Control circuit of variable-pitch motor and variable-pitch driver

Abstract

The utility model provides a control circuit of a variable pitch motor and a variable pitch driver. The control circuit comprises a first rectification unit, a first capacitor, a battery device, a bus capacitor and a second rectification unit. The first rectifying unit, the first capacitor, the battery device, the bus capacitor and the second rectifying unit are connected in parallel; the first rectifying unit is used for rectifying electric energy output by a power grid and transmitting the rectified electric energy to the first capacitor and the bus capacitor; when the capacitor voltage of the first capacitor reaches a preset target voltage, the second rectifying unit inverts the capacitor voltage to obtain an inverted voltage, and the variable-pitch motor is controlled to operate through the inverted voltage; when the variable-pitch motor generates power and operates, the second rectifying unit rectifies the generating voltage to the bus; and when the bus voltage at the two ends of the bus capacitor rises to a preset voltage threshold value, the first capacitor charges the battery device. According to the mode, on one hand, braking resistance is saved, on the other hand, electric energy is fully utilized, and energy waste is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of wind power, in particular to a control circuit and a pitch-changing driver of a pitch-changing motor. Background Art

[0002] The pitch drive is mainly used to control the blade angle and is an important core component in the wind turbine. If the pitch motor in the pitch drive is frequently braked or passively enters the power generation mode, high voltage will be fed into the DC bus. To prevent the bus voltage from being too high and damaging the components, discharge can be performed through a brake resistor; this method requires the addition of a power-matched brake resistor, and during the discharge process, if the pitch motor is running in the power generation mode, the discharged energy can only be consumed by the brake resistor, so this method causes energy waste. Utility Model Content

[0003] In view of this, the purpose of the utility model is to provide a control circuit and a pitch drive of a pitch motor, which on the one hand saves braking resistance, and on the other hand makes full use of electric energy and avoids energy waste.

[0004] In the first aspect, an embodiment of the utility model provides a control circuit for a variable pitch motor, the control circuit comprising a first rectifier unit, a first capacitor, a battery device, a bus capacitor, and a second rectifier unit; the first rectifier unit is used to connect to a power grid; the first rectifier unit, the first capacitor, the battery device, the bus capacitor, and the second rectifier unit are connected in parallel; the second rectifier unit is used to connect to the variable pitch motor; the first rectifier unit is used to rectify the electric energy output by the power grid, and transmit the rectified electric energy to the first capacitor and the bus capacitor; when the capacitor voltage of the first capacitor reaches a preset target voltage, the second rectifier unit inverts the capacitor voltage to obtain an inversion voltage, and controls the operation of the variable pitch motor by the inversion voltage; when the variable pitch motor generates electricity, the second rectifier unit rectifies the generated voltage to the bus; when the bus voltage at both ends of the bus capacitor rises to a preset voltage threshold, the first capacitor charges the battery device.

[0005] The above-mentioned first rectifying unit includes a plurality of switching tubes; when the battery device is fully charged, the bus voltage is inverted by the first rectifying unit, and the inverted voltage is fed back to the power grid.

[0006] The above-mentioned first rectifier unit includes: a first branch, a second branch and a third branch connected in parallel; wherein the first branch includes: a first switch tube and a second switch tube connected in series; the second branch includes: a third switch tube and a fourth switch tube connected in series; the third branch includes: a fifth switch tube and a sixth switch tube connected in series.

[0007] The three-phase power supply of the above-mentioned power grid includes a first output interface, a second output interface and a third output interface; the first output interface is connected between the first switch tube and the second switch tube; the second output interface is connected between the third switch tube and the fourth switch tube; the third output interface is connected between the fifth switch tube and the sixth switch tube.

[0008] The first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube are all IGBT devices.

