HVDC transmission system for offshore wind power based on uncontrolled rectifier topology, its black start method and related devices

Abstract

The present invention provides an offshore wind power DC transmission system based on an uncontrolled rectifier topology, a black start method thereof, and related devices. Based on the offshore wind power DC transmission system based on an uncontrolled rectifier topology, the present invention adds an offshore converter and an onshore converter to the offshore converter station and the onshore converter station, respectively. The AC side of the offshore converter is connected to the AC busbar through a station transformer, and the DC side is connected to the DC side of the onshore converter through a DC submarine cable, and the DC side of the onshore converter is connected to the onshore station transformer. The present invention can realize the black start of the offshore wind power DC transmission system by executing the black start timing control steps through the offshore converter and the onshore converter. The present invention can complete the black start control in a low-cost manner by simply adding two low-voltage and small-capacity converters.

Description

Technical Field

[0001] The present invention belongs to the technical field of offshore wind power transmission systems, and in particular relates to an offshore wind power direct current transmission system based on an uncontrolled rectifier topology, a black start method thereof, and related devices. Background Art

[0002] Currently, offshore wind power primarily utilizes nearshore AC and offshore DC transmission methods, with individual projects boasting capacities of approximately one million kilowatts. With nearshore offshore wind power development reaching its peak, deep-sea offshore wind power is a key focus for future offshore wind power development in my country. AC transmission solutions are unsuitable for large-scale deep-sea offshore wind power development, while traditional DC transmission solutions are costly and inadequate for the economic development of large-scale offshore wind power. There is a need to explore new, low-cost transmission solutions to provide new technological options for deep-sea offshore wind power development. Large-scale offshore wind power generation utilizes AC transmission and various DC transmission conversion schemes. Currently, the mainstream DC transmission solution in practical applications is flexible DC transmission technology based on the MMC topology. However, its platform is bulky and heavy, leading to high costs. Therefore, large-scale offshore wind power transmission solutions require further optimization. To accommodate diverse application scenarios and reduce transmission project costs, various unique transmission schemes have been proposed, including the use of unidirectional, current-source uncontrolled rectifier converters based on diode elements at the sending end, DC wind turbine-based step-up transmission, and low-frequency transmission.

[0003] However, the use of a unidirectional current-type uncontrolled rectifier converter based on diode elements at the sending end helps to achieve lightweight offshore platforms, but there is currently a problem that wind farms cannot be black-started. Summary of the Invention

[0004] In view of this, the present invention aims to propose an offshore wind power direct current transmission system based on an uncontrolled rectifier topology and its black start method and related devices, which are used to solve the problem that the wind farm cannot be black started in the offshore wind power transmission scheme that uses a unidirectional current-type uncontrolled rectifier converter based on diode elements at the sending end.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides an offshore wind power direct current transmission system based on an uncontrolled rectifier topology, comprising:

[0007] Wind farm units, offshore converter stations, onshore converter stations, AC power grids, offshore converters, and onshore converters;

[0008] The wind farm units are connected to the AC side of the offshore converter station via AC busbars;

[0009] The DC side of the offshore converter station is connected to the DC side of the onshore converter station via a DC submarine cable;

[0010] The AC side of the onshore converter station is connected to the AC grid;

[0011] The AC side of the offshore converter is connected to the AC busbar through the first station transformer;

[0012] The DC side of the offshore converter is connected to the DC side of the onshore converter via a DC submarine cable;

[0013] The AC side of the onshore converter is connected to the second station transformer.

[0014] Furthermore, the system further comprises: an offshore converter station side switch and an onshore converter station side switch;

[0015] The DC side of the offshore converter station is connected to the DC submarine cable through a switch on the offshore converter station side;

[0016] The DC side of the onshore converter station is connected to the DC submarine cable through a switch on the onshore converter station side.

[0017] Furthermore, the first connection point between the offshore converter and the DC submarine cable and the second connection point between the onshore converter and the DC submarine cable are both on the DC submarine cable between the offshore converter station side switch and the onshore converter station side switch.

[0018] Furthermore, it also includes: an offshore converter switch and an onshore converter switch;

[0019] The offshore converter switch is connected between the offshore converter and the first connection point;

[0020] The onshore converter switch is connected between the onshore converter and the second connection point.

