Black-start control method, system and equipment for fan converter and medium

Abstract

The invention discloses a fan converter black-start control method, system and device and a medium. A voltage starting mode or a current starting mode is judged to be entered according to the voltage of a power grid side. The starting control methods of the motor side converter in the starting process in the two starting modes are consistent, direct current voltage is controlled, the starting process of the power grid side converter is switched according to the modes, and switching is convenient and flexible; compared with starting in a direct network construction mode, a transition process is added in the middle, the current and the alternating voltage are kept stable in the starting process, after starting is completed, a network construction control mode is switched, safety and reliability are achieved, the starting failure problem is effectively avoided, and the starting success rate is increased.

Description

Technical Field

[0001] The present invention belongs to the field of renewable energy power generation, and in particular relates to a black start control method, system, equipment and medium for a wind turbine converter. Background Art

[0002] Traditional grid black start technology uses hydropower and gas-fired power generation as internal black start power sources. However, in the receiving grid with scarce hydropower resources, pumped storage and gas-fired units are scarce, and a small number of pumped storage units frequently participate in peak load regulation and frequency regulation. At the same time, due to the rapid growth of load, the number of grid power supply partitions without black start power sources continues to increase. The small number of black start power sources and the solidified partition recovery scheme seriously restrict the black start capability and recovery speed of the grid after a major power outage. With the construction of new power systems, grid-building new energy technologies based on the "voltage source control mode" have developed rapidly. Grid-building new energy units such as wind turbines can be independently networked and operated, and can achieve active support and autonomous operation of the grid, which is a potential grid black start power source. It has become an industry consensus to use grid-type new energy units to build a new power system. In regional power grids with a high proportion of new energy installed capacity, the black start support capability of grid-type new energy units should be brought into play. Research on using grid-type new energy units as black start power sources after serious power grid faults can not only provide a new solution for power grid black start, but also greatly improve the grid and load recovery speed after a major power outage through multi-zone parallel black start, which is of great significance to shortening the power outage time and ensuring my country's energy security and social stability.

[0003] In the prior art, the mainstream method of black start is to use voltage source control, namely, grid control. However, this method is difficult to implement in actual engineering. The main reason is that for wind farms, the distribution of wind turbines is discrete, and the line parameters and system parameters are also discrete. If multiple wind turbines are started using the "voltage source control mode", they will have a control impact on each other, making coordinated control difficult. If the control parameters are not appropriate, the startup process will cause a certain impact on the power grid, affecting the success rate of the black start. Therefore, at this stage, a highly reliable and more successful wind turbine converter black start method is needed. Summary of the invention

[0004] The purpose of the present invention is to provide a black start control method, system, device and medium for a wind turbine converter, which can improve the black start success rate of the wind turbine converter.

[0005] In order to achieve the above object, the solution of the present invention is:

[0006] A black start control method for a wind turbine converter, the wind turbine converter comprising a motor side converter and a grid side converter, wherein the AC end of the motor side converter is connected to a wind turbine generator, and its DC end is connected to the DC end of the grid side converter, and the AC end of the grid side converter is connected to an AC grid via an AC switch; the method comprises:

[0007] Obtain the grid voltage. If the grid voltage is lower than the starting threshold, use the voltage starting mode; otherwise, use the current starting mode.

[0008] Among them, the voltage start mode includes:

[0009] First start the motor-side converter, then close the AC switch, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to gradually increase the AC terminal voltage of the grid-side converter from 0 to the AC terminal rated value;

[0010] Among them, the current start mode includes:

[0011] First start the motor-side converter, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to make the output AC terminal voltage of the grid-side converter track the grid voltage;

[0012] When the grid-connected conditions are met, the AC switch is closed, and the control target of the grid-side converter is to make the current at the AC end of the grid-side converter 0; when the current at the AC end of the grid-side converter is 0, the control target of the grid-side converter is to make the output voltage of the AC end of the grid-side converter track the grid voltage.

