Method and system for controlling the pitch of a wind turbine

Abstract

This invention provides a control method and system for wind turbine pitch control. Under AC power supply, the rectifier unit provides a first DC voltage to the DC bus. During pitch control, the pitch motor is driven according to the first DC voltage, and the maximum back electromotive force (EMF) of the pitch motor is preset to be less than the first DC voltage. When AC power supply stops, the rectifier unit stops providing DC voltage to the DC bus, and the energy storage unit provides a second DC voltage to the DC bus that is less than the first DC voltage, with the rated voltage output by the energy storage unit being less than the first DC voltage. The pitch motor is driven to operate according to a set speed curve based on the second DC voltage. From the start to the end of pitch control, the second DC voltage provided to the DC bus decreases from the rated voltage to the final DC voltage. The maximum back EMF of the pitch motor during operation is preset to be less than the rated voltage and greater than the final DC voltage. The energy storage unit is a lithium-ion battery or an electrical double-layer capacitor with a rated voltage of 100V ≤ rated voltage ≤ 240V.

Description

Technical Field

[0001] This invention relates to the field of wind power generation, and more specifically to a control method and system for pitch control of wind turbine generators. Background Technology

[0002] The pitch control system is a critical subsystem in a wind turbine. When the power grid fails or malfunctions, a backup DC power supply is input to the DC bus of the drive unit. The drive unit then uses the DC voltage provided by this DC bus to drive the pitch motor, thereby urgently rotating the blades to a safe position.

[0003] Existing technologies include a method for controlling the pitch of wind turbines. During the operation of the pitch motor driven by a backup power source, the operating speed of the pitch motor is controlled in real time by detecting the DC voltage on the DC bus to prevent the pitch motor from entering the field weakening region, thereby reducing the driver current. Summary of the Invention

[0004] Based on the above situation, the main objective of this invention is to provide a control method and system for wind turbine pitch control, which avoids large drive currents caused by entering non-constant torque operating ranges at least for a certain operating range, while reducing system size, based on lower real-time control requirements and complexity.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for controlling the pitch of a wind turbine includes the following steps: Under AC power supply, a rectifier unit rectifies the AC voltage into a first DC voltage and provides the first DC voltage to a DC bus. When pitch adjustment is required, an inverter drives the pitch motor according to the first DC voltage, wherein the maximum back electromotive force (EMF) of the pitch motor during operation is preset to be less than the first DC voltage. Under AC power supply interruption, the rectifier unit stops providing DC voltage to the DC bus, and an energy storage unit provides a second DC voltage to the DC bus that is less than the first DC voltage, wherein the rated voltage output by the energy storage unit is less than the first DC voltage. The inverter drives the pitch motor to operate according to a set speed curve based on the second DC voltage. From the start to the end of pitch adjustment, the second DC voltage provided by the energy storage unit to the DC bus decreases from the rated voltage to the final DC voltage. The maximum back EMF of the pitch motor during operation is preset to be less than the rated voltage and greater than the final DC voltage. The energy storage unit is a lithium-ion battery or an electrical double-layer capacitor, and 100V ≤ rated voltage ≤ 240V.

[0007] Preferably, when AC power is interrupted, the back electromotive force of the pitch motor during operation is pre-set to gradually decrease from the maximum back electromotive force from the start to the end of pitch control.

[0008] Preferably, the energy storage unit includes an energy storage unit housing, an energy storage unit core assembly, and a heater. An AC cable passes through the energy storage unit housing and connects to the heater. In the case of AC power supply, AC power is supplied to the heater inside the energy storage unit housing through the AC cable introduced into the housing. The heater uses the AC power to heat the energy storage unit core assembly inside the housing according to the ambient temperature and control strategy, so as to maintain the temperature of the energy storage unit core assembly within a preset temperature range.

[0009] Preferably, the energy storage unit includes an energy storage unit housing, an energy storage unit core assembly, and an energy storage management system. A DC power supply cable is connected to the energy storage management system through the energy storage unit housing. In the case of AC power supply, the rectifier unit also rectifies the AC voltage into an energy storage management power supply voltage. This energy storage management voltage is then provided to the energy storage management system inside the energy storage unit housing via a DC power supply cable introduced into the housing. The energy storage management system uses this energy storage management power supply voltage to monitor and manage the energy storage core assembly inside the housing and sends monitoring information to the main control unit of the wind turbine pitch control unit outside the housing.

