Multi-port low-voltage flexible interconnection system ac-dc fault protection control device and method

Abstract

The application discloses a kind of multiport low-voltage flexible interconnection system ac / dc fault protection control device and method, belong to the field of power system relay protection.The device includes flexible direct current converter, area integrated control terminal, DC protection control device, coordination controller and mobile energy storage vehicle, each DC protection control device is separately networked, and all access acquisition communication network;Integrated control terminal, mobile energy storage vehicle, coordination controller, flexible direct current converter are all accessed acquisition communication network and control communication network, information is exchanged between each equipment by GOOSE communication mechanism, transmission control instruction;Coordination controller issues control instruction to flexible direct current converter, area integrated control terminal and mobile energy storage vehicle according to system operating state by control communication network.The application also proposes corresponding protection control method for a variety of possible faults, so that the system can quickly restore non-fault area power supply, guarantee the safe and stable and reliable operation of multiport low-voltage flexible interconnection system.

Description

Technical Field

[0001] This invention belongs to the field of power system relay protection, and particularly relates to a multi-port low-voltage flexible interconnection system AC / DC fault protection control device and method. Background Technology

[0002] With the steady and proactive advancement of the national "dual-carbon" initiative, a new power system based on new energy sources is under construction. The integration of numerous distributed energy sources has led to power backflow from distribution transformers, posing risks of overvoltage and overload. The backflow process for photovoltaic power involves a "boost and buck" process to supply power to the load, resulting in low efficiency. Furthermore, the rapid growth of new energy sources such as distributed photovoltaic systems and electric vehicle charging stations has led to capacity shortages and degraded power quality in existing distribution transformer areas. Therefore, low-voltage flexible interconnection technology, which enables fault support, power transfer, and load balancing across multiple distribution transformer areas, has received considerable attention and application.

[0003] Multi-port low-voltage flexible interconnection systems typically use a segmented DC bus configuration, i.e., a distributed layout, to flexibly interconnect multiple distribution substations via DC cables. This involves numerous AC and DC elements, strong coupling, and long DC lines. Faults can occur in the DC bus, tie lines, 10kV incoming lines, transformers, flexible DC converters, and low-voltage AC lines. If these faults are not isolated and addressed promptly, they can expand the fault area and affect the power supply to more loads. Therefore, there is an urgent need to propose protection and control strategies for AC and DC faults in multi-port low-voltage flexible interconnection systems. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-port low-voltage flexible interconnection system AC / DC fault protection control device and method, which can realize rapid fault isolation, maintain system stability, and quickly restore power supply to non-faulty areas.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, a multi-port low-voltage flexible interconnection system AC / DC fault protection and control device is provided, including an AC / DC flexible DC converter and a comprehensive control terminal for each transformer substation, a coordination controller for one of the substations, a mobile energy storage vehicle for one of the substations, and several DC protection and control devices for the incoming and outgoing lines of the DC bus in each substation. The mobile energy storage vehicle is connected to the DC bus via an energy storage converter. The comprehensive control terminal for the substations is used to collect the incoming voltage of the AC substation, the voltage and current information of the low-voltage AC main switch of the substation, and the on / off position. The system determines the location and, according to the control strategy, controls the operation of the low-voltage AC main switch in the control area; each DC protection and control device is networked independently, and each DC protection and control device is connected to the data acquisition and communication network; the integrated control terminal, energy storage converter, coordination controller, and AC / DC flexible DC converter are all connected to the data acquisition and communication network and the control communication network, and the devices exchange information and transmit control commands through the GOOSE communication mechanism; the coordination controller is used to issue control commands to the AC / DC flexible DC converter, the integrated control terminal of the distribution area, and the energy storage converter through the control communication network according to the system operating status.

[0006] Furthermore, the various DC protection and control devices form DC protection control network A and DC protection control network B, creating a redundant dual-network configuration, and each transmits the DC protection GOOSE signal independently.

