A wind power converter with direct current side unloading function, a system and an unloading method

Abstract

The application relates to a wind power converter with a direct-current side unloading function, a system and an unloading method, and belongs to the technical field of power electronics, and comprises a grid-side alternating-current circuit, a machine-side alternating-current circuit, a grid-side full-controlled device circuit, a machine-side full-controlled device circuit and a direct-current side circuit; the first end of the grid-side alternating-current circuit is connected to three-phase lines of a power grid, the second end of the grid-side alternating-current circuit is connected to the first end of the direct-current side circuit through the grid-side full-controlled device circuit, and the second end of the direct-current side circuit is connected to the machine-side alternating-current circuit through the machine-side full-controlled device circuit. The application realizes fault unloading and normal frequent unloading of a machine through a chopping circuit and a second-stage discharge circuit, improves the service life of the wind power converter, indirectly realizes bus grounding through a discharge resistor in the second-stage discharge circuit, eliminates the safety hidden danger when a maintenance personnel mistakenly touches the bus, and can also give an unloading prompt through a display circuit.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and specifically relates to a wind power converter, system and unloading method with DC side unloading function. Background Technology

[0002] There are stringent requirements for the DC-side unloading time setting. However, current traditional wind turbine converters, when using a fixed load for DC-side discharge, often require unloading times on the order of minutes, which is slow and cannot meet the requirements. To achieve rapid unloading, the only option is to drive a chopper circuit. Given the relatively high cost of chopper circuits, frequent starting could shorten the lifespan of the wind turbine converter. Furthermore, traditional wind turbine converters do not have a bus grounding wire, posing a safety hazard during maintenance. This is a shortcoming of the existing technology.

[0003] In view of this, it is very necessary to provide a wind power converter, system and unloading method with DC side unloading function to solve the above-mentioned defects in the prior art. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing wind power converters, such as their inability to quickly unload and the lack of bus grounding wires, by providing a wind power converter, system, and unloading method with DC-side unloading function, thereby solving the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a wind power converter with DC-side unloading function, comprising: grid-side AC circuit, machine-side AC circuit, grid-side fully controlled device circuit, machine-side fully controlled device circuit and DC-side circuit; The first end of the grid-side AC circuit is connected to the three-phase line of the power grid. The second end of the grid-side AC circuit is connected to the first end of the DC-side circuit through the grid-side fully controlled device circuit. The second end of the DC-side circuit is connected to the machine-side AC circuit through the machine-side fully controlled device circuit. The DC-side circuit includes a voltmeter, a display circuit, a drive circuit, a second-stage bleeder circuit, resistors R3 and R4, and a chopper circuit. The display circuit includes diode D1, resistor R1, and LED D2. The drive circuit includes a drive power supply and a circuit breaker. The drive power supply is connected to the second-stage bleeder circuit via the normally closed auxiliary contact of the circuit breaker. The second-stage bleeder circuit includes resistor R2 and transistor Q1. The chopper circuit includes resistors R5 and R6, capacitors C1 and C2, and fully controlled switching transistors Q2 and Q3. The voltmeter is connected in parallel across the DC-side circuit. The cathode of diode D1 is connected to the grid-side fully controlled device circuit, and the anode of diode D1 is connected to the cathode of LED D2 via resistor R1. The anode of LED D2 is connected to the first terminal of the normally closed auxiliary contact of the circuit breaker, and the second terminal of the normally closed auxiliary contact of the circuit breaker is connected to the drive power supply. The first terminal of resistor R2 is connected to... The circuit consists of: a diode D1 cathode terminal, a resistor R2 second terminal connected to the emitter of transistor Q1, a transistor Q1 base connected to the first terminal of the normally closed auxiliary contact of the circuit breaker, and a transistor Q1 collector connected to the grid-side fully controlled device circuit; a resistor R3 first terminal connected to the cathode of diode D1, a resistor R3 second terminal connected to the grid-side fully controlled device circuit, the machine-side fully controlled device circuit, and the first terminal of resistor R4, and a resistor R4 second terminal connected to the collector of transistor Q1; a capacitor C1 connected in parallel across resistor R3, a resistor R5 connecting the first terminal of resistor R3 to the collector of fully controlled switching transistor Q2, and a fully controlled switching transistor Q2 emitter connected to the second terminal of resistor R3; a capacitor C2 connected in parallel across resistor R4, a resistor R6 connecting the first terminal of resistor R4 to the collector of fully controlled switching transistor Q3, and a fully controlled switching transistor Q3 emitter connected to the second terminal of resistor R4.