[0010] This invention also provides a control method for pitch control of a wind turbine, comprising the following steps: Under AC power supply, a rectifier unit rectifies the AC voltage into a first DC voltage and provides the first DC voltage to the DC bus. When pitch control is required, an inverter drives the pitch motor according to the first DC voltage, wherein the maximum back electromotive force of the pitch motor during operation is preset to be less than the first DC voltage. Under AC power supply interruption, the rectifier unit stops providing DC voltage to the DC bus, and an energy storage unit provides a second DC voltage to the DC bus that is less than the first DC voltage, wherein the rated voltage output by the energy storage unit is less than the first DC voltage. The inverter drives the pitch motor to operate according to a set speed curve based on the second DC voltage. From the start to the end of pitch control, the second DC voltage provided by the energy storage unit to the DC bus decreases from the rated voltage to the final DC voltage, and the maximum back electromotive force of the pitch motor during operation is preset to be less than the final DC voltage. The energy storage unit is a lithium-ion battery or an electrical double-layer capacitor, and 100V ≤ rated voltage ≤ 240V.

[0011] Preferably, when AC power is interrupted, the back electromotive force of the pitch motor during operation is pre-set to gradually decrease from the maximum back electromotive force from the start to the end of pitch control.

[0012] Preferably, the energy storage unit includes an energy storage unit housing, an energy storage unit core assembly, and an energy storage management system. A DC power supply cable is connected to the energy storage management system through the energy storage unit housing. In the case of AC power supply, the rectifier unit also rectifies the AC voltage into an energy storage management power supply voltage. This energy storage management voltage is then provided to the energy storage management system inside the energy storage unit housing via a DC power supply cable introduced into the housing. The energy storage management system uses this energy storage management power supply voltage to monitor and manage the energy storage core assembly inside the housing and sends monitoring information to the main control unit of the wind turbine pitch control unit outside the housing.

[0013] Preferably, the energy storage unit includes an energy storage unit housing, an energy storage unit core assembly, and a heater. An AC cable passes through the energy storage unit housing and connects to the heater. In the case of AC power supply, AC power is supplied to the heater inside the energy storage unit housing through the AC cable introduced into the housing. The heater uses the AC power to heat the energy storage unit core assembly inside the housing according to the ambient temperature and control strategy, so as to maintain the temperature of the energy storage unit core assembly within a preset temperature range.

[0014] This invention also provides a control system for wind turbine pitch control, including a rectifier unit, an inverter, and an energy storage unit. Under AC power supply, the rectifier unit rectifies the AC voltage into a first DC voltage and provides this first DC voltage to the DC bus. When pitch control is required, the inverter drives the pitch motor according to the first DC voltage, wherein the maximum back electromotive force (EMF) of the pitch motor during operation is preset to be less than the first DC voltage. When AC power supply stops, the rectifier unit stops providing DC voltage to the DC bus, and the energy storage unit provides a second DC voltage to the DC bus that is less than the first DC voltage, with the rated voltage output by the energy storage unit being less than the first DC voltage. The inverter drives the pitch motor according to the second DC voltage, operating it according to a set speed curve. From the start to the end of pitch control, the second DC voltage provided by the energy storage unit to the DC bus decreases from the rated voltage to the final DC voltage. The maximum back EMF of the pitch motor during operation is preset to be less than the rated voltage and greater than the final DC voltage. The energy storage unit is a lithium-ion battery or an electrical double-layer capacitor, and its rated voltage is 100V ≤ 240V.

[0015] This invention also provides a control system for wind turbine pitch control, including a rectifier unit, an inverter, and an energy storage unit. The system is characterized in that, under AC power supply, the rectifier unit rectifies the AC voltage into a first DC voltage and provides this first DC voltage to the DC bus. When pitch control is required, the inverter drives the pitch motor according to the first DC voltage, wherein the maximum back electromotive force (EMF) of the pitch motor during operation is preset to be less than the first DC voltage. When AC power supply stops, the rectifier unit stops providing DC voltage to the DC bus, and the energy storage unit provides a second DC voltage to the DC bus that is less than the first DC voltage, with the rated voltage output by the energy storage unit being less than the first DC voltage. The inverter drives the pitch motor according to the second DC voltage, operating it according to a set speed curve. From the start to the end of pitch control, the second DC voltage provided by the energy storage unit to the DC bus decreases from the rated voltage to the final DC voltage, and the maximum back EMF of the pitch motor during operation is preset to be less than the final DC voltage. The energy storage unit is a lithium-ion battery or an electrical double-layer capacitor, and its rated voltage is 100V ≤ 240V.

[0016] In some embodiments, by pre-setting the set speed curve of the pitch motor, the pitch motor is controlled to operate according to the set speed curve when AC power is interrupted. Compared with the method of adjusting the speed of the pitch motor in real time according to the voltage on the DC bus to maintain the pitch motor in the constant torque operating range, this solution has lower real-time control requirements and lower control complexity. In addition, since the maximum back electromotive force of the pitch motor during the pitching process is pre-set to be less than the rated voltage, the pitch motor is in the constant torque operating range for a period of time at the beginning of operation. Therefore, at least for a certain operating range, it can avoid entering the non-constant torque operating range. The large drive current (inverter output current) generated reduces the risk of demagnetization of the pitch motor. The maximum back EMF is preset to be greater than the final DC voltage. The last period of operation of the pitch motor is in the non-constant torque operating region (i.e., the field weakening operating region, in which the pitch motor performs field weakening control). The drive current in this region may be greater than the rated output current of the inverter, but since the duration of this region is very short (e.g., only about 10 seconds), the risk of demagnetization of the pitch motor is greatly reduced. In addition, compared with the maximum back EMF being preset to be less than the final DC voltage, the total energy capacity of the energy storage unit does not need to be set too large, resulting in lower cost.

