respectively (for example, mean values in the wind speed bands). The wind bands include wind speeds that becomes higher in order of wind speed band WB1 < wind speed band WB2 < wind speed band WB3 < wind speed band WB4 < wind speed band WB5 < wind speed band WB6. That is, the wind speed becomes higher in order of wind speed W1 < wind speed W2 < wind speed W3 < wind speed W4 < wind speed W5 < wind speed W6.

Here, for example, it is assumed that the current wind speed is a wind speed included in wind speed band WB5. For example, assuming that the input voltage at this time is V5, control device <NUM> controls each of the units to operate at an operating point A5 in accordance with reference map <NUM>, and outputs output power P5. However, when the wind speed is a wind speed included in wind speed band WB5, the operating point (hereinafter also referred to as a "maximum efficiency point") at which power generation system <NUM> is operated at the maximum efficiency is an operating point B5. When generator <NUM> is operated at operating point B5 rather than operating point A5, a larger output power can be taken out from power generation system <NUM> (P5 < P5a). As described above, reference map <NUM> is generated on the basis of a test result, simulation, or the like at an arbitrary observation point. Therefore, although it is difficult to assume that the operating point largely deviates from the maximum efficiency point, depending on an environment of a location where wind power generation device <NUM> is installed, there may be an operating point at which the efficiency can be higher than an operating point according to reference map <NUM>. Power generation system <NUM> is desirably operated at the maximum efficiency point.

Therefore, control device <NUM> according to the first embodiment executes correction control for correcting reference map <NUM> when the start condition (described later) is satisfied. The correction control is control of searching for a maximum efficiency point at which a maximum output power can be taken out from power generation system <NUM> for each output voltage of generator <NUM> by maximum power point tracking (MPPT) control, and correcting reference map <NUM> to the searched maximum efficiency point. Referring to <FIG>, a specific example of the MPPT control will be described.

<FIG> is a diagram for describing the MPPT control. In <FIG>, the output characteristics of power generation system <NUM> at wind speed W5 in <FIG> are picked up and illustrated. It is assumed that the input voltage to control device <NUM> is V5 in the normal control before the start condition for starting the MPPT control is satisfied. In this case, control device <NUM> controls power conversion device <NUM> to output output power P5 in accordance with reference map <NUM>. That is, power generation system <NUM> is operated at operating point A5. Hereinafter, the operating point determined in accordance with reference map <NUM> is also referred to as a "reference operating point".

When the start condition is satisfied, control device <NUM> starts the MPPT control, increases or decreases the output voltage of generator <NUM> (input voltage to control device <NUM>) from voltage V5 by a predetermined voltage ΔV, and searches for an operating point at which the output power of power generation system <NUM> exceeds the maximum efficiency point. In the example of <FIG>, control device <NUM> starts the MPPT control when the start condition is satisfied, and controls power conversion device <NUM> to increase the output voltage of generator <NUM> (input voltage to control device <NUM>) from voltage V5 by predetermined voltage ΔV. That is, control device <NUM> controls power conversion device <NUM> such that power generation system <NUM> operates at operating point B5 (voltage V5 + ΔV). Control device <NUM> controls, for example, power conversion device <NUM> to adjust the load and controls the output voltage of generator <NUM>. Control device <NUM> calculates output power P5a of power generation system <NUM> at this time on the basis of the detection results of second sensor group <NUM> (voltage sensor <NUM> and current sensor <NUM>).

Control device <NUM> compares output power P5a with output power P5 of power generation system <NUM> when power generation system <NUM> is operated at reference operating point A5. Since output power P5a is larger than output power P5, control device <NUM> further increases the output voltage of generator <NUM> by predetermined voltage ΔV and continues the search for the maximum efficiency point. That is, control device <NUM> controls power conversion device <NUM> such that power generation system <NUM> operates at an operating point C5 (voltage V5 + 2ΔV).

Control device <NUM> calculates an output power P5b of power generation system <NUM> when power generation system <NUM> is operated at operating point C5. Control device <NUM> compares output power P5b with output power P5a. Since output power P5b is smaller than output power P5a, control device <NUM> decreases the output voltage of generator <NUM> from operating point C5 by predetermined voltage ΔV. That is, the operating point is set to operating point B5. Control device <NUM> determines the operating point at which the maximum output power can be taken out from power generation system <NUM> to be operating point B5, and maintains setting of the load such that power generation system <NUM> operates at operating point B5, that is, the output voltage of generator <NUM> is maintained.