[0007] Secondly, a method for AC / DC fault protection control of a multi-port low-voltage flexible interconnection system is provided, implemented based on the device of the first aspect, including: When a DC bus fault occurs in a transformer area, the DC protection and control device of the faulty transformer area trips all circuit breakers on the DC bus. Because the DC bus is in closed-loop operation, all AC / DC flexible DC converters in all transformer areas detect the DC side fault. If the fault current is large, all AC side circuit breakers of the AC / DC flexible DC converters will experience overcurrent, and all internal AC grid-connected contactors will trip after a delay, breaking the circuit. After confirming that all switches in the faulty area are open and the faulty area is isolated, if all AC / DC flexible DC converters have been taken out of operation, the AC / DC flexible DC converter in any non-faulty transformer area is selected to operate in UDC mode to establish a DC bus. Then, the AC / DC flexible DC converters in other non-faulty transformer areas are put into operation in sequence. If only the AC / DC flexible DC converters in the faulty transformer area are taken out of operation, the coordinating controller will remove the AC / DC flexible DC converters in the faulty transformer area from the operation control logic.

[0008] Furthermore, the AC / DC fault protection control method for the multi-port low-voltage flexible interconnection system further includes: When a permanent fault occurs in the 10kV AC incoming line, causing the entire system to go black, the low-voltage AC main switch of all distribution areas will trip due to undervoltage. The AC side switch of the AC / DC flexible DC converter will trip after a delay. The coordination controller will issue a mode switching command to the mobile energy storage vehicle. All mobile energy storage vehicles will switch to working in constant DC bus voltage mode. After a delay, the coordination controller will issue a start command to the mobile energy storage vehicle. The mobile energy storage vehicle will start working and establish DC bus voltage. Once the coordinating controller determines that the DC bus voltage has been established, it issues a command after a delay to switch all AC / DC flexible DC converters to VF mode. After the switching time, all distribution areas are restored to power, the photovoltaic system begins generating electricity, and the mobile energy storage vehicle discharges or charges according to the power demand of the entire distribution area.

[0009] Furthermore, the AC / DC fault protection control method for the multi-port low-voltage flexible interconnection system further includes: When a transformer in a certain area fails, if the high-voltage side of the transformer cannot isolate the fault, the fault will be isolated by the tripping of the upstream boundary switch, section switch or substation outlet switch. At this time, the system will be completely black. The fault handling procedure for the flexible interconnection system is the same as the handling procedure after a permanent fault in the 10kV AC incoming line causes the system to be completely black.

[0010] Furthermore, the AC / DC fault protection control method for the multi-port low-voltage flexible interconnection system further includes: When a transformer in a certain distribution area fails, if the high-voltage side of the transformer can isolate the fault, only the low-voltage AC main switch of the faulty distribution area will trip due to undervoltage. Because of the AC side undervoltage, the undervoltage protection of the AC side switch of the AC / DC flexible DC converter will trip after a delay. After confirming that the low-voltage AC main switch of the faulty distribution area is in the open position, the delay coordination controller will issue a command to switch the AC / DC flexible DC converter of the faulty distribution area to VF mode. After the switching time, the load connected to the faulty distribution area will be restored to power supply.

[0011] Furthermore, the AC / DC fault protection control method for the multi-port low-voltage flexible interconnection system further includes: When a fault occurs in the IGBT of an AC / DC flexible DC converter in a certain distribution area, the AC / DC flexible DC converter is locked out. After a time delay, the AC side switch is tripped, the DC protection device of the DC protection and control device is activated, the DC side switch is tripped, and a lockout signal is sent to the coordination controller. The coordination controller removes the AC / DC flexible DC converter from the operation control logic and rationally transfers the DC load and DC photovoltaic power to the remaining distribution areas according to the current redundancy capacity of each distribution area.

[0012] Furthermore, the AC / DC fault protection control method for the multi-port low-voltage flexible interconnection system further includes: When a fault occurs on a branch line on the low-voltage side of a JP cabinet in a certain distribution area, the overcurrent protection of the switch on that line trips, isolating the fault, while other branches in the same distribution area continue to operate normally.