[0009] The above-mentioned second rectifier unit includes: a fourth branch, a fifth branch and a sixth branch connected in parallel; wherein the fourth branch includes: a seventh switch tube and an eighth switch tube connected in series; the fifth branch includes: a ninth switch tube and a tenth switch tube connected in series; the sixth branch includes: an eleventh switch tube and a twelfth switch tube connected in series.

[0010] The above-mentioned variable pitch motor includes a first input interface, a second input interface and a third input interface; the first input interface is connected between the seventh switch tube and the eighth switch tube; the second input interface is connected between the ninth switch tube and the tenth switch tube; the third input interface is connected between the eleventh switch tube and the twelfth switch tube.

[0011] The seventh switch tube, the eighth switch tube, the ninth switch tube, the tenth switch tube, the eleventh switch tube and the twelfth switch tube are all IGBT devices.

[0012] The control circuit also includes a control module for the first rectifier unit; the control module is used to collect the input voltage and current of the power grid and the bus voltage across the bus capacitor, and output a control signal for the first rectifier unit.

[0013] In a second aspect, an embodiment of the utility model provides a pitch drive, which includes a pitch motor and a control circuit of the pitch motor; the pitch motor is connected to the control circuit.

[0014] The embodiments of the present invention bring the following beneficial effects:

[0015] The control circuit and pitch drive of the pitch motor, the control circuit includes a first rectifier unit, a first capacitor, a battery device, a bus capacitor and a second rectifier unit; the first rectifier unit is used to connect to the power grid; the first rectifier unit, the first capacitor, the battery device, the bus capacitor and the second rectifier unit are connected in parallel; the second rectifier unit is used to connect to the pitch motor; the first rectifier unit is used to rectify the electric energy output by the power grid, and transmit the rectified electric energy to the first capacitor and the bus capacitor; when the capacitor voltage of the first capacitor reaches the preset target voltage, the second rectifier unit inverts the capacitor voltage to obtain the inverted voltage, and controls the operation of the pitch motor by the inverted voltage; when the pitch motor generates electricity, the second rectifier unit rectifies the generated voltage to the bus; when the bus voltage at both ends of the bus capacitor rises to the preset voltage threshold, the first capacitor charges the battery device. In the control circuit, by setting the battery device, when the bus voltage is high, the battery device is charged, on the one hand, there is no need to set the brake resistor, saving the brake resistor, on the other hand, the electric energy is stored through the battery, and can be supplied to other devices for use, so that the electric energy is fully utilized and energy waste is avoided.

[0016] Other features and advantages of the utility model will be described in the following description, and partly become apparent from the description, or understood by practicing the utility model. The purpose and other advantages of the utility model are realized and obtained by the structures specifically pointed out in the description, claims and drawings.

[0017] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are some implementation methods of the utility model. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A schematic diagram of a control circuit for a variable pitch motor provided by an embodiment of the utility model;

[0020] Figure 2 A topological schematic diagram of a control circuit of a pitch motor provided by an embodiment of the utility model;

[0021] Figure 3 A schematic diagram of a calculation method of a control signal output by a control module of a first rectifier unit provided in an embodiment of the utility model;

[0022] Figure 4 A schematic structural diagram of a variable pitch drive provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the utility model clearer, the technical solution of the utility model will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0024] The variable pitch system is a key control component of wind power transmission equipment. Its main function is to use the frequency converter to control the operation of the motor, which then drives the gears and blades to rotate, thereby controlling the vertical wind direction of the blades, so that the blades are in a safer working state. The wind turbine can operate and generate electricity efficiently without being dismembered due to excessive wind volume or excessive blade speed, thus protecting the entire wind turbine from long-term safe and efficient operation.

