Outgoing line closed-loop superconducting switching station and working method thereof

Abstract

The invention relates to a superconducting switching station with an outlet closed loop and a working method thereof, the superconducting switching station is connected with a transformer substation through a superconducting cable, the transformer substation supplies power to the superconducting switching station, the outlet closed loop of the superconducting switching station is connected, the outlet is connected with a superconducting current limiter in series, and a petal type power distribution network is further designed. Comprising the steps that two superconducting switching stations are connected with two substations through superconducting cables respectively, power is supplied by the two substations, two looped networks of the two superconducting switching stations are connected through a normally-closed interconnection switch, the interconnection switch is connected with a superconducting current limiter in series, and a superconducting reactor is installed on a bus of one superconducting switching station. Compared with the prior art, the high-capacity switching station, the superconducting cable, the superconducting reactor, the superconducting current limiter and other devices are integrated to establish the superconducting switching station, the outgoing line closed-loop design and closed-loop operation are achieved, short-circuit current can be limited, the breaking pressure of a circuit breaker can be relieved, and the power supply capacity and the power supply reliability can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of superconducting power equipment, and in particular to a superconducting switch station with a closed-loop outgoing line and a working method thereof. Background Art

[0002] At present, substations in urban center areas often have the limitations of small construction land area and tight outgoing line storage space. When users apply for power supply, they will face the problem of no available storage space. Traditionally, most of them adopt the method of deploying switch stations to expand the power supply range of substations, but ordinary switch stations are limited by the transmission capacity of incoming lines, and the power supply capacity of a single station cannot effectively match the substation capacity.

[0003] Based on this, existing technologies consider applying superconducting power equipment such as superconducting cables, superconducting reactors, and superconducting current limiters in urban central areas to improve the power supply capacity and reliability of the central urban power grid. Among them, the outstanding advantages of superconducting cables are large capacity, low loss, self-current limiting, and environmental friendliness. Their transmission capacity can replace at least 4 to 6 conventional cables of the same voltage, or replace conventional cables with two higher voltage levels. For example, a 35kV superconducting cable is equivalent to the transmission capacity of a 220kV ordinary cable, and a 10kV superconducting cable is equivalent to the transmission capacity of a 110kV ordinary cable. The use of superconducting cables for power transmission can significantly reduce the voltage level of substations and realize the relocation of high-voltage substation equipment in central urban areas to suburbs. In addition, with the increasing number of power cables in the grid, a large amount of reactive power is being fed back, resulting in insufficient inductive reactive power compensation and high voltage levels. This necessitates the installation of shunt reactors. However, due to the high noise levels of oil-immersed reactors and the large footprint of dry-type reactors, their application in urban substations with limited space is very difficult. Superconducting reactors, which use superconducting materials as working windings, have the advantages of smaller footprint and lower noise compared to conventional reactors. The superconducting current limiter is in a "superconducting state" during normal operation, with very low impedance. When a fault occurs, it can respond quickly and become a larger impedance to suppress the short-circuit current. After the fault is cleared, it can automatically return to the "superconducting state" in a timely manner. It can quickly, smoothly and effectively limit the short-circuit current of the system, greatly reducing the breaking pressure of the circuit breaker. The conventional method is mainly to increase the impedance of the power grid through high-impedance transformers or current-limiting reactors. These measures will undoubtedly increase the transmission loss and voltage drop of the power grid.

[0004] However, in order to fully utilize the advantages of superconducting power equipment, it is not enough to replace a single superconducting device. Therefore, there is an urgent need to integrate large-capacity switch stations, superconducting cables, superconducting reactors, superconducting current limiters and other equipment to establish superconducting switch stations.