[0013] Furthermore, the AC / DC fault protection control method for the multi-port low-voltage flexible interconnection system further includes: When a fault occurs on a branch line of the low-voltage side of a JP cabinet in a certain distribution area, if the faulty branch line switch cannot trip, the AC / DC flexible DC converter in the faulty distribution area will trip after a delay, open the AC side switch, and send a blocking signal to the coordination controller. The coordination controller will then remove the AC / DC flexible DC converter from the operation control logic.

[0014] Compared with the prior art, the beneficial technical effects achieved by the present invention are as follows: This invention uses a coordinating controller as the control center and a fast control network based on the GOOSE mechanism to transmit control commands to the AC / DC flexible DC converter, the integrated control terminal of the distribution area, and the energy storage converter, greatly shortening the control delay. The DC protection and control device is separately networked with GOOSE, which can achieve precise fault isolation, reduce the power outage area, and propose corresponding protection and control strategies for various possible faults, enabling the system to quickly restore power supply to non-faulty areas and ensure the safe, stable and reliable operation of the multi-port low-voltage flexible interconnection system. Attached Figure Description

[0015] Figure 1 This is an overall topology diagram of a five-port low-voltage flexible interconnect system according to an embodiment of the present invention; Figure 2 This is a communication topology diagram of a five-port low-voltage flexible interconnect system according to an embodiment of the present invention; Figure 3 This is a block diagram of an AC / DC fault protection and control method for a five-port low-voltage flexible interconnection system according to an embodiment of the present invention. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments. These embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0017] Example 1

[0018] Figure 1 This is the overall topology diagram of the five-port low-voltage flexible interconnection system. Each of the five transformer substations (1# to 5#) is equipped with a set of low-voltage flexible interconnection equipment to form a virtual DC transformer substation.

[0019] Each low-voltage flexible interconnection system includes an AC / DC flexible DC converter. The AC side of each AC / DC flexible DC converter is connected to the low-voltage side of the transformer in the corresponding distribution area, and the DC side is connected to the DC bus.

[0020] One AC power source is drawn from the 0.4kV bay of each transformer substation. After conversion by an AC / DC flexible DC converter, a DC bus voltage of 750V is established. DC distribution ports are drawn from each transformer substation for connecting distributed photovoltaic systems, charging piles, energy storage, and DC power loads to construct a low-voltage flexible interconnection system.

[0021] Combination Figure 1 and Figure 2 As shown in the figure, the present invention provides a five-port low-voltage flexible interconnection system AC / DC fault protection and control device, including AC / DC flexible DC converters and integrated control terminals of transformer substations 1#-5#, a coordination controller of transformer substation 4#, an integrated mobile energy storage vehicle of transformer substation 1#, and several DC protection and control devices of transformer substations 1#-5# on the DC bus side incoming line and each outgoing line.

[0022] The mobile energy storage vehicle is connected to the DC bus via an energy storage converter. Of course, the mobile energy storage vehicle can also be deployed in other transformer substations.

[0023] Each transformer substation's DC bus incoming line and each outgoing line are equipped with a separate DC protection and control device, which can realize overcurrent protection and network topology protection functions.

[0024] The integrated control terminal for the distribution area is installed near the JP cabinet in the distribution area. It is used to collect information such as the incoming voltage of the AC distribution area, the voltage and current information of the AC main switch of the distribution area, and the open / close position of the AC main switch of the distribution area. It also has a remote control function, which can remotely control the opening and closing of the AC main switch of the distribution area according to the corresponding control strategy.

[0025] Figure 2 The diagram shows the communication topology of a five-port low-voltage flexible interconnection system. The AC / DC flexible DC converters in all five distribution areas are connected to the data acquisition communication network (MMS+GOOSE) and the control communication network (GOOSE). The coordination controller located in distribution area #4 is also connected to both the data acquisition communication network (MMS+GOOSE) and the control communication network (GOOSE). The integrated control terminals in all five distribution areas are connected to both the data acquisition communication network (MMS+GOOSE) and the control communication network (GOOSE). The energy storage converter located in distribution area #1 is connected to both the data acquisition communication network (MMS+GOOSE) and the control communication network (GOOSE). All DC protection and control devices in all distribution areas are connected to the data acquisition communication network (MMS+GOOSE).