[0017] In other embodiments, by pre-setting the set speed curve of the pitch motor, the pitch motor is controlled to operate according to the set speed curve when the AC power supply is stopped. Compared with the method of adjusting the speed of the pitch motor in real time according to the voltage on the DC bus to keep the pitch motor in the constant torque operating region, this solution has lower real-time control requirements and lower control complexity. In addition, since the maximum back electromotive force of the pitch motor during the pitching process is pre-set to be less than the final DC voltage, the pitch motor is always in the constant torque operating region during the operation. Therefore, it can avoid the large drive current generated when entering the non-constant torque operating region, thereby reducing the risk of demagnetization of the pitch motor.

[0018] Other beneficial effects of the present invention will be explained in detail through the introduction of specific technical features and technical solutions in specific embodiments. Those skilled in the art should be able to understand the beneficial technical effects brought about by these technical features and technical solutions through the introduction of these technical features and technical solutions. Attached Figure Description

[0019] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. In the drawings:

[0020] Figure 1 This is a schematic diagram of a wind turbine pitch control system according to a preferred embodiment of the present invention.

[0021] Figure 2 The TN curve of an example pitch motor according to the present invention;

[0022] Figure 3 The waveform diagram is for a waveform that does not employ the control method of this invention.

[0023] Figure 4 The waveform diagram shows the control method of Embodiment 2 of the present invention. Detailed Implementation

[0024] The present invention is described below based on embodiments, but the present invention is not limited to these embodiments. In the following detailed description of the present invention, some specific details are described in detail, but well-known methods, processes, procedures, and elements are not described in detail in order to avoid obscuring the essence of the present invention.

[0025] Unless the context explicitly requires it, the words "comprising," "including," or similar terms throughout the specification and claims should be interpreted as encompassing rather than being exclusive or exhaustive; that is, meaning "including but not limited to."

[0026] like Figure 1The diagram shows a schematic of a wind turbine pitch control system according to one embodiment. The control system includes a rectifier unit 210, an inverter 220, and an energy storage unit 100. This control system is typically installed in the pitch control cabinet of the wind turbine. The rectifier unit 210 and the inverter 220 may be components of what is commonly referred to as a drive 200. The input of the rectifier unit 210 is connected to the AC power grid 600, and the output is connected to the DC bus 230; the input of the inverter 220 is connected to the DC bus 230, and the output is connected to the pitch motor 300; the energy storage unit 100 is connected to the DC bus 230. Compared with traditional supercapacitors, the energy density of this energy storage unit 100 is greatly improved (e.g., more than 7 times), such as high-energy-density lithium-ion batteries or electrical double-layer capacitors. In addition, the rated voltage of the energy storage unit 100 is low, 100V≤rated voltage≤240V; due to the use of the high-energy-density energy storage unit 100, the volume of the energy storage unit 100 is smaller, so the pitch control cabinet can be made smaller; in addition, larger single units can be used, resulting in higher reliability.

[0027] Example 1

[0028] In AC power supply mode, rectifier unit 210 rectifies the AC voltage output from the AC grid into a first DC voltage and provides this first DC voltage (e.g., over 500 volts) to DC bus 230. When pitch adjustment is required, inverter 220 drives pitch motor 300 (e.g., permanent magnet synchronous motor) according to the first DC voltage. Pitch motor 300 can drive blade 500 to rotate via gear 400, thereby completing pitch adjustment. The maximum back electromotive force (EMF) of pitch motor 300 during AC power supply operation is preset to be less than the first DC voltage. Since the magnitude of the back EMF of pitch motor 300 is related to the number of coil turns and rotational speed, the maximum rotational speed of pitch motor 300 under AC power supply conditions can be determined based on the first DC voltage and the set number of coil turns. By controlling the speed of pitch motor 300 to be less than this maximum rotational speed, it can be ensured that its maximum back EMF is preset to be less than the first DC voltage. In the case of AC power supply, the DC bus 230 also charges the energy storage unit 100 to ensure that the energy storage unit 100 stores sufficient electrical energy to drive the pitch when AC power supply is stopped. Since the maximum back electromotive force of the pitch motor 300 is preset to be less than the first DC voltage when AC power supply is used, the pitch motor 300 always operates in the constant torque operating region under this condition, and will not demagnetize the pitch motor due to excessive drive current caused by entering the non-constant torque operating region (weak field operating region).

