Pre-charging circuit of converter, control method and direct-current wind generating set

Abstract

The invention provides a pre-charging circuit of a converter, a control method and a direct-current wind generating set, the pre-charging circuit comprises a switching device and a current limiting device which are connected in series, and the pre-charging circuit is connected to a direct-current switch on a direct-current bus of the converter in parallel, when the switching device is switched on and the direct current switch is switched off, the pre-charging circuit pre-charges the two sides of the direct current switch, so that the difference between the voltages on the two sides of the direct current switch is within a preset difference range. According to the pre-charging circuit of the converter, the control method of the converter, the converter and the direct-current wind generating set disclosed by the invention, the problem that a switch and a device possibly lose efficacy due to impact caused by large voltage difference between voltages at two ends of a direct-current switch in a direct-current power transmission form is solved, and impact current generated when the direct-current switch is closed can be reduced; and the risk that the direct-current switch and related devices are damaged by impact current is reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of wind power generation, and more specifically, to a pre-charging circuit and control method of a converter and a DC wind power generator set. Background Art

[0002] The output forms of wind power generation include direct current transmission and alternating current transmission. DC transmission refers to the direct current output of wind turbines to the power grid.

[0003] With the rapid development of wind power generation technology, the application scenarios and transmission demands of DC power transmission are increasing. DC transmission has gradually become a major trend in wind turbines. The voltage difference across the high-voltage DC switch is getting larger and larger, which makes the impact current at the moment of closing the switch very large, which may impact the DC switch and subsequent devices and cause the switch and devices to fail. Summary of the invention

[0004] In view of the problem that the voltage difference between both ends of a DC switch is large in the form of DC power transmission, which may cause the switch and components to fail due to impact, the present disclosure provides a pre-charging circuit and control method of a converter and a DC wind turbine generator set.

[0005] A first aspect of the present disclosure provides a pre-charging circuit of an inverter, wherein the inverter is applied to a DC wind turbine generator set, wherein the pre-charging circuit includes a switching device and a current limiting device connected in series, wherein the pre-charging circuit is connected in parallel to a DC switch on a DC bus of the inverter, wherein when the switching device is turned on and the DC switch is turned off, the pre-charging circuit pre-charges both sides of the DC switch so that the difference between the voltages on both sides of the DC switch is within a preset difference range.

[0006] Optionally, the DC bus includes a positive bus and a negative bus, and the positive bus and the negative bus are respectively provided with the pre-charging circuit, wherein the switching device of the pre-charging circuit arranged in the positive bus and the switching device of the pre-charging circuit arranged in the negative bus are turned on or off at the same time.

[0007] Optionally, the DC bus includes a positive bus and a negative bus, the switching device includes a DC contactor, the DC contactor has two phases, the two phases of the DC contactor are respectively connected to the positive bus and the negative bus, and the two phases of the DC contactor are turned on or off at the same time.

[0008] Optionally, the switching device includes one of a polar switching device and a non-polar switching device, wherein, in the process of pre-charging both sides of the DC switch, charging is performed from the high voltage end to the low voltage end of the polar switching device.

[0009] Optionally, the current limiting device includes a resistor device or an inductor device, wherein the resistance value of the resistor device is determined based on a preset pre-charge time, a preset pre-charge voltage and a bus voltage of the DC bus, wherein the difference between the pre-charge voltage and the bus voltage is within a preset difference range, and the preset difference range is that the difference between the voltages on both sides of the DC switch is less than or equal to 5%.

[0010] Optionally, the converter is applied to a DC wind turbine generator set, and the converter includes a pre-charging circuit according to the present disclosure, wherein the pre-charging control method includes: in response to a control requirement to close a DC switch on a DC bus of the converter, turning on a switching device in the pre-charging circuit to pre-charge both sides of the DC switch; in response to a difference between the voltages pre-charged to both sides of the DC switch being within a preset difference range, closing the DC switch.

[0011] Optionally, the pre-charging control method further comprises: in response to a failure of the wind turbine generator set during the process of pre-charging both sides of the DC switch, or in response to the DC switch being closed, disconnecting the switching device.

[0012] Optionally, the pre-charging control method further includes: in response to receiving an instruction to disconnect the DC switch, disconnecting the switching device or maintaining the switching device in an disconnected state; in response to the switching device being in an disconnected state, disconnecting the DC switch.

