Fault isolation method and circuit based on SiC-MOSFET multi-port hybrid DC circuit breaker

Abstract

The invention discloses a fault isolation method and circuit based on a Si C-MOSFET multi-port hybrid direct-current circuit breaker, and belongs to the field of power systems, and the method comprises the steps: triggering a protection signal according to a fault current in a voltage source converter direct-current power grid; wherein the fault current flows to a main branch of the fault isolation circuit; the protection signal is a trigger signal of a protection device and is received by the fault isolation circuit; and according to the protection signal, switching on and switching off of a main branch and a transfer branch in the fault isolation circuit are controlled, so that fault current flows through the transfer branch and the energy consumption branch in sequence, the fault current is attenuated to zero by a metal oxide piezoresistor on the energy consumption branch, and fault isolation is completed. By implementing the invention, the problem of low fault isolation speed of the direct-current power grid of the voltage source converter in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and in particular, to a fault isolation method and circuit based on a SiC-MOSFET multi-port hybrid DC circuit breaker. Background Art

[0002] With the transformation of the global energy structure, the access ratio of renewable energy is continuously increasing. As an effective technical means to realize the transmission and distribution of clean energy, the voltage source converter DC grid has gradually become a key direction for the development of power systems. However, during the operation of the voltage source converter DC grid, once a short-circuit fault occurs, the fault current will rapidly rise to dozens of kiloamperes within a very short time. Due to its low damping characteristics, the fault influence range is wide, and it is extremely easy to cause local faults, thus leading to the paralysis of the entire DC grid, seriously affecting the continuous and reliable operation of the grid. Therefore, how to quickly and accurately isolate the fault line has become the core issue for ensuring the stable operation of the voltage source converter DC grid.

[0003] Currently, the fault isolation method based on DC circuit breakers and fast protection is one of the effective technical means to ensure the continuous and reliable transmission of active power in the voltage source converter DC grid. Existing DC circuit breakers are mainly divided into three types: mechanical DC circuit breakers, solid-state DC circuit breakers, and hybrid DC circuit breakers. Among them, the mechanical DC circuit breaker realizes the interruption of DC current by injecting a high-frequency reverse current to form an artificial current zero point; the solid-state DC circuit breaker uses the controllable characteristics of power electronic devices to achieve the rapid interruption of DC current; the hybrid DC circuit breaker combines the low conduction loss of the mechanical DC circuit breaker and the fast disconnection ability of the solid-state DC circuit breaker, and is regarded as the most potential DC circuit breaker for fault isolation. However, the traditional fault isolation method based on the coordination strategy of "fast protection acts first, and then the DC circuit breaker disconnects" has a long fault current interruption time, which is likely to cause local converter valve locking and permanent damage to power electronic devices; at the same time, the traditional fault isolation method uses a DC circuit breaker based on silicon-based MOSFET (metal oxide semiconductor field effect transistor). Due to the limited switching frequency of silicon-based MOSFET, the fault isolation speed is further reduced. Summary of the Invention

[0004] The present invention provides a fault isolation method and circuit based on a SiC-MOSFET multi-port hybrid DC circuit breaker, which can solve the problem of slow fault isolation speed in the existing technology for the voltage source converter DC grid.

[0005] An embodiment of the present invention provides a fault isolation method based on a SiC-MOSFET multi-port hybrid DC circuit breaker, which is applicable to a fault isolation circuit based on a SiC-MOSFET multi-port hybrid DC circuit breaker; wherein, the fault isolation circuit is located in a voltage source converter DC power grid, and the fault isolation circuit includes: a main branch composed of a mechanical switch and an electronic power module based on SiC-MOSFET, a transfer branch composed of a diode full-bridge module based on SiC-MOSFET, a dissipative branch, and an auxiliary unit;

[0006] The fault isolation method based on the SiC-MOSFET multi-port hybrid DC circuit breaker includes:

[0007] According to the fault current in the voltage source converter DC power grid, a protection signal is triggered; wherein, the fault current flows to the main branch of the fault isolation circuit; the protection signal is a trigger signal of a protection device and is received by the fault isolation circuit;

[0008] According to the protection signal, the conduction and cutoff of the main branch and the transfer branch in the fault isolation circuit are controlled, so that the fault current flows through the transfer branch and the dissipative branch in sequence, so that the metal oxide varistor on the dissipative branch attenuates the fault current to zero, completing fault isolation.