Referring again to <FIG>, upon determining the maximum efficiency point at which the maximum output power can be taken out from generator <NUM>, control device <NUM> corrects reference map <NUM>. Specifically, control device <NUM> corrects the operating point at wind speed W5 from reference operating point A5 to operating point B5. The reference map is corrected by, for example, linear interpolation on the basis of a correction amount from operating point A5 to operating point B5. When reference map <NUM> is represented by a formula, the formula may be corrected on the basis of the correction amount. As a result, the reference map after correction may be obtained.

Power generation system <NUM> is controlled on the basis of corrected reference map <NUM>, which allows power generation system <NUM> to exhibit the maximum efficiency.

In the first embodiment, since reference map <NUM> as a base exists, the maximum efficiency point (operating point) at which the efficiency of power generation system <NUM> is maximized can be searched for early as compared with a case where reference map <NUM> as a base does not exist, and the correction control can be completed early. Therefore, the predetermined voltage ΔV is set small, and search accuracy of the maximum efficiency point can be improved. Even when predetermined voltage ΔV is set small, the correction control can be completed without requiring an excessive time. Specifically, in the case where reference map <NUM> as a base does not exist, it is necessary to perform the entire search in order to search for the maximum efficiency point, and it is necessary to set predetermined voltage ΔV described above, which is an operation amount per one time, to be large. This is because if predetermined voltage ΔV is set small in the entire search, when there is a change in the wind speed, the wind speed cannot follow the change, so that there is a possibility of causing excessive rotation of windmill <NUM>. When predetermined voltage ΔV is set large, the search accuracy of the operating point at which the maximum efficiency is obtained is lowered. In the first embodiment, reference map <NUM> serving as a base is stored in storage device <NUM> of control device <NUM>. Since it is assumed that the reference operating point of the reference map, and the maximum efficiency point do not greatly deviate from each other, by searching for the maximum efficiency point with the reference operating point serving as a base as described above, a so-called search range of the operating point (change range of the voltage of generator <NUM>) can be limited. Limiting the search range allows predetermined voltage ΔV to be set small. This can improve the search accuracy of the maximum efficiency point.

Next, the start condition of the correction control will be described. As the start condition, a first start condition and a second start condition described below can be applied. The start condition may be satisfied when the first start condition is satisfied, the start condition may be satisfied when both the first start condition and the second start condition are satisfied, or the start condition may be satisfied when either the first start condition or the second start condition is satisfied.

The first start condition is that a user has operated control device <NUM> (specifically, for example, an operation unit not illustrated).

The second start condition is that a threshold time has elapsed since the previous correction control was executed, the wind speed is equal to or less than the threshold wind speed, and the rotational speed of generator <NUM> is less than or equal to a threshold rotational speed. The threshold time is a time that can be appropriately set in accordance with the environment or the like of the location where wind power generation device <NUM> is installed. The threshold wind speed is a threshold value for restraining windmill <NUM> from reaching excessive rotation. The threshold wind speed may be set to, for example, an upper limit value of wind speed band WB6. The threshold rotational speed is a threshold value for confirming that generator <NUM> (windmill <NUM>) does not reach the excessive rotation.

For example, a timer not illustrated that is included in control device <NUM> is used for an elapsed time from the previous execution of the correction control. When the correction control ends and the control shifts to the normal control, the timer is activated by CPU <NUM>.

The detection result of wind speed sensor <NUM> is used as the wind speed to be compared with the threshold wind speed. The rotational speed of generator <NUM> to be compared to the threshold rotational speed is calculated on the basis of the output voltage of generator <NUM> detected by voltage sensor <NUM>. Alternatively, the rotational speed of generator <NUM> to be compared with the threshold rotational speed may be calculated on the basis of the rotational speed of windmill <NUM> (main shaft <NUM>) detected by rotational speed sensor <NUM>.

Next, the end condition of the correction control will be described. As the end condition, a first end condition and/or a second end condition described below can be applied. Alternatively, a third end condition to a fifth end condition may be appropriately combined with the first end condition and/or the second end condition.

The first end condition is that a preset set time has elapsed since the correction control was executed, and a number of times of the correction of reference map <NUM> has reached a preset set number of times. The set time is a time that can be appropriately set. As the set time, a time when at least one correction control can be completed is set. The set number of times is appropriately set to be greater than or equal to one.