[0006] In one embodiment, the grid-side fully controlled device circuit includes fully controlled switching transistors Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q11, Q12, Q13, Q14, and Q15, diodes D3, D4, D5, D6, D7, and D8.

[0007] In one embodiment, the collectors of fully controlled transistors Q4, Q5, and Q6 are all connected to the cathode of diode D1. The emitter of fully controlled transistor Q4 is connected to the cathode of diode D3 and the collector of fully controlled transistor Q7. The anode of diode D3 is connected to the second terminal of resistor R3. The emitter of fully controlled transistor Q7 is connected to the grid-side AC circuit and the collector of fully controlled transistor Q10. The emitter of fully controlled transistor Q5 is connected to the cathode of diode D3 and the collector of fully controlled transistor Q10. The cathode of diode D4 and the collector of fully controlled switch Q8 are connected. The anode of diode D4 is connected to the second terminal of resistor R3. The emitter of fully controlled switch Q8 is connected to the grid-side AC circuit and the collector of fully controlled switch Q11. The emitter of fully controlled switch Q6 is connected to the cathode of diode D5 and the collector of fully controlled switch Q9. The anode of diode D5 is connected to the second terminal of resistor R3. The emitter of fully controlled switch Q9 is connected to the grid-side AC circuit and the collector of fully controlled switch Q12. The emitter of the fully controlled switch Q10 is connected to the collector of the fully controlled switch Q13 and the anode of diode D6. The cathode of diode D6 is connected to the second terminal of resistor R3. The emitter of the fully controlled switch Q13 is connected to the collector of transistor Q1. The emitter of the fully controlled switch Q11 is connected to the collector of the fully controlled switch Q14 and the anode of diode D7. The cathode of diode D7 is connected to the second terminal of resistor R3. The emitter of the fully controlled switch Q14 is connected to the collector of transistor Q1. The emitter of the fully controlled switch Q12 is connected to the collector of the fully controlled switch Q15 and the anode of diode D8. The cathode of diode D8 is connected to the second terminal of resistor R3. The emitter of the fully controlled switch Q15 is connected to the collector of transistor Q1.

[0008] In one embodiment, the machine-side fully controlled device circuit includes fully controlled switching transistors Q16, Q17, Q18, Q19, Q20, Q21, Q22, Q23, Q24, Q25, Q26, and Q27, diodes D9, D10, D11, D12, D13, and D14.

[0009] In one embodiment, the collectors of fully controlled transistors Q16, Q17, and Q18 are all connected to the cathode of diode D1. The emitter of fully controlled transistor Q16 is connected to the collector of fully controlled transistor Q19. The emitter of fully controlled transistor Q19 is connected to the machine-side AC circuit, the collector of fully controlled transistor Q22, and the cathode of diode D9. The anode of diode D9 is connected to the second terminal of resistor R3. The emitter of fully controlled transistor Q17 is connected to the fully controlled... The collector of the fully controlled switch Q20 is connected to the machine-side AC circuit; the collector of the fully controlled switch Q23 is connected to the negative terminal of diode D10; the positive terminal of diode D10 is connected to the second terminal of resistor R3; the emitter of the fully controlled switch Q18 is connected to the collector of the fully controlled switch Q21; the emitter of the fully controlled switch Q21 is connected to the machine-side AC circuit; the collector of the fully controlled switch Q24 is connected to the negative terminal of diode D11; the positive terminal of diode D11 is connected to the second terminal of resistor R3. The collector of the fully controlled switch Q22 is also connected to the anode of diode D12, and the cathode of diode D12 is connected to the second terminal of resistor R3. The collector of the fully controlled switch Q23 is also connected to the anode of diode D13, and the cathode of diode D13 is connected to the second terminal of resistor R3. The collector of the fully controlled switch Q24 is also connected to the anode of diode D14, and the cathode of diode D14 is connected to the second terminal of resistor R3. The emitter of the fully controlled switch Q22 is connected to the collector of the fully controlled switch Q25. The emitter of the fully controlled switch Q23 is connected to the collector of the fully controlled switch Q26. The emitter of the fully controlled switch Q24 is connected to the collector of the fully controlled switch Q27. The emitters of the fully controlled switches Q25, Q26, and Q27 are all connected to the collector of transistor Q1.