[0009] By using the trigger signal of the fast protection as the instruction for the first commutation and the second commutation of the fault isolation circuit based on the SiC-MOSFET multi-port hybrid DC circuit breaker, when the fast protection completes the protection trigger, the fault isolation circuit immediately executes the fault isolation action. Compared with the prior art, the present application can improve the speed of fault isolation.

[0010] Further, the fault isolation circuit is located in a voltage source converter DC power grid, and includes:

[0011] The fault isolation circuit is connected to the voltage source converter DC power grid through a positive bus and a negative bus;

[0012] The main branch, the transfer branch, and the dissipative branch are connected in parallel.

[0013] An embodiment of the present invention realizes a fault isolation method based on a SiC-MOSFET multi-port hybrid DC circuit breaker by constructing a fault isolation circuit.

[0014] Further, the main branch includes: a mechanical switch and a power electronic module;

[0015] After the mechanical switch is connected in series with the power electronic module, one end is connected to the positive bus as the input end, and the other end is connected to the negative bus as the output end; wherein, the power electronic module is composed of SiC-MOSFETs, and the drain of the SiC-MOSFET is connected to the mechanical switch, and the source is connected to the negative bus.

[0016] In the embodiment of the present invention, by constructing a main branch composed of a mechanical switch and a power electronic module, a current flow path is provided for the normal operation of the DC grid of the voltage source converter. At the same time, the fast switching characteristics of the SiC-MOSFET contribute to achieving faster current commutation.

[0017] Further, the transfer branch includes: a diode full-bridge module;

[0018] One end of the diode full-bridge module is connected to the positive bus as the input end, and the other end is connected to the negative bus as the output end; wherein, the diode full-bridge module is composed of a full-bridge structure formed by four SiC-MOSFETs. After two SiC-MOSFETs are connected in series, the drain is connected to the positive bus, and the source is connected to the intermediate node. After the other two SiC-MOSFETs are connected in series, the drain is connected to the intermediate node, and the source is connected to the negative bus.

[0019] In the embodiment of the present invention, by constructing a transfer branch composed of multiple diode full-bridge modules, the fault current during a fault is transferred from the main branch to the energy-consuming branch. At the same time, the fast switching characteristics of the SiC-MOSFET contribute to achieving faster current commutation.

[0020] Further, the energy-consuming branch includes: a metal oxide varistor;

[0021] One end of the metal oxide varistor is connected to the positive bus as the input end, and the other end is connected to the negative bus as the output end.

[0022] In the embodiment of the present invention, by constructing an energy-consuming branch composed of metal oxide varistors, the energy dissipation of the fault current is completed, and fault isolation is achieved.

[0023] Further, the auxiliary unit includes: a diode or a thyristor;

[0024] The cathode of the diode or thyristor is connected to the output ends of the transfer branch and the energy-consuming branch, and the anode is connected to the negative bus.

[0025] In the embodiment of the present invention, by constructing an auxiliary unit composed of multiple diodes or thyristors, an additional current flow path is provided for the fault current during a fault, ensuring that the fault current can be effectively guided and isolated.

[0026] Further, controlling the conduction and cutoff of the main branch and the transfer branch in the fault isolation circuit according to the protection signal includes:

[0027] According to the protection signal, turn off the SiC-MOSFET on the main branch;

[0028] According to the protection signal, turn on the SiC-MOSFET on the transfer branch.