[0013] Optionally, the control requirement includes: receiving a start-up instruction to start the DC wind generator set during the start-up process of the DC wind generator set; and / or receiving an instruction to close the DC switch when the DC wind generator set is in an operating state.

[0014] A second aspect of the present disclosure provides a controller for a DC wind turbine generator set, comprising: at least one processor; and at least one memory storing computer executable instructions, wherein the computer executable instructions, when executed by the at least one processor, prompt the at least one processor to execute the pre-charging control method of the converter according to the present disclosure.

[0015] A third aspect of the present disclosure provides a converter, comprising a pre-charging circuit of the converter according to the present disclosure.

[0016] A fourth aspect of the present disclosure provides a DC wind turbine generator set, which includes a controller of the DC wind turbine generator set according to the present disclosure and / or a converter according to the present disclosure.

[0017] According to the pre-charging circuit, control method and DC wind turbine generator set of the converter disclosed in the present invention, for the DC switch on the DC bus of the converter, a pre-charging circuit connected in parallel to the DC switch is adopted. The pre-charging circuit may include a switching device and a current limiting device connected in series, so that when the switching device is turned on and the DC switch is turned off, the pre-charging circuit can pre-charge both sides of the DC switch so that the difference between the voltages on both sides of the DC switch is within a preset difference range. In this way, the voltage difference on both sides of the DC switch can be limited, so that the impact current generated when the DC switch is closed can be reduced, reducing the risk of the impact current damaging the DC switch and its associated devices, thereby ensuring the safety of the converter and the unit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic block diagram showing a converter including a pre-charging circuit according to an exemplary embodiment of the present disclosure.

[0019] Figure 2 is a schematic flow chart illustrating a pre-charging control method of a converter according to an exemplary embodiment of the present disclosure.

[0020] Figure 3 is a schematic flowchart showing an example of a pre-charging control method of a converter according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0021] The following specific embodiments are provided to help the reader obtain a comprehensive understanding of the methods, devices and / or systems described herein. However, after understanding the disclosure of the present application, various changes, modifications and equivalents of the methods, devices and / or systems described herein will be clear. For example, the order of operations described herein is only an example and is not limited to those orders set forth herein, but can be changed as will be clear after understanding the disclosure of the present application, except for operations that must occur in a specific order. In addition, for greater clarity and simplicity, the description of features known in the art may be omitted.

[0022] The features described herein can be implemented in different forms and should not be construed as being limited to the examples described herein. Rather, the examples described herein have been provided to illustrate only some of the many possible ways to implement the methods, devices, and / or systems described herein, which will be clear after understanding the disclosure of the present application.

[0023] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more.

[0024] Although terms such as "first", "second", and "third" may be used herein to describe various members, components, regions, layers, or portions, these members, components, regions, layers, or portions should not be limited by these terms. Instead, these terms are only used to distinguish one member, component, region, layer, or portion from another member, component, region, layer, or portion. Therefore, without departing from the teachings of the examples described herein, the first member, first component, first region, first layer, or first portion referred to in the examples may also be referred to as the second member, second component, second region, second layer, or second portion.

[0025] In the specification, when an element (such as a layer, a region, or a substrate) is described as being “on”, “connected to”, or “coupled to” another element, the element may be directly “on”, “connected to”, or “coupled to” another element, or one or more other elements may be present therebetween. Conversely, when an element is described as being “directly on”, “directly connected to”, or “directly coupled to” another element, there may be no other elements present therebetween.

[0026] The terms used herein are only used to describe various examples and are not intended to limit the disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. The terms "comprise", "include" and "have" indicate the presence of the described features, quantities, operations, components, elements and / or combinations thereof, but do not exclude the presence or addition of one or more other features, quantities, operations, components, elements and / or combinations thereof.

[0027] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by a person of ordinary skill in the art to which the present disclosure belongs after understanding the present disclosure. Unless explicitly defined as such herein, terms (such as those defined in a general dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and should not be interpreted in an idealized or overly formal manner.

[0028] Furthermore, in the description of examples, when it is considered that a detailed description of a well-known related structure or function would cause vague interpretation of the present disclosure, such a detailed description will be omitted.

[0029] As mentioned above, in the DC power transmission of the wind turbine generator set, the voltage difference across the DC switch is large, which may cause impact on the DC switch and devices.