[0013] Among them, the voltage start mode also includes:

[0014] After the grid-side converter is started, a virtual synchronous generator is used to control the grid-side converter.

[0015] Among them, the voltage start mode also includes:

[0016] During the voltage start-up process, the grid voltage is acquired in real time, and when the grid voltage is higher than the start-up threshold, the current start-up mode is adopted.

[0017] Among them, in the voltage start-up mode, the grid-side converter is started, and the grid-side converter current is obtained in real time during the process that the AC terminal voltage gradually rises from 0 to the AC terminal rated value. When the grid-side converter current is higher than the current rated value, the voltage start-up process is exited.

[0018] Among them, the current start mode also includes:

[0019] The grid voltage is acquired in real time; when the grid voltage is lower than the voltage threshold, the current start-up process is exited; when the grid voltage is lower than the start-up threshold, the voltage start-up mode is adopted.

[0020] Among them, in the current start-up mode, the grid connection conditions are met, including:

[0021] The voltage difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the starting threshold, and the phase difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the phase threshold.

[0022] Among them, in the current start-up mode, the control target of the grid-side converter is switched from current to AC terminal voltage, and also includes:

[0023] The control target of the grid-side converter controlled by the virtual synchronous generator is switched from current to AC terminal voltage.

[0024] A wind turbine converter black start control system, the wind turbine converter comprises a motor side converter and a grid side converter, wherein the AC end of the motor side converter is connected to a wind turbine generator, and its DC end is connected to the DC end of the grid side converter, and the AC end of the grid side converter is connected to an AC grid through an AC switch; the system comprises:

[0025] A grid voltage acquisition module, configured to acquire a grid voltage; and

[0026] A start-up mode control module is configured to compare the grid voltage with a start-up threshold, adopt a voltage start-up mode when the grid voltage is lower than the start-up threshold, and adopt a current start-up mode when the grid voltage is not lower than the start-up threshold;

[0027] Among them, the voltage start mode includes:

[0028] First start the motor-side converter, then close the AC switch, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to gradually increase the AC terminal voltage of the grid-side converter from 0 to the AC terminal rated value;

[0029] Among them, the current start mode includes:

[0030] First start the motor-side converter, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to make the output AC terminal voltage of the grid-side converter track the grid voltage;

[0031] When the grid-connected conditions are met, the AC switch is closed, and the control target of the grid-side converter is to make the current at the AC end of the grid-side converter 0; when the current at the AC end of the grid-side converter is 0, the control target of the grid-side converter is to make the output voltage of the AC end of the grid-side converter track the grid voltage.

[0032] Among them, the voltage start mode also includes:

[0033] After the grid-side converter is started, a virtual synchronous generator is used to control the grid-side converter.

[0034] Among them, the voltage start mode also includes:

[0035] During the voltage start-up process, the grid voltage is acquired in real time, and when the grid voltage is higher than the start-up threshold, the current start-up mode is adopted.

[0036] Among them, in the voltage start-up mode, the grid-side converter is started, and the grid-side converter current is obtained in real time during the process that the AC terminal voltage gradually rises from 0 to the AC terminal rated value. When the grid-side converter current is higher than the current rated value, the voltage start-up process is exited.

[0037] Among them, the current start mode also includes:

[0038] The grid voltage is acquired in real time; when the grid voltage is lower than the voltage threshold, the current start-up process is exited; when the grid voltage is lower than the start-up threshold, the voltage start-up mode is adopted.

[0039] Among them, in the current start-up mode, the grid connection conditions are met, including:

[0040] The voltage difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the starting threshold, and the phase difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the phase threshold.

[0041] Among them, in the current start-up mode, the control target of the grid-side converter is switched from current to AC terminal voltage, and also includes:

[0042] The control target of the grid-side converter controlled by the virtual synchronous generator is switched from current to AC terminal voltage.

[0043] A wind turbine converter black start control device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, the steps of the wind turbine converter black start control method as described above are implemented.