[0005] Furthermore, in traditional distribution networks, outgoing lines from substations mostly utilize a "closed-loop design, open-loop operation" power supply method. Under normal operation, the tie switch is in the open position, and only in special circumstances such as maintenance or failures is an appropriate closing point and power supply path selected for load transfer. This traditional power supply method cannot guarantee uninterrupted power supply to dual power sources and critical users in the event of a fault. Existing technical designs use two outgoing lines to form a ring network and operate in a closed-loop mode. However, due to the dense interconnection of the current central urban area power grid and the large short-circuit capacity of the system, short-circuit currents at all voltage levels are easily exceeded, and this also makes the selection of circuit breakers difficult. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a superconducting switch station with a closed-loop outgoing line and its working method, so as to realize closed-loop operation of the outgoing line, improve the power supply capacity and reliability, limit the short-circuit current, and reduce the breaking pressure of the circuit breaker.

[0007] The objectives of the present invention can be achieved through the following technical solutions: a superconducting switch station with a closed-loop outgoing line is connected to a substation via a superconducting cable, and the substation supplies power to the superconducting switch station. The outgoing lines of the superconducting switch station are connected in a closed-loop, and a superconducting current limiter is connected in series on the outgoing lines.

[0008] Furthermore, a plurality of normally closed switches are provided on the output line.

[0009] A method for operating a superconducting switch station includes: using a substation to supply power to the superconducting switch station via a superconducting cable; The outgoing lines of the superconducting switch station are designed and operated in a closed loop; The short-circuit current is limited by a superconducting current limiter connected in series on the outgoing line.

[0010] A petal-shaped power distribution network based on superconducting switch stations includes a first superconducting switch station and a second superconducting switch station. The first superconducting switch station and the second superconducting switch station are respectively connected to two substations via superconducting cables and supplied with power by the two substations. The two ring networks of the first superconducting switch station and the second superconducting switch station are connected via a normally closed tie switch.

[0011] Furthermore, the connecting switch includes two normally closed switches connected in series.

[0012] Furthermore, a superconducting current limiter is connected in series between the two normally closed switches.

[0013] Furthermore, a superconducting reactor is installed on the busbar of the first superconducting switch station.

[0014] Furthermore, the superconducting reactor is connected to a tap changer.

[0015] Furthermore, the capacity of the superconducting reactor is specifically designed according to the reactive power reverse transmission conditions under different operation modes of the incoming and outgoing lines of the two superconducting switch stations.

[0016] A method for operating a petal-type power distribution network based on a superconducting switch station comprises: utilizing two substations to supply power to two superconducting switch stations via superconducting cables; Both superconducting switch stations adopt outgoing line closed-loop operation mode to achieve balanced load distribution; Use superconducting reactors for inductive reactive power compensation; When a short circuit fault occurs at any point of the two superconducting switch stations and their outgoing lines, the superconducting current limiter is used to limit the current from the non-faulty switch station; When the superconducting current limiter fails or needs maintenance, the connecting switch between the two superconducting switch station ring networks is disconnected to cut off the power supply to the superconducting current limiter, so that the two superconducting switch stations and their outgoing lines can still operate normally.

[0017] Furthermore, the superconducting reactor realizes segmented adjustment of compensation capacity through a tap changer.

[0018] Furthermore, the cold box of the superconducting cable is equipped with a refrigerator. The cold box of the superconducting cable and the cold box of the superconducting power conversion equipment are respectively provided with a first coil heat exchanger and a second coil heat exchanger. The superconducting power conversion equipment includes a superconducting reactor and a superconducting current limiter. The first coil heat exchanger is filled with first liquid nitrogen, which is connected to the liquid nitrogen inside the superconducting cable. The first coil heat exchanger is filled with second liquid nitrogen outside. The cold head of the refrigerator is immersed in the second liquid nitrogen. The interior of the second coil heat exchanger is filled with third liquid nitrogen, which is connected to the liquid nitrogen inside the superconducting power conversion equipment, and the exterior of the second coil heat exchanger is filled with fourth liquid nitrogen; The outlet of the first coil heat exchanger is connected to the inlet of a superconducting power conversion equipment cold box, and the outlet of the superconducting power conversion equipment cold box is connected to the liquid nitrogen inlet of the superconducting cable.