[0026] In addition, all DC protection and control devices are networked separately to form a redundant dual-network configuration of DC protection control network A and DC protection control network B, and transmit DC protection GOOSE signals separately to ensure the stability and reliability of DC protection functions.

[0027] The DC protection and control device, through a separate GOOSE network, shares DC protection information and communicates point-to-point, ensuring the reliability and speed requirements of the low-voltage flexible interconnection system protection. It can isolate faults in a very short time and trip related DC circuit breakers in parallel to prevent the fault from escalating further.

[0028] The data acquisition and communication network is the key data transmission architecture of this invention. It is responsible for data acquisition, transmission, processing, and control command issuance, and works in collaboration with other devices. It can acquire voltage and current information of transformers in the distribution area, obtain operating parameters such as analog quantities and status quantities of networked devices, and realize data interaction between various devices. This enables the coordinating controller to issue commands to various devices according to the current system status, and complete corresponding remote control and adjustment operations.

[0029] The integrated control terminal, energy storage converter, coordination controller, and AC / DC flexible DC converter are all connected to the data acquisition and communication network and the control communication network. The devices exchange information and transmit control commands through the GOOSE communication mechanism.

[0030] The coordination controller acts as the control center, issuing control commands to the AC / DC flexible DC converter, integrated control terminal, and energy storage converter through the control communication network, achieving millisecond-level control response.

[0031] The coordination controller formulates strategies based on the system's operating status, thereby enabling rapid fault isolation, reducing the scope of power outages, quickly restoring power supply to non-faulty areas, and ensuring the safe, stable, and reliable operation of equipment within the five-port low-voltage flexible interconnection system.

[0032] Based on the characteristics of the five-port low-voltage flexible interconnection system, such as long lines, many AC and DC elements, and high coupling, protection and control methods are proposed for the following faults: DC bus or tie line faults, 10kV incoming line faults, transformer body faults, flexible DC converter body faults, and AC low-voltage line faults.

[0033] Example 2

[0034] like Figure 3 As shown, this embodiment of the invention provides an AC / DC fault protection control method for a five-port low-voltage flexible interconnection system. This method is implemented based on the device of Embodiment 1 and includes: Under normal operating conditions, select any AC / DC flexible DC converter in the zone to operate in Udc mode, and the remaining AC / DC flexible DC converters to operate in PQ mode. When a DC bus fault occurs in a certain distribution area, the DC protection and control device of the faulty distribution area trips all the circuit breakers on the DC bus. Because the DC bus is in closed-loop operation, the AC / DC flexible DC converters in all 5 distribution areas detect the DC side fault. If the fault current is large, the AC side circuit breakers of all AC / DC flexible DC converters will experience overcurrent, and all internal AC grid-connected contactors will trip after a delay, thus disconnecting the circuit. Once it is confirmed that all switches in the faulty area are disconnected and the faulty area is isolated, the DC bus voltage of the faulty area drops to 0, all photovoltaic power generation in the system stops, and the mobile energy storage vehicle stops working. If all AC / DC flexible DC converters have been taken out of operation, select any AC / DC flexible DC converter in a non-faulty area to operate in UDC mode, establish a DC 750V DC bus, and then put the AC / DC flexible DC converters in other non-faulty areas into operation in sequence. If only the AC / DC flexible DC converter in the faulty area is taken out of operation, the coordinating controller removes that AC / DC flexible DC converter from the operation control logic.

[0035] In a further embodiment, the method further includes: When a permanent fault occurs in the 10kV AC incoming line, causing the entire system to go black, the low-voltage AC main switch of the five distribution areas trips due to undervoltage. The AC side switch of the AC / DC flexible DC converter trips after a delay. The coordination controller sends a mode switching command to the mobile energy storage vehicle. All mobile energy storage vehicles switch to working in constant DC bus voltage mode. After a certain delay, the coordination controller sends a start command to the mobile energy storage vehicle. The mobile energy storage vehicle starts working. After a total delay of 500ms from receiving the command, the mobile energy storage vehicle establishes a DC 750V DC bus voltage. Once the coordinating controller determines that the DC bus voltage has been established, it issues a command after a delay to switch all AC / DC flexible DC converters to VF mode. After a switching time of approximately 20ms, all distribution areas are restored to power, the photovoltaic system begins generating electricity, and the mobile energy storage vehicle discharges or charges according to the power demand of the entire distribution area.