[0029] In the embodiment of the present invention, by turning off the SiC-MOSFET on the main branch and turning on the SiC-MOSFET on the transfer branch, conditions are created for the first commutation of the fault current.

[0030] Further, controlling the conduction and cutoff of the main branch and the transfer branch in the fault isolation circuit according to the protection signal further includes:

[0031] According to the protection signal, turn on the mechanical switch on the main branch;

[0032] According to the protection signal, turn off the SiC-MOSFET on the transfer branch.

[0033] In the embodiment of the present invention, by turning on the mechanical switch on the main branch and turning off the SiC-MOSFET on the transfer branch, conditions are created for the second commutation of the fault current.

[0034] Further, making the fault current flow through the transfer branch and the energy-consuming branch in sequence specifically means:

[0035] After the SiC-MOSFET on the main branch is turned off and the SiC-MOSFET on the transfer branch is turned on, the fault current flows from the main branch to the transfer branch;

[0036] After the mechanical switch on the main branch is turned on and the SiC-MOSFET on the transfer branch is turned off, the fault current flows from the transfer branch to the energy-consuming branch.

[0037] In the embodiment of the present invention, by controlling the conduction and cutoff of the main branch and the transfer branch, the flow direction of the fault current is controlled to flow through the energy-consuming branch for fault isolation.

[0038] Another embodiment of the present invention further provides a fault isolation circuit based on an SiC-MOSFET multi-port hybrid DC circuit breaker, and the fault isolation circuit is controlled by a fault isolation method based on an SiC-MOSFET multi-port hybrid DC circuit breaker of the present invention. Description of the Drawings

[0039] Figure 1Schematic flowchart of the fault isolation method for a SiC-MOSFET multi-port hybrid DC circuit breaker provided by an embodiment of the present invention;

[0040] Figure 2 Schematic structural diagram of the fault isolation circuit for a SiC-MOSFET multi-port hybrid DC circuit breaker provided by an embodiment of the present invention;

[0041] Figure 3 Schematic diagram of the operation of the fault isolation method for a SiC-MOSFET multi-port hybrid DC circuit breaker provided by an embodiment of the present invention at times t0 to t1;

[0042] Figure 4 Schematic diagram of the operation of the fault isolation method for a SiC-MOSFET multi-port hybrid DC circuit breaker provided by an embodiment of the present invention at times t1 to t3;

[0043] Figure 5 Schematic diagram of the operation of the fault isolation method for a SiC-MOSFET multi-port hybrid DC circuit breaker provided by an embodiment of the present invention at times t3 to t5;

[0044] Figure 6 Schematic diagram of the operation of the fault isolation method for a SiC-MOSFET multi-port hybrid DC circuit breaker provided by an embodiment of the present invention at time t5;

[0045] Figure 7 Schematic diagram of the operation of the fault isolation method for a SiC-MOSFET multi-port hybrid DC circuit breaker provided by an embodiment of the present invention at times t5 to t6;

[0046] Figure 8 Timing diagram of the completion of fault isolation by the traditional fault isolation method provided by an embodiment of the present invention;

[0047] Figure 9 Timing diagram of the completion of fault isolation by the fault isolation method for a SiC-MOSFET multi-port hybrid DC circuit breaker provided by an embodiment of the present invention. Detailed implementation manners

[0048] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present application belong to the scope of protection of the present application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "comprising" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0050] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0051] Referring to "embodiments" herein means that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0052] In the description of the embodiments of this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0053] In the description of the embodiments of this application, the term "a plurality" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0054] See Figure 1 In order to solve the problem of slow fault isolation speed of the voltage source converter DC grid in the prior art, a fault isolation method based on a SiC-MOSFET multi-port hybrid DC circuit breaker provided by an embodiment of the present invention is applicable to a fault isolation circuit based on a SiC-MOSFET multi-port hybrid DC circuit breaker; wherein, the fault isolation circuit is located in the voltage source converter DC grid, and the fault isolation circuit includes: a main branch composed of a mechanical switch and an electronic power module based on SiC-MOSFET, a transfer branch composed of a diode full-bridge module based on SiC-MOSFET, a dissipative branch, and an auxiliary unit;