[0030] In this regard, in some cases, AC pre-charging can be used to reduce the impact current. Specifically, AC pre-charging refers to the use of a pre-charging circuit in conjunction with an AC reactor. After the pre-charging circuit of a two-phase circuit is closed, the AC power can be rectified into DC power through uncontrolled rectification by a diode, so that the rectified voltage is about 70% of the full bus voltage. At the moment the circuit breaker is closed, the reactor acts as an inductive load to suppress the peak of the current change (di / dt) and reduce the impact on the device. DC pre-charging generally has no inductance, and the pre-charging is pre-charged to 70%. There is no inductance suppression, and the instantaneous current impact current change (di / dt) of the DC disconnector when it is closed is infinite, which can easily cause damage to the disconnector.

[0031] In view of the above-mentioned problems, the present disclosure provides a pre-charging circuit of a converter, a pre-charging control method of a converter, a controller of a DC wind turbine generator set, a converter and a DC wind turbine generator set to solve or at least alleviate the above-mentioned problems.

[0032] According to a first aspect of an exemplary embodiment of the present disclosure, a pre-charging circuit of a converter is provided, and the converter can be applied to a DC wind turbine generator set.

[0033] like Figure 1 As shown, the converter may include a converter unit, a pre-charging circuit 110, a DC switch 120 located on a DC bus, a braking circuit 130, and a discharging circuit 140, and a voltage sensor 150 may be provided between the positive bus and the negative bus of the DC bus. The pre-charging circuit 110 may include a switch device 111 and a current limiting device 112 connected in series, and the pre-charging circuit 110 may be connected in parallel to the DC switch 120 on the DC bus of the converter 100. The DC bus may be connected to the main bus of the wind farm, for example.

[0034] When the switch device 111 is turned on and the DC switch 120 is turned off, the pre-charging circuit 110 can pre-charge both sides of the DC switch 120 so that the difference between the voltages on both sides of the DC switch 120 is within a preset difference range.

[0035] Specifically, when the DC switch 120 is not closed, after the switch device 111 of the pre-charging circuit 110 is turned on, the two sides of the DC switch 120 can be pre-charged, and the current limiting device 112 can limit the current impact and protect the device. When the pre-charge voltage on both sides of the DC switch 120 tends to be stable, the DC switch 120 can be closed. In this way, it is possible to avoid closing the DC switch without pre-charging and without inductance to suppress current changes, resulting in large impact current and current changes, and having little impact on the device.

[0036] Here, the preset difference range may be that the difference between the voltages on both sides of the DC switch is less than or equal to 5%. Specifically, the voltage on one side of the DC switch is V1, and the voltage on the other side is V2. The preset difference range may be (V1-V2) / V1≤5%.

[0037] The switch device 111 may include, for example, but is not limited to, a DC contactor, a DC switch, and an IGBT device. The switch device 111 may be a high-voltage switch device, such as a high-voltage DC contactor. As an example, the switch device may include one of a polarized switch device and a non-polarized switch device.

[0038] In the case where the switch device is a polar switch device, during the process of precharging both sides of the DC switch 120, charging can be performed from the high voltage end to the low voltage end of the polar switch device, such as Figure 1 As shown, in the case of power transmission from the generator side to the grid side, the generator side of the switch device 111 can be a high voltage end, and the grid side thereof can be a low voltage end; in the case of power transmission from the grid side to the generator side, the grid side of the switch device 111 can be a high voltage end, and the generator side thereof can be a low voltage end. In this example, the polarity switch device can be controlled more accurately and has higher reliability.

[0039] The current limiting device 112 may be a device capable of limiting the current of a circuit, for example, may include a resistor or an inductor. In the case where the current limiting device 112 may include a resistor, the resistance value of the resistor may be determined according to a preset pre-charge time, a preset pre-charge voltage, and a bus voltage of the DC bus.

[0040] Specifically, if Figure 1 As shown, the converter may further include capacitors C1 and C2, and the capacitors C1 and C2 are connected between the positive bus and the negative bus of the DC bus. For example, the resistance value of the resistor device may be determined by the following formula (1):

[0041] t=-R·C·ln(1-u / U) (1)

[0042] Where R represents the resistance value of the resistor, t represents the pre-charge time, and C represents the capacitance of the capacitor set on the DC bus (e.g. Figure 1 The capacitors C1 and C2 are shown in the figure, u represents the pre-charge voltage, and U represents the voltage of the DC bus.