The second end condition is that the wind speed band including the wind speed has changed and a rotational acceleration of windmill <NUM> has exceeded a threshold acceleration. The change in the wind speed band means that, for example, when the wind speed at the start of the correction control is included in wind speed band WB5, the wind speed has changed to the wind speed included in the other wind speed band (WB1 to WB4, WB6). The threshold acceleration is a threshold value for restraining windmill <NUM> from reaching excessive rotation. The rotational acceleration of windmill <NUM> can be calculated on the basis of, for example, the detection value of rotational speed sensor <NUM> or the detection value of voltage sensor <NUM>.

The third end condition is that an average wind speed has exceeded a threshold wind speed. The fourth end condition is that the rotational speed of generator <NUM> has exceeded a threshold rotational speed. The fifth end condition is that the output power from wind power generation device <NUM> (input power to control device <NUM>) has exceeded a rated power. The third end condition to the fifth end condition are set in order to restrain windmill <NUM> from reaching excessive rotation.

<FIG> is a flowchart illustrating a procedure of processing executed by CPU <NUM> of control device <NUM>. While each step (hereinafter, the step is abbreviated as "S") of the flowchart illustrated in <FIG> will be described in a case where it is implemented by software processing by CPU <NUM>, a part or all of the steps may be implemented by hardware (electric circuit) manufactured in CPU <NUM>. The processing of the flowchart in <FIG> is executed by CPU <NUM> at every predetermined control period.

CPU <NUM> determines whether or not the start condition is satisfied (S10). If the start condition is not satisfied (NO in S10), CPU <NUM> executes the normal control (S30).

On the other hand, if the start condition is satisfied (YES in S10), CPU <NUM> determines whether or not the end condition is satisfied (S20). If the end condition is satisfied (YES in S20), CPU <NUM> executes the normal control (S30). Note that if the start condition is satisfied, CPU <NUM> maintains the satisfaction of the start condition until the end condition is satisfied.

If the end condition is not satisfied (NO in S20), CPU <NUM> executes correction control (S40).

<FIG> is a flowchart illustrating a procedure of processing executed by CPU <NUM> of control device <NUM> in the normal control.

CPU <NUM> reads reference map <NUM> from storage device <NUM> (S301). Subsequently, CPU <NUM> acquires the input voltage (output voltage of generator <NUM>) to control device <NUM> from voltage sensor <NUM> of second sensor group <NUM> (S303). CPU <NUM> collates the input voltage acquired in S303 with reference map <NUM> read in S301 (S305). This allows CPU <NUM> to determine output power P of control device <NUM>.

CPU <NUM> controls power conversion device <NUM> to output output power P determined in S305 (S307). This allows power generation system <NUM> to be operated at the operating point according to reference map <NUM>.

<FIG> is a flowchart illustrating a procedure of processing executed by CPU <NUM> of control device <NUM> in the correction control.

First, CPU <NUM> executes the normal control (S30). This allows the operating point of power generation system <NUM> to be determined. CPU <NUM> executes the MPPT control with the above operating point as a start. Here, as one specific example, it is assumed that in S30, reference map <NUM> is read and the operating point of power generation system <NUM> is determined as reference operating point A5. CPU <NUM> sets voltage V5 at reference operating point A5 as a reference voltage Vref and sets output power P5 at reference operating point A5 as a reference power Pref (Vref = V5, Pref = P5), respectively.

CPU <NUM> changes the load on generator <NUM> such that an input voltage (output voltage of generator <NUM>) Vin to control device <NUM> increases by predetermined voltage ΔV (S401). Specifically, input voltage Vin to control device <NUM> is changed in accordance with the following formula (<NUM>) (Vin = V5 + ΔV).

CPU <NUM> acquires detection values (voltage and current) from second sensor group <NUM>, and calculates an output power Pa of power generation system <NUM> after the increase in the input voltage. CPU <NUM> compares output power Pa with reference power Pref (S403).

When output power Pa is larger than reference power Pref (YES in S403), CPU <NUM> updates the reference (S405). Specifically, CPU <NUM> updates reference power Pref to power Pa and updates reference voltage Vref to voltage Vin (= V5 + ΔV).