[0029] When AC power supply is interrupted, rectifier unit 210 stops supplying DC voltage to DC bus 230, and energy storage unit 100 supplies a second DC voltage to DC bus 230 that is lower than the first DC voltage, with the rated voltage output by energy storage unit 100 being lower than the first DC voltage. Inverter 220 drives pitch motor 300 to operate according to a set speed curve based on the second DC voltage. Pitch motor 300 can drive blade 500 to rotate via gear 400, rotating the blade to a safe position, thus completing pitch control. From the start to the end of pitch control, the second DC voltage supplied by energy storage unit 100 to DC bus 230 decreases from the rated voltage to the final DC voltage. The maximum back electromotive force of pitch motor 300 during operation is preset to be lower than the rated voltage and higher than the final DC voltage. For example, the rated voltage is 240V, and the final DC voltage is 180V.

[0030] The process of presetting the maximum back electromotive force (EMF) can be as follows: Based on the set speed curve of the pitch motor 300, determine the energy consumed to complete the set pitch attitude; determine the final DC voltage according to the rated voltage of the energy storage unit 100, the capacitance of the energy storage unit 100, and the consumed energy; specifically, determine the final DC voltage according to the formula W = 0.5 * C * (U0 - Ue)², where W is the energy consumed by the pitch motor 300 to complete the set pitch attitude under the set speed curve, C and U0 are the capacitance and rated voltage of the energy storage unit 100, respectively, and Ue is the final voltage. Since the magnitude of the back EMF of the pitch motor 300 is related to the number of coil turns and the speed, the maximum speed of the pitch motor 300 when the AC power supply is stopped can be determined based on the rated voltage and the final DC voltage, under the condition of a set number of coil turns, thereby ensuring that its maximum back EMF is pre-set to be less than the first DC voltage and greater than the final DC voltage. The set speed curve refers to the trajectory of speed change over time, which can be linear or nonlinear. By pre-setting this set speed curve of the pitch motor 300, the pitch motor 300 is controlled to operate according to this set speed curve when AC power is interrupted. Compared to the method of adjusting the speed of the pitch motor 300 in real time according to the voltage on the DC bus 230 to maintain the pitch motor 300 in the constant torque operating range, this solution has lower real-time control requirements and lower control complexity. In addition, since the maximum back electromotive force of the pitch motor 300 during the pitching process is pre-set to be less than the rated voltage, the pitch motor 300 is in the constant torque operating range for a period of time at the beginning of operation. Therefore, at least during the pitching process... This operating range avoids the large drive current (output current of inverter 220) generated by entering the non-constant torque operating region, thereby reducing the risk of demagnetization of the pitch motor. The maximum back EMF is preset to be greater than the final DC voltage. The last period of operation of the pitch motor 300 is in the non-constant torque operating region (i.e., the field weakening operating region, in which the pitch motor 300 performs field weakening control). The drive current in this region may be greater than the rated output current of the inverter, but since the duration of this region is short (e.g., only about 10 seconds), the risk of demagnetization of the pitch motor is greatly reduced. In addition, compared with the maximum back EMF being preset to be less than the final DC voltage, the total energy capacity of the energy storage unit 100 does not need to be set too large, resulting in lower cost.

[0031] It should be noted that there is no boost module between the energy storage unit 100 and the DC bus 230 to boost the DC voltage output by the energy storage unit 100.

[0032] like Figure 2The figure shows the TN curve (i.e., torque-speed curve) of an example pitch motor. This example pitch motor is a stator and rotor lamination motor. The three curves are the TN curves of this example pitch motor under different back EMF design values ​​under the same DC bus voltage (bus voltage) of inverter 220. It can be seen that the lower the back EMF, the wider the speed range of the constant torque operating region of the pitch motor, that is, the higher the power of the pitch motor when running at the turning speed. This means that the pitch motor can operate at higher speeds without entering the field weakening region.

[0033] Preferably, when AC power supply is interrupted, the back electromotive force (EMF) of the pitch motor 300 during operation is pre-set to gradually decrease from the maximum back EMF from the start to the end of pitch control. Since the second DC voltage supplied by the energy storage unit 100 to the DC bus 230 gradually decreases from the rated voltage to the final DC voltage from the start to the end of pitch control, both the second DC voltage and the back EMF gradually decrease. Therefore, compared to adjusting the speed of the pitch motor 300 in real time based on the voltage on the DC bus 230 to maintain the pitch motor 300 in the constant torque operating range, this solution, with lower control complexity, can minimize the difference between the back EMF of the pitch motor 300 and the voltage of the DC bus 230, thereby minimizing the excessive drive current of the inverter 220.

[0034] In addition, when AC power is supplied, the drive current of inverter 220 is less than the maximum drive current of inverter 220 when AC power is cut off, and the maximum drive current of inverter 220 exceeds the rated drive current of inverter 220 (e.g., any value in 55-75A) when AC power is cut off. However, since the time exceeding the rated drive current is very short, the risk of demagnetization of the pitch motor is very small.