[0044] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the steps of the wind turbine converter black start control method as described above are implemented.

[0045] After adopting the above scheme, the present invention enters the voltage starting mode or the current starting mode according to the grid side voltage, and can automatically identify the starting order of the wind turbine itself. If it is the first start, it is started in voltage mode. If a wind turbine has been started before, it can be started in current mode to avoid starting conflicts. The starting control methods of the motor side converter in the starting processes of the two starting modes provided by the present invention are consistent, both of which control the DC voltage. The grid side converter starting process is switched according to the mode, and the switching is convenient and flexible. Compared with directly starting in the networking mode, a transition process is added in the middle to maintain the current and AC voltage stable during the starting process. After the startup is completed, it switches to the networking control mode, which is safe and reliable, effectively avoids the problem of starting failure, and improves the success rate of starting. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the composition and connection method of the fan converter of the present invention;

[0047] Figure 2 It is a flow chart of the black start control method of the wind turbine converter of the present invention;

[0048] Figure 3 This is a circuit structure embodiment of the grid-side converter and the motor-side converter of the present invention. DETAILED DESCRIPTION

[0049] The technical solutions and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0050] This embodiment provides a black start control method for a wind turbine converter, wherein the wind turbine converter comprises a motor-side converter, a grid-side converter and a control unit, wherein the AC end of the motor-side converter is connected to the wind turbine, and the DC end thereof is connected to the DC end of the grid-side converter, and the AC end of the grid-side converter is connected to the AC grid via an AC switch. The components and connection methods of the wind turbine converter are as follows: Figure 1 As shown in Figure 2, the circuit structure of the grid-side converter and the motor-side converter is as follows: Figure 3 shown.

[0051] The control unit receives a superior control command and controls the operation of the wind turbine converter, wherein the wind turbine converter black start control method includes:

[0052] The control unit detects the grid voltage. If the voltage value is lower than 5% of the rated voltage, it enters the voltage start control mode, otherwise it enters the current start mode;

[0053] In the voltage start mode, the motor side converter is started first, and its control target is to stabilize the DC terminal voltage at the DC terminal rated value, close the AC switch first, and then start the grid side converter, and its control target is to gradually increase the AC terminal voltage of the grid side converter from 0 to the AC terminal rated value;

[0054] The voltage start mode in this embodiment is usually used to start the first wind turbine converter in a wind farm. At this time, the AC grid has no voltage source. The first started wind turbine converter serves as a voltage source to provide starting power for subsequent other wind turbine converters.

[0055] In the current starting mode, the motor side converter is started first, and its control target is to stabilize the DC terminal voltage at the DC terminal rated value, and then the grid side converter is started, and its control target is to make the AC terminal voltage output by the grid side converter track the grid voltage. When the grid connection conditions are met, the AC switch is closed to control the grid side converter current to 0; after stabilization, the control target of the grid side converter is switched from current to AC terminal voltage.

[0056] The current start-up mode in this embodiment is usually used to start the inverter of a wind turbine other than the first one in a wind farm. At this time, the AC power grid already has a voltage source, and the wind turbine inverter can be started in a current source mode. During startup, a control before grid connection is added to allow the AC terminal voltage output by the grid-side inverter to track the grid voltage. The AC switch is closed after the grid-connection conditions are met. In this way, the grid-connection impact current can be effectively limited.

[0057] like Figure 2 As shown, it is a flow chart of the black start control method of the wind turbine converter.

[0058] Wherein: the motor-side converter and the grid-side converter are three-phase half-bridge circuits composed of DC capacitors and fully controlled power semiconductor devices. Figure 3 As shown, in this embodiment, the motor-side converter and the grid-side converter are two-level three-phase half-bridge circuits composed of DC capacitors and 6 groups of fully-controlled power semiconductor devices.

