Power generation system control device

Abstract

To stop brake action at a timing when generation efficiency is not lowered, while suppressing an increase in costs.SOLUTION: A generation system is equipped with a rotator, a generator, a brake circuit, a voltage sensor, and a control device. The control device executes brake action by the brake circuit when the rotation speed of the rotator exceeds a first threshold value. After the rotation speed of the rotator falls below the first threshold value, when a releasing condition determined based on at least one of the value of generation voltage detected by the voltage sensor and the rotation speed of the rotator is established, the control device stops the brake action by the brake circuit.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a control device for a power generation system, and more particularly to brake control in wind and hydroelectric power generation systems. [Background technology]

[0002] Conventionally, in wind power generation systems, when strong winds occur due to a typhoon or other event, causing the rotational speed of the wind turbine to become too fast, braking is initiated on the wind turbine for mechanical protection, and braking is continued until the wind speed subsides. Such wind power generation systems sometimes use an anemometer to determine whether the wind speed has sufficiently weakened to enable safe power generation. When the anemometer measurement falls below a certain threshold, the wind power generation system stops braking from a state in which braking is continuously performed, and continues rotating the wind turbine to perform normal power generation control. Hereinafter, stopping braking from a state in which braking is continuously performed may be referred to as "releasing the brake." In wind power generation systems that do not have an anemometer, the wind power generation system stops braking when a predetermined period of time has elapsed since braking began. The same phenomenon can be seen in hydroelectric power generation systems.

[0003] The wind turbine generator described in International Publication No. 2012 / 164637 (Patent Document 1) starts the electric brake operation when strong winds occur, and then determines the timing to stop the electric brake operation based on the temperature of the wind turbine generator body surface, the temperature of the resistors, the temperature of the cables, etc. This effectively prevents the wind turbine generator of Patent Document 1 from frequently switching between starting and stopping the electric brake operation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 164637 Summary of the Invention [Problem to be solved by the invention]

[0005] If the electric brake is continuously applied in response to the occurrence of strong winds, power generation efficiency may decrease depending on the timing of stopping the electric brake. For example, if the electric brake is stopped after a predetermined period of time has elapsed, if the predetermined period is too long, there may be a period during which normal power generation control cannot be started even though the wind speed has sufficiently weakened, resulting in a decrease in power generation efficiency.

[0006] In contrast, if an anemometer is used to determine when to stop the operation of the electric brake, it becomes easy to determine whether the wind speed has weakened sufficiently, but the cost of installing the anemometer increases. Also, installing a water flow meter in a hydroelectric power generation system increases costs. The wind power generation system of Patent Document 1 also requires installing multiple temperature sensors to detect the temperatures of multiple heat sources, which may increase costs.

[0007] The present disclosure has been made to solve such problems, and its purpose is to stop braking operation in a control device for a power generation system equipped with an electric brake at a timing that does not reduce power generation efficiency while suppressing increases in costs. [Means for solving the problem]

[0008] A control device according to the present disclosure is a control device for controlling a power generation system that supplies electric power to a supply target. The power generation system includes a rotating body, a generator, a brake circuit, a voltage sensor, and a control device. The generator is rotated by the rotating body and generates three-phase AC power. The brake circuit is connected to the generator and generates a braking force on the rotating body by short-circuiting the phases. The voltage sensor detects the value of the generated voltage of the generator. The control device controls the brake circuit. When the rotational speed of the rotating body exceeds a first threshold, the control device performs a braking operation using the brake circuit. After the rotational speed of the rotating body falls below the first threshold, the control device stops the braking operation using the brake circuit when a release condition is met that is determined based on at least one of the value of the generated voltage detected by the voltage sensor and the rotational speed of the rotating body. [Effects of the Invention]