[0010] In one embodiment, the grid-side AC circuit includes inductors L1, L2, and L3 connected in series on the three-phase lines of the power grid, and current transformers CT1, CT2, and CT3 installed on the three-phase lines of the power grid.

[0011] In one embodiment, the machine-side AC circuit includes inductors L4, L5, and L6 connected in series on the three-phase lines of the power grid, and current transformers CT4, CT5, and CT6 installed on the three-phase lines of the power grid.

[0012] In one embodiment, the first end of the grid-side AC circuit is connected to the three-phase line of the power grid via the normally open auxiliary contact of the circuit breaker.

[0013] Secondly, the present invention provides a system with DC-side unloading function, including a control module, a generator, and a wind power converter with DC-side unloading function as described in any one of the above.

[0014] Thirdly, the present invention provides an unloading method based on the above system, comprising: The control module determines whether the system is under maintenance, whether the system has experienced a complete failure, and whether the wind power converter itself has a fault. If the system is under maintenance, or if the system experiences a complete failure, or if the wind power converter itself has a fault, the chopper circuit will be activated to unload the load. If the system is not under maintenance and there is no overall system failure, and the wind power converter itself is not faulty, then the system is determined to be in a non-fault shutdown state. When the system is in a non-fault shutdown state, it is determined whether the circuit breaker is in the open state. If the circuit breaker is in the open state, the load is unloaded through the second-stage discharge circuit; if the circuit breaker is in the closed state, it is determined whether the DC side voltage obtained by the voltmeter is greater than or equal to 80% of the DC side reference voltage. If the obtained DC-side voltage is greater than or equal to 80% of the DC-side reference voltage, then determine whether a start-up command and a grid-side start-up command have been received; if the obtained DC-side voltage is less than 80% of the DC-side reference voltage, then perform pre-charging. If a start-up command and a grid-side start-up command are received, the grid-side AC circuit and the grid-side fully controlled device circuit are started first, and then the machine-side AC circuit and the machine-side fully controlled device circuit are started; otherwise, the system re-determines whether a start-up command and a grid-side start-up command have been received.

[0015] The beneficial effects of this invention are that it achieves fault unloading and normal frequent start-up unloading through the chopper circuit and the second-stage discharge circuit, thereby improving the service life of the wind power converter; at the same time, the bus grounding is indirectly achieved through the discharge resistor in the second-stage discharge circuit, eliminating the safety hazard when maintenance personnel accidentally touch the bus; in addition, this invention can also provide unloading prompts through the display circuit.

[0016] Furthermore, the design principle of this invention is reliable, the structure is simple, and it has a very wide range of application prospects.

[0017] Therefore, it is evident that the present invention has outstanding substantive features and significant progress compared with the prior art, and the beneficial effects of its implementation are also obvious. Attached Figure Description

[0018] Figure 1 This is the circuit diagram of a wind power converter.

[0019] Figure 2 This is a schematic diagram of the system relationships.

[0020] Figure 3 This is a flowchart illustrating the unloading method.

[0021] 1 is the wind power converter, 11 is the grid-side AC circuit, 12 is the machine-side AC circuit, 13 is the grid-side fully controlled device circuit, 14 is the machine-side fully controlled device circuit, 15 is the DC side circuit, QF-1 is the normally closed auxiliary contact of the circuit breaker, QF-0 is the normally open auxiliary contact of the circuit breaker, 6 is the voltmeter, 7 is the controller, and 8 is the generator. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following implementation methods.

