Offshore wind power direct current sending-out system and starting control method thereof

Abstract

The invention relates to the technical field of flexible direct-current power transmission, and provides an offshore wind power direct-current sending-out system and a starting control method thereof.The system is characterized in that part of wind turbine generators are gathered through an offshore alternating-current gathering bus, then connected to an offshore booster station, connected to a DRU converter valve of a diode uncontrolled rectifying unit and then connected to an offshore direct-current bus through a first switch; an onshore converter valve of the onshore converter station is connected through a direct-current line, and is finally connected to an onshore alternating-current power grid; part of the wind turbine generators are gathered through the offshore direct current gathering bus, then connected to the direct current transformer, then connected to the offshore direct current bus, connected to the land converter valve of the land converter station through a direct current line and finally connected to the land alternating current power grid. According to the offshore wind power direct-current sending-out system, the DRU converter valve and the direct-current transformer are adopted, the DRU does not need to adopt a series / parallel MMC structure, the problem of black start of the DRU converter valve is solved through the power bidirectional flow characteristic of the direct-current transformer, and the direct-current transformer can conduct power transmission.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible DC power transmission, and particularly to an offshore wind power DC transmission system and a starting control method thereof. Background Art

[0002] At present, the current solutions for offshore wind power transmission projects are power frequency AC power transmission and DC power transmission. With the construction of offshore wind power transmission, in the future, the medium and far - sea wind power resources will be intensively developed. The power frequency AC power transmission is limited by the cable capacitance effect and can no longer meet the application requirements in scenarios more than 70 km away from the shore. Adopting flexible DC power transmission is the most practical and feasible solution under the current technical conditions. At present, the flexible DC power transmission system based on the Modular Multilevel Converter (MMC) is a typical solution for far - sea wind power grid connection. The use of a Diode Rectifier Unit (DRU) can further improve the economy and reliability of the power transmission system. The DRU converter valve needs to commutate with the help of an external power supply and the power transmission has unidirectionality. Therefore, neither the DRU rectifier station nor the on - shore power grid can start the offshore wind farm, and the DRU converter valve has the problem that it cannot independently achieve black start.

[0003] For the hybrid DC transmission solution using parallel connection of DRU and MMC, this solution requires the DC side voltages of DRU and MMC to be equal, resulting in a large number of MMC sub - modules; for the hybrid far - sea wind power transmission solution using series connection of DRU and MMC, the AC grid on the MMC fan side adopts an AC collection method, and the rectification, inversion, and boosting of electric energy multiple times in the path increase the losses. By increasing the cable voltage level, black start is achieved but the system insulation requirements are improved; for the solution using series connection of DRU and a full - bridge MMC on the DC side, and regulating the DC line power through the full - bridge MMC, the problem of black start of the offshore wind farm is not solved. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one technical problem in the background art, and provide an offshore wind power DC transmission system and a control method thereof.

[0005] To achieve the above purpose, the present invention provides an offshore wind power DC transmission system, including: wind turbines, an offshore AC collection bus, an offshore DC collection bus, an offshore booster station, a DRU converter valve, a DC transformer, an offshore DC bus, a DC line, an on - shore converter station, and an on - shore AC power grid; Among them, some wind turbines are collected through the offshore AC collection bus and then connected to the offshore booster station, connected to the DRU converter valve, then connected to the offshore DC bus through a first switch, connected to the on - shore converter valve of the on - shore converter station through the DC line, and finally connected to the on - shore AC power grid; Part of the wind turbines are collected through an offshore DC collection busbar, connected to a DC transformer, then connected to the offshore DC busbar, connected to the onshore converter valves of the onshore converter station through a DC line, and finally connected to the onshore AC power grid; The DC transformer is respectively connected to the DC capacitors of some wind turbines through a second switch, a third switch; The DC transformer is directly connected to the DC capacitors of some wind turbines.

[0006] According to one aspect of the present invention, a reactive power compensation device is configured in the offshore booster station to filter out harmonics and provide reactive power support for the DRU converter valves.