[0009] A control device for a power generation system according to the present disclosure decelerates the rotor using a brake circuit when the rotational speed of the rotor exceeds a first threshold. The control device then estimates the wind speed based on the power generation voltage of the generator, and releases the brake circuit when it estimates that the wind speed will not again exceed the first threshold even if the brake circuit is released. This allows the control device for a power generation system to estimate the wind speed using a voltage sensor required for power generation control, without providing an anemometer or temperature sensor. Therefore, the control device for a power generation system can release the brake at a timing that does not reduce power generation efficiency while suppressing increases in costs. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a configuration of a wind power generation system according to a first embodiment. [Figure 2] FIG. 4 is a diagram for explaining a braking operation by a braking circuit. [Figure 3] FIG. 10 is a diagram showing the configuration of a modified example of a brake circuit. [Figure 4]FIG. 2 is a block diagram for explaining the function of the wind power generation system. [Figure 5] FIG. 10 is a diagram for explaining map control. [Figure 6] FIG. 1 is a diagram for explaining the relationship between wind speed and voltage in wind power generation. [Figure 7] 10 is a flowchart illustrating an example of releasing an electric brake using a voltage sensor. [Figure 8] FIG. 10 is a diagram for explaining that the relationship between voltage and wind speed changes due to a change in resistance value. [Figure 9] 10A and 10B are diagrams illustrating an example in which the detected value of the voltage sensor VS is corrected based on temperature. [Figure 10] FIG. 1 is a diagram illustrating the configuration of a wind power generation system for acquiring a learning model. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0012] [Embodiment 1] FIG. 1 is a schematic diagram showing the configuration of a wind power generation system 100 according to the first embodiment. The wind power generation system 100 is an example of a horizontal axis (propeller) wind power generation system. As shown in FIG. 1, the wind power generation system 100 includes a wind turbine 1, a generator 3, and a control device 5. When the power generation system of this embodiment is a hydroelectric power generation system, a water turbine is provided instead of the wind turbine 1.

[0013] The wind turbine 1 includes a main shaft 2. The generator 3 includes a three-phase synchronous generator that uses permanent magnets. The generator 3 is fastened to the main shaft 2 with a coupling or the like. If necessary, a step-up gear may be provided between the main shaft 2 and the generator 3. The wind turbine 1 is rotated by the kinetic energy of the wind, and the main shaft 2 rotates the generator 3. In the wind power generation system 100, a control device 5 is connected to the generator 3 via a brake circuit 4. The generator 3 sends generated power to the control device 5 via the brake circuit 4. The generated power is converted by the control device 5 into DC power or AC power of a different frequency, and then supplied to a power supply target 6. The power supply target 6 is, for example, a battery or a grid power supply.

[0014] FIG. 2 is a diagram illustrating the braking operation by the brake circuit 4. The generator 3 outputs the generated power generated by its rotational operation as three-phase (U-phase, V-phase, and W-phase) generated power to power lines Pu, Pv, and Pw, respectively. The control device 5 includes a power conversion unit 51. A rectifier circuit 51R included in the power conversion unit 51 receives the three-phase generated power from power lines Pu, Pv, and Pw, respectively. The rectifier circuit 51R is an AC (Alternate Current) / DC (Direct Current) converter. The rectifier circuit 51R converts the three-phase generated power into DC power. A voltage sensor VS detects the generated voltage of the generator 3.

[0015] The brake circuit 4 includes a switch Sw1, a switch Sw2, a switch Sw3, and resistors R1, R2, and R3. The switch Sw1 and the resistor R1 are connected in series between the power line Pu and the power line Pv. The switch Sw2 and the resistor R2 are connected in series between the power line Pv and the power line Pw. The switch Sw3 and the resistor R3 are connected in series between the power line Pw and the power line Pu.