[0035] like Figure 1 As shown, the wind turbine pitch control system may further include a decoupling diode 240 connected between the DC bus 230 and the output of the energy storage unit 100. When AC power is interrupted, and the DC bus voltage drops to near its rated voltage, the energy storage unit 100 begins to supply a second DC voltage to the DC bus 230. The wind turbine pitch control system may also include a DC-DC converter 250 connected between the DC bus 230 and the output of the energy storage unit 100. In the case of AC power, the DC-DC converter 250 steps down the DC voltage on the DC bus 230 to a lower DC voltage to charge the energy storage unit 100.

[0036] Typically, the control system for wind turbine pitch is installed inside a pitch control cabinet, which is located within the turbine hub. The turbine hub is situated at a high altitude with low ambient temperatures. To ensure more reliable and efficient operation of the energy storage unit 100 in the event of an AC power outage, in some configurations, the energy storage unit 100 includes an energy storage unit housing, an energy storage unit core assembly, and a heater. AC cables connect the heater to the energy storage unit housing. In AC power supply mode, AC power is supplied to the heater inside the energy storage unit housing via the AC cables introduced into the housing. The heater, based on the ambient temperature and control strategy, uses the AC power to heat the energy storage unit core assembly inside the housing, maintaining its temperature within a preset range for more reliable and efficient operation. Once the AC power supply stops, the energy storage unit 100 can immediately start supplying power to the DC bus 230 within a better preset temperature range. In the above configuration, the energy storage unit 100 can not only be in a better preset temperature range at all times to be in a more reliable and efficient operating range, but also, since the external AC power is introduced to power the heater instead of using the energy storage unit 100's own power to power the heater, it will not occupy the energy of the energy storage unit 100, nor will it consume the number of charge and discharge cycles of the energy storage unit 100. In comparison, the energy storage unit 100 can have more power to drive the operation of the pitch motor 300, and the total number of charge and discharge cycles can be used only for pitch.

[0037] In some configurations, the energy storage unit 100 includes an energy storage unit housing, an energy storage unit core assembly, and an energy storage management system (e.g., CMS). A DC power supply cable is connected to the energy storage management system through the energy storage unit housing. In the case of AC power supply, the rectifier unit 210 also rectifies the AC voltage into an energy storage management power supply voltage (which is a low DC voltage, such as 24V DC voltage). This voltage is then supplied to the energy storage management system inside the energy storage unit housing via a DC power supply cable introduced into the housing. The energy storage management system uses this voltage to monitor and manage the energy storage core assembly inside the housing and sends monitoring information to the main control unit of the wind turbine pitch control unit outside the housing. In this configuration, since an external energy storage management supply voltage is introduced to power the energy storage management system instead of using the energy storage unit 100's own electrical energy, the energy storage unit 100's electrical energy is not occupied, nor is the number of charge-discharge cycles of the energy storage unit 100 consumed. In comparison, the energy storage unit 100 can have more electrical energy to drive the operation of the pitch motor 300, and the total number of charge-discharge cycles can be used only for pitch control.

[0038] Example 2

[0039] In AC power supply mode, rectifier unit 210 rectifies the AC voltage output from the AC grid into a first DC voltage and provides this first DC voltage (e.g., over 500 volts) to DC bus 230. When pitch adjustment is required, inverter 220 drives pitch motor 300 based on the first DC voltage. Pitch motor 300 can drive blade 500 to rotate via gear 400, thereby completing pitch adjustment. The maximum back electromotive force (EMF) of pitch motor 300 during AC power supply operation is preset to be less than the first DC voltage. Since the magnitude of the back EMF of pitch motor 300 is related to the number of coil turns and rotational speed, the maximum rotational speed of pitch motor 300 under AC power supply conditions can be determined based on the first DC voltage and the set number of coil turns. By controlling the speed of pitch motor 300 to be less than this maximum rotational speed, it can be ensured that its maximum back EMF is preset to be less than the first DC voltage.

[0040] When AC power supply is interrupted, rectifier unit 210 stops supplying DC voltage to DC bus 230, and energy storage unit 100 supplies a second DC voltage to DC bus 230 that is lower than the first DC voltage, with the rated voltage output by energy storage unit 100 being lower than the first DC voltage. Inverter 220 drives pitch motor 300 to operate according to a set speed curve based on the second DC voltage. Pitch motor 300 can drive blade 500 to rotate via gear 400, thereby completing pitch control. From the start to the end of pitch control, the second DC voltage supplied by energy storage unit 100 to DC bus 230 decreases from the rated voltage to the final DC voltage. The maximum back electromotive force of pitch motor 300 during operation is preset to be lower than the final DC voltage. For example, the rated voltage is 240V, and the final DC voltage is 180V.