[0021] Furthermore, both the offshore converter and the onshore converter are connected to the corresponding station transformer through the station transformer dedicated winding.

[0022] In a second aspect, the present invention further provides a black start method for an offshore wind power DC transmission system based on an uncontrolled rectifier topology, which is applied to the offshore wind power DC transmission system based on an uncontrolled rectifier topology as in the first aspect, comprising the following steps:

[0023] In response to a black start instruction, disconnecting the offshore converter station, the onshore converter station, and the DC submarine cable;

[0024] Connect the offshore converter and the onshore converter;

[0025] The onshore converter and offshore converter are charged through the second station transformer;

[0026] The AC voltage of the offshore converter is uniformly increased to the rated voltage, and the offshore converter transformer of the offshore converter station is charged through the AC busbar;

[0027] Select a set number of wind turbines from the wind farm units to draw power from the AC bus and start and unlock them;

[0028] Increase the operating power of the wind turbine until the operating power of the offshore converter is reduced to zero;

[0029] The offshore converter is locked and exited, and the wind turbine and the offshore converter station operate independently.

[0030] Disconnect the offshore converter, onshore converter and DC submarine cable;

[0031] Connect the onshore converter station to the DC submarine cable, charge the onshore converter station, and unlock it until the DC submarine cable voltage is increased to the DC voltage of the uncontrolled rectification at the sending end;

[0032] The connection between the offshore converter station and the DC submarine cable is connected to complete the black start timing control.

[0033] Furthermore, the offshore converter and the onshore converter are also used to provide auxiliary power for the offshore converter platform. The control steps include:

[0034] In response to the control instruction, disconnecting the offshore converter station, the onshore converter station and the DC submarine cable;

[0035] Connect the offshore converter and the onshore converter;

[0036] The onshore converter and offshore converter are charged through the second station transformer;

[0037] The AC voltage of the offshore converter is uniformly increased to the rated voltage, thereby providing station power for the offshore converter platform. The offshore converter is connected to the AC bus, while the offshore converter station and wind farm units are not connected to the AC bus.

[0038] Furthermore, when the voltage of the DC submarine cable rises to the DC voltage of the sending end uncontrolled rectification, the condition is satisfied that the voltage difference at the connection point between the offshore converter station and the DC submarine cable is less than the set value.

[0039] Accordingly, the present invention further provides a computer device, comprising a processor and a memory:

[0040] The memory is used to store computer programs and send instructions of the computer programs to the processor;

[0041] The processor executes a black start method for an offshore wind power direct current transmission system based on an uncontrolled rectifier topology according to the instructions of the computer program as described in the second aspect.

[0042] Accordingly, the present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, a black start method for an offshore wind power direct current transmission system based on an uncontrolled rectifier topology is implemented as in the second aspect.

[0043] In summary, the present invention provides an offshore wind power DC transmission system based on an uncontrolled rectifier topology, a black start method thereof, and related devices. Based on the offshore wind power DC transmission system based on an uncontrolled rectifier topology, the present invention adds an offshore converter and an onshore converter to the offshore converter station and the onshore converter station, respectively. The AC side of the offshore converter is connected to the AC busbar through a station transformer, and the DC side is connected to the DC side of the onshore converter through a DC submarine cable, and the DC side of the onshore converter is connected to the onshore station transformer. The present invention can realize the black start of the offshore wind power DC transmission system by executing the black start timing control steps through the offshore converter and the onshore converter. The present invention can complete the black start control in a low-cost manner by simply adding two low-voltage and small-capacity converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 A topological diagram of an offshore wind power direct current transmission system based on an uncontrolled rectifier topology provided in an embodiment of the present invention;

[0046] Figure 2 A schematic flow chart of a method for offshore wind power direct current transmission based on an uncontrolled rectifier topology provided in an embodiment of the present invention;

[0047] Figure 3 A block diagram of a computer device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to make the purposes, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0049] As mentioned above, the offshore wind power transmission solution that uses a unidirectional current-type uncontrolled rectifier converter based on diode elements at the sending end can adapt to various application scenarios and reduce transmission project costs.