[0023] like Figure 1 As shown, the present invention provides a wind power converter with DC-side unloading function, comprising: a grid-side AC circuit, a turbine-side AC circuit, a grid-side fully controlled device circuit, a turbine-side fully controlled device circuit, and a DC-side circuit; the first end of the grid-side AC circuit is connected to the three-phase line of the power grid, specifically, the first end of the grid-side AC circuit is connected to the three-phase line of the power grid through the normally open auxiliary contact of the circuit breaker; the second end of the grid-side AC circuit is connected to the first end of the DC-side circuit through the grid-side fully controlled device circuit, and the second end of the DC-side circuit is connected to the turbine-side AC circuit through the turbine-side fully controlled device circuit.

[0024] Specifically, the DC-side circuit includes a voltmeter, a display circuit, a drive circuit, a second-stage bleeder circuit, resistors R3 and R4, and a chopper circuit; the display circuit includes diode D1, resistor R1, and LED D2; the drive circuit includes a drive power supply and a circuit breaker, with the drive power supply connected to the second-stage bleeder circuit via the normally closed auxiliary contact of the circuit breaker. The second-stage bleeder circuit includes resistor R2 and transistor Q1; the chopper circuit includes resistors R5 and R6, capacitors C1 and C2, fully controlled switching transistors Q2 and Q3; the voltmeter is connected in parallel across the DC-side circuit; the cathode of diode D1 is connected to the grid-side fully controlled device circuit; the anode of diode D1 is connected to the cathode of LED D2 via resistor R1; the anode of LED D2 is connected to the first terminal of the normally closed auxiliary contact of the circuit breaker; the second terminal of the normally closed auxiliary contact of the circuit breaker is connected to the drive power supply; the first terminal of resistor R2... A resistor is connected to the negative terminal of diode D1. The second terminal of resistor R2 is connected to the emitter of transistor Q1. The base of transistor Q1 is connected to the first terminal of the normally closed auxiliary contact of the circuit breaker. The collector of transistor Q1 is connected to the grid-side fully controlled device circuit. The first terminal of resistor R3 is connected to the negative terminal of diode D1. The second terminal of resistor R3 is connected to the grid-side fully controlled device circuit, the machine-side fully controlled device circuit, and the first terminal of resistor R4. The second terminal of resistor R4 is connected to the collector of transistor Q1. Capacitor C1 is connected in parallel across resistor R3. The first terminal of resistor R3 is connected to the collector of fully controlled switching transistor Q2 through resistor R5. The emitter of fully controlled switching transistor Q2 is connected to the second terminal of resistor R3. Capacitor C2 is connected in parallel across resistor R4. The first terminal of resistor R4 is connected to the collector of fully controlled switching transistor Q3 through resistor R6. The emitter of fully controlled switching transistor Q3 is connected to the second terminal of resistor R4.

[0025] The grid-side fully controlled device circuit includes fully controlled switching transistors Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q11, Q12, Q13, Q14, and Q15; diodes D3, D4, D5, D6, D7, and D8; and the collectors of fully controlled switching transistors Q4 and Q5. The collectors of all fully controlled switching transistors Q6 are connected to the cathodes of diode D1. The emitters of fully controlled switching transistor Q4 are connected to the cathodes of diode D3 and the collectors of fully controlled switching transistor Q7. The anode of diode D3 is connected to the second terminal of resistor R3. The emitter of fully controlled switching transistor Q7 is connected to the AC grid circuit and the collector of fully controlled switching transistor Q10. The emitter of fully controlled switching transistor Q5 is connected to the cathodes of diode D4 and the collectors of fully controlled switching transistor Q8. The anode of diode D4 is connected to the second terminal of resistor R3. The emitter of fully controlled switching transistor Q8... The emitter of fully controlled transistor Q6 is connected to the negative terminal of diode D5 and the collector of fully controlled transistor Q9. The positive terminal of diode D5 is connected to the second terminal of resistor R3. The emitter of fully controlled transistor Q9 is connected to the AC circuit on the grid side and the collector of fully controlled transistor Q12. The emitter of fully controlled transistor Q10 is connected to the collector of fully controlled transistor Q13 and the positive terminal of diode D6. The negative terminal of diode D6 is connected to the second terminal of resistor R3. The emitter of transistor Q1 is connected to the collector of transistor Q1; the emitter of fully controlled transistor Q11 is connected to the collector of fully controlled transistor Q14 and the anode of diode D7, the cathode of diode D7 is connected to the second terminal of resistor R3, and the emitter of fully controlled transistor Q14 is connected to the collector of transistor Q1; the emitter of fully controlled transistor Q12 is connected to the collector of fully controlled transistor Q15 and the anode of diode D8, the cathode of diode D8 is connected to the second terminal of resistor R3, and the emitter of fully controlled transistor Q15 is connected to the collector of transistor Q1.