[0055] The fault isolation method based on the SiC-MOSFET multi-port hybrid DC circuit breaker includes step S101 and step S102:

[0056] Step S101, trigger a protection signal according to the fault current in the DC grid of the voltage source converter; wherein, the fault current flows to the main branch of the fault isolation circuit; the protection signal is the trigger signal of the protection device and is received by the fault isolation circuit;

[0057] Step S102, according to the protection signal, control the conduction and turn-off of the main branch and the transfer branch in the fault isolation circuit, so that the fault current flows through the transfer branch and the energy-consuming branch in sequence, so that the metal oxide varistor on the energy-consuming branch attenuates the fault current to zero, completing fault isolation.

[0058] It should be noted that SiC-MOSFET (Silicon Carbide Metal-Oxide-Semiconductor Field-Effect Transistor) is a new type of wide-bandgap semiconductor device. Compared with traditional silicon-based MOSFETs, SiC-MOSFET has the following characteristics and advantages:

[0059] The breakdown field strength of silicon carbide (SiC) material is higher than that of silicon material, enabling SiC-MOSFET to withstand higher voltages and be suitable for high-voltage environments;

[0060] Under high voltage conditions, the on-resistance of SiC-MOSFET is lower, which can reduce the conduction loss and improve the energy efficiency of the device;

[0061] SiC-MOSFET has a faster switching speed and can work efficiently at high frequencies, which helps to improve the power density and performance of the system;

[0062] Silicon carbide material has good high-temperature resistance characteristics, enabling SiC-MOSFET to work stably at higher temperatures and reducing the heat dissipation requirements.

[0063] In the embodiment of the present invention, by using the trigger signal of the fast protection as the instruction for the first commutation and the second commutation of the fault isolation circuit based on the SiC-MOSFET multi-port hybrid DC circuit breaker, when the fast protection completes the protection trigger, the fault isolation circuit immediately executes the fault isolation action. Compared with the prior art, the present application can improve the speed of fault isolation.

[0064] Further, the fault isolation circuit is located in the DC grid of the voltage source converter and includes:

[0065] The fault isolation circuit is connected to the DC grid of the voltage source converter through the positive bus and the negative bus;

[0066] The main branch, the transfer branch, and the energy-consuming branch are connected in parallel.

[0067] It should be noted that the fault isolation circuit adopts a multi-port design. By sharing the transfer branch, the number of modules used is effectively reduced. Compared with the traditional two-port hybrid DC circuit breaker, this multi-port topology realizes the fault isolation function for multiple DC lines without adding too much cost, improves the cost performance and practicality of the equipment, and is especially suitable for the application scenario of large-scale voltage source converter DC grids.

[0068] In the embodiment of the present invention, a fault isolation method based on a SiC-MOSFET multi-port hybrid DC circuit breaker is realized by constructing a fault isolation circuit.

[0069] As Figure 2 shown, an embodiment of the present invention provides a specific circuit structure of a fault isolation circuit based on a SiC-MOSFET multi-port hybrid DC circuit breaker.

[0070] In one embodiment, the main branch includes: a mechanical switch and a power electronic module When the DC grid of the voltage source converter is operating normally, the main branch provides a current flow path for the DC line of the DC grid of the voltage source converter. One DC line corresponds to one main branch;

[0071] Optionally, the mechanical switch is an ultra-fast mechanical switch (UMS1~UMS m ); among them, the action time of the mechanical switch is between dozens of microseconds and hundreds of microseconds.

[0072] After the mechanical switch is connected in series with the power electronic module, one end is connected to the positive bus as the input end, and the other end is connected to the negative bus as the output end; among them, the power electronic module is composed of SiC-MOSFETs. The drain of the SiC-MOSFET is connected to the mechanical switch, and the source is connected to the negative bus.