[0043] Based on the above formula (1), when the deviation between u and U satisfies less than or equal to 5%, the capacitance is known, and the appropriate resistance value and withstand voltage level can be selected according to the expected pre-charging time.

[0044] In the above manner, the selection of the resistance value of the current limiting device can be associated with the voltage difference of the DC switch, thereby ensuring the protective effect of the pre-charging on the DC switch.

[0045] In addition, for the switching device 111, for example, I=U / R can be used for selection, where I represents the pre-charging current. Specifically, the pre-charging current I can be obtained based on the resistance value R of the resistor and the voltage U of the DC bus. The rated current of the switching device 111 can be less than or equal to the pre-charging current.

[0046] Here, it should be noted that although the above reference formula (1) shows an example method for determining the resistance value of the resistor device, the embodiments of the present disclosure are not limited thereto. For example, the above formula (1) may also be modified or weighted.

[0047] According to an embodiment of the present disclosure, a DC bus may include a positive bus (DC+) and a negative bus (DC-). In one example, the positive bus and the negative bus may be provided with a pre-charging circuit 110, respectively. Specifically, the switch device of the pre-charging circuit 110 provided on the positive bus and the switch device of the pre-charging circuit 110 provided on the negative bus may be turned on or off at the same time. Here, the pre-charging circuit of each bus may pre-charge the DC+ / DC-, control the switching device to turn on (or close), charge the two ends of the DC switch from high voltage to low voltage, and the voltage tends to balance. When the voltage on both sides of the DC switch reaches a preset difference range, the DC switch may be closed, which can reduce the impact current and reduce the impact of the current change on the positive bus and the negative bus.

[0048] In another example, the switching device may include a DC contactor having two phases, the two phases of the DC contactor being respectively connected to a positive bus and a negative bus, and the two phases of the DC contactor may be turned on or off at the same time. Specifically, the two-phase DC contactor may have the same control terminal, so that in response to receiving a control signal, the positive bus and the negative bus may be turned on or off at the same time to achieve more precise circuit on-off control.

[0049] The pre-charging circuit of the converter is described above. According to the second aspect of the exemplary embodiment of the present disclosure, a pre-charging control method of the converter is also provided. The converter is applied to a DC wind turbine generator set. The converter may include the pre-charging circuit described in the first aspect of the exemplary embodiment of the present disclosure.

[0050] like Figure 2 As shown, the pre-charging control method may include:

[0051] In step S210, in response to a control requirement for closing a DC switch on a DC bus of the converter, a switch device in the pre-charging circuit may be turned on to pre-charge both sides of the DC switch.

[0052] In step S220 , the DC switch may be closed in response to the difference between the voltages pre-charged to both sides of the DC switch being within a preset difference range.

[0053] As described in the first aspect of the embodiment of the present disclosure, by controlling the pre-charging circuit, the voltage difference between the two sides of the DC switch can be limited, thereby reducing the impact current generated when the DC switch is closed.

[0054] As an example, the control requirements may include: receiving a start-up instruction to start the DC wind turbine during the start-up process of the DC wind turbine; and / or receiving a command to close a DC switch while the DC wind turbine is in operation.

[0055] Specifically, the pre-charging circuit and control method of the embodiment of the present disclosure are used for pre-charging, which can start at zero voltage. The pre-charging circuit can raise the zero voltage end to meet the unit starting condition. In addition, since the pre-charging circuit and control method of the embodiment of the present disclosure do not require inductive current suppression, the scheme is also applicable to any load condition under the unit operating condition, making the application condition of the scheme more universal.

[0056] In addition, according to an embodiment of the present disclosure, the pre-charging control method may further include: during the process of pre-charging both sides of the DC switch, if a fault occurs in the wind turbine generator set or the DC switch is closed, the switching device is disconnected.

[0057] Specifically, in the case of a fault in the pre-charging process, the pre-charging circuit can be controlled to be disconnected in time to ensure circuit safety. In addition, the pre-charging circuit can also be disconnected after the DC switch is closed.

[0058] In addition, as an example, the pre-charging control method may also include: when receiving an instruction to disconnect the DC switch, disconnecting the switching device, such as when the switching device itself is in a disconnected state, maintaining the disconnected state of the switching device; if the switching device is in a disconnected state, disconnecting the DC switch.