[0026] The machine-side fully controlled device circuit includes fully controlled switching transistors Q16, Q17, Q18, Q19, Q20, Q21, Q22, Q23, Q24, Q25, Q26, and Q27; diodes D9, D10, D11, D12, D13, and D14; the collector of fully controlled switching transistor Q16; the collector of fully controlled switching transistor Q17; and the fully controlled... The collectors of all transistors in the fully controlled switching transistor Q18 are connected to the negative terminal of diode D1. The emitter of the fully controlled switching transistor Q16 is connected to the collector of the fully controlled switching transistor Q19. The emitter of the fully controlled switching transistor Q19 is connected to the machine-side AC circuit. The collector of the fully controlled switching transistor Q22 and the negative terminal of diode D9 are also connected. The positive terminal of diode D9 is connected to the second terminal of resistor R3. The emitter of the fully controlled switching transistor Q17 is connected to the collector of the fully controlled switching transistor Q20. The emitter of the fully controlled switching transistor Q20 is connected to the machine-side AC circuit. The collector of the fully controlled switching transistor Q23 and the negative terminal of diode D10 are also connected. The positive terminal of transistor Q18 is connected to the second terminal of resistor R3; the emitter of fully controlled transistor Q18 is connected to the collector of fully controlled transistor Q21, the emitter of fully controlled transistor Q21 is connected to the machine-side AC circuit, the collector of fully controlled transistor Q24 and the negative terminal of diode D11, and the positive terminal of diode D11 is connected to the second terminal of resistor R3; the collector of fully controlled transistor Q22 is also connected to the positive terminal of diode D12, the negative terminal of diode D12 is connected to the second terminal of resistor R3; the collector of fully controlled transistor Q23 is also connected to the positive terminal of diode D13, and the negative terminal of diode D13 is connected to... The collector of the fully controlled switch Q24 is connected to the positive terminal of diode D14 at the second end of resistor R3, and the negative terminal of diode D14 is connected to the second end of resistor R3. The emitter of the fully controlled switch Q22 is connected to the collector of the fully controlled switch Q25, the emitter of the fully controlled switch Q23 is connected to the collector of the fully controlled switch Q26, the emitter of the fully controlled switch Q24 is connected to the collector of the fully controlled switch Q27, and the emitters of the fully controlled switches Q25, Q26, and Q27 are all connected to the collector of transistor Q1.

[0027] The grid-side AC circuit includes inductors L1, L2, and L3 connected in series on the three-phase lines of the power grid, and current transformers CT1, CT2, and CT3 installed on the three-phase lines of the power grid; the machine-side AC circuit includes inductors L4, L5, and L6 connected in series on the three-phase lines of the power grid, and current transformers CT4, CT5, and CT6 installed on the three-phase lines of the power grid.

[0028] Once the circuit breaker trips, the wind turbine converter will unload through resistor R2, with the unloading time typically on the order of seconds. In this way, resistor R2 can also act as a grounding resistor, achieving bus grounding and eliminating the safety hazard of maintenance personnel accidentally touching the bus.