[0007] According to one aspect of the present invention, the wind turbine includes a first wind turbine converter and a second wind turbine converter; The first wind turbine converter connected to the offshore booster station through the offshore AC collection busbar is an AC-DC-AC converter, and the second wind turbine converter connected to the DC transformer through the offshore DC collection busbar is an AC-DC converter.

[0008] According to one aspect of the present invention, some of the first wind turbine converters adopt a grid-forming control strategy to obtain the control result of grid-forming wind turbine characteristics to maintain the voltage of the AC collection busbar and transmit electric energy; some of the first wind turbine converters adopt a grid-following control strategy to obtain the control result of grid-following wind turbine characteristics to transmit electric energy.

[0009] According to one aspect of the present invention, the second wind turbine converter adopts maximum power tracking and constant AC voltage control.

[0010] According to one aspect of the present invention, the DC transformer is respectively connected to the DC capacitors of the first wind turbine converter through a second switch, a third switch; The DC transformer is directly connected to the DC capacitors of the second wind turbine converter.

[0011] To achieve the above object, the present invention also provides a starting control method for an offshore wind power DC transmission system, including: Switch the onshore converter station to the operating state and charge the offshore DC busbar; Start the wind turbines configured with grid-forming first wind turbine converters; Start the wind turbines configured with grid-following first wind turbine converters; Start the wind turbines configured with grid-following second wind turbine converters; Start the DRU converter valves and switch the DC transformer to the system operating state.

[0012] According to one aspect of the present invention, starting the wind turbines configured with grid-forming first wind turbine converters and the wind turbines configured with grid-following first wind turbine converters includes: The onshore converter station is switched to the operating state, and the onshore AC grid charges the offshore DC bus through the onshore converter station via the DC line; When the voltage U of the offshore DC bus dc_offshore = 1 p.u., close the second switch and the third switch, start the DC transformer, and charge the DC capacitor of the first wind turbine converter through the DC transformer; When the DC capacitor voltage U of the first wind turbine converter cap_conI ≥ 0.8 p.u., start the grid-forming wind turbine machine-side converter. When the DC capacitor voltage U cap_conI = 1 p.u., open the second switch, start the grid-forming wind turbine grid-side converter, and charge the offshore AC collection bus; When the voltage U of the offshore AC collection bus acp_offshore = 1 p.u., open the third switch, start the grid-following first wind turbine grid-side converter of the first wind turbine, and the grid-following first wind turbine grid-side converter is connected to the offshore AC collection bus.

[0013] According to one aspect of the present invention, starting a wind turbine unit configured with a grid-following second wind turbine converter includes: The onshore converter station is switched to the operating state, and the onshore AC grid charges the offshore DC bus through the onshore converter station via the DC line; When the voltage U of the offshore DC bus dc_offshore = 1 p.u., start the DC transformer, and charge the DC capacitor of the second wind turbine converter through the DC transformer; When the DC capacitor voltage U of the second wind turbine converter cap_conII ≥ 0.8 p.u., start the machine-side converter. After the second wind turbine converter enters the operating state, the DC transformer is switched to the power transmission state.

[0014] According to one aspect of the present invention, the method for starting the DRU converter valve includes: The onshore converter station is switched to the operating state, and the onshore AC grid charges the DC bus voltage U dc_offshore to 1 p.u. through the onshore converter station; After the grid-forming first wind turbine converter starts, it establishes the voltage of the offshore AC collection bus. When the voltage U of the offshore AC collection bus acp_offshore = 1 p.u., close the first switch, and the start of the DRU converter valve is completed.