[0050] While the use of a unidirectional, current-type, uncontrolled rectifier converter based on diode elements at the sending end helps to lightweight offshore platforms, it also presents the problem of wind farms being unable to perform a black start. Prior art uses diodes in series or parallel with MMCs. These MMCs are high-voltage or high-capacity, resulting in high costs, bulk, and weight, which prevents the full utilization of the low-cost advantages of the diode topology. Laying a separate submarine cable for black starts is costly and occupies submarine routes. Therefore, the present invention proposes an offshore wind power DC transmission system based on an uncontrolled rectifier topology, a black start method, and related devices.

[0051] An embodiment of an offshore wind power direct current transmission system based on an uncontrolled rectifier topology according to the present invention is described in detail below.

[0052] This embodiment provides an offshore wind power direct current transmission system based on an uncontrolled rectifier topology, including:

[0053] Wind farm units, offshore converter stations, onshore converter stations, AC power grids, offshore converters, and onshore converters;

[0054] The wind farm units are connected to the AC side of the offshore converter station via AC busbars;

[0055] The DC side of the offshore converter station is connected to the DC side of the onshore converter station via a DC submarine cable;

[0056] The AC side of the onshore converter station is connected to the AC grid;

[0057] The AC side of the offshore converter is connected to the AC busbar through the first station transformer;

[0058] The DC side of the offshore converter is connected to the DC side of the onshore converter via a DC submarine cable;

[0059] The AC side of the onshore converter is connected to the second station transformer.

[0060] It should be noted that an uncontrolled rectifier circuit inserts a diode or diode circuit between an AC power source and a DC load, utilizing the unidirectional conductivity of the diode to achieve AC / DC power conversion. This embodiment proposes an offshore wind power DC transmission system based on an uncontrolled rectifier topology, which is an uncontrolled rectifier system.

[0061] The main structure of the system includes wind farm units, offshore converter stations, onshore converter stations, AC power grids, offshore converters and onshore converters.

[0062] The wind farm unit consists of several wind farms, each connected to the AC busbar via feeders. The offshore converter station includes YY and YD converter transformers. The DC side of the offshore converter station is connected to the DC side of the onshore converter station via a DC submarine cable, while the AC side of the onshore converter station is connected to the AC grid.

[0063] It is worth noting that, based on the above system structure topology, this embodiment adds an offshore converter and an onshore converter to the offshore converter station and the onshore converter station respectively. The AC side of the offshore converter is connected to the AC busbar through the offshore station transformer; the DC side of the offshore converter is connected to the DC side of the onshore converter through a DC submarine cable; and the AC side of the onshore converter is connected to the onshore station transformer.

[0064] The offshore wind power DC transmission system based on the uncontrolled rectifier topology proposed in this embodiment can complete black start control in a low-cost manner by simply adding two low-voltage and small-capacity converters.

[0065] In a preferred embodiment of the present invention, the system further comprises: an offshore converter station side switch and an onshore converter station side switch;

[0066] The DC side of the offshore converter station is connected to the DC submarine cable through a switch on the offshore converter station side;

[0067] The DC side of the onshore converter station is connected to the DC submarine cable through a switch on the onshore converter station side.

[0068] The switches on the offshore converter station side and the switches on the onshore converter station side facilitate the control of the offshore converter station and the onshore converter station.

[0069] In a preferred embodiment of the present invention, the first connection point between the offshore converter and the DC submarine cable and the second connection point between the onshore converter and the DC submarine cable are both on the DC submarine cable between the offshore converter station side switch and the onshore converter station side switch.

[0070] In a preferred embodiment of the present invention, the device further comprises: an offshore converter switch and an onshore converter switch;

[0071] The offshore converter switch is connected between the offshore converter and the first connection point;

[0072] The onshore converter switch is connected between the onshore converter and the second connection point.

[0073] See also Figure 1 , Figure 1 An offshore wind power DC transmission system based on uncontrolled rectifier topology is shown. Figure 1 A specific implementation of the above embodiment is introduced.

[0074] In a specific implementation of this embodiment, a low-voltage, small-capacity flexible DC converter is constructed in each of the offshore converter station and the onshore converter station, for example, ±10kV~±20kV / 10~20MW.