[0041] The process of presetting the maximum back electromotive force (EMF) can be as follows: Based on the set speed curve of the pitch motor 300, determine the energy consumed to complete the set pitch attitude; determine the final DC voltage according to the rated voltage of the energy storage unit 100, the capacitance of the energy storage unit 100, and the consumed energy; specifically, determine the final DC voltage according to the formula W = 0.5 * C * (U0 - Ue)², where W is the energy consumed by the pitch motor 300 to complete the set pitch attitude under the set speed curve, C and U0 are the capacitance and rated voltage of the energy storage unit 100, respectively, and Ue is the final voltage. Since the magnitude of the back EMF of the pitch motor 300 is related to the number of coil turns and the speed, the maximum speed of the pitch motor 300 when the AC power supply is stopped can be determined based on the final DC voltage and under the condition of the set number of coil turns, thereby ensuring that its maximum back EMF is pre-set to be less than the final DC voltage. The set speed curve refers to the trajectory of speed change over time, which can be linear or nonlinear. By pre-setting the set speed curve of the pitch motor 300, the pitch motor 300 is controlled to operate according to the set speed curve when the AC power supply is stopped. Compared with the method of adjusting the speed of the pitch motor 300 in real time according to the voltage on the DC bus 230 to keep the pitch motor 300 in the constant torque operating region, this solution has lower real-time control requirements and lower control complexity. In addition, since the maximum back electromotive force of the pitch motor 300 during the pitching process is pre-set to be less than the final DC voltage, the pitch motor 300 is always in the constant torque operating region during operation. Therefore, it can avoid the large drive current generated when entering the non-constant torque operating region, thereby reducing the risk of demagnetization of the pitch motor.

[0042] It should be noted that there is no boost module between the energy storage unit 100 and the DC bus 230 to boost the DC voltage output by the energy storage unit 100.

[0043] like Figure 2 The figure shows the TN curve (i.e., torque-speed curve) of an example pitch motor. This example pitch motor is a stator and rotor lamination motor. The three curves are the TN curves of this example pitch motor under different back EMF design values ​​under the same DC bus voltage (bus voltage) of inverter 220. It can be seen that the lower the back EMF, the wider the speed range of the constant torque operating region of the pitch motor, that is, the higher the power of the pitch motor when running at the turning speed. This means that the pitch motor can operate at higher speeds without entering the field weakening region.

[0044] Preferably, when AC power supply is interrupted, the back electromotive force (EMF) of the pitch motor 300 during operation is pre-set to gradually decrease from the maximum back EMF from the start to the end of pitch control. Since the second DC voltage supplied by the energy storage unit 100 to the DC bus 230 gradually decreases from the rated voltage to the final DC voltage from the start to the end of pitch control, both the second DC voltage and the back EMF gradually decrease. Therefore, compared to adjusting the speed of the pitch motor 300 in real time based on the voltage on the DC bus 230 to maintain the pitch motor 300 in the constant torque operating range, this solution, with lower control complexity, can minimize the difference between the back EMF of the pitch motor 300 and the voltage of the DC bus 230, thereby minimizing the excessive drive current of the inverter 220.

[0045] In addition, the drive current of inverter 220 is less than the maximum drive current of inverter 220 when AC power is cut off, and the maximum drive current of inverter 220 when AC power is cut off is less than the rated drive current of inverter 220, for example, the rated drive current can be any value in the range of 55-75A.

[0046] like Figure 1 As shown, the wind turbine pitch control system may further include a decoupling diode 240 connected between the DC bus 230 and the output of the energy storage unit 100. When AC power is interrupted, and the DC bus voltage drops to near its rated voltage, the energy storage unit 100 begins to supply a second DC voltage to the DC bus 230. The wind turbine pitch control system may also include a DC-DC converter 250 connected between the DC bus 230 and the output of the energy storage unit 100. In the case of AC power, the DC-DC converter 250 steps down the DC voltage on the DC bus 230 to a lower DC voltage to charge the energy storage unit 100.

[0047] Typically, the control system for wind turbine pitch is installed inside a pitch control cabinet, which is located within the turbine hub. The turbine hub is situated at a high altitude with low ambient temperatures. To ensure more reliable and efficient operation of the energy storage unit 100 in the event of an AC power outage, in some configurations, the energy storage unit 100 includes an energy storage unit housing, an energy storage unit core assembly, and a heater. AC cables connect the heater to the energy storage unit housing. In AC power supply mode, AC power is supplied to the heater inside the energy storage unit housing via the AC cables introduced into the housing. The heater, based on the ambient temperature and control strategy, uses the AC power to heat the energy storage unit core assembly inside the housing, maintaining its temperature within a preset range for more reliable and efficient operation. Once the AC power supply stops, the energy storage unit 100 can immediately start supplying power to the DC bus 230 within a better preset temperature range. In the above configuration, the energy storage unit 100 can not only be in a better preset temperature range at all times to be in a more reliable and efficient operating range, but also, since the external AC power is introduced to power the heater instead of using the energy storage unit 100's own power to power the heater, it will not occupy the energy of the energy storage unit 100, nor will it consume the number of charge and discharge cycles of the energy storage unit 100. In comparison, the energy storage unit 100 can have more power to drive the operation of the pitch motor 300, and the total number of charge and discharge cycles can be used only for pitch.