Subsequently, CPU <NUM> changes the operating point of power generation system <NUM> such that input voltage Vin to control device <NUM> increases by predetermined voltage ΔV (S407). That is, input voltage Vin is set to V5 + 2ΔV.

CPU <NUM> calculates output power Pa after execution of the processing in S407 and compares output power Pa with reference power Pref as in S403 (S409).

If output power Pa is larger than reference power Pref (YES in S409), CPU <NUM> returns the processing to S405 to continue the search for the operating point at which the output power is maximized.

On the other hand, if output power Pa is less than or equal to reference power Pref (NO in S409), CPU <NUM> updates the operating point of power generation system <NUM> such that input voltage Vin to control device <NUM> decreases by predetermined voltage ΔV (S411). CPU <NUM> maintains input voltage Vin, that is, the operating point of power generation system <NUM>.

CPU <NUM> determines the operating point of power generation system <NUM> in S411 as the maximum efficiency point, and corrects reference map <NUM> (S413). By controlling power conversion device <NUM> in accordance with reference map <NUM> after the correction, the maximum output power can be taken out from power generation system <NUM>, and power generation system <NUM> can exhibit the maximum efficiency.

If in step S403, output power Pa is less than or equal to reference power Pref (NO in S403), CPU <NUM> updates the operating point of power generation system <NUM> such that input voltage Vin to control device <NUM> decreases from reference voltage Vref by predetermined voltage ΔV (S415). Specifically, input voltage Vin to control device <NUM> is changed in accordance with the following formula (<NUM>) (Vin = V5 - ΔV).

CPU <NUM> calculates output power Pa after execution of the processing in S415 and compares output power Pa with reference power Pref as in S403 (S417).

If output power Pa is larger than reference power Pref (YES in S417), CPU <NUM> returns the processing to S415 to continue the search for the operating point at which the output power is maximized.

On the other hand, if output power Pa is less than or equal to reference power Pref (NO in S417), CPU <NUM> updates the operating point of power generation system <NUM> such that input voltage Vin to control device <NUM> increases by predetermined voltage ΔV (S419). CPU <NUM> maintains input voltage Vin, that is, the operating point of power generation system <NUM>.

CPU <NUM> determines the operating point of power generation system <NUM> in S419 as the maximum efficiency point, and corrects the reference map (S413). By controlling power conversion device <NUM> in accordance with reference map <NUM> after the correction, the maximum output power can be taken out from power generation system <NUM>, and power generation system <NUM> can exhibit the maximum efficiency.

As described above, control device <NUM> according to the first embodiment controls power conversion device <NUM> in accordance with reference map <NUM> indicating the relationship between the input voltage to control device <NUM> and the output power from control device <NUM>. Control device <NUM> executes the correction control and corrects reference map <NUM> so as to be optimal in accordance with the environment of the installation location of wind power generation device <NUM>. By correcting reference map <NUM> in accordance with the environment of the installation location of wind power generation device <NUM>, the maximum output power can be taken out from power generation system <NUM> regardless of the installation location, and power generation system <NUM> can exhibit the maximum efficiency.

Note that while an example in which power generation system <NUM> is a wind power generation system has been described above, power generation system <NUM> may be a hydraulic power generation system. In the case where power generation system <NUM> is a hydraulic power generation system, a hydraulic power generation device is applied instead of wind power generation device <NUM>.

In wind power generation, for example, a case is assumed in which a gust of wind occurs and the wind power increases suddenly. In such a case, it is desirable to perform control to prevent windmill <NUM> from reaching excessive rotation. In the correction control, as described above, the input voltage is changed by predetermined voltage ΔV at one time by the MPPT control. When the wind speed exceeding wind speed band WB6 in <FIG> is generated, there is a possibility that in the correction control, the control cannot cope with this, and windmill <NUM> reaches excessive rotation.

Therefore, control device <NUM> according to a first modification monitors the wind speed at the same time as the start of the correction control, and immediately ends the correction control when the wind speed exceeds a threshold value. The end of the correction control allows control device <NUM> to execute the normal control. While as described in the embodiment, the third end condition (that the average wind speed has exceeded the threshold wind speed) is set as the end condition of the correction control, according to the first modification, it is possible to cope with a sudden increase in wind power such as a gust of wind. The threshold value may be the same value as the threshold wind speed in the embodiment, or may be a value different from the value of the threshold wind speed.