[0059] Specifically, after closing the DC switch, if it is necessary to disconnect the DC switch again, the pre-charging circuit can be first ensured to be disconnected, and then the DC switch can be disconnected when the pre-charging circuit is disconnected, thereby ensuring that there is no current in the pre-charging circuit after the DC switch is disconnected.

[0060] According to the pre-charging circuit and control method of the embodiment of the present disclosure, the problem that the DC bus of the converter cannot suppress the instantaneous current mutation when the DC switch is closed is solved. By pre-charging the high-voltage DC switch, the voltage on both sides of the DC switch is pulled up to the same level, reducing the instantaneous current impact of the switch closing, the damage to the DC switch and components, reducing the current impact, and extending the service life of each component. This solution is particularly suitable for high-voltage and high-power DC wind turbines.

[0061] In addition, the pre-charging circuit and control method of the embodiments of the present invention have the advantages of small devices, low power consumption, convenient layout, and low cost. Compared with the AC pre-charging circuit, the DC pre-charging circuit of the embodiments of the present invention can solve the problem of current mutation in the AC pre-charging circuit, can solve the problem of DC bus impact, and at the same time has a zero-start pressure reduction function, and has the advantage of full bus voltage building that the AC pre-charging circuit cannot have.

[0062] Figure 3 Taking the start-up condition of a wind turbine generator set as an example, an example process of a pre-charging control method of a converter according to an exemplary embodiment of the present disclosure is shown. Figure 3 As shown, in step S301, it can be detected whether there is a fault in the wind turbine generator set. In response to no fault, in step S302, the current modulation state of the set can be stopped, waiting for the start command, and entering the start process; in response to the presence of a fault, the process can be ended.

[0063] In step S303, it can be determined whether a start command is received. In response to receiving the start command, in step S304, the switch device can be turned on to connect the pre-charging circuit and start pre-charging both sides of the DC switch on the DC bus of the converter. In step S305, it can be determined whether the pre-charging is completed. If not, it can continue to wait until the pre-charging is completed; after the pre-charging is completed, the DC switch can be closed in step S306. In step S307, it can be determined whether the DC switch closure is completed. If not, it can be tried again until the DC switch is closed; if the DC switch closure is completed, the current process ends.

[0064] In addition, after the pre-charging circuit is turned on, during the pre-charging process, in response to a unit failure or a pre-charging circuit failure in step S308, pre-charging cannot continue. The pre-charging circuit can be disconnected in step S309, and then in step S310, it can be determined whether the DC switch is in the disconnected state. When the DC switch is ensured to be disconnected, the process ends.

[0065] According to a third aspect of an embodiment of the present disclosure, a controller of a DC wind turbine generator set is provided, the controller comprising: at least one processor; at least one memory storing computer executable instructions, wherein the computer executable instructions, when executed by the at least one processor, prompt the at least one processor to execute a pre-charging control method for the converter according to an embodiment of the present disclosure.

[0066] According to a fourth aspect of an embodiment of the present disclosure, a converter is provided, which includes a pre-charging circuit of the converter according to an embodiment of the present disclosure.

[0067] According to a fifth aspect of an embodiment of the present disclosure, a DC wind turbine generator set is provided, which includes a controller of the DC wind turbine generator set according to an embodiment of the present disclosure and / or a converter according to an embodiment of the present disclosure.

[0068] As an example, the controller can be implemented by a computer device, which can be a PC, a tablet device, a personal digital assistant, a smart phone, or other device capable of executing the above instruction set. Here, the computer device is not necessarily a single electronic device, but can also be any device or circuit capable of executing the above instructions (or instruction sets) individually or in combination. The computer device can also be part of an integrated control system or system manager, or can be configured as a portable electronic device interconnected with a local or remote (e.g., via wireless transmission) interface.

[0069] In a computer device, a processor may include a central processing unit (CPU), a graphics processing unit (GPU), a programmable logic device, a dedicated processor system, a microcontroller or a microprocessor. As an example and not limitation, a processor may also include an analog processor, a digital processor, a microprocessor, a multi-core processor, a processor array, a network processor, etc.

[0070] The processor can execute instructions or codes stored in the memory, wherein the memory can also store data. Instructions and data can also be sent and received through the network via the network interface device, wherein the network interface device can adopt any known transmission protocol.