[0016] The control device 5 closes the switches Sw1 to Sw3 of the brake circuit 4 to generate an electrical braking force and reduce the rotational speed of the wind turbine 1. By shorting the phases of the generator 3 with the brake circuit 4, a current due to the electromotive voltage generated by power generation flows in the armature of the generator 3. Electromagnetic induction caused by this current generates a braking force that acts in the opposite direction to the direction in which the armature rotates due to the wind. Hereinafter, the brake that shorts the phases with the brake circuit 4 and applies a braking force to the wind turbine 1 will be referred to as the "electric brake." Also, shorting the phases with the brake circuit 4 will be referred to as "activating the electric brake." Also, opening the switches Sw1 to Sw3 of the brake circuit 4 will be referred to as "stopping the electric brake" and "releasing the brake."

[0017] In Figure 2, a configuration has been described in which the phases of the power lines Pu, Pv, and Pw are short-circuited to activate the electric brake, but as shown in Figure 3, the electric brake may also be activated by short-circuiting between the power lines Pu to Pw and the earth.

[0018] Fig. 3 is a diagram showing the configuration of a modified brake circuit. Fig. 3 shows a brake circuit 4 in which switches Sw1 to Sw3 are provided between the power lines Pu, Pw, Pv and the ground, respectively. In the configuration shown in Fig. 3 as well, when the switches Sw1 to Sw3 are closed in response to a control signal from the control device 5, the phases of the generator 3 are short-circuited via the ground and current flows in the armature. This makes it possible to generate a braking force for the wind turbine 1. The brake circuit 4 is provided with a current sensor IS2 that measures the value of the current.

[0019] 4 is a block diagram for explaining the functions of the wind power generation system 100. The control device 5 includes a power conversion unit 51 and a control unit 52. The power conversion unit 51 converts the generated power received from the power lines Pu, Pv, and Pw shown in FIG. 2 into a format for supply to the supply target 6.

[0020] The power conversion unit 51 also includes an internal sensor unit InS and a rectifier circuit 51R. The internal sensor unit InS includes a voltage sensor VS and a current sensor IS. The voltage sensor VS detects the rectified voltage generated by the generator 3. The current sensor IS detects the current flowing through the circuit within the power conversion unit 51. The rectifier circuit 51R converts the three-phase generated power received by the control device 5 into DC power.

[0021] The control unit 52 includes an electric brake control unit EB and a calculation unit 53. The calculation unit 53 includes a CPU (Central Processing Unit) and a memory (neither of which are shown). As described in FIG. 1, in the wind power generation system 100, a braking force is generated against the rotation of the wind turbine 1 by shorting the phases using the brake circuit 4. That is, a braking force is generated against the rotation of the wind turbine 1 by closing the switches Sw1 to Sw3 of the brake circuit 4 by a control signal from the electric brake control unit EB.

[0022] The calculation unit 53 receives detection signals from the external sensor unit ExS and the temperature sensor 41. The external sensor unit ExS includes a tachometer 11 and a torque meter 12. The tachometer 11 measures the rotation speed of the wind turbine 1. The torque meter 12 detects the torque generated in the wind turbine 1 by the wind. The temperature sensor 41 detects the temperature of the brake circuit 4 including the resistors R1 to R3. If the supply target 6 is a battery, the external sensor unit ExS may be configured to be able to detect the charge amount of the supply target 6.

[0023] FIG. 5 is a diagram for explaining map control. The horizontal axis in FIG. 5 represents the rotational speed of the wind turbine 1, and the vertical axis in FIG. 5 represents the output value (generated power) of the generator 3. In map control, the output value of the generator 3 is controlled by adjusting the duty ratio when performing switching control to a duty ratio that is determined in advance according to the rotational speed. This allows the control device 5 to uniquely determine the output value of the generator 3 for a certain rotational speed. For example, when the wind turbine 1 is rotating at a rotational speed a, the generator 3 outputs an output value b.