[0075] The DC side of the offshore low-voltage, small-capacity converter is connected to the DC submarine cable via high-voltage disconnectors K1 and K2. The AC side is connected to a dedicated winding on the station transformer. The winding voltage is designed based on the requirements of the low-voltage, small-capacity converter. For example, if the low-voltage, small-capacity converter is ±10kV / 10MW, a 10kV winding can be designed on the station transformer and connected to the low-voltage, small-capacity converter.

[0076] The DC side of the onshore low-voltage, small-capacity converter is connected to the DC submarine cable via high-voltage disconnectors K3 and K4. The AC side is connected to a dedicated winding on the station transformer. The winding voltage is designed based on the requirements of the low-voltage, small-capacity converter. For example, if the low-voltage, small-capacity converter is ±10kV / 10MW, a 10kV winding can be designed on the station transformer and connected to the low-voltage, small-capacity converter.

[0077] The above is a detailed introduction to an embodiment of an offshore wind power DC transmission system based on an uncontrolled rectifier topology of the present invention. The following is a detailed introduction to a black start method of an offshore wind power DC transmission system based on an uncontrolled rectifier topology of the present invention.

[0078] See also Figure 2 This embodiment provides a black start method for an offshore wind power DC transmission system based on an uncontrolled rectifier topology, which is applied to the offshore wind power DC transmission system based on an uncontrolled rectifier topology as in the above embodiment, and includes the following steps:

[0079] S101: In response to a black start instruction, disconnect the connection between the offshore converter station, the onshore converter station, and the DC submarine cable;

[0080] S102: Connecting the offshore converter and the onshore converter;

[0081] S103: charging the onshore converter and the offshore converter through the second station transformer;

[0082] S104: increasing the AC voltage of the offshore converter to the rated voltage at a uniform speed, and charging the offshore converter transformer of the offshore converter station through the AC bus;

[0083] S105: Selecting a set number of wind turbines from the wind farm units to draw power from the AC bus, starting them, and unlocking them;

[0084] S106: increasing the operating power of the wind turbine until the operating power of the offshore converter is reduced to zero;

[0085] S107: Lock and exit the offshore converter. At this time, the wind turbine and the offshore converter station operate independently.

[0086] S108: disconnecting the offshore converter, the onshore converter, and the DC submarine cable;

[0087] S109: Connecting the onshore converter station to the DC submarine cable, charging the onshore converter station and unlocking it until the DC submarine cable voltage is increased to the DC voltage of the sending-end uncontrolled rectification;

[0088] S110: Connect the offshore converter station and the DC submarine cable to complete the black start timing control.

[0089] by Figure 1 Taking the structural topology of the offshore wind power direct current transmission system based on the uncontrolled rectifier topology as an example, in a specific implementation of this embodiment, the black start sequence includes the following steps:

[0090] (1) Disconnect K offP , K offN , K onP , K onN ;

[0091] (2) Close K1, K2, K3, and K4.

[0092] (3) The onshore low-voltage small-capacity converter charges the offshore and onshore low-voltage small-capacity converters through the station's low-voltage transformer winding.

[0093] (4) The offshore station transformer is connected to the AC busbar, and the YY and YD converter transformers are also connected to the AC busbar. The AC voltage of the offshore low-voltage small-capacity converter gradually increases from 0 to the rated voltage at a certain slope, completing the charging of the offshore converter transformer.

[0094] (5) A small number of wind turbines are selected to draw power from the AC bus and start and unlock them. The wind turbines adopt a grid-type control strategy. The power of the started wind turbines should be greater than the station power consumption of the offshore converter station.

[0095] (6) Gradually increase the wind turbine operating power until the operating power of the low-voltage small-capacity converter is reduced to 0.

[0096] (7) The low-voltage and small-capacity converter is locked and exited. At this time, the wind turbine converter and the offshore converter station operate independently.

[0097] (8) Disconnect K1, K2, K3, and K4.

[0098] (9) Close K onP , K onN , the onshore high-voltage large-capacity converter is charged and unlocked, raising the DC cable voltage to the DC voltage of the sending end uncontrolled rectification. offP , K offN The pressure difference between the two ends is small enough.

[0099] (10) Close K offP , K offN , fan power increase.