[0029] When the DC side circuit unloading is completed, that is, when the bus voltage is lower than the preset voltage of the drive circuit, the LED D2 will provide a prompt.

[0030] like Figure 2 As shown, the present invention provides a system with DC-side unloading function, including a control module, a generator, and a wind power converter with DC-side unloading function as described in any one of the above-mentioned methods. The controller is connected to the generator through the wind power converter.

[0031] like Figure 3 As shown, the present invention provides an unloading method based on the above system, comprising: S1. The control module determines whether the system is under maintenance, whether the system has a complete fault, and whether the wind power converter itself has a fault. S2. If the system is under maintenance, or the system experiences a complete failure, or the wind power converter itself has a fault, the chopper circuit will be started to unload the load. S3. If the system is not under maintenance and there is no overall system failure, and the wind power converter itself is not faulty, then the system is determined to be in a non-fault shutdown state. When the system is in a non-fault shutdown state, determine whether the circuit breaker is in the open state. S4. If the circuit breaker is in the open state, the load is unloaded through the second-stage discharge circuit; if the circuit breaker is in the closed state, it is determined whether the DC side voltage obtained by the voltmeter is greater than or equal to 80% of the DC side reference voltage. S5. If the obtained DC-side voltage is greater than or equal to 80% of the DC-side reference voltage, determine whether a start-up command and a grid-side start-up command have been received; if the obtained DC-side voltage is less than 80% of the DC-side reference voltage, perform pre-charging. S6. If a start-up command and a grid-side start-up command are received, the grid-side AC circuit and the grid-side fully controlled device circuit are started first, and then the machine-side AC circuit and the machine-side fully controlled device circuit are started; otherwise, the start-up command and the grid-side start-up command are re-evaluated.

[0032] The above-disclosed embodiments are merely preferred embodiments of the present invention, but the present invention is not limited thereto. Any non-creative variations that can be conceived by those skilled in the art, as well as any improvements and modifications made without departing from the principles of the present invention, should fall within the protection scope of the present invention.

Claims

1. A wind power converter with DC-side unloading function, characterized in that, include: Grid-side AC circuit, machine-side AC circuit, grid-side fully controlled device circuit, machine-side fully controlled device circuit, and DC-side circuit; The first end of the grid-side AC circuit is connected to the three-phase line of the power grid. The second end of the grid-side AC circuit is connected to the first end of the DC-side circuit through the grid-side fully controlled device circuit. The second end of the DC-side circuit is connected to the machine-side AC circuit through the machine-side fully controlled device circuit. The DC-side circuit includes a voltmeter, a display circuit, a drive circuit, a second-stage bleeder circuit, resistors R3 and R4, and a chopper circuit. The display circuit includes diode D1, resistor R1, and LED D2. The drive circuit includes a drive power supply and a circuit breaker. The drive power supply is connected to the second-stage bleeder circuit via the normally closed auxiliary contact of the circuit breaker. The second-stage bleeder circuit includes resistor R2 and transistor Q1. The chopper circuit includes resistors R5 and R6, capacitors C1 and C2, and fully controlled switching transistors Q2 and Q3. The voltmeter is connected in parallel across the DC-side circuit. The cathode of diode D1 is connected to the grid-side fully controlled device circuit, and the anode of diode D1 is connected to the cathode of LED D2 via resistor R1. The anode of LED D2 is connected to the first terminal of the normally closed auxiliary contact of the circuit breaker, and the second terminal of the normally closed auxiliary contact of the circuit breaker is connected to the drive power supply. The first terminal of resistor R2 is connected to... The circuit is connected as follows: The first terminal of resistor R2 is connected to the cathode of diode D1; the second terminal of resistor R2 is connected to the emitter of transistor Q1; the base of transistor Q1 is connected to the first terminal of the normally closed auxiliary contact of the circuit breaker; and the collector of transistor Q1 is connected to the grid-side fully controlled device circuit. The first terminal of resistor R3 is connected to the cathode of diode D1; the second terminal of resistor R3 is connected to the grid-side fully controlled device circuit, the machine-side fully controlled device circuit, and the first terminal of resistor R4; and the second terminal of resistor R4 is connected to the collector of transistor Q1. Capacitor C1 is connected in parallel across resistor R3; the first terminal of resistor R3 is connected to the collector of fully controlled switching transistor Q2 through resistor R5; and the emitter of fully controlled switching transistor Q2 is connected to the second terminal of resistor R3. Capacitor C2 is connected in parallel across resistor R4; the first terminal of resistor R4 is connected to the collector of fully controlled switching transistor Q3 through resistor R6; and the emitter of fully controlled switching transistor Q3 is connected to the second terminal of resistor R4. The wind power converter with DC-side unloading function is used in the unloading of a system with DC-side unloading function; wherein, the system with DC-side unloading function includes a control module, a generator and the wind power converter with DC-side unloading function. The unloading method of the system with DC-side unloading function includes: The control module determines whether the system is under maintenance, whether the system has experienced a complete failure, and whether the wind power converter itself has a fault. If the system is under maintenance, or if the system experiences a complete failure, or if the wind power converter itself has a fault, the chopper circuit will be activated to unload the load. If the system is not under maintenance and there is no overall system failure, and the wind power converter itself is not faulty, then the system is determined to be in a non-fault shutdown state. When the system is in a non-fault shutdown state, it is determined whether the circuit breaker is in the open state. If the circuit breaker is in the open state, the load is unloaded through the second-stage discharge circuit.