[0015] According to one aspect of the present invention, during the startup process of the offshore wind power DC transmission system, the DC transformer sequentially completes the following control steps: Before the wind turbine unit starts, the DC transformer starts first and receives the electrical energy of the offshore DC bus to charge the DC capacitors of the first wind turbine converter and the second wind turbine converter. The DC capacitor voltages U of the first wind turbine converter and the second wind turbine convertercap_con Rise to 0.8 p.u.; After the wind turbine unit equipped with the network-forming type first wind turbine converter starts, turn on the second switch; after the wind turbine unit equipped with the grid-following type first wind turbine converter starts, turn on the third switch; after the wind turbine unit equipped with the grid-following type second wind turbine converter starts, the DC transformer switches to the power transmission state.

[0016] To achieve the above object, the present invention further provides an electronic device, including a processor, a memory, and a computer program stored on the memory and executable on the processor. When the computer program is executed by the processor, the startup control method described above is implemented.

[0017] To achieve the above object, the present invention further provides a computer-readable storage medium. A computer program is stored on the computer-readable storage medium. When the computer program is executed by a processor, the startup control method described above is implemented.

[0018] According to the solution of the present invention, the offshore wind power DC transmission system proposed by the present invention adopts a DRU converter valve and a DC transformer. Among them, the DRU does not need to adopt a series / parallel MMC structure, and solves the black start problem of the DRU converter valve through the power bi-directional flow characteristic of the DC transformer. At the same time, the DC transformer can also perform power transmission.

[0019] According to the solution of the present invention, the present invention introduces a DC transformer in the topology to charge the DC capacitor of the network-forming wind turbine converter during the startup phase, enabling the network-forming wind turbine converter to establish a converged AC voltage, solving the black start problem, and eliminating the need to configure a diesel engine on the offshore platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematically shows a system structure diagram of an offshore wind power DC transmission system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Now, the content of the present invention will be described with reference to exemplary embodiments. It should be understood that the described embodiments are only for enabling those of ordinary skill in the art to better understand and thus implement the content of the present invention, rather than implying any limitation to the scope of the present invention.

[0022] As used herein, the term "comprising" and its variants are to be construed as open-ended terms meaning "including but not limited to". The term "based on" is to be construed as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be construed as "at least one embodiment".

[0023] Figure 1Schematically show the system structure diagram of an offshore wind power DC transmission system according to an embodiment of the present invention. As Figure 1 shown, in this embodiment, the offshore wind power DC transmission system includes: wind turbines, an offshore AC collection bus 1, an offshore DC collection bus 2, an offshore booster station 3, a diode uncontrolled rectifier unit 4, a DC transformer 5, an offshore DC bus 6, a DC line 7, an onshore converter station 8, and an onshore AC power grid 9; Among them, some wind turbines are collected through the offshore AC collection bus and connected to the offshore booster station, connected to the DRU converter valve, and then connected to the offshore DC bus through the first switch 10, connected to the onshore converter valve of the onshore converter station through the DC line, and finally connected to the onshore AC power grid; Some wind turbines are collected through the offshore DC collection bus and then connected to the DC transformer, then connected to the offshore DC bus, connected to the onshore converter valve of the onshore converter station through the DC line, and finally connected to the onshore AC power grid; The DC transformer is respectively connected to the DC capacitors of some wind turbines through the second switch 11, the third switch 12; The DC transformer is directly connected to the DC capacitors of some wind turbines.

[0024] Further, according to an embodiment of the present invention, a reactive power compensation device is configured in the offshore booster station to filter out harmonics and provide reactive power support for the DRU converter valve.

[0025] Further, according to an embodiment of the present invention, the wind turbine includes a first wind turbine converter 13 and a second wind turbine converter 14; The first wind turbine converter connected to the offshore booster station through the offshore AC collection bus is an AC-DC-AC converter, and the second wind turbine converter connected to the DC transformer through the offshore DC collection bus is an AC-DC converter.

[0026] Further, according to an embodiment of the present invention, some first wind turbine converters adopt a grid-forming control strategy to obtain a grid-forming wind turbine characteristic control result for maintaining the voltage of the AC collection bus and transmitting electric energy; some first wind turbine converters adopt a grid-following control strategy to obtain a grid-following wind turbine characteristic control result for transmitting electric energy.