[0025] The existing variable pitch system is mainly composed of a variable pitch cabinet and a variable pitch motor. The variable pitch cabinet is composed of a variable pitch drive, a backup power supply, and electrical components. Among them, the electrical components include reactors, heaters, sensors, fuses, switches, external switching power supplies, etc. The variable pitch drive, variable pitch motor, and backup power supply are the three core components of the variable pitch system. The main functions are realized by the variable pitch drive. The variable pitch drive is a single component with highly concentrated functions. All power devices can directly rely on the variable pitch drive for heat dissipation. The variable pitch drive can directly and independently drive the motor to operate, and can also be sold separately. Traditional variable pitch drives usually use thyristors or rectifier bridges to achieve three-phase electrical rectification. When the motor brakes, the bus voltage will increase, and a brake resistor will be used to release the bus voltage.

[0026] This way of processing feedback energy has two disadvantages: first, it is necessary to add a braking resistor with power matching according to the system; second, the energy flow is single-phase and can only flow from the grid side to the motor side. When the variable pitch motor operates in the power generation mode, the generated energy can only be consumed by the braking resistor, resulting in energy waste.

[0027] Based on the above problems, this embodiment provides a control circuit of a pitch motor and a pitch driver, which can be applied in the field of wind power.

[0028] First, see Figure 1 A structural schematic diagram of a control circuit of a pitch motor is shown, the control circuit comprising a first rectifier unit 10, a first capacitor 11, a battery device 12, a bus capacitor 13 and a second rectifier unit 14;

[0029] The first rectifier unit 10 is connected to the power grid; the first rectifier unit 10, the first capacitor 11, the battery device 12, the bus capacitor 13 and the second rectifier unit 14 are connected in parallel; the second rectifier unit 14 is connected to the pitch motor;

[0030] The first rectifier unit 10 is used to rectify the electric energy output by the power grid, and transmit the rectified electric energy to the first capacitor and the bus capacitor; when the capacitor voltage of the first capacitor reaches the preset target voltage, the second rectifier unit inverts the capacitor voltage to obtain an inverter voltage, and controls the operation of the variable pitch motor by the inverter voltage; when the variable pitch motor generates electricity, the second rectifier unit rectifies the generated voltage to the bus; when the bus voltage at both ends of the bus capacitor rises to a preset voltage threshold, the first capacitor charges the battery device.

[0031] The first rectifier unit usually includes multiple switching tubes, diodes and other devices, and multiple devices are connected in series and in parallel to form the first rectifier unit. The first capacitor usually has a large capacitance and current parameter; the battery device has a charge and discharge function. The bus capacitor is connected in parallel between the positive cable and the negative cable of the bus. The second rectifier unit usually includes multiple switching tubes, diodes and other devices, and multiple devices are connected in series and in parallel to form the second rectifier unit.

[0032] In the above-mentioned control circuit, when the first rectifier power supply is connected to the grid and powered on, the grid power is rectified by the first rectifier unit and then transmitted to the bus capacitor. Since the bus capacitor and the first capacitor are connected in parallel, the grid power is simultaneously transmitted to the first capacitor; the voltage of the first capacitor begins to increase continuously; when the voltage of the first capacitor reaches the above-mentioned target voltage, the pitch motor starts to run and the pitch drive starts normally.

[0033] When the pitch motor is running, the second rectifier unit inverts the bus voltage at both ends of the bus capacitor and then transmits it to the pitch motor; when the pitch motor is generating electricity, the second rectifier unit rectifies the voltage generated by the pitch motor to the bus, at which point the bus voltage at both ends of the bus capacitor increases. After the bus voltage increases, the battery device starts to be charged with a larger current, and during the charging process, the bus voltage decreases.