[0059] Wherein: in the voltage start-up mode, after the grid-side converter is started, it switches to the grid-building control method, in which the grid-side converter adopts virtual synchronous generator control. The virtual synchronous generator control simulates the behavior of the synchronous generator, including the regulation of active and reactive power, and the stability of voltage and frequency. This control method simulates the behavior of the synchronous generator by adjusting the virtual potential and angular frequency to create a fictitious three-phase voltage waveform, which is a method of making the converter present voltage source characteristics through control.

[0060] Wherein: in the voltage start mode, the grid voltage is still monitored during the start process. If it is detected that the grid voltage exceeds 5% of the rated voltage before the grid converter is started, the mode is switched to the current start mode.

[0061] This method is to avoid the problem of conflict in starting multiple wind turbine converters. When starting itself, it monitors whether other wind turbine converters have started before itself. If so, it switches itself to current starting mode.

[0062] Wherein: in the voltage starting mode, during the process of controlling the AC terminal voltage of the grid-side converter to gradually rise from 0 to the rated value, the grid-side converter current is monitored. If the current exceeds the rated value, all the switches closed during the starting process are separated, the grid-side converter and the motor-side converter are locked, and the voltage starting process is exited.

[0063] Wherein: in the current starting mode, while controlling the grid-side converter output AC terminal voltage to track the grid voltage, the grid voltage is monitored. If it is lower than 90% of the rated voltage, all the switches closed during the starting process are separated, the grid-side converter and the motor-side converter are locked, and the current starting process is exited. If it is further lower than 5% of the rated voltage, it is switched to the voltage starting mode.

[0064] Wherein: in the current starting mode, the grid-connected conditions include amplitude conditions and phase conditions, the amplitude condition is that the voltage difference between the AC terminal voltage of the grid-side converter and the grid voltage is less than 5% of the rated voltage, and the phase condition is that the phase difference between the AC terminal voltage of the grid-side converter and the grid voltage is less than 5°.

[0065] Wherein: after the control target of the grid-side converter is switched from current to AC terminal voltage, it is switched to a grid-building control method, in which the grid-side converter adopts a virtual synchronous generator control.

[0066] Among them: the wind turbine converter also includes an energy storage system, the energy storage system includes an energy storage unit and an inverter unit, the energy storage unit is connected to the AC power grid through the inverter unit, and the inverter unit is a three-phase half-bridge circuit composed of power semiconductor devices; the energy storage system is started first to control the stability of the AC voltage of the power grid, and then the wind turbine converter is started according to the current starting mode.

[0067] Wherein: the superior control command includes a command from the chain fan master control or a command from a superior dispatching system.

[0068] The embodiment of the present invention further provides a wind turbine converter black start control system, wherein the wind turbine converter comprises a motor side converter and a grid side converter, wherein the AC end of the motor side converter is connected to the wind turbine generator, and its DC end is connected to the DC end of the grid side converter, and the AC end of the grid side converter is connected to the AC grid through an AC switch; the system comprises:

[0069] A grid voltage acquisition module, configured to acquire a grid voltage; and

[0070] A start-up mode control module is configured to compare the grid voltage with a start-up threshold, adopt a voltage start-up mode when the grid voltage is lower than the start-up threshold, and adopt a current start-up mode when the grid voltage is not lower than the start-up threshold;

[0071] Among them, the voltage start mode includes:

[0072] First start the motor-side converter, then close the AC switch, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to gradually increase the AC terminal voltage of the grid-side converter from 0 to the AC terminal rated value;

[0073] Among them, the current start mode includes:

[0074] First start the motor-side converter, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to make the output AC terminal voltage of the grid-side converter track the grid voltage;

[0075] When the grid-connected conditions are met, the AC switch is closed, and the control target of the grid-side converter is to make the current at the AC end of the grid-side converter 0; when the current at the AC end of the grid-side converter is 0, the control target of the grid-side converter is to make the output voltage of the AC end of the grid-side converter track the grid voltage.

[0076] Among them, the voltage start mode also includes:

[0077] After the grid-side converter is started, a virtual synchronous generator is used to control the grid-side converter.