[0071] The memory may be integrated with the processor, for example, RAM or flash memory is arranged within an integrated circuit microprocessor or the like. In addition, the memory may include a separate device, such as an external disk drive, a storage array, or any other storage device that can be used by a database system. The memory and the processor may be operatively coupled, or may communicate with each other, such as through an I / O port, a network connection, etc., so that the processor can read files stored in the memory.

[0072] In addition, the computer device may also include a video display (such as a liquid crystal display) and a user interaction interface (such as a keyboard, a mouse, a touch input device, etc.) All components of the computer device may be connected to each other via a bus and / or a network.

[0073] The specific implementation methods of the present disclosure have been described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that these embodiments may be modified and varied without departing from the principles and spirit of the present disclosure, the scope of which is defined by the claims and their equivalents. These modifications and variations should also be within the scope of protection of the claims of the present disclosure.

Claims

1. A pre-charging circuit for a converter, characterized in that: The converter is applied to a DC wind turbine generator set. The pre-charging circuit comprises a switch device and a current limiting device connected in series, and the pre-charging circuit is connected in parallel to a DC switch on a DC bus of the converter. Wherein, when the switch device is turned on and the DC switch is turned off, the pre-charging circuit pre-charges both sides of the DC switch so that the difference between the voltages on both sides of the DC switch is within a preset difference range.

2. The precharge circuit according to claim 1, characterized in that The DC bus includes a positive bus and a negative bus, and the positive bus and the negative bus are respectively provided with the pre-charging circuit. Wherein, the switch device of the pre-charging circuit arranged in the positive bus and the switch device of the pre-charging circuit arranged in the negative bus are turned on or turned off at the same time.

3. The precharge circuit according to claim 1, characterized in that: The DC bus includes a positive bus and a negative bus, the switching device includes a DC contactor, the DC contactor has two phases, the two phases of the DC contactor are respectively connected to the positive bus and the negative bus, and the two phases of the DC contactor are simultaneously turned on or disconnected.

4. The precharge circuit according to any one of claims 1 to 3, characterized in that: The switch device includes one of a polar switch device and a non-polar switch device, wherein, in the process of precharging both sides of the DC switch, charging is performed from the high voltage end to the low voltage end of the polar switch device.

5. The precharge circuit according to any one of claims 1 to 3, characterized in that: The current limiting device includes a resistor device or an inductor device, wherein the resistance value of the resistor device is determined according to a preset pre-charge time, a preset pre-charge voltage and a bus voltage of the DC bus, wherein the difference between the pre-charge voltage and the bus voltage is within the preset difference range, and the preset difference range is that the difference between the voltages on both sides of the DC switch is less than or equal to 5%.

6. A pre-charging control method for a converter, characterized in that: The converter is applied to a DC wind turbine generator set, and the converter comprises a pre-charging circuit according to any one of claims 1 to 5, wherein the pre-charging control method comprises: In response to a control demand for closing a DC switch on a DC bus of the converter, turning on a switch device in the pre-charging circuit to pre-charge both sides of the DC switch; In response to a difference between voltages pre-charged to both sides of the DC switch being within a preset difference range, the DC switch is closed.

7. The pre-charge control method according to claim 6, characterized in that: The pre-charging control method further comprises: In response to a failure of the wind turbine generator set during precharging of both sides of the DC switch, or in response to the DC switch being closed, the switch device is opened.

8. The pre-charge control method according to claim 6, characterized in that: The pre-charging control method further comprises: In response to receiving an instruction to disconnect the DC switch, disconnecting the switch device or maintaining the disconnected state of the switch device; In response to the switching device being in an off state, the DC switch is turned off.

9. The pre-charge control method according to claim 6, characterized in that: The control requirements include: During the startup process of the DC wind turbine generator set, a startup instruction for starting the DC wind turbine generator set is received; and / or, When the DC wind turbine generator set is in operation, an instruction to close the DC switch is received.

10. A controller for a DC wind turbine generator set, characterized in that: include: at least one processor; at least one memory storing computer executable instructions, Wherein, when the computer executable instructions are executed by the at least one processor, the at least one processor is prompted to execute the pre-charging control method of the converter according to any one of claims 6 to 9.

11. A converter, characterized in that: The converter comprises a pre-charging circuit of the converter according to any one of claims 1 to 5.

12. A DC wind turbine generator set, characterized in that: The DC wind turbine generator set comprises the controller of the DC wind turbine generator set according to claim 10 and / or the converter according to claim 11.

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