2. A wind power converter with DC-side unloading function according to claim 1, characterized in that, The grid-side fully controlled device circuit includes fully controlled switching transistors Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q11, Q12, Q13, Q14, and Q15, diodes D3, D4, D5, D6, D7, and D8.

3. A wind power converter with DC-side unloading function according to claim 2, characterized in that, The collectors of fully controlled transistors Q4, Q5, and Q6 are all connected to the cathode of diode D1. The emitter of fully controlled transistor Q4 is connected to the cathode of diode D3 and the collector of fully controlled transistor Q7. The anode of diode D3 is connected to the second terminal of resistor R3. The emitter of fully controlled transistor Q7 is connected to the AC grid circuit and the collector of fully controlled transistor Q10. The emitter of fully controlled transistor Q5 is connected to diode D4. The negative terminal and collector of the fully controlled switch Q8 are connected to the positive terminal of the diode D4, which is connected to the second terminal of the resistor R3. The emitter of the fully controlled switch Q8 is connected to the grid-side AC circuit and the collector of the fully controlled switch Q11. The emitter of the fully controlled switch Q6 is connected to the negative terminal of the diode D5 and the collector of the fully controlled switch Q9. The positive terminal of the diode D5 is connected to the second terminal of the resistor R3. The emitter of the fully controlled switch Q9 is connected to the grid-side AC circuit and the collector of the fully controlled switch Q12. The emitter of the fully controlled switch Q10 is connected to the collector of the fully controlled switch Q13 and the anode of diode D6. The cathode of diode D6 is connected to the second terminal of resistor R3. The emitter of the fully controlled switch Q13 is connected to the collector of transistor Q1. The emitter of the fully controlled switch Q11 is connected to the collector of the fully controlled switch Q14 and the anode of diode D7. The cathode of diode D7 is connected to the second terminal of resistor R3. The emitter of the fully controlled switch Q14 is connected to the collector of transistor Q1. The emitter of the fully controlled switch Q12 is connected to the collector of the fully controlled switch Q15 and the anode of diode D8. The cathode of diode D8 is connected to the second terminal of resistor R3. The emitter of the fully controlled switch Q15 is connected to the collector of transistor Q1.

4. A wind power converter with DC-side unloading function according to claim 3, characterized in that, The machine-side fully controlled device circuit includes fully controlled switching transistors Q16, Q17, Q18, Q19, Q20, Q21, Q22, Q23, Q24, Q25, Q26, and Q27, as well as diodes D9, D10, D11, D12, D13, and D14.