[0036] In a further embodiment, the method further includes: When a transformer in a certain area fails, if the high-voltage side of the transformer cannot isolate the fault, the fault will be isolated by the tripping of the upper-level boundary switch, section switch or substation outlet switch. At this time, the system will be completely black. The fault handling procedures for the flexible interconnection system are the same as those for the system after a permanent fault in the 10kV AC incoming line causes the system to be completely black. If the high-voltage side of the transformer can isolate the fault, only the low-voltage AC main switch of the faulty distribution area will trip due to undervoltage. Because of the AC side undervoltage, the undervoltage protection of the AC side switch of the AC / DC flexible DC converter will trip after a delay. After confirming that the low-voltage AC main switch of the faulty distribution area is in the open position, the delay coordination controller will issue a command to switch the AC / DC flexible DC converter of the faulty distribution area to VF mode. After the switching time, the load connected to the faulty distribution area will be restored to power supply.

[0037] In a further embodiment, the method further includes: When a fault occurs in the IGBT of an AC / DC flexible DC converter in a certain distribution area, the AC / DC flexible DC converter is locked out. After a certain delay, it trips, opening the AC side switch. The DC protection and control device activates, opening the DC side switch and sending a lockout signal to the coordination controller. The coordination controller removes the AC / DC flexible DC converter from the operation control logic and, based on the current redundancy capacity of each distribution area, rationally transfers the DC load and DC photovoltaic power to the remaining four distribution areas.

[0038] In a further embodiment, the method further includes: When a fault occurs on a branch line of the low-voltage side of a JP cabinet in a certain distribution area, the overcurrent protection of the switch on that line trips, isolating the fault, while other branches in the distribution area continue to operate normally. If the switch on the faulty branch line fails to trip, the AC / DC flexible DC converter in the faulty distribution area trips after a delay, opens the AC side switch, and sends a blocking signal to the coordination controller. The coordination controller then removes the AC / DC flexible DC converter from the operation control logic.

[0039] The present invention also provides an electronic device comprising one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs comprising instructions for performing any of the methods described above.

[0040] The present invention also provides a readable storage medium having stored thereon one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform any of the methods described above.

[0041] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0042] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0043] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0044] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0045] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A method for AC / DC fault protection and control of a multi-port low-voltage flexible interconnection system, implemented based on a multi-port low-voltage flexible interconnection system AC / DC fault protection and control device. The device includes an AC / DC flexible DC converter and a comprehensive control terminal for each transformer substation, a coordination controller for one substation, a mobile energy storage vehicle for one substation, and several DC protection and control devices for the incoming and outgoing lines of the DC bus in each substation. The mobile energy storage vehicle is connected to the DC bus via an energy storage converter. The comprehensive control terminal for the substation is used to collect data on the incoming AC voltage of the substation and the low-voltage AC main switch of the substation. The system monitors voltage and current information and switching positions, and controls the operation of the low-voltage AC main switch in the control area according to the control strategy; each DC protection and control device is networked independently, and each DC protection and control device is connected to the data acquisition and communication network; the integrated control terminal, energy storage converter, coordination controller, and AC / DC flexible DC converter are all connected to the data acquisition and communication network and the control communication network, and the devices exchange information and transmit control commands through the GOOSE communication mechanism; the coordination controller is used to issue control commands to the AC / DC flexible DC converter, the integrated control terminal of the distribution area, and the energy storage converter through the control communication network according to the system operating status; its characteristic is that... The method includes: When a DC bus fault occurs in a certain distribution area, the DC protection and control device of the faulty distribution area trips all circuit breakers on the DC bus. Because the DC bus is in closed-loop operation, all AC / DC flexible DC converters in all distribution areas detect the DC side fault. If the fault current is large, all AC side circuit breakers of the AC / DC flexible DC converters will experience overcurrent, and all internal AC grid-connected contactors will trip after a delay, breaking the circuit. After confirming that all switches in the faulty area are open and the faulty area is isolated, if all AC / DC flexible DC converters have been taken out of operation, the AC / DC flexible DC converter in any non-faulty distribution area is selected to operate in UDC mode to establish a DC bus. Then, the AC / DC flexible DC converters in other non-faulty distribution areas are put into operation in sequence.