In the normal control, control device <NUM> controls power generation system <NUM> in accordance with reference map <NUM> (if corrected, the reference map after the correction). Specifically, control device <NUM> controls power conversion device <NUM> in accordance with reference map <NUM>. If the wind speed has exceeded the threshold value (for example, wind speed band WB6), control device <NUM> controls power conversion device <NUM> to operate at reference operating point A6 (if corrected, operating point B6).

As a result, even if the wind power applied to windmill <NUM> increases, the load applied to generator <NUM> is increased so as to operate at the operating point (reference operating point A6) according to reference map <NUM>, and thus, it is possible to restrain windmill <NUM> from reaching excessive rotation.

<FIG> is a flowchart illustrating a procedure of processing executed by CPU <NUM> of control device <NUM> according to the first modification. This flowchart is started when the correction control is started.

CPU <NUM> acquires the detection value of wind speed sensor <NUM> (S51). CPU <NUM> compares the wind speed (current wind speed) acquired in S51 with the threshold value (S53).

If the wind speed is lower than or equal to the threshold value (NO in S53), CPU <NUM> returns the processing to S51 and continues the monitoring of the wind speed.

If the wind speed has exceeded the threshold value (YES in S53), CPU <NUM> ends the correction control (S55). This allows CPU <NUM> to execute the normal control.

As described above, according to the first modification, if the wind speed has exceeded the threshold value, the correction control is immediately ended and the control is switched to the normal control. In the normal control, power generation system <NUM> is controlled in accordance with reference map <NUM>. Even if the wind power applied to windmill <NUM> increases, the load applied to generator <NUM> is increased so as to operate at the operating point according to reference map <NUM>, and thus, it is possible to restrain windmill <NUM> from reaching excessive rotation.

While in the first modification, an example has been described in which if the wind speed has exceeded the threshold value, the correction control is immediately ended, and the control is switched to the normal control to restrain windmill <NUM> from reaching excessive rotation. However, if the wind speed has exceeded the threshold value, windmill <NUM> may be restrained from reaching excessive rotation by other means.

Referring again to <FIG>, wind power generation device <NUM> according to a second modification further includes a brake device <NUM> between speed increasing gear <NUM> and generator <NUM>. Brake device <NUM> is, for example, a disc brake.

If the wind speed has exceeded the threshold value, control device <NUM> activates brake device <NUM> to suppress the rotation of windmill <NUM>. This can restrain windmill <NUM> from reaching excessive rotation.

In the embodiment, an example in which the reference operating point of reference map <NUM> is corrected on the basis of one search result in the correction control has been described. However, the search may be performed a plurality of times, and the reference operating point of reference map <NUM> may be corrected on the basis of an average of search results.

For example, even if the wind speed falls within wind speed band WB5 during the execution of the correction control, the winds peed may fluctuate within the wind speed band WB5. Then, the operating point at which the efficiency of wind power generation device <NUM> can be maximized may be changed.

Therefore, the search is executed a plurality of times, and an average value of the output voltages of generator <NUM> at which output power P of wind power generation device <NUM> is maximized is calculated. On the basis of this average value, the operating point of generator <NUM> is determined. The reference operating point is corrected to the above-described operating point. This can improve accuracy of the correction of reference map <NUM>.

In the normal control in the first embodiment, the operating point is determined on the basis of the input voltage to control device <NUM> without considering the wind speed at that time. Specifically, the input voltage to control device <NUM> is collated with reference map <NUM> to determine the output power of control device <NUM>. However, in the normal control, the operating point may be determined in consideration of the wind speed. Note that a configuration of a power generation system according to a second embodiment is similar to that of the first embodiment, and thus, a description thereof will not be repeated.

Referring again to <FIG>, control device <NUM> (CPU <NUM>) according to the second embodiment determines an intersection between reference map <NUM> and each of the wind speeds (W1 to W6) as a reference operating point of power generation system <NUM> at each of the wind speeds. That is, in the second embodiment, the reference operating point is determined for each of the wind speeds. For example, the operating points such as A5, A6 represented by the intersections between reference map <NUM> and the respective wind speeds in <FIG> are determined as the reference operating points of power generation system <NUM>. In other words, in the second embodiment, the operating point of power generation system <NUM> is determined in according to the wind speed.