[0048] In some configurations, the energy storage unit 100 includes an energy storage unit housing, an energy storage unit core assembly, and an energy storage management system (e.g., CMS). A DC power supply cable is connected to the energy storage management system through the energy storage unit housing. In the case of AC power supply, the rectifier unit 210 also rectifies the AC voltage into an energy storage management power supply voltage (which is a low DC voltage, such as 24V DC voltage). This voltage is then supplied to the energy storage management system inside the energy storage unit housing via a DC power supply cable introduced into the housing. The energy storage management system uses this voltage to monitor and manage the energy storage core assembly inside the housing and sends monitoring information to the main control unit of the wind turbine pitch control unit outside the housing. In this configuration, since an external energy storage management supply voltage is introduced to power the energy storage management system instead of using the energy storage unit 100's own electrical energy, the energy storage unit 100's electrical energy is not occupied, nor is the number of charge-discharge cycles of the energy storage unit 100 consumed. In comparison, the energy storage unit 100 can have more electrical energy to drive the operation of the pitch motor 300, and the total number of charge-discharge cycles can be used only for pitch control.

[0049] like Figure 3The figure shows a waveform diagram without the control method of the present invention. In the figure, since the maximum back electromotive force of the pitch motor 300 is greater than the rated voltage of the energy storage unit 100, when the energy storage unit 100 starts to work, the pitch motor 300 enters the non-constant torque working area, and the current of the driver increases sharply and instantaneously, approaching 100A. The pitch motor 300 has a large risk of demagnetization.

[0050] like Figure 4 The diagram shown is a waveform diagram of the control method of this embodiment. Since the maximum back electromotive force of the pitch motor 300 is configured to be less than the final voltage of the energy storage unit 100, when the energy storage unit 100 starts to work, the pitch motor 300 is always in the constant torque operating region and will not enter the non-constant torque operating region. The current of the driver is maintained at about 52A, which is less than the rated drive current of 75A, and the risk of demagnetization of the pitch motor 300 is greatly reduced.

[0051] Those skilled in the art will understand that, without conflict, the above-mentioned preferred solutions can be freely combined and superimposed.

[0052] It should be understood that the above embodiments are merely exemplary and not restrictive. Various obvious or equivalent modifications or substitutions that can be made by those skilled in the art regarding the above details without departing from the basic principles of the present invention will be included within the scope of the claims of the present invention.

Claims

1. A control method of a wind turbine generator variable pitch, characterized by, Includes the following steps: In the case of AC power supply, the rectifier unit rectifies the AC voltage into a first DC voltage and provides the first DC voltage to the DC bus. When pitch is required, the inverter drives the pitch motor according to the first DC voltage. The maximum back electromotive force of the pitch motor during operation is preset to be less than the first DC voltage. When AC power supply is interrupted, the rectifier unit stops supplying DC voltage to the DC bus, and the energy storage unit supplies a second DC voltage to the DC bus that is lower than the first DC voltage. The rated voltage output by the energy storage unit is also lower than the first DC voltage. The inverter drives the pitch motor to operate according to a set speed curve based on the second DC voltage. From the start to the end of the pitch change, the second DC voltage supplied by the energy storage unit to the DC bus decreases from the rated voltage to the final DC voltage. The maximum back electromotive force of the pitch motor during operation is preset to be lower than the rated voltage and higher than the final DC voltage. The energy storage unit is a lithium-ion battery or an electrical double-layer capacitor, and the rated voltage is 100V≤240V.

2. The control method according to claim 1, characterized in that, When AC power is interrupted, the back electromotive force of the pitch motor during operation is pre-set to gradually decrease from the maximum back electromotive force from the start to the end of pitch control.

3. The control method according to claim 1, characterized in that, The energy storage unit includes an energy storage unit housing, an energy storage unit core assembly, and a heater, with an AC cable connecting the heater through the energy storage unit housing; In the case of AC power supply, AC power is supplied to the heater inside the energy storage unit housing through an AC cable introduced into the housing. The heater uses the AC power to heat the energy storage unit core inside the housing according to the ambient temperature and control strategy, so as to maintain the temperature of the energy storage unit core within a preset temperature range.

4. The control method according to claim 1, characterized in that, The energy storage unit includes an energy storage unit shell, an energy storage unit core assembly, and an energy storage management system. A DC power supply cable is connected to the energy storage management system through the energy storage unit shell. In the case of AC power supply, the rectifier unit also rectifies the AC voltage into the energy storage management power supply voltage, and provides the energy storage management power supply voltage to the energy storage management system inside the energy storage unit through the DC power supply cable introduced into the housing of the energy storage unit. The energy storage management system uses the energy storage management power supply voltage to monitor and manage the energy storage core group inside the housing of the energy storage unit, and sends monitoring information to the main control unit of the wind turbine pitch control outside the housing of the energy storage unit.