[0078] Among them, the voltage start mode also includes:

[0079] During the voltage start-up process, the grid voltage is acquired in real time, and when the grid voltage is higher than the start-up threshold, the current start-up mode is adopted.

[0080] Among them, in the voltage start-up mode, the grid-side converter is started, and the grid-side converter current is obtained in real time during the process that the AC terminal voltage gradually rises from 0 to the AC terminal rated value. When the grid-side converter current is higher than the current rated value, the voltage start-up process is exited.

[0081] Among them, the current start mode also includes:

[0082] The grid voltage is acquired in real time; when the grid voltage is lower than the voltage threshold, the current start-up process is exited; when the grid voltage is lower than the start-up threshold, the voltage start-up mode is adopted.

[0083] Among them, in the current start-up mode, the grid connection conditions are met, including:

[0084] The voltage difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the starting threshold, and the phase difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the phase threshold.

[0085] Among them, in the current start-up mode, the control target of the grid-side converter is switched from current to AC terminal voltage, and also includes:

[0086] The control target of the grid-side converter controlled by the virtual synchronous generator is switched from current to AC terminal voltage.

[0087] An embodiment of the present invention also provides another wind turbine inverter black start control device, including a processor and a memory configured to store a computer program that can be run on the processor; wherein, when the processor is configured to run the computer program, the method steps in the aforementioned embodiment are executed.

[0088] In practical applications, the processor includes a field programmable gate array (FPGA), and the processor may be a central processing unit (CPU) or a digital signal processor (DSP). It is understandable that for different devices, the electronic device used to implement the function of the processor may be other, and the embodiment of the present invention does not specifically limit it.

[0089] The above-mentioned memory can be a volatile memory (volatile memory), such as a random access memory (RAM); or a non-volatile memory (non-volatile memory), such as a read-only memory (ROM), a flash memory, a hard disk (HDD) or a solid-state drive (SSD); or a combination of the above-mentioned types of memory, and provide instructions and data to the processor.

[0090] In an exemplary embodiment, an embodiment of the present invention further provides a computer-readable storage medium for storing a computer program.

[0091] Optionally, the computer-readable storage medium can be applied to any one of the methods in the embodiments of the present invention, and the computer program enables the computer to execute the corresponding processes implemented by the processor in each method in the embodiments of the present invention. For the sake of brevity, they are not described here.

[0092] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0093] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0094] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0095] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0096] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0097] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0098] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A black start control method for a wind turbine converter, wherein the wind turbine converter comprises a motor side converter and a grid side converter, wherein: The AC end of the motor-side converter is connected to the wind turbine, and its DC end is connected to the DC end of the grid-side converter. The AC end of the grid-side converter is connected to the AC grid through an AC switch; the method includes: Obtain the grid voltage. If the grid voltage is lower than the starting threshold, use the voltage starting mode; otherwise, use the current starting mode. Among them, the voltage start mode includes: First start the motor-side converter, then close the AC switch, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to gradually increase the AC terminal voltage of the grid-side converter from 0 to the AC terminal rated value; Among them, the current start mode includes: First start the motor-side converter, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to make the output AC terminal voltage of the grid-side converter track the grid voltage; When the grid-connected conditions are met, the AC switch is closed, and the control target of the grid-side converter is to make the current at the AC end of the grid-side converter 0; when the current at the AC end of the grid-side converter is 0, the control target of the grid-side converter is to make the output voltage of the AC end of the grid-side converter track the grid voltage.

2. The method according to claim 1, characterized in that: Voltage start mode also includes, After the grid-side converter is started, a virtual synchronous generator is used to control the grid-side converter.

3. The method according to claim 1, characterized in that: Voltage start mode also includes, During the voltage start-up process, the grid voltage is acquired in real time, and when the grid voltage is higher than the start-up threshold, the current start-up mode is adopted.