[0019] A shared refrigerator operating method for a superconducting switch station. The refrigerator provides cooling to a cold box of a superconducting cable to maintain a low temperature of a second liquid nitrogen. The second liquid nitrogen transfers the cooling to the first liquid nitrogen via a first coil heat exchanger. The first liquid nitrogen flows between the first coil heat exchanger and the superconducting cable to transfer the cooling to the superconducting cable, ensuring that the superconducting cable maintains a low-temperature superconducting state. The first liquid nitrogen also transfers cold energy to the fourth liquid nitrogen through flow, and the fourth liquid nitrogen transfers cold energy to the third liquid nitrogen through the second coil heat exchanger. The third liquid nitrogen flows between the second coil heat exchanger and the superconducting power conversion equipment, thereby transferring cold energy to the superconducting power conversion equipment, ensuring that the superconducting power conversion equipment is maintained in a low-temperature superconducting state.

[0020] Furthermore, the cold box of the superconducting cable is equipped with a refrigerator. The cold box of the superconducting cable and the thermostat of the superconducting power conversion equipment are respectively provided with a first coil heat exchanger and a second coil heat exchanger. The superconducting power conversion equipment includes a superconducting reactor and a superconducting current limiter. The first coil heat exchanger is filled with first liquid nitrogen, which is connected to the liquid nitrogen inside the superconducting cable. The first coil heat exchanger is filled with second liquid nitrogen outside. The cold head of the refrigerator is immersed in the second liquid nitrogen. The inlet of the second coil heat exchanger is connected to the outlet of the first coil heat exchanger, and the outlet of the second coil heat exchanger is connected to the liquid nitrogen inlet of the superconducting cable.

[0021] A shared refrigerator operating method for a superconducting switch station. The refrigerator provides cooling to a cold box of a superconducting cable to maintain a low temperature of a second liquid nitrogen. The second liquid nitrogen transfers the cooling to the first liquid nitrogen via a first coil heat exchanger. The first liquid nitrogen flows between the first coil heat exchanger and the superconducting cable to transfer the cooling to the superconducting cable, ensuring that the superconducting cable maintains a low-temperature superconducting state. The first liquid nitrogen also transfers cold energy to the second coil heat exchanger through flow, ensuring that the thermostat of the superconducting power conversion equipment is maintained in a low-temperature superconducting state.

[0022] Compared with the prior art, the present invention has the following advantages: The present invention is designed to connect a superconducting switch station to a substation via a superconducting cable. The substation supplies power to the superconducting switch station. The outgoing lines of the superconducting switch station are designed to be closed-loop connected, and a superconducting current limiter is connected in series with the outgoing lines. This enables the outgoing lines of the superconducting switch station to adopt a "closed-loop design and closed-loop operation" mode, thereby improving power supply reliability. At the same time, the superconducting current limiter can be used to limit the short-circuit current, reducing the breaking pressure of the circuit breaker.

[0023] The present invention also designs a petal-type distribution network based on a superconducting switch station, which uses two substations to supply power to two superconducting switch stations with closed-loop outgoing lines, and connects a normally closed interconnecting switch in the middle of the two ring networks of the two superconducting switch stations and a superconducting current limiter in series, that is, adopts an interconnecting switch closed-loop operation mode, thereby greatly improving the power supply reliability. A fault in any of the two power supply lines will not cause power interruption, and load balance distribution can be achieved, so that the equipment capacity is fully utilized, effectively improving the overall power supply capacity, and when a short-circuit fault occurs at any point of the two superconducting switch stations and their outgoing lines, the superconducting current limiter can play a role and limit the current from the non-fault switch station, thereby avoiding excessive short-circuit current at the fault point and reducing the breaking pressure of the circuit breaker.