[0027] Further, according to an embodiment of the present invention, the second wind turbine converter adopts maximum power tracking and constant AC voltage control.

[0028] Further, according to an embodiment of the present invention, the DC transformer is respectively connected to the DC capacitors of the first wind turbine converter through the second switch and the third switch; The DC transformer is directly connected to the DC capacitors of the second wind turbine converter.

[0029] According to the above solution of the present invention, the offshore wind power DC transmission system proposed by the present invention adopts a DRU converter valve and a DC transformer. The DRU does not need to adopt a series / parallel MMC structure, and solves the black start problem of the DRU converter valve through the power bi-directional flow characteristic of the DC transformer. At the same time, the DC transformer can also perform power transmission.

[0030] Furthermore, to achieve the above object, the present invention also provides a start control method for an offshore wind power DC transmission system, which combines Figure 1 As shown, the method includes: Switch the onshore converter station to the operating state and charge the offshore DC bus. Start the wind turbine unit configured with a grid-forming first wind turbine converter. Start the wind turbine unit configured with a grid-following first wind turbine converter. Start the wind turbine unit configured with a grid-following second wind turbine converter. Start the DRU converter valve and switch the DC transformer to the system operating state.

[0031] Furthermore, according to an embodiment of the present invention, starting the wind turbine unit configured with a grid-forming first wind turbine converter and the wind turbine unit configured with a grid-following first wind turbine converter includes: The onshore converter station is switched to the operating state, and the onshore AC grid charges the offshore DC bus through the onshore converter station via a DC line. When the voltage U of the offshore DC bus dc_offshore = 1 p.u., close the second switch and the third switch, start the DC transformer, and charge the DC capacitor of the first wind turbine converter through the DC transformer. When the DC capacitor voltage U of the first wind turbine converter cap_conI ≥ 0.8 p.u., start the grid-forming wind turbine machine-side converter. When the DC capacitor voltage U cap_conI = 1 p.u., open the second switch, start the grid-forming wind turbine grid-side converter, and charge the offshore AC collection bus. In this embodiment, the wind turbine converter of the AC collection is of an AC-DC-AC structure. The AC-DC near the wind turbine side is called the wind turbine machine-side converter, and the DC-AC near the grid side is called the wind turbine grid-side converter. When the voltage U of the offshore AC collection bus acp_offshore = 1 p.u., open the third switch, start the grid-following wind turbine grid-side first wind turbine converter, and the grid-following first wind turbine converter is connected to the offshore AC collection bus.

[0032] Furthermore, according to an embodiment of the present invention, starting the wind turbine unit configured with a second wind turbine converter includes: The onshore converter station is switched to the operating state, and the onshore AC grid charges the offshore DC bus through the onshore converter station via a DC line. When the DC bus voltage U dc_offshore on the sea = 1 p.u., start the DC transformer and charge the DC capacitor of the second wind turbine converter through the DC transformer; When the DC capacitor voltage U cap_conII of the second wind turbine converter ≥ 0.8 p.u., start the machine-side converter. After the second wind turbine converter enters the operating state, the DC transformer switches to the power transmission state.

[0033] Furthermore, according to an embodiment of the present invention, the method for starting the DRU converter valve includes: The onshore converter station switches to the operating state, and the onshore AC power grid charges the DC bus voltage U dc_offshore to 1 p.u. through the onshore converter station; After the grid-forming type first wind turbine converter is started, it establishes the sea AC collection bus voltage. When the sea AC collection bus voltage U acp_offshore = 1 p.u., close the first switch, and the start of the DRU converter valve is completed.

[0034] Furthermore, according to an embodiment of the present invention, during the start-up process of the offshore wind power DC transmission system, the DC transformer sequentially completes the following control steps: Before the wind turbine starts, the DC transformer starts first and receives the electric energy of the sea DC bus to charge the DC capacitors of the first wind turbine converter and the second wind turbine converter. The DC capacitor voltages U cap_con of the first wind turbine converter and the second wind turbine converter rise to 0.8 p.u.; After the wind turbine equipped with the grid-forming type first wind turbine converter starts, open the second switch; after the wind turbine equipped with the grid-following type first wind turbine converter starts, open the third switch; after the wind turbine equipped with the grid-following type second wind turbine converter starts, the DC transformer switches to the power transmission state.