[0034] The control circuit of the above-mentioned variable pitch motor includes a first rectifier unit, a first capacitor, a battery device, a bus capacitor, and a second rectifier unit; the first rectifier unit is used to connect to the power grid; the first rectifier unit, the first capacitor, the battery device, the bus capacitor, and the second rectifier unit are connected in parallel; the second rectifier unit is used to connect to the variable pitch motor; the first rectifier unit is used to rectify the electric energy output by the power grid, and transmit the rectified electric energy to the first capacitor and the bus capacitor; when the capacitor voltage of the first capacitor reaches the preset target voltage, the second rectifier unit inverts the capacitor voltage to obtain the inverted voltage, and controls the operation of the variable pitch motor by the inverted voltage; when the variable pitch motor generates electricity, the second rectifier unit rectifies the generated voltage to the bus; when the bus voltage at both ends of the bus capacitor rises to the preset voltage threshold, the first capacitor charges the battery device. In the control circuit, by setting the battery device, when the bus voltage is high, the battery device is charged, on the one hand, there is no need to set the brake resistor, saving the brake resistor, on the other hand, the electric energy is stored through the battery, and can be supplied to other devices for use, so that the electric energy is fully utilized and energy waste is avoided.

[0035] Furthermore, the first rectifying unit includes a plurality of switching tubes; when the battery device is fully charged, the bus voltage is inverted by the first rectifying unit, and the inverted voltage is fed back to the power grid.

[0036] When the battery device is fully charged and can no longer absorb electric energy, the bus voltage can be inverted by the first rectifier unit, and the inverted electric energy is fed back to the grid. In most cases, the battery device mainly absorbs electric energy, and the voltage is fed back to the grid as a supplement.

[0037] This method can gather electric energy into the power grid so that other devices can use the electric energy through the power grid, further improving the utilization rate of electric energy.

[0038] When the capacitance value of the first capacitor decays, the battery device can provide power for retracting the propellers; when low-voltage breakdown occurs and the motor load is large, the battery device can stabilize the bus voltage.

[0039] Figure 2 A topological schematic diagram of a control circuit of a variable pitch motor is provided.

[0040] The above-mentioned first rectifier unit includes: a first branch, a second branch and a third branch connected in parallel; wherein the first branch includes: a first switch tube Q1 and a second switch tube Q2 connected in series; the second branch includes: a third switch tube Q3 and a fourth switch tube Q4 connected in series; the third branch includes: a fifth switch tube Q5 and a sixth switch tube Q6 connected in series.

[0041] Figure 2The supercapacitor in is the aforementioned first capacitor, the battery PACK is the aforementioned battery device, C is the bus capacitor; and M is the variable pitch motor.

[0042] Among them, the emitter of the first switch tube can be connected to the collector of the second switch tube, similarly, the emitter of the third switch tube can be connected to the collector of the fourth switch tube, and the emitter of the fifth switch tube can be connected to the collector of the sixth switch tube.

[0043] The three-phase power supply of the above-mentioned power grid includes a first output interface, a second output interface and a third output interface; the first output interface is connected between the first switch tube and the second switch tube; the second output interface is connected between the third switch tube and the fourth switch tube; the third output interface is connected between the fifth switch tube and the sixth switch tube.

[0044] See also Figure 2 In the embodiment, the three-phase power supply includes three branches, namely, Ua, Ub and Uc, each of which includes a resistor R and an inductor L connected in series, and then connected to the first rectifier unit; wherein, in the branch of Ua, the cable extending from the inductor is connected to the cable between the first switch tube Q1 and the second switch tube Q2; in the branch of Ub, the cable extending from the inductor is connected to the cable between the third switch tube Q3 and the fourth switch tube Q4; in the branch of Uc, the cable extending from the inductor is connected to the cable between the fifth switch tube Q5 and the sixth switch tube Q6.

[0045] Furthermore, the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube are all IGBT (Insulate Gate Bipolar Transistor) devices.

[0046] In the related art, the switch tube in the first rectifier unit can be realized by a diode, but the first rectifier unit composed of a diode can only realize unidirectional rectification, that is, the rectification function from the grid side to the pitch motor side, and cannot realize reverse inversion.

[0047] In this embodiment, the switch tube in the first rectifier unit is an IGBT tube, so the first rectifier unit has an inverter function. After adding the inverter function of the first rectifier unit, the variable pitch motor will have the following two working conditions: one is the motor mode, the electric energy on the grid side is transmitted to the motor side after being rectified by the IGBT in the first rectifier unit to drive the motor to run; the other is the generator mode, the electric energy on the motor side is transmitted to the grid side after being inverted by the IGBT for use by other components of the wind turbine.