[0024] The interconnecting switch of the present invention comprises two normally closed switches connected in series, which can be operated in open loop when necessary. If the superconducting current limiter fails or requires maintenance, the two switches are disconnected, thereby shutting down the superconducting current limiter and ensuring that the two superconducting switch stations and their outgoing lines can still operate normally.

[0025] The present invention installs a superconducting reactor on the busbar connection of one of the superconducting switch stations, which can effectively solve the problems of insufficient inductive reactive power compensation and high voltage level. In practice, the capacity of the superconducting reactor can be designed according to the reactive power backflow conditions under different operating modes of the incoming and outgoing lines of the two superconducting switch stations. In addition, designing a tap switch on the reactor can realize segmented adjustment of the compensation capacity.

[0026] The present invention proposes a solution in which a superconducting cable and superconducting transformer equipment (including a superconducting reactor and a superconducting current limiter) share a refrigerator. A first coil heat exchanger and a second coil heat exchanger are respectively disposed in the superconducting cable cold box and the superconducting transformer equipment cold box. The outlet of the first coil heat exchanger is connected to the inlet of the superconducting transformer equipment cold box, and the outlet of the superconducting transformer equipment cold box is connected to the liquid nitrogen inlet of the superconducting cable. As a result, only the superconducting cable cold box needs to be equipped with a refrigerator, while the superconducting transformer equipment cold box does not need to be equipped with a refrigerator and only needs to be connected to the liquid nitrogen pipeline of the superconducting cable. After the refrigerator's cooling capacity is transferred to the superconducting cable, the remaining cooling capacity can be transferred to the superconducting transformer equipment. This improves refrigerator utilization, reduces the number of refrigerators, and allows for more flexible refrigerator layout in substation space, meeting various substation design requirements.

[0027] The present invention addresses the problem of sharing a refrigerator between superconducting cables and superconducting transformer equipment. A first coil heat exchanger and a second coil heat exchanger are respectively installed in the superconducting cable cold box and the superconducting transformer equipment thermostat. The inlet of the second coil heat exchanger is connected to the outlet of the first coil heat exchanger, and the outlet of the second coil heat exchanger is connected to the liquid nitrogen inlet of the superconducting cable. This achieves a more compact design, eliminating the need for a cold box for the superconducting transformer equipment. This not only achieves the goal of sharing a refrigerator, but also makes the superconducting transformer equipment simpler and smaller in size, facilitating the installation of multiple superconducting power equipment in a superconducting switch station and improving the economic efficiency of construction and operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a superconducting switch station operating in a closed loop for outgoing lines; Figure 2 This is a schematic diagram of a conventional petal-type power distribution network; Figure 3 This is the petal-type power distribution network based on the superconducting switch station in the present invention; Figure 4 This is a schematic diagram of the working scheme of a traditional refrigerator for superconducting cables; Figure 5 This is a schematic diagram of a shared refrigerator solution for a superconducting switch station in Example 3; Figure 6 Schematic diagram of the shared refrigerator solution for the superconducting switch station in Example 4. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] like Figure 1 As shown, a superconducting switch station with a closed-loop outgoing line is connected to a substation via a superconducting cable, and the substation supplies power to the superconducting switch station. The outgoing lines of the superconducting switch station are connected in a closed-loop manner, a superconducting current limiter is connected in series on the outgoing lines, and multiple normally closed switches are provided on the outgoing lines. In this embodiment, four normally closed switches are provided on the outgoing lines.

[0032] The above-mentioned method for operating the superconducting switch station includes: using a substation to supply power to the superconducting switch station via a superconducting cable; The outgoing line of the superconducting switch station is designed and operated in a closed loop, which can realize the outgoing line closed loop design and closed loop operation under the same power supply, thereby improving the power supply reliability. A superconducting current limiter connected in series on the outgoing line is used to limit the short-circuit current and reduce the breaking pressure of the circuit breaker.