5. A wind power converter with DC-side unloading function according to claim 4, characterized in that, The collectors of fully controlled transistors Q16, Q17, and Q18 are all connected to the cathode of diode D1. The emitter of fully controlled transistor Q16 is connected to the collector of fully controlled transistor Q19. The emitter of fully controlled transistor Q19 is connected to the machine-side AC circuit, the collector of fully controlled transistor Q22, and the cathode of diode D9. The anode of diode D9 is connected to the second terminal of resistor R3. The emitter of fully controlled transistor Q17 is connected to the cathode of fully controlled transistor Q18. The collector of transistor Q20, the emitter of fully controlled transistor Q20 is connected to the machine-side AC circuit, the collector of fully controlled transistor Q23 is connected to the negative terminal of diode D10, and the positive terminal of diode D10 is connected to the second terminal of resistor R3; the emitter of fully controlled transistor Q18 is connected to the collector of fully controlled transistor Q21, the emitter of fully controlled transistor Q21 is connected to the machine-side AC circuit, the collector of fully controlled transistor Q24 is connected to the negative terminal of diode D11, and the positive terminal of diode D11 is connected to the second terminal of resistor R3; The collector of the fully controlled switch Q22 is also connected to the anode of diode D12, and the cathode of diode D12 is connected to the second terminal of resistor R3. The collector of the fully controlled switch Q23 is also connected to the anode of diode D13, and the cathode of diode D13 is connected to the second terminal of resistor R3. The collector of the fully controlled switch Q24 is also connected to the anode of diode D14, and the cathode of diode D14 is connected to the second terminal of resistor R3. The emitter of the fully controlled switch Q22 is connected to the collector of the fully controlled switch Q25. The emitter of the fully controlled switch Q23 is connected to the collector of the fully controlled switch Q26. The emitter of the fully controlled switch Q24 is connected to the collector of the fully controlled switch Q27. The emitters of the fully controlled switches Q25, Q26, and Q27 are all connected to the collector of transistor Q1.

6. A wind power converter with DC-side unloading function according to claim 2, characterized in that, The grid-side AC circuit includes inductors L1, L2, and L3 connected in series on the three-phase lines of the power grid, and current transformers CT1, CT2, and CT3 installed on the three-phase lines of the power grid.

7. A wind power converter with DC-side unloading function according to claim 2, characterized in that, The machine-side AC circuit includes inductors L4, L5, and L6 connected in series on the three-phase lines of the power grid, and current transformers CT4, CT5, and CT6 installed on the three-phase lines of the power grid.

8. A wind power converter with DC-side unloading function according to claim 1, characterized in that, The first end of the grid-side AC circuit is connected to the three-phase power grid line through the normally open auxiliary contact of the circuit breaker.

9. A system with DC-side unloading function, characterized in that, It includes a control module, a generator, and a wind power converter with DC-side unloading function as described in any one of claims 1-8.

10. A method for unloading the system according to claim 9, characterized in that, include: The control module determines whether the system is under maintenance, whether the system has experienced a complete failure, and whether the wind power converter itself has a fault. If the system is under maintenance, or if the system experiences a complete failure, or if the wind power converter itself has a fault, the chopper circuit will be activated to unload the load. If the system is not under maintenance and there is no overall system failure, and the wind power converter itself is not faulty, then the system is determined to be in a non-fault shutdown state. When the system is in a non-fault shutdown state, it is determined whether the circuit breaker is in the open state. If the circuit breaker is in the open state, the load is unloaded through the second-stage discharge circuit; if the circuit breaker is in the closed state, it is determined whether the DC side voltage obtained by the voltmeter is greater than or equal to 80% of the DC side reference voltage. If the obtained DC-side voltage is greater than or equal to 80% of the DC-side reference voltage, then determine whether a start-up command and a grid-side start-up command have been received; if the obtained DC-side voltage is less than 80% of the DC-side reference voltage, then perform pre-charging. If a start command and a grid-side start command are received, the grid-side AC circuit and the grid-side fully controlled device circuit will be started first, and then the machine-side AC circuit and the machine-side fully controlled device circuit will be started. Conversely, if no power-on command and network-side startup command are received, a new determination will be made.

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