[0035] According to the above solution of the present invention, the offshore wind power DC transmission system proposed by the present invention adopts a DRU converter valve and a DC transformer. Among them, the DRU does not need to adopt a series / parallel MMC structure, and solves the black start problem of the DRU converter valve through the power bi-directional flow characteristic of the DC transformer. At the same time, the DC transformer can also perform power transmission.

[0036] Furthermore, to achieve the above object, the present invention also provides an electronic device, including a processor, a memory, and a computer program stored on the memory and executable on the processor. When the computer program is executed by the processor, it implements the start control method as described above.

[0037] Further, to achieve the above object, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the above-mentioned startup control method is implemented.

[0038] Those of ordinary skill in the art can realize that the modules and algorithm steps described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0039] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the above-described devices and equipment can refer to the corresponding processes in the foregoing method embodiments, and will not be described herein again.

[0040] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the modules is only a logical function division. In actual implementation, there may be other division methods. For example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the devices or modules can be in an electrical, mechanical or other form.

[0041] The modules described as separate components may or may not be physically separated. The components shown as modules may or may not be physical modules, that is, they may be located in one place, or may be distributed to multiple network modules. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of the embodiments of the present invention.

[0042] In addition, the various functional modules in the embodiments of the present invention can be integrated into one processing module, or each module can exist physically alone, or two or more modules can be integrated into one module.

[0043] When the above functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method for sending / receiving energy-saving signals in various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, ROM, RAM, magnetic disks, or optical discs that can store program codes.

[0044] The above description is only the preferred embodiment of the present application and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) disclosed in the present application that have similar functions.

[0045] It should be understood that the magnitudes of the sequence numbers of the steps in the inventive content and the embodiments of the present invention do not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

Claims

1. Offshore wind power DC transmission system, characterized in that, Including: Wind turbine generators, offshore AC collection busbars, offshore DC collection busbars, offshore booster stations, diode uncontrolled rectifier units, DC transformers, offshore DC busbars, DC lines, onshore converter stations, and onshore AC power grids; Among them, some wind turbine generators are collected through the offshore AC collection busbar and then connected to the offshore booster station, connected to the DRU converter valve of the diode uncontrolled rectifier unit, then connected to the offshore DC busbar through the first switch, connected to the onshore converter valve of the onshore converter station through the DC line, and finally connected to the onshore AC power grid; Some wind turbine generators are collected through the offshore DC collection busbar and then connected to the DC transformer, then connected to the offshore DC busbar, connected to the onshore converter valve of the onshore converter station through the DC line, and finally connected to the onshore AC power grid; The DC transformer is respectively connected to the DC capacitors of some wind turbine generators through the second switch, the third switch; The DC transformer is directly connected to the DC capacitors of some wind turbine generators.

2. The offshore wind power DC transmission system according to claim 1, wherein Reactive power compensation devices are configured in the offshore booster station to filter out harmonics and provide reactive power support for the DRU converter valve.

3. The offshore wind power DC transmission system according to claim 1, wherein The wind turbine generator includes a first wind turbine converter and a second wind turbine converter; The first wind turbine converter connected to the offshore booster station through the offshore AC collection busbar is an AC-DC-AC converter, and the second wind turbine converter connected to the DC transformer through the offshore DC collection busbar is an AC-DC converter.

4. The offshore wind power DC transmission system according to claim 1, wherein Some of the first wind turbine converters adopt a network-forming control strategy to obtain the control results of network-forming wind turbine characteristics to maintain the voltage of the AC collection busbar and transmit electric energy; some of the first wind turbine converters adopt a grid-following control strategy to obtain the control results of grid-following wind turbine characteristics to transmit electric energy.