[0024] The rotational speed L shown in FIG. 5 is the rotational speed at which cutout is performed. Cutout is a mechanical and electrical protection function for preventing over-rotation of the wind turbine 1. If the wind turbine 1 rotates at a speed faster than a certain speed from a mechanical and electrical perspective, the mechanical and electrical reliability of the wind turbine 1 will decrease. Hereinafter, the state in which the wind turbine 1 rotates at a rotational speed that decreases its mechanical and electrical reliability will be referred to as "over-rotation." In the wind power generation system 100, to prevent over-rotation of the wind turbine 1, a braking force is generated on the wind turbine 1 to slow it down. The rotational speed L is predetermined based on the allowable rotational speed determined by the mechanical and electrical specifications of the wind turbine 1. Note that the rotational speed L may be set to a speed slower than the allowable rotational speed rather than the allowable rotational speed itself. It is desirable to set the rotational speed L at a speed at which sufficient deceleration can be achieved by continuously operating the electric brake. For example, there may be cases in which the mechanical strength of the wind turbine 1 is high and the rotational speed L can be set to a high speed. However, if rotational speed L is too high when cutout is performed, the torque acting due to the wind may exceed the braking force of the electric brake, making it impossible to sufficiently slow down the rotational speed of the wind turbine 1. For this reason, rotational speed L is set as a speed that can at least slow down the rotational speed of the wind turbine 1 when the electric brake is activated.

[0025] The timing at which the cutout is performed may also be determined based on the electrical tolerance range (rated voltage, rated current, etc.) set for the power conversion unit 51. This is because if a voltage exceeding the tolerance range is applied to the power conversion unit 51, a malfunction of the power conversion unit 51 may occur. In this case, the timing at which the cutout is performed is determined depending on whether the value of the output value M is within the tolerance range of the power conversion unit 51.

[0026] In this way, when strong winds occur in wind power generation system 100, the rotational speed of wind turbine 1 is reduced based on the rotational speed of wind turbine 1 or the power generated by generator 3 from the standpoint of mechanical and electrical protection. That is, when wind turbine 1 rotates at rotational speed L, control device 5 shorts the phases of generator 3 using brake circuit 4, and starts operating the electric brake. After starting operation of the electric brake, control device 5 of wind power generation system 100 of this embodiment continues to operate the electric brake until a release condition is met.

[0027] Due to the characteristics of the electric brake, if the wind turbine 1 is exposed to wind while the phases are short-circuited by the brake circuit 4, the rotation of the wind turbine 1 will not stop completely. After cutout is performed, the electric brake continues to operate, so the rotation speed of the wind turbine 1 gradually decelerates from rotation speed L. After that, an equilibrium state is reached when the braking force applied by the electric brake and the torque caused by the wind to rotate the main shaft 2 are balanced. As described above, the electric brake generates braking force using the electrical energy that acts on the armature of the generator 3 when exposed to wind.

[0028] Even when the wind turbine 1 reaches equilibrium, it continues to rotate at a relatively slow rotational speed due to the characteristics of the electric brake, which has internal resistance. The rotational speed of the wind turbine 1 in equilibrium is affected by the wind speed. That is, if the wind speed in equilibrium is high, the torque that rotates the main shaft 2 increases, and the wind turbine 1 continues to rotate at a predetermined speed even in equilibrium. On the other hand, if the wind speed in equilibrium is low, the torque that rotates the main shaft 2 decreases, and the wind turbine 1 rotates at a speed close to that of a stopped state in equilibrium. In this way, the electric brake is activated when a strong wind occurs, and the rotation of the wind turbine 1 can be maintained at a speed slower than rotational speed L, thereby protecting the wind turbine 1 mechanically and electrically.

[0029] If the timing for releasing the electric brake is inappropriate, the power generation efficiency of the wind power generation system 100 may decrease or the wind turbine 1 may be damaged. For example, if the timing for releasing the electric brake is too late, the wind turbine 1 may not be able to rotate even though the wind speed has weakened enough to allow normal power generation control. In this case, even though the wind speed has weakened sufficiently to prevent the wind turbine 1 from over-rotating, the electric brake continues to operate, making it impossible to perform normal power generation control. This reduces power generation efficiency.