[0033] Example 2

[0034] The current conventional petal-type distribution network is as follows Figure 2 As shown in the figure, every two outgoing lines from a substation form a ring network, forming a petal-shaped structure, with the ring network operating in a closed loop. Tie switches connect each two ring networks from different power substations, forming a petal-shaped, tangential network. This petal-shaped distribution network offers high reliability, but if a power substation fails, the system still undergoes the process of power outage, fault location, fault isolation, load transfer, and power restoration. Furthermore, load imbalance and the coexistence of heavy and light loads are still common during operation.

[0035] Therefore, based on the first embodiment, this embodiment is designed to use a petal-type power distribution network for the outgoing lines of the two superconducting switch stations, such as Figure 3 As shown, it includes a first superconducting switch station and a second superconducting switch station. The first superconducting switch station and the second superconducting switch station are respectively connected to two substations through superconducting cables and powered by the two substations. The two ring networks of the first superconducting switch station and the second superconducting switch station are connected through a normally closed connecting switch. The connecting switch includes two normally closed switches connected in series, and a superconducting current limiter is connected in series between the two normally closed switches.

[0036] In addition, superconducting reactors are installed on the busbars of the first superconducting switch station to effectively address the issues of insufficient inductive reactive power compensation and high voltage levels. Tap changers are connected to the superconducting reactors to enable segmented adjustment of compensation capacity. The capacity of the superconducting reactors is specifically designed based on the reactive power reverse flow under the different operating modes of the incoming and outgoing lines of the two superconducting switch stations.

[0037] The working method of the petal-shaped power distribution network based on superconducting switch stations includes: using two substations to supply power to two superconducting switch stations through superconducting cables; Both superconducting switch stations adopt outgoing line closed-loop operation mode to achieve balanced load distribution; Use superconducting reactors for inductive reactive power compensation; When a short circuit fault occurs at any point of the two superconducting switch stations and their outgoing lines, the superconducting current limiter is used to limit the current from the non-faulty switch station; When the superconducting current limiter fails or needs maintenance, the connecting switch between the two superconducting switch station ring networks is disconnected to cut off the power supply to the superconducting current limiter, so that the two superconducting switch stations and their outgoing lines can still operate normally.

[0038] Example 3

[0039] like Figure 4 As shown, in the current superconducting cable refrigerator operating scheme, a coil heat exchanger is immersed in the superconducting cable cold box. The coil heat exchanger contains a first liquid nitrogen, which is connected to the liquid nitrogen inside the superconducting cable. The coil heat exchanger is outside the cold box and is filled with a second liquid nitrogen. The cold head of the refrigerator is immersed in the second liquid nitrogen in the cold box, providing cooling for the cold box to maintain the low temperature of the second liquid nitrogen. The second liquid nitrogen passes through the coil heat exchanger and transfers the cooling energy to the first liquid nitrogen in the tube. The first liquid nitrogen flows between the coil heat exchanger and the superconducting cable, thereby transferring the cooling energy to the superconducting cable, ensuring that the superconducting cable maintains a low-temperature superconducting state.

[0040] If a cooling design is implemented for the superconducting switch station proposed in the embodiment, it is often necessary to equip the superconducting cables and superconducting transformer equipment (superconducting reactors or superconducting current limiters) with refrigerators respectively, and redundant backup refrigerators are also required, which will undoubtedly increase the construction cost and structural complexity of the superconducting switch station.

[0041] This embodiment takes into account that superconducting cables generally require a large amount of cooling capacity, while superconducting transformers require a smaller amount of cooling capacity, with a difference of up to one order of magnitude. Therefore, based on the first embodiment, this embodiment proposes a working mode in which superconducting cables and superconducting transformers (superconducting reactors or superconducting current limiters) share a refrigerator, such as Figure 5 This embodiment is described by taking a superconducting reactor as an example, wherein the cold box of the superconducting cable is Figure 4The structures are similar. The superconducting reactor cold box is not equipped with a refrigerator. The coil heat exchanger in the superconducting reactor cold box is filled with third liquid nitrogen, which is connected to the liquid nitrogen inside the superconducting reactor. The coil heat exchanger in the superconducting reactor cold box is filled with fourth liquid nitrogen. The outlet of the coil heat exchanger in the superconducting cable cold box is connected to the inlet of the superconducting reactor cold box, and the outlet of the superconducting reactor cold box is connected to the liquid nitrogen inlet of the superconducting cable.