[0073] Optionally, the power electronic module includes multiple SiC-MOSFETs, which are connected in a certain topology to meet the requirements of the voltage and current levels of the main branch.

[0074] In the embodiment of the present invention, a main branch composed of a mechanical switch and a power electronic module is constructed to provide a current flow path when the DC grid of the voltage source converter is operating normally. At the same time, the fast switching characteristics of the SiC-MOSFET contribute to realizing faster current commutation.

[0075] In one embodiment, the transfer branch includes: a diode full-bridge module (PEM1 to PEM n );

[0076] One end of the diode full-bridge module is connected to the positive bus as the input end, and the other end is connected to the negative bus as the output end; wherein, the diode full-bridge module is composed of a full-bridge structure formed by four SiC-MOSFETs. After two SiC-MOSFETs are connected in series, the drain is connected to the positive bus, and the source is connected to the intermediate node. After the other two SiC-MOSFETs are connected in series, the drain is connected to the intermediate node, and the source is connected to the negative bus.

[0077] Optionally, the transfer branch includes a plurality of diode full-bridge modules, and the diode full-bridge modules are connected in parallel with each other.

[0078] In the embodiment of the present invention, by constructing a transfer branch composed of a plurality of diode full-bridge modules, the fault current during a fault is transferred from the main branch to the energy-consuming branch. At the same time, the fast switching characteristic of the SiC-MOSFET helps to achieve a faster current commutation.

[0079] In one embodiment, the energy-consuming branch includes: metal oxide varistors (MOV1 to MOV n );

[0080] One end of the metal oxide varistor is connected to the positive bus as the input end, and the other end is connected to the negative bus as the output end.

[0081] In the embodiment of the present invention, by constructing an energy-consuming branch composed of metal oxide varistors, the energy dissipation of the fault current is completed to achieve fault isolation.

[0082] In one embodiment, the auxiliary unit includes: a diode or a thyristor;

[0083] The cathode of the diode or thyristor is connected to the output ends of the transfer branch and the energy-consuming branch, and the anode is connected to the negative bus.

[0084] In the embodiment of the present invention, by constructing an auxiliary unit composed of a plurality of diodes or thyristors, an additional current path is provided for the fault current during a fault to ensure that the fault current can be effectively guided and isolated.

[0085] In step S102, the controlling the conduction and cutoff of the main branch and the transfer branch in the fault isolation circuit according to the protection signal includes:

[0086] According to the protection signal, turn off the SiC-MOSFET on the main branch;

[0087] Turn on the SiC-MOSFET on the transfer branch according to the protection signal.

[0088] In the embodiment of the present invention, by turning off the SiC-MOSFET on the main branch and turning on the SiC-MOSFET on the transfer branch, conditions are created for the first commutation of the fault current.

[0089] In step S102, the controlling the conduction and turn-off of the main branch and the transfer branch in the fault isolation circuit according to the protection signal further includes:

[0090] Open the mechanical switch on the main branch according to the protection signal;

[0091] Turn off the SiC-MOSFET on the transfer branch according to the protection signal.

[0092] In the embodiment of the present invention, by opening the mechanical switch on the main branch and turning off the SiC-MOSFET on the transfer branch, conditions are created for the second commutation of the fault current.

[0093] In step S102, the making the fault current flow through the transfer branch and the energy-consuming branch in sequence specifically is:

[0094] After the SiC-MOSFET on the main branch is turned off and the SiC-MOSFET on the transfer branch is turned on, the fault current flows from the main branch to the transfer branch;

[0095] After the mechanical switch on the main branch is opened and the SiC-MOSFET on the transfer branch is turned off, the fault current flows from the transfer branch to the energy-consuming branch.

[0096] In the embodiment of the present invention, by controlling the conduction and turn-off of the main branch and the transfer branch, the fault current flow direction is controlled to flow through the energy-consuming branch for fault isolation.