5. The offshore wind power DC transmission system according to claim 1, wherein The second wind turbine converter adopts maximum power tracking and constant AC voltage control.

6. The offshore wind power DC transmission system according to any one of claims 1-5, characterized in that, The DC transformer is respectively connected to the DC capacitors of the first wind turbine converter through the second switch, the third switch; The DC transformer is directly connected to the DC capacitors of the second wind turbine converter.

7. The starting control method for the offshore wind power DC transmission system according to any one of claims 1-6, characterized in that Including: Switch the onshore converter station to the operating state and charge the offshore DC busbar; Start the wind turbine generators equipped with network-forming first wind turbine converters; Start the wind turbine generators equipped with grid-following first wind turbine converters; Start the wind turbine generators equipped with grid-following second wind turbine converters; Start the DRU converter valve and switch the DC transformer to the system operating state.

8. The start control method according to claim 7, wherein Starting the wind turbine generators equipped with network-forming first wind turbine converters and grid-following first wind turbine converters includes: The onshore converter station is switched to the operating state, and the onshore AC power grid charges the offshore DC busbar through the onshore converter station and the DC line; When the DC bus voltage U dc_offshore on the sea is 1 p.u., close the second switch and the third switch, start the DC transformer, and charge the DC capacitor of the first wind turbine converter through the DC transformer; When the DC capacitor voltage U of the first wind turbine converter cap_conI ≥ 0.8 p.u., start the machine-side converter of the grid-forming wind turbine. When the DC capacitor voltage U cap_conI = 1 p.u., disconnect the second switch and start the grid-side converter of the grid-forming wind turbine to charge the offshore AC collection bus; The voltage U of the offshore AC collection busbar to be awaited acp_offshore = 1 p.u., disconnect the third switch, start the first converter on the grid side of the grid-connected wind turbine, and the first grid-connected wind turbine converter is connected to the offshore AC collection busbar.

9. The startup control method according to claim 7, wherein Starting the wind turbine generators equipped with grid-following second wind turbine converters includes: The onshore converter station is switched to the operating state, and the onshore AC power grid charges the offshore DC busbar through the onshore converter station and the DC line; When the DC bus voltage U dc_offshore = 1 p.u. on the sea, start the DC transformer and charge the DC capacitor of the second fan converter through the DC transformer; When the DC capacitor voltage U of the second wind turbine converter cap_conII ≥ 0.8 p.u., start the machine-side converter. After the second wind turbine converter enters the operating state, the DC transformer switches to the power transmission state.

10. The startup control method according to claim 7, wherein The method for starting the DRU converter valve includes: The onshore converter station is switched to the operating state, and the onshore AC power grid charges the DC bus voltage U dc_offshore to 1 p.u. through the onshore converter station; After the grid-forming type first wind turbine converter is started, the offshore AC collection bus voltage is established. When the offshore AC collection bus voltage U acp_offshore = 1 p.u., the first switch is closed, and the start-up of the DRU converter valve is completed.

11. The startup control method according to claim 7, characterized in that During the startup process of the offshore wind power DC transmission system, the DC transformer sequentially completes the following control steps: Before the wind turbine starts, the DC transformer starts first and receives the electrical energy from the offshore DC bus to charge the DC capacitors of the first and second wind turbine converters. The DC capacitor voltages U of the first and second wind turbine converters cap_con rise to 0.8 p.u.; After the wind turbine generators equipped with network-forming first wind turbine converters are started, open the second switch; After the wind turbine equipped with the grid-connected type first wind turbine converter is started, the third switch is turned on; after the wind turbine equipped with the grid-connected type second wind turbine converter is started, the DC transformer is switched to the power transmission state.

12. An electronic device, characterized in that, It includes a processor, a memory, and a computer program stored on the memory and executable on the processor. When the computer program is executed by the processor, it implements the start control method according to any one of claims 7-11.

13. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium. When the computer program is executed by the processor, it implements the start control method according to any one of claims 7-11.

Images