[0100] In a preferred embodiment of the present invention, the offshore converter and onshore converter are also used to provide auxiliary power for the offshore converter platform. Specifically, when the flexible DC system is shut down due to DC blocking, maintenance, or other reasons, corresponding control steps can be used to enable the low-voltage, small-capacity converter to provide auxiliary power to the offshore converter platform, reducing the demand for operating diesel generators at the offshore station. The control steps include:

[0101] S201: In response to a control instruction, disconnect the offshore converter station, the onshore converter station, and the DC submarine cable;

[0102] S202: Connecting the offshore converter and the onshore converter;

[0103] S203: charging the onshore converter and the offshore converter through the second station transformer;

[0104] S204: The AC voltage of the offshore converter is uniformly increased to the rated voltage, thereby providing station power for the offshore converter platform. The offshore converter is connected to the AC bus, and the offshore converter station and wind farm units are not connected to the AC bus.

[0105] by Figure 1 Taking the structural topology of the offshore wind power direct current transmission system based on the uncontrolled rectifier topology as an example, in a specific implementation of this embodiment, the following steps are included:

[0106] (1) Disconnect K offP , K offN , K onP , K onN ;

[0107] (2) Close K1, K2, K3, and K4.

[0108] (3) The onshore low-voltage small-capacity converter charges the offshore and onshore low-voltage small-capacity converters through the station's low-voltage transformer winding.

[0109] (4) The offshore station transformer is connected to the AC busbar, while the converter transformer and all wind turbine feeders are not connected to the AC busbar. The AC voltage of the offshore low-voltage, small-capacity converter gradually increases from 0 to the rated voltage at a certain slope to provide station power for the offshore converter platform.

[0110] The present invention only adds two low-voltage small-capacity converters and four high-voltage isolation switches, and has low cost.

[0111] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the system can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0112] Reference Figure 3 An embodiment of the present invention further provides a computer device 3, comprising: a memory 302, a processor 301, and a computer program 303 stored in the memory 302. When the computer program 303 is executed on the processor 301, a black start method for an offshore wind power direct current transmission system based on an uncontrolled rectifier topology as described in any one of the above methods is implemented.

[0113] The computer device 3 may be a desktop computer, a notebook computer, a PDA, a cloud server or other computing devices. The computer device 3 may include, but is not limited to, a processor 301 and a memory 302. Those skilled in the art will understand that Figure 3 This is merely an example of the computer device 3 and does not constitute a limitation on the computer device 3 . The computer device 3 may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device 3 may also include input and output devices, network access devices, etc.

[0114] The processor 301 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. A general-purpose processor may be a microprocessor or any conventional processor.

[0115] In some embodiments, the memory 302 may be an internal storage unit of the computer device 3, such as a hard drive or memory of the computer device 3. In other embodiments, the memory 302 may also be an external storage device of the computer device 3, such as a plug-in hard drive, a Smart Media Card (SMC), a Secure Digital (SD) card, a flash memory card, etc. equipped on the computer device 3. Furthermore, the memory 302 may include both an internal storage unit of the computer device 3 and an external storage device. The memory 302 is used to store an operating system, application programs, a boot loader, data, and other programs, such as the program code of the computer program. The memory 302 may also be used to temporarily store data that has been output or is about to be output.

[0116] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the black start method of an offshore wind power direct current transmission system based on an uncontrolled rectifier topology as described in any one of the above methods is implemented.

[0117] In this embodiment, if the integrated unit is implemented as a software functional unit and sold or used as a standalone product, it can be stored in a computer-readable storage medium. Based on this understanding, the present application can implement all or part of the process steps in the above-mentioned method embodiments by using a computer program to instruct the relevant hardware. The computer program can be stored in a computer-readable storage medium. When executed by a processor, the computer program can implement the steps of each of the above-mentioned method embodiments. The computer program includes computer program code, which can be in source code form, object code form, executable file, or some intermediate form. The computer-readable medium can include at least: any entity or device capable of carrying computer program code to a camera / terminal device, recording medium, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signals, telecommunication signals, and software distribution media. Examples include USB flash drives, removable hard drives, magnetic disks, or optical disks. In some jurisdictions, based on legislation and patent practice, computer-readable media cannot be electric carrier signals or telecommunication signals.