[0030] Furthermore, if the electric brake is released too early, the wind turbine 1 will start rotating even though the wind speed has not yet weakened sufficiently. With the braking force no longer acting on the wind turbine 1, the wind turbine 1 will accelerate in rotation due to strong winds, causing over-rotation and causing cutout to be executed again. In other words, if the electric brake is released too early, the process of releasing the electric brake and cutout will be repeated frequently. As a result, the electric brake operation will be started and stopped frequently, and the rotation of the wind turbine 1 will be accelerated and decelerated repeatedly. This will result in excessive repetition of the opening and closing operations of the switches Sw1 to Sw3, which may accelerate deterioration of the brake circuit 4. Furthermore, excessive repetition of acceleration and deceleration of the wind turbine 1 may accelerate deterioration of the wind turbine 1.

[0031] Therefore, in the wind power generation system 100, it is desirable to release the operation of the electric brake when the wind speed has weakened to the point where the wind turbine 1 does not over-rotate. While an anemometer can be used to determine the wind speed, anemometers are relatively expensive and can increase costs. Below, we will explain control that determines the timing to release the electric brake in the wind power generation system 100 of this embodiment without using an anemometer.

[0032] FIG. 6 is a diagram illustrating the relationship between wind speed and voltage in wind power generation. FIG. 6(a) is a diagram illustrating the relationship with the torque acting on the main shaft 2 due to wind. The wind speed is the wind speed around the wind turbine 1. The torque is the torque acting on the main shaft 2 included in the wind turbine 1 due to the wind. The torque is detected by a torque meter 12. As shown in FIG. 6(a), in wind power generation, the torque acting on the main shaft 2 due to the wind is generally proportional to the square of the wind speed.

[0033] FIG. 6(b) shows the relationship between current and torque. The current shown in FIG. 6(b) is the current generated by the generator 3. As shown in FIG. 6(b), in wind power generation, the torque acting on the main shaft 2 due to wind is generally proportional to the current flowing through the generator 3. Furthermore, when the resistance is constant, the current is proportional to the voltage. Therefore, by considering the relationship between the detected value of the voltage sensor VS and the wind speed based on the relationship shown in FIG. 6(a) and FIG. 6(b), we can derive the relationship shown in FIG. 6(c), in which the voltage is proportional to the square of the wind speed. Therefore, by using the relationship between voltage and wind speed shown in FIG. 6(c), the wind speed can be uniquely estimated from the detected value of the voltage sensor VS. As mentioned above, due to the characteristics of the electric brake, if a strong wind occurs while the electric brake is still operating after braking due to cutout, the wind turbine 1 does not completely stop rotating but continues to rotate at a relatively slow speed. Therefore, the relationship between voltage and wind speed shown in FIG. 6(c) holds even when the electric brake is engaged.

[0034] The reference wind speed shown in Figure 6(c) refers to the wind speed at which the wind turbine 1 will not accelerate to rotational speed L even if the electric brake is released in an equilibrium state after braking is performed due to cutout. In other words, even if the electric brake is released when the rotational speed of the wind turbine 1 reaches the reference speed, the control device 5 can determine that normal power generation control can be performed without frequently starting and stopping the electric brake. The reference wind speed is determined appropriately through experiments using actual equipment or simulations. As shown in Figure 6(c), at the reference wind speed, the detection value of the voltage sensor VS is the voltage value Vth. Therefore, the release condition for releasing the electric brake is when the detection value of the voltage sensor VS falls below the voltage value Vth.

[0035] In the wind power generation system 100 of this embodiment, without using an anemometer, the relationship between the detected value of the voltage sensor VS and the wind speed shown in Figure 6(c) is used to determine whether the wind speed has fallen below a reference wind speed from the detected value of the voltage sensor VS. This allows the wind power generation system 100 to release the electric brake, which was activated due to the occurrence of strong winds, at an appropriate timing. If the electric brake were released when the wind speed was above the reference wind speed, the electric brake would be frequently started and stopped, which would accelerate deterioration of the wind turbine 1.