2. The method according to claim 1, characterized in that, Also includes: Once it is confirmed that all switches in the faulty area are disconnected and the faulty area is isolated, if only the AC / DC flexible DC converter in the faulty area is taken out of operation, the coordinating controller will remove the AC / DC flexible DC converter in the faulty area from the operation control logic.

3. The method according to claim 1, characterized in that, Also includes: When a permanent fault occurs in the 10kV AC incoming line, causing the entire system to go black, the low-voltage AC main switch of all distribution areas will trip due to undervoltage. The AC side switch of the AC / DC flexible DC converter will trip after a delay. The coordination controller will issue a mode switching command to the mobile energy storage vehicle. All mobile energy storage vehicles will switch to working in constant DC bus voltage mode. After a delay, the coordination controller will issue a start command to the mobile energy storage vehicle. The mobile energy storage vehicle will start working and establish DC bus voltage. Once the coordinating controller determines that the DC bus voltage has been established, it issues a command after a delay to switch all AC / DC flexible DC converters to VF mode. After the switching time, all distribution areas are restored to power, the photovoltaic system begins generating electricity, and the mobile energy storage vehicle discharges or charges according to the power demand of the entire distribution area.

4. The method according to claim 1, characterized in that, Also includes: When a transformer in a certain area fails, if the high-voltage side of the transformer cannot isolate the fault, the fault will be isolated by the tripping of the upstream boundary switch, section switch or substation outlet switch. At this time, the system will be completely black. The fault handling procedure for the flexible interconnection system is the same as the handling procedure after a permanent fault in the 10kV AC incoming line causes the system to be completely black.

5. The method according to claim 1, characterized in that, Also includes: When a transformer in a certain distribution area fails, if the high-voltage side of the transformer can isolate the fault, only the low-voltage AC main switch of the faulty distribution area will trip due to undervoltage. Because of the AC side undervoltage, the undervoltage protection of the AC side switch of the AC / DC flexible DC converter will trip after a delay. After confirming that the low-voltage AC main switch of the faulty distribution area is in the open position, the delay coordination controller will issue a command to switch the AC / DC flexible DC converter of the faulty distribution area to VF mode. After the switching time, the load connected to the faulty distribution area will be restored to power supply.

6. The method according to claim 1, characterized in that, Also includes: When a fault occurs in the IGBT of an AC / DC flexible DC converter in a certain distribution area, the AC / DC flexible DC converter is locked out. After a time delay, the AC side switch is tripped, the DC protection device of the DC protection and control device is activated, the DC side switch is tripped, and a lockout signal is sent to the coordination controller. The coordination controller removes the AC / DC flexible DC converter from the operation control logic and rationally transfers the DC load and DC photovoltaic power to the remaining distribution areas according to the current redundancy capacity of each distribution area.

7. The method according to claim 1, characterized in that, Also includes: When a fault occurs on a branch line on the low-voltage side of a JP cabinet in a certain distribution area, the overcurrent protection of the switch on that line trips, isolating the fault, while other branches in the same distribution area continue to operate normally.

8. The method according to claim 1, characterized in that, Also includes: When a fault occurs on a branch line of the low-voltage side of a JP cabinet in a certain distribution area, if the faulty branch line switch cannot trip, the AC / DC flexible DC converter in the faulty distribution area will trip after a delay, open the AC side switch, and send a blocking signal to the coordination controller. The coordination controller will then remove the AC / DC flexible DC converter from the operation control logic.

9. The method according to claim 1, characterized in that, Each DC protection and control device forms a DC protection control network A and a DC protection control network B, creating a redundant dual-network configuration, and transmits the DC protection GOOSE signal independently.

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