5. A control method of a wind power generator variable pitch, characterized by, Includes the following steps: In the case of AC power supply, the rectifier unit rectifies the AC voltage into a first DC voltage and provides the first DC voltage to the DC bus. When pitch is required, the inverter drives the pitch motor according to the first DC voltage. The maximum back electromotive force of the pitch motor during operation is preset to be less than the first DC voltage. When AC power supply is interrupted, the rectifier unit stops supplying DC voltage to the DC bus, and the energy storage unit supplies a second DC voltage to the DC bus that is lower than the first DC voltage. The rated voltage output by the energy storage unit is also lower than the first DC voltage. The inverter drives the pitch motor to operate according to a set speed curve based on the second DC voltage. From the start to the end of the pitch change, the second DC voltage supplied by the energy storage unit to the DC bus decreases from the rated voltage to the final DC voltage. The maximum back electromotive force of the pitch motor during operation is preset to be lower than the final DC voltage. The energy storage unit is a lithium-ion battery or an electrical double-layer capacitor, and the rated voltage is 100V≤240V.

6. The control method according to claim 5, characterized in that, When AC power is interrupted, the back electromotive force of the pitch motor during operation is pre-set to gradually decrease from the maximum back electromotive force from the start to the end of pitch control.

7. The control method according to claim 4, characterized in that, The energy storage unit includes an energy storage unit shell, an energy storage unit core assembly, and an energy storage management system. A DC power supply cable is connected to the energy storage management system through the energy storage unit shell. In the case of AC power supply, the rectifier unit also rectifies the AC voltage into the energy storage management power supply voltage, and provides the energy storage management power supply voltage to the energy storage management system inside the energy storage unit through the DC power supply cable introduced into the housing of the energy storage unit. The energy storage management system uses the energy storage management power supply voltage to monitor and manage the energy storage core group inside the housing of the energy storage unit, and sends monitoring information to the main control unit of the wind turbine pitch control outside the housing of the energy storage unit.

8. The control method according to claim 4, characterized in that, The energy storage unit includes an energy storage unit housing, an energy storage unit core assembly, and a heater, with an AC cable connecting the heater through the energy storage unit housing; In the case of AC power supply, AC power is supplied to the heater inside the energy storage unit housing through an AC cable introduced into the housing. The heater uses the AC power to heat the energy storage unit core inside the housing according to the ambient temperature and control strategy, so as to maintain the temperature of the energy storage unit core within a preset temperature range.

9. A control system for pitch control of a wind turbine generator, comprising a rectifier unit, an inverter, and an energy storage unit, characterized in that, In the case of AC power supply, the rectifier unit rectifies the AC voltage into a first DC voltage and provides the first DC voltage to the DC bus. When pitch is required, the inverter drives the pitch motor according to the first DC voltage. The maximum back electromotive force of the pitch motor during operation is preset to be less than the first DC voltage. When AC power supply is interrupted, the rectifier unit stops supplying DC voltage to the DC bus, and the energy storage unit supplies a second DC voltage to the DC bus that is lower than the first DC voltage. The rated voltage output by the energy storage unit is also lower than the first DC voltage. The inverter drives the pitch motor to operate according to a set speed curve based on the second DC voltage. From the start to the end of the pitch change, the second DC voltage supplied by the energy storage unit to the DC bus decreases from the rated voltage to the final DC voltage. The maximum back electromotive force of the pitch motor during operation is preset to be lower than the rated voltage and higher than the final DC voltage. The energy storage unit is a lithium-ion battery or an electrical double-layer capacitor, and the rated voltage is 100V≤240V.

10. A control system for pitch control of a wind turbine generator, comprising a rectifier unit, an inverter, and an energy storage unit, characterized in that, In the case of AC power supply, the rectifier unit rectifies the AC voltage into a first DC voltage and provides the first DC voltage to the DC bus. When pitch is required, the inverter drives the pitch motor according to the first DC voltage. The maximum back electromotive force of the pitch motor during operation is preset to be less than the first DC voltage. When AC power supply is interrupted, the rectifier unit stops supplying DC voltage to the DC bus, and the energy storage unit supplies a second DC voltage to the DC bus that is lower than the first DC voltage. The rated voltage output by the energy storage unit is also lower than the first DC voltage. The inverter drives the pitch motor to operate according to a set speed curve based on the second DC voltage. From the start to the end of the pitch change, the second DC voltage supplied by the energy storage unit to the DC bus decreases from the rated voltage to the final DC voltage. The maximum back electromotive force of the pitch motor during operation is preset to be lower than the final DC voltage. The energy storage unit is a lithium-ion battery or an electrical double-layer capacitor, and the rated voltage is 100V≤240V.

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