[0036] Furthermore, if the operation of the electric brake is not released even when the wind speed is below the reference wind speed, normal power generation control cannot be performed, resulting in a decrease in power generation efficiency. In the wind power generation system 100, the decrease in power generation efficiency can also be suppressed by releasing the brake when the wind speed falls below the reference wind speed. Since a voltage sensor VS used for power conversion is used without providing an anemometer, it is possible to realize a wind power generation system 100 that performs brake control while suppressing increases in costs.

[0037] Furthermore, since the number of turns of the coil of the generator 3 is constant, the rotation speed of the rotor of the generator 3 is proportional to the induced electromotive force. That is, the control device 5 can derive the wind speed based on the rotation speed measured by the tachometer 11 without using the voltage sensor VS. For example, as shown in FIG. 6(c), the control device 5 can determine that the detected value of the voltage sensor VS is the voltage value Vth when the rotation speed reaches Rth. The wind power generation system 100 can use the rotation speed Rth to determine whether it is the reference wind speed.

[0038] 7 is a flowchart illustrating an example of releasing the electric brake using the voltage sensor VS after the start of braking due to cutout. The control device 5 determines whether the rotational speed of the wind turbine 1 has exceeded a predetermined rotational speed L (step S11). If the rotational speed of the wind turbine 1 is equal to or less than rotational speed L (NO in step S11), the control device 5 repeats the process of step S11. In other words, it is determined that no strong wind is occurring, and the wind power generation system 100 performs normal power generation control.

[0039] If the rotational speed of the wind turbine 1 exceeds rotational speed L (YES in step S11), the control device 5 starts the operation of the electric brake (step S12). That is, the control device 5 controls the electric brake control unit EB to close the switches Sw1 to Sw3 of the brake circuit. The electric brake is configured to generate a braking force sufficient to decelerate the rotational speed of the wind turbine 1, which rotates at rotational speed L. As a result, the rotational speed of the wind turbine 1 becomes slower than rotational speed L.

[0040] After step S12, while the electric brake continues to operate, as explained above, the braking force and the torque acting due to the wind are in equilibrium, and the wind turbine 1 rotates at a relatively slow speed. The control device 5 determines whether the release condition is met based on the detection value of the voltage sensor VS or the rotation speed in the equilibrium state (step S13).

[0041] In this embodiment, the release condition is that the detection value of the voltage sensor VS falls below the voltage value Vth. The release condition may also be that the rotation speed falls below the rotation speed Rth. Alternatively, the release condition may be that both the detection value of the voltage sensor VS falls below the voltage value Vth and the rotation speed falls below the rotation speed ThR are satisfied.

[0042] The control device 5 determines whether the detection value of the voltage sensor VS detected by the voltage sensor VS has fallen below the voltage value Vth. If the detection value of the voltage sensor VS is equal to or greater than the voltage value Vth (NO in step S13), the control device 5 repeats the process of step S13. If the detection value of the voltage sensor VS has fallen below the voltage value Vth (YES in step S13), the control device 5 determines that the release condition is met and releases the electric brake (step S14). That is, the wind power generation system 100 resumes normal power generation control and supplies power to the supply target 6.

[0043] If the release condition is that the rotational speed value falls below the rotational speed Rth, the control device 5 determines that the release condition is met when the rotational speed measured by the tachometer 11 falls below the rotational speed Rth in an equilibrium state in which the electric brake is operating. Alternatively, the control device 5 determines that the release condition is met when both the condition that the detected value of the voltage sensor VS falls below the voltage value Vth and the condition that the detected value falls below the rotational speed Rth are met.