[0048] When the wind turbine loses power, the electric energy of the first capacitor or battery device can be inverted and transmitted to the power grid to support the yaw or main control system to implement anti-typhoon, anti-vortex and other strategies; on the other hand, when a large current flows into the DC bus, since the first rectifier unit has an inverter function, the excess current can be supplied to other components of the wind turbine, avoiding the waste of electric energy, and also eliminating the configuration of high-power braking resistors, saving space in the cabinet.

[0049] Continue to refer Figure 2 The above-mentioned second rectifier unit includes: a fourth branch, a fifth branch and a sixth branch connected in parallel; wherein the fourth branch includes: a seventh switch tube Q1' and an eighth switch tube Q2' connected in series; the fifth branch includes: a ninth switch tube Q3' and a tenth switch tube Q4' connected in series; the sixth branch includes: an eleventh switch tube Q5' and a twelfth switch tube Q6' connected in series.

[0050] Among them, the emitter of the seventh switch tube can be connected to the collector of the eighth switch tube. Similarly, the emitter of the ninth switch tube can be connected to the collector of the tenth switch tube, and the emitter of the eleventh switch tube can be connected to the collector of the twelfth switch tube.

[0051] The above-mentioned variable pitch motor includes a first input interface U, a second input interface V and a third input interface W; the first input interface is connected between the seventh switch tube and the eighth switch tube; the second input interface is connected between the ninth switch tube and the tenth switch tube; the third input interface is connected between the eleventh switch tube and the twelfth switch tube.

[0052] The seventh switch tube, the eighth switch tube, the ninth switch tube, the tenth switch tube, the eleventh switch tube and the twelfth switch tube are all IGBT devices.

[0053] Furthermore, the above-mentioned control circuit also includes a control module of the first rectifier unit; the control module is used to: collect the input voltage of the power grid, the input current of the power grid, and the bus voltage across the bus capacitor C, and output a control signal for the first rectifier unit.

[0054] like Figure 3 As shown, the input voltages Ua and Ub of the power grid are collected and input into the abc-dq converter; the abc-dq converter is used to convert the abc three-phase coordinate system into the dq two-phase coordinate system, and output conversion voltages Ud and Uq; Ua and Ub are input into the phase-locked loop PLL, and sinθ and cosθ are output; the input currents Ia and Ib of the power grid, together with sinθ and cosθ, are input into the abc-dq converter, and Iq and Id are output.

[0055] The bus voltage Udc at both ends of the bus capacitor is subtracted from the command voltage Udc* and input to the PI controller. The PI controller is a linear controller and outputs the current Id*. The current Id* is subtracted from the current Id and input to the PI controller to obtain the output result 1. The voltage sum of the compensation voltage wLIq and the voltage Ud is subtracted from the output result 1 to obtain the output result 2. The compensation voltage wLIq is the compensation voltage of the voltage Ud.

[0056] The current Iq is subtracted from the given current Iq* and input into the PI controller to obtain output result 3; the difference between the voltage Uq and the compensation voltage wLId is subtracted from the output result 3 to obtain output result 4. Output results 3 and 4 are input into the abc-dq converter to output voltage given values ​​Udref and Uqref. Udref and Uqref are input into the space vector debugging algorithm SVPWM to output control signals Sa, Sb and Sc. The control signals Sa, Sb and Sc are used to control the above Figure 2 The switch tube in the first rectifier unit is turned on or off.

[0057] See also Figure 4 A structural schematic diagram of a pitch drive is shown; the pitch drive includes a pitch motor 40 and a control circuit 41 of the pitch motor; the pitch motor is connected to the control circuit; the pitch drive may also include other components.