In the second embodiment, the reference operating point of power generation system <NUM> is determined for each of the wind speeds. Therefore, in the MPPT control, the search for the maximum efficiency point can be started from the reference operating point determined for each of the wind speeds. It is assumed that the reference operating point and the maximum operating point do not greatly deviate from each other, and the maximum efficiency point of power generation system <NUM> can be searched for earlier and the correction control can be completed earlier as compared with the first embodiment in which the operating point is determined on the basis of the input voltage to control device <NUM>.

<FIG> is a flowchart illustrating a procedure of processing executed by CPU <NUM> of control device <NUM> in normal control according to the second embodiment.

CPU <NUM> reads reference map <NUM> from storage device <NUM> (S311). Subsequently, CPU <NUM> acquires a current wind speed from wind speed sensor <NUM> of first sensor group <NUM> (S313). CPU <NUM> collates the wind speed acquired in S313 with reference map <NUM> read in S311 (S315). This allows CPU <NUM> to determine the operating point of power generation system <NUM>.

CPU <NUM> controls power conversion device <NUM> such that power generation system <NUM> operates at the operating point determined in S315 (S317). This allows power generation system <NUM> to be operated at the operating point according to reference map <NUM>.

In the MPPT control, the maximum efficiency point of power generation system <NUM> can be searched for earlier by starting the search for the maximum efficiency point from the operating point determined as described above.

In the second embodiment, upon determining the maximum efficiency point at a certain wind speed, control device <NUM> corrects the reference operating point at the wind speed. Specifically, referring to <FIG>, for example, when the current wind speed is wind speed W5, reference operating point A5 is corrected to B5. Control device <NUM> similarly corrects the reference operating point at each of the other wind speeds by the correction control when the wind at the wind speed occurs. Note that when the reference operating point at a certain wind speed is corrected, the other reference operating points may be corrected by a method described in a fourth modification below.

Depending on the wind speed band, frequency of occurrence of the wind at the relevant wind speed included in the wind speed band may be low. Typically, it is wind speed band WB6, which is a high wind speed band. If wind having the wind speed included in wind speed band WB6 does not occur, the correction control for wind speed band WB6 cannot be executed, and reference map <NUM> (specifically, the reference operating point of wind speed W6) cannot be corrected.

Therefore, for the operating point of the wind speed band (wind speed band WB6) that is expected to occur less frequently, the reference operating point in wind speed band WB6 may be corrected on the basis of a result of the correction control (corrected reference operating point) of the other wind speed band (for example, wind speed band WB5) and a relationship between the reference operating point of wind speed band WB5 and the reference operating point of wind speed band WB6 derived from initial (theoretical) reference map <NUM>. For example, when reference map <NUM> is generated, if reference map <NUM> is formulated, it is possible to correct the reference operating point of the wind speed band whose occurrence frequency is expected to be low by using the corrected reference operating point of the other wind speed band.

For example, wind speed band WB6 is set in advance as a wind speed band to be corrected by a mathematical formula. When the reference operating point of any of the wind speed bands other than wind speed band WB6 is corrected, the reference operating point of wind speed band WB6 can be corrected by using the corrected operating point and the mathematical formula. Note that the reference operating point of wind speed band WB6 may be corrected by using a plurality of corrected reference operating points and a mathematical formula.

It should be considered that the embodiments disclosed this time are examples in all respects and are not restrictive. The scope of the present invention is defined not by the description above but by the claims.

Claim 1:
A control device (<NUM>) for a power generation device (<NUM>) including a generator (<NUM>) that converts rotational energy of a rotating body configured of a windmill (<NUM>) or a waterwheel into electric energy, the control device (<NUM>) comprising:
a power converter (<NUM>) that converts an output power of the generator (<NUM>) into a power to be supplied to a power supply target (<NUM>);
a storage (<NUM>) that stores a reference map (<NUM>) defining a relationship between an input voltage from the generator (<NUM>) and an output power of the power converter (<NUM>); and
a controller that controls the power converter (<NUM>) to output a power according to the input voltage in accordance with the reference map (<NUM>), characterised in that
the controller is configured to be capable of executing correction control in which (i) a search for the input voltage at which the output power of the power converter (<NUM>) is maximized is started from an operating point according to the reference map, (ii) the operating point according to the reference map is corrected on the basis of a result of the search for the input voltage, and (iii) the reference map (<NUM>) is corrected on the basis of a correction amount of the operating point.