4. The method according to claim 1, characterized in that: In the voltage start-up mode, the grid-side converter is started, and the grid-side converter current is obtained in real time as the AC terminal voltage gradually rises from 0 to the AC terminal rated value. When the grid-side converter current is higher than the current rated value, the voltage start-up process is exited.

5. The method according to claim 1, characterized in that: Current start mode also includes, Acquire the grid voltage in real time; when the grid voltage is lower than the voltage threshold, exit the current start-up process; When the grid voltage is lower than the starting threshold, the voltage starting mode is adopted.

6. The method according to claim 1, characterized in that: In the current start mode, the grid connection conditions are met, including: The voltage difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the starting threshold, and the phase difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the phase threshold.

7. The method according to claim 1, characterized in that: In the current start-up mode, the control target of the grid-side converter is switched from current to AC terminal voltage, and also includes: The control target of the grid-side converter controlled by the virtual synchronous generator is switched from current to AC terminal voltage.

8. A wind turbine converter black start control system, the wind turbine converter comprising a motor side converter and a grid side converter, wherein: The AC end of the motor-side converter is connected to the wind turbine, and its DC end is connected to the DC end of the grid-side converter. The AC end of the grid-side converter is connected to the AC grid through an AC switch. The system includes: A grid voltage acquisition module, configured to acquire a grid voltage; and A start-up mode control module is configured to compare the grid voltage with a start-up threshold, adopt a voltage start-up mode when the grid voltage is lower than the start-up threshold, and adopt a current start-up mode when the grid voltage is not lower than the start-up threshold; Among them, the voltage start mode includes: First start the motor-side converter, then close the AC switch, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to gradually increase the AC terminal voltage of the grid-side converter from 0 to the AC terminal rated value; Among them, the current start mode includes: First start the motor-side converter, and then start the grid-side converter; wherein the control target of the motor-side converter is to stabilize the DC terminal voltage of the motor-side converter at the DC terminal rated value, and the control target of the grid-side converter is to make the output AC terminal voltage of the grid-side converter track the grid voltage; When the grid-connected conditions are met, the AC switch is closed, and the control target of the grid-side converter is to make the current at the AC end of the grid-side converter 0; when the current at the AC end of the grid-side converter is 0, the control target of the grid-side converter is to make the output voltage of the AC end of the grid-side converter track the grid voltage.

9. The system according to claim 8, characterized in that: Voltage start mode also includes, After the grid-side converter is started, a virtual synchronous generator is used to control the grid-side converter.

10. The system according to claim 8, characterized in that: Voltage start mode also includes, During the voltage start-up process, the grid voltage is acquired in real time, and when the grid voltage is higher than the start-up threshold, the current start-up mode is adopted.

11. The system according to claim 8, characterized in that: In the voltage start-up mode, the grid-side converter is started, and the grid-side converter current is obtained in real time as the AC terminal voltage gradually rises from 0 to the AC terminal rated value. When the grid-side converter current is higher than the current rated value, the voltage start-up process is exited.

12. The system of claim 8, wherein: Current start mode also includes, Acquire the grid voltage in real time; when the grid voltage is lower than the voltage threshold, exit the current start-up process; When the grid voltage is lower than the starting threshold, the voltage starting mode is adopted.

13. The system of claim 8, wherein: In the current start mode, the grid connection conditions are met, including: The voltage difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the starting threshold, and the phase difference between the AC terminal voltage of the grid-side converter and the grid voltage is smaller than the phase threshold.

14. The system of claim 8, wherein: In the current start-up mode, the control target of the grid-side converter is switched from current to AC terminal voltage, and also includes: The control target of the grid-side converter controlled by the virtual synchronous generator is switched from current to AC terminal voltage.

15. A wind turbine converter black start control device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, the steps of the wind turbine converter black start control method according to any one of claims 1 to 7 are implemented.

16. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by a processor, the steps of the wind turbine converter black start control method according to any one of claims 1 to 7 are implemented.

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