[0044] In this way, in wind power generation system 100 of this embodiment, if a release condition is met while braking is being performed due to cutout, the release condition is determined based on at least one of the detected value of voltage sensor VS and the rotational speed of wind turbine 1, and the braking operation by brake circuit 4 is released. This makes it possible to release the electric brake at an appropriate time while suppressing increases in costs without using an anemometer, thereby preventing a decrease in power generation efficiency.

[0045] <Variation 1> As described above, in the first embodiment, the wind speed is estimated based on the detection value of the voltage sensor VS in a balanced state, and the brake is released based on whether the estimated wind speed is lower than the reference wind speed. In the first modification, a configuration will be described in which the wind speed is more accurately estimated from the detection value of the voltage sensor VS by focusing on the resistance of the brake circuit 4.

[0046] FIG. 8 is a diagram illustrating how the relationship between voltage and wind speed changes with changes in resistance value. As described above, in wind power generation system 100, the reference wind speed is estimated based on the detection value of voltage sensor VS. As explained in FIG. 6(c), the detection value of voltage sensor VS is proportional to the square of the wind speed. However, the shape of the curve showing the relationship between the detection value of voltage sensor VS and wind speed as shown in FIG. 6(c) changes due to various external factors. For example, if the combined resistance value of resistors R1 to R3 included in brake circuit 4 fluctuates, the line showing the relationship between the detection value of voltage sensor VS and wind speed will change to line L1, line L2, etc., as shown in FIG. 8(a).

[0047] The resistance value of each of the resistors R1 to R3 can change depending on the ambient temperature of the brake circuit 4. Therefore, the combined resistance value of the resistors R1 to R3 also changes depending on the ambient temperature of the brake circuit 4. Generally, the resistance value of a resistor increases as the temperature increases and decreases as the temperature decreases. As shown in Figure 8(a), line L1 is a curve that shows the relationship between the detection value of the voltage sensor VS and the wind speed when the ambient temperature of the brake circuit 4 is temperature T1. At temperature T1, the combined resistance value of the resistors R1 to R3 is X. Line L2 is a curve that shows the relationship between the detection value of the voltage sensor VS and the wind speed when the ambient temperature of the brake circuit 4 is temperature T2, which is lower than temperature T1. At temperature T2, the combined resistance value of the resistors R1 to R3 is Y, which is smaller than X.

[0048] As described above, since the combined resistance value of the resistors R1 to R3 of the brake circuit 4 changes with temperature, an error may occur when estimating the wind speed based only on the detection value of the voltage sensor VS. Therefore, the control device 5 of the first modification estimates the wind speed taking the temperature into consideration. FIG. 9 is a diagram showing an example of correcting the detection value of the voltage sensor VS based on temperature. FIG. 9(a) is a flowchart for correcting the detection value of the voltage sensor VS. The control device 5 executes the flowchart shown in FIG. 9(a) in step S13 of FIG. 7. The control device 5 acquires the temperature detected by the temperature sensor 41 (step S20). After acquiring the temperature, the control device 5 acquires the resistance temperature coefficient corresponding to the acquired temperature (step S21). The resistance temperature coefficient is a coefficient that indicates the rate of change in the resistance value of the resistors R1 to R3 due to a change in temperature.

[0049] The control device 5 corrects the combined resistance value based on the resistance temperature coefficient (step S22). After correcting the combined resistance value, the control device 5 corrects the detection value of the voltage sensor VS using the calculation formula shown in FIG. 9(b).

[0050] This allows the wind power generation system 100 to estimate the wind speed with greater accuracy. That is, the control device 5 can estimate the wind speed more accurately from the value detected by the voltage sensor VS, taking into account changes in resistance value due to temperature changes, and therefore can release the electric brake at an appropriate timing.

[0051] <Variation 2> As described above, the wind power generation system 100 is configured to estimate wind speed based on the relationships between parameters such as voltage, torque, current, rotational speed, resistance, and temperature without using an anemometer. However, in a real environment, the relationships between the above parameters are affected by various external factors other than the above parameters. These external factors are diverse and it is difficult to consider all of them. Therefore, in Modification 2, an example will be described in which more accurate estimation is performed using artificial intelligence that uses training data to identify characteristics of the relationships between each parameter.