[0042] During operation of the refrigerator, the refrigerator transfers cold energy to the first liquid nitrogen through the coil heat exchanger in the superconducting cable cold box. The first liquid nitrogen transfers cold energy to the fourth liquid nitrogen through the flow. The fourth liquid nitrogen transfers cold energy to the third liquid nitrogen through the coil heat exchanger in the superconducting reactor cold box. The third liquid nitrogen flows between the coil heat exchanger in the superconducting reactor cold box and the superconducting reactor, thereby transferring cold energy to the superconducting reactor, ensuring that the superconducting reactor is maintained in a low-temperature superconducting state.

[0043] Therefore, after the cooling capacity of the refrigerator is transferred to the superconducting cable, the remaining cooling capacity can be transferred to the superconducting reactor; thereby greatly improving the utilization rate of the refrigerator and reducing the number of refrigerators.

[0044] Furthermore, refrigerators are large and noisy, so their installation locations have high requirements, and noise reduction measures are required in the refrigeration room. In substations, cables, reactors, and current limiters may be installed at some distance from each other. This makes centralized placement of refrigerators difficult in conventional solutions, resulting in a large footprint and difficult placement. In the solution proposed in this embodiment, the cold box of the superconducting substation equipment does not require a refrigerator; it only needs to be connected to the liquid nitrogen pipeline of the superconducting cable to receive the cooling capacity. This provides greater flexibility in substation spatial layout and easily meets various substation design requirements.

[0045] Example 4

[0046] This embodiment proposes a working mode in which the superconducting cable and the superconducting power conversion equipment (superconducting reactor or superconducting current limiter) share a refrigerator, such as Figure 6 As shown, this embodiment is also described using a superconducting reactor as an example. The difference from the third embodiment is that in this embodiment, the coil heat exchanger is arranged inside the thermostat of the superconducting reactor, the inlet of the coil heat exchanger inside the thermostat of the superconducting reactor is connected to the outlet of the coil heat exchanger of the superconducting cable, and the outlet of the coil heat exchanger inside the thermostat of the superconducting reactor is connected to the liquid nitrogen inlet of the superconducting cable. The rest of the structural design is the same as that of the third embodiment.

[0047] Therefore, this embodiment can realize the sharing of a refrigerator by the superconducting cable and the superconducting substation equipment, and at the same time can eliminate the cold box of the superconducting substation equipment, realize a more compact structural design of the superconducting substation equipment, and reduce the installation volume of the superconducting substation equipment.

[0048] In summary, the superconducting switch station proposed in this scheme adopts a "closed-loop design and closed-loop operation" mode for its outgoing lines, which can effectively improve the power supply reliability. The superconducting current limiter connected in series in the outgoing line can limit the short-circuit current and reduce the breaking pressure of the circuit breaker; installing superconducting reactors on the busbar of the superconducting switch station can effectively solve the problems of insufficient inductive reactive power compensation and high voltage level; in addition, a closed-loop operation scheme for outgoing lines under different power sources is proposed, that is, the outgoing lines of the two superconducting switch stations both adopt a petal-type distribution network, and the normally closed interconnecting switches in the middle of the two ring networks of the two superconducting switch stations are connected in series with superconducting current limiters, that is, the interconnecting switch closed-loop operation mode is adopted to further improve the power supply capacity and power supply reliability. The application of this technical solution has the following advantages: (1) Limiting short-circuit current If a short circuit fault occurs at any point of the two superconducting switch stations and their outgoing lines, the superconducting current limiter can play a role in limiting the current from the non-fault switch station, thereby avoiding excessive short-circuit current at the fault point and reducing the breaking pressure of the circuit breaker.