[0118] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0119] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0120] In the embodiments disclosed in the present application, it should be understood that the disclosed devices / terminal equipment and methods can be implemented in other ways. For example, the device / terminal equipment embodiments described above are merely schematic. For example, the division of the modules or units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0121] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. Offshore wind power DC transmission system based on uncontrolled rectifier topology, characterized by: include: Wind farm units, offshore converter stations, onshore converter stations, AC power grids, offshore converters, and onshore converters; The wind farm unit is connected to the AC side of the offshore converter station via an AC busbar; The DC side of the offshore converter station is connected to the DC side of the onshore converter station via a DC submarine cable; The AC side of the onshore converter station is connected to the AC power grid; The AC side of the offshore converter is connected to the AC busbar via the first station transformer; The DC side of the offshore converter is connected to the DC side of the onshore converter via the DC submarine cable; The AC side of the onshore converter is connected to the second station transformer; The system further comprises: an offshore converter station side switch and an onshore converter station side switch; The DC side of the offshore converter station is connected to the DC submarine cable via the offshore converter station side switch; The DC side of the onshore converter station is connected to the DC submarine cable via the onshore converter station switch; The first connection point between the offshore converter and the DC submarine cable and the second connection point between the onshore converter and the DC submarine cable are both on the DC submarine cable between the offshore converter station side switch and the onshore converter station side switch; Also included: offshore converter switches and onshore converter switches; The offshore converter switch is connected between the offshore converter and the first connection point; The onshore converter switch is connected between the onshore converter and the second connection point; The offshore converter and the onshore converter are both connected to the corresponding station transformer through the station transformer dedicated winding.

2. A black start method for an offshore wind power DC transmission system based on an uncontrolled rectifier topology, characterized in that: The method is applied to the offshore wind power direct current transmission system based on the uncontrolled rectifier topology as claimed in claim 1, comprising the following steps: In response to a black start instruction, disconnecting the connection between the offshore converter station, the onshore converter station, and the DC submarine cable; connecting the offshore converter and the onshore converter; charging the onshore converter and the offshore converter through the second station transformer; causing the AC voltage of the offshore converter to rise uniformly to a rated voltage, and charging the offshore converter transformer of the offshore converter station through the AC bus; Selecting a set number of wind turbines from the wind farm units to draw power from the AC bus and starting and unlocking them; increasing the operating power of the wind turbine until the operating power of the offshore converter decreases to zero; Locking and exiting the offshore converter, at which point the wind turbine drives the offshore converter station to operate independently; Disconnecting the connection between the offshore converter, the onshore converter, and the DC submarine cable; Connecting the onshore converter station to the DC submarine cable, charging and unlocking the onshore converter station until the DC submarine cable voltage is increased to the DC voltage of the sending-end uncontrolled rectification; Connecting the offshore converter station to the DC submarine cable to complete black start timing control; The offshore converter and the onshore converter are also used to provide auxiliary power for the offshore converter platform. The control steps include: In response to a control instruction, disconnecting the connection between the offshore converter station, the onshore converter station, and the DC submarine cable; connecting the offshore converter and the onshore converter; charging the onshore converter and the offshore converter through the second station transformer; The AC voltage of the offshore converter is uniformly increased to the rated voltage, thereby providing station power for the offshore converter platform, wherein the offshore converter is connected to the AC bus, and the offshore converter station and the wind farm unit are not connected to the AC bus.

3. The black start method of an offshore wind power direct current transmission system based on an uncontrolled rectifier topology according to claim 2, characterized in that: When the voltage of the DC submarine cable rises to the DC voltage of the uncontrolled rectification at the sending end, the condition is met that the voltage difference at the connection point between the offshore converter station and the DC submarine cable is less than a set value.

4. A computer device, characterized in that: The device includes a processor and a memory: The memory is used to store a computer program and send instructions of the computer program to the processor; The processor executes the black start method of an offshore wind power direct current transmission system based on an uncontrolled rectifier topology according to the instructions of the computer program as claimed in claim 2 or 3.

5. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by the processor, it implements the black start method of the offshore wind power direct current transmission system based on the uncontrolled rectifier topology as claimed in claim 2 or 3.

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