[0097] Based on the above method item embodiment, a specific embodiment is provided to show the specific actions of the fault isolation method based on the SiC-MOSFET multi-port hybrid DC circuit breaker at each moment.

[0098] As Figure 3 shown, at time t0, a fault occurs at port 1, the fault current rises rapidly, triggering the protection signal of the fast protection device; at time t1, the protection signal is sent to the fault isolation circuit of the SiC-MOSFET multi-port hybrid DC circuit breaker.

[0099] As Figure 4 shown, after a delay of 0.3 milliseconds, the fault isolation circuit receives the protection signal at time t2; the power electronic module in the main branch 1 is turned off, while the multiple diode full-bridge modules (PEM1 - PEM n ) in the transfer branch are turned on; the fault current gradually flows from the main branch 1 to the transfer branch; the first commutation of the fault current is completed within 0.6 milliseconds.

[0100] As Figure 5 shown, after the fault current is completely transferred to the transfer branch, the ultra-fast mechanical switch (UMS1) starts to open without arc under the protection signal at time t3 until it reaches the rated open position at time t5, which takes a total of 0.6 milliseconds; meanwhile, at time t4, the fast protection device completes the fast protection action, which takes a total of 3 milliseconds.

[0101] As Figure 6 shown, at time t5, PEM1 - PEM n in the transfer branch is quickly turned off, causing the capacitors in PEM1 - PEM n to be charged by the fault current.

[0102] As Figure 7 shown, when the voltage of the capacitors in PEM1 - PEM n reaches the starting threshold voltage of the metal oxide varistors (MOV1 - MOV n ), MOV1 - MOV n in the energy-consuming branch is triggered to conduct; the fault current flows from the transfer branch to the energy-consuming branch, and the second commutation of the fault current is completed within 0.1 milliseconds; under the action of the transient interruption voltage, the fault current is forced to decay to zero, and the isolation process of the fault current is completed at time t6.

[0103] To better demonstrate the beneficial effects of the present invention, another specific embodiment is provided to show the advantages of the fault isolation method based on the SiC-MOSFET multi-port hybrid DC circuit breaker compared to the traditional fault isolation method.

[0104] As Figure 8 shown, the time taken for the traditional fault isolation method to complete fault isolation is 6 milliseconds; as Figure 9 shown, the time taken for the fault isolation method based on the SiC-MOSFET multi-port hybrid DC circuit breaker to complete fault isolation is 3 + Δt milliseconds; thus, it can be seen that adopting the fault isolation method based on the SiC-MOSFET multi-port hybrid DC circuit breaker can shorten the fault isolation time from the traditional 6 milliseconds to 3 + Δt milliseconds, reducing the risk of damage to power electronic modules due to long-term exposure to high current and high voltage, and improving the stability and reliability of the voltage source converter DC grid.

[0105] Based on the above method embodiments, another embodiment of the present invention provides a fault isolation circuit for a SiC-MOSFET multi-port hybrid DC circuit breaker, and the fault isolation circuit is controlled by a fault isolation method for a SiC-MOSFET multi-port hybrid DC circuit breaker according to the present invention.

[0106] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A fault isolation method for a multi-port hybrid DC circuit breaker based on SiC-MOSFET, characterized in that, Fault isolation circuit applicable to a multi-port hybrid DC circuit breaker based on SiC-MOSFET; wherein, the fault isolation circuit is located in a voltage source converter DC power grid, and the fault isolation circuit includes: a main branch composed of a mechanical switch and an electronic power module based on SiC-MOSFET, a transfer branch composed of a diode full-bridge module based on SiC-MOSFET, a dissipative branch, and an auxiliary unit; The fault isolation method for the multi-port hybrid DC circuit breaker based on SiC-MOSFET includes: Trigger a protection signal according to the fault current in the voltage source converter DC power grid; wherein, the fault current flows to the main branch of the fault isolation circuit; the protection signal is a trigger signal of a protection device and is received by the fault isolation circuit; According to the protection signal, control the conduction and cutoff of the main branch and the transfer branch in the fault isolation circuit, so that the fault current flows through the transfer branch and the dissipative branch in sequence, thereby enabling the metal oxide varistor on the dissipative branch to attenuate the fault current to zero and complete fault isolation.