[0052] 10 is a diagram showing the configuration of a wind power generation system 101 for acquiring a learning model. Of the components of the wind power generation system 101 shown in FIG. 10, the same components as those of the wind power generation system 100 will not be described repeatedly. The external sensor unit ExS of the wind power generation system 101 includes an anemometer 13.

[0053] The wind power generation system 101 generates learning data. That is, the calculation unit 53 of the wind power generation system 101 stores the wind speed actually measured by the anemometer 13 in the database 200. The calculation unit 53 of the wind power generation system 101 also acquires the detected value of the voltage sensor VS, the temperature detected by the temperature sensor 41, the rotational speed measured by the tachometer 11, and the torque detected by the torque meter 12 at the same time as the wind speed is measured, and stores these as learning data in the database 200. The database 200 is stored in a server or the like separate from the wind power generation system 101.

[0054] Database 200 stores the actual wind speed as well as the detected value of voltage sensor VS at the same time. That is, database 200 associates the detected value of voltage sensor VS with the wind speed. Similarly, database 200 associates the rotation speed with the wind speed. Wind power generation system 100 of this embodiment generates a learning model using artificial intelligence from the learning data generated by wind power generation system 101. The generated learning model can estimate wind speed with higher accuracy using parameters such as the detected value of voltage sensor VS as input values. As a result, if further features can be found from the relationship between each parameter using artificial intelligence, wind power generation system 100 can improve the accuracy of the estimated wind power value by using the learning model.

[0055] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, the control device of the present invention can be applied not only to wind power generation systems but also to hydroelectric power generation systems, etc. [Explanation of symbols]

[0056] 1 wind turbine, 2 main shaft, 3 generator, 4 brake circuit, 5 control device, 6 supply target, 11 tachometer, 12 torque meter, 13 anemometer, 41 temperature sensor, 51 power conversion unit, 51R rectifier circuit, 52 control unit, 53 calculation unit, 100, 100A, 101 wind power generation system, 200 database, EB electric brake control unit, ExS external sensor unit, IS, IS2 current sensor, InS internal sensor unit, L, Rth, a rotation speed L1, L2 lines, M, b output value, Pu, Pv, Pw power lines, R1 to R3 resistance, Sw1 to Sw3 switches, T1 to T3 temperature, Vth voltage value, VS voltage sensor, X, Y, Z combined resistance value, c1 to c3 coils, r1 to r3 internal resistance.

Claims

1. A control device for a power generation system that supplies power to a supply target, The power generation system includes: A rotating body; a generator that is rotated by the rotor and generates three-phase AC power; a brake circuit connected to the generator and configured to generate a braking force on the rotating body by short-circuiting between phases; a voltage sensor for detecting a value of a generated voltage of the generator; a control device for controlling the brake circuit, The control device When the rotation speed of the rotating body exceeds a first threshold value, a braking operation is performed by the brake circuit; after the rotation speed falls below the first threshold value, if a release condition is established based on both the value of the generated voltage detected by the voltage sensor and the rotation speed, stopping the braking operation by the brake circuit; the release condition is that both of the following conditions are met: the value of the generated voltage is lower than a second threshold value; and the value of the rotation speed is lower than a third threshold value. The power generation system includes: a temperature sensor for detecting an ambient temperature of the brake circuit; A control device that determines the second threshold value in accordance with the temperature detected by the temperature sensor.

2. The rotating body is rotated by wind, The control device according to claim 1 , wherein the second threshold value is estimated based on learning data that associates the generated voltage with a wind speed at a location where the rotating body is installed.

3. The rotating body is rotated by wind, The control device according to claim 1 , wherein the third threshold value is estimated based on learning data that associates the rotation speed with a wind speed at a location where the rotating body is installed.

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