[0058] In addition, in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the utility model can be embodied in the form of a software product in essence or in other words, the part that contributes to the prior art or the part of the technical solution. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the utility model. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0060] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0061] Finally, it should be noted that the above embodiments are only specific implementation methods of the utility model, which are used to illustrate the technical solution of the utility model, rather than to limit it. The protection scope of the utility model is not limited thereto. Although the utility model is described in detail with reference to the above embodiments, those skilled in the art should understand that any technician familiar with the technical field can still modify the technical solution recorded in the above embodiments within the technical scope disclosed by the utility model, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solution of the embodiment of the utility model, and should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model shall be based on the protection scope of the claims.

Claims

1. A control circuit for a pitch motor, characterized in that: The control circuit includes a first rectifying unit, a first capacitor, a battery device, a bus capacitor and a second rectifying unit; The first rectifier unit is used to connect to the power grid; the first rectifier unit, the first capacitor, the battery device, the bus capacitor and the second rectifier unit are connected in parallel; the second rectifier unit is used to connect to the pitch motor; The first rectifying unit is used to rectify the electric energy output by the power grid, and transmit the rectified electric energy to the first capacitor and the bus capacitor; When the capacitor voltage of the first capacitor reaches a preset target voltage, the second rectifier unit inverts the capacitor voltage to obtain an inverter voltage, and controls the operation of the pitch motor through the inverter voltage; When the variable pitch motor generates electricity, the second rectifier unit rectifies the generated voltage to the bus; when the bus voltage across the bus capacitor increases to a preset voltage threshold, the first capacitor charges the battery device.

2. The control circuit according to claim 1, characterized in that: The first rectifying unit includes a plurality of switch tubes; When the battery device is fully charged, the bus voltage is inverted by the first rectifying unit, and the inverted voltage is fed back to the power grid.

3. The control circuit according to claim 1, characterized in that: The first rectifying unit comprises: a first branch, a second branch and a third branch connected in parallel; Wherein, the first branch includes: a first switch tube and a second switch tube connected in series; The second branch includes: a third switch tube and a fourth switch tube connected in series; The third branch includes: a fifth switch tube and a sixth switch tube connected in series.

4. The control circuit according to claim 3, characterized in that: The three-phase power supply of the power grid includes a first output interface, a second output interface and a third output interface; The first output interface is connected between the first switch tube and the second switch tube; The second output interface is connected between the third switch tube and the fourth switch tube; The third output interface is connected between the fifth switch tube and the sixth switch tube.

5. The control circuit according to claim 3, characterized in that: The first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube are all IGBT devices.

6. The control circuit according to claim 1, characterized in that: The second rectifying unit comprises: a fourth branch, a fifth branch and a sixth branch connected in parallel; Wherein, the fourth branch includes: a seventh switch tube and an eighth switch tube connected in series; The fifth branch includes: a ninth switch tube and a tenth switch tube connected in series; The sixth branch includes: an eleventh switch tube and a twelfth switch tube connected in series.

7. The control circuit according to claim 6, characterized in that: The pitch motor comprises a first input interface, a second input interface and a third input interface; The first input interface is connected between the seventh switch tube and the eighth switch tube; The second input interface is connected between the ninth switch tube and the tenth switch tube; The third input interface is connected between the eleventh switch tube and the twelfth switch tube.

8. The control circuit according to claim 6, characterized in that: The seventh switch tube, the eighth switch tube, the ninth switch tube, the tenth switch tube, the eleventh switch tube and the twelfth switch tube are all IGBT devices.

9. The control circuit according to claim 1, characterized in that: The control circuit further includes a control module of the first rectifier unit; The control module is used to collect the input voltage of the power grid, the input current of the power grid, and the bus voltage across the bus capacitor, and output a control signal for the first rectifier unit.

10. A variable pitch drive, characterized in that: The pitch drive comprises a pitch motor and a control circuit of the pitch motor according to any one of claims 1 to 9; the pitch motor is connected to the control circuit.

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