2. The fault isolation method of a multi-port hybrid DC circuit breaker based on SiC-MOSFET as claimed in claim 1, wherein The fault isolation circuit is located in a voltage source converter DC power grid and includes: The fault isolation circuit is connected to the voltage source converter DC power grid through a positive bus and a negative bus; The main branch, the transfer branch, and the dissipative branch are connected in parallel.

3. A fault isolation method for a multi-port hybrid DC circuit breaker based on SiC-MOSFET, as described in claim 2, characterized in that, The main branch includes: a mechanical switch and a power electronic module; After the mechanical switch is connected in series with the power electronic module, one end is connected to the positive bus as an input end, and the other end is connected to the negative bus as an output end; wherein, the power electronic module is composed of SiC-MOSFET, the drain of the SiC-MOSFET is connected to the mechanical switch, and the source is connected to the negative bus.

4. The fault isolation method of a multi-port hybrid DC circuit breaker based on SiC-MOSFET according to claim 2, characterized in that The transfer branch includes: a diode full-bridge module; One end of the diode full-bridge module is connected to the positive bus as an input end, and the other end is connected to the negative bus as an output end; wherein, the diode full-bridge module is composed of a full-bridge structure formed by four SiC-MOSFETs. After two SiC-MOSFETs are connected in series, the drain is connected to the positive bus, and the source is connected to the intermediate node. After the other two SiC-MOSFETs are connected in series, the drain is connected to the intermediate node, and the source is connected to the negative bus.

5. A fault isolation method for a multi-port hybrid DC circuit breaker based on SiC-MOSFET, as described in claim 2, wherein The dissipative branch includes: a metal oxide varistor; One end of the metal oxide varistor is connected to the positive bus as an input end, and the other end is connected to the negative bus as an output end.

6. The fault isolation method of a multi-port hybrid DC circuit breaker based on SiC-MOSFET according to claim 2, characterized in that, The auxiliary unit includes: a diode or a thyristor; The cathode of the diode or the thyristor is connected to the output ends of the transfer branch and the dissipative branch, and the anode is connected to the negative bus.

7. A fault isolation method for a multi-port hybrid DC circuit breaker based on SiC-MOSFET, as claimed in claim 1, wherein The controlling the conduction and cutoff of the main branch and the transfer branch in the fault isolation circuit according to the protection signal includes: Turn off the SiC-MOSFET on the main branch according to the protection signal; Turn on the SiC-MOSFET on the transfer branch according to the protection signal.

8. The fault isolation method of a multi-port hybrid DC circuit breaker based on SiC-MOSFET according to claim 1, characterized in that The controlling the conduction and cutoff of the main branch and the transfer branch in the fault isolation circuit according to the protection signal further includes: Open the mechanical switch on the main branch according to the protection signal; Turn off the SiC-MOSFET on the transfer branch according to the protection signal.

9. The fault isolation method of a multi-port hybrid DC circuit breaker based on SiC-MOSFET according to claim 1, characterized in that So that the fault current flows through the transfer branch and the energy-consuming branch in sequence, specifically: After the SiC-MOSFET on the main branch is turned off and the SiC-MOSFET on the transfer branch is turned on, the fault current flows from the main branch to the transfer branch; After the mechanical switch on the main branch is opened and the SiC-MOSFET on the transfer branch is turned off, the fault current flows from the transfer branch to the energy-consuming branch.

10. A fault isolation circuit for a multi-port hybrid DC circuit breaker based on SiC-MOSFET, characterized in that, The fault isolation circuit is controlled by a fault isolation method of a multi-port hybrid DC circuit breaker based on SiC-MOSFET according to any one of claims 1-9.

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