[0049] (2) High reliability The power supply is highly reliable and a failure in any of the two power supply lines will not cause power interruption.

[0050] (3) Strong power supply capacity The loads on the outgoing lines of the two superconducting switch stations are evenly distributed, the capacity of the equipment is fully utilized, and the overall power supply capacity is improved.

[0051] The centralized inductive reactive power compensation of the shared superconducting reactors between the two superconducting switch stations saves equipment quantity, cost and space compared with the multi-point multi-device compensation method.

[0052] (4) High utilization rate of refrigerator Installing multiple superconducting power equipment in a superconducting switch station can share refrigerators and improve the economy of construction and operation and maintenance.

[0053] (5) The tie switch consists of two normally closed switches connected in series, which can be operated in an open loop when necessary. When the superconducting current limiter fails or needs maintenance, the two normally closed switches can be disconnected to shut down the superconducting current limiter, ensuring that the two superconducting switch stations and their outgoing lines can still operate normally.

Claims

1. A superconducting switch station with a closed-loop outgoing line, characterized in that: The superconducting switch station is connected to a transformer substation via a superconducting cable, and the transformer substation supplies power to the superconducting switch station. Outgoing lines of the superconducting switch station are connected in a closed loop, and a superconducting current limiter is connected in series on the outgoing lines.

2. The superconducting switch station with closed-loop outgoing line according to claim 1, characterized in that: A plurality of normally closed switches are provided on the output line.

3. A superconducting switch station operating method, applied to the superconducting switch station with an outgoing line closed loop as claimed in claim 1, characterized in that: include: Use the substation to supply power to the superconducting switch station through superconducting cables; The outgoing lines of the superconducting switch station are designed and operated in a closed loop; The short-circuit current is limited by a superconducting current limiter connected in series on the outgoing line.

4. A petal-type power distribution network based on a superconducting switch station, using a superconducting switch station with a closed-loop outgoing line as claimed in claim 1 or 2, characterized in that: The system comprises a first superconducting switch station and a second superconducting switch station, wherein the first superconducting switch station and the second superconducting switch station are respectively connected to two substations via superconducting cables and are powered by the two substations, and the two ring networks of the first superconducting switch station and the second superconducting switch station are connected via a normally closed tie switch.

5. The petal-type power distribution network based on superconducting switch stations according to claim 4, characterized in that: The contact switch includes two normally closed switches connected in series.

6. The petal-type power distribution network based on superconducting switch stations according to claim 5, characterized in that: A superconducting current limiter is connected in series between the two normally closed switches.

7. The petal-type power distribution network based on superconducting switch stations according to claim 4, characterized in that: A superconducting reactor is installed on the busbar of the first superconducting switch station.

8. The petal-type power distribution network based on superconducting switch stations according to claim 7, characterized in that: The superconducting reactor is connected to a tap changer.

9. The petal-type power distribution network based on superconducting switch stations according to claim 7, characterized in that: The capacity of the superconducting reactor is specifically designed according to the reactive power reverse transmission conditions of the incoming and outgoing lines of the two superconducting switch stations in different operating modes.

10. A method for operating a petal-type power distribution network based on a superconducting switch station, applied to the petal-type power distribution network based on a superconducting switch station according to claim 8, characterized in that: include: Use two substations to supply power to two superconducting switch stations through superconducting cables; Both superconducting switch stations adopt outgoing line closed-loop operation mode to achieve balanced load distribution; Use superconducting reactors for inductive reactive power compensation; When a short circuit fault occurs at any point of the two superconducting switch stations and their outgoing lines, the superconducting current limiter is used to limit the current from the non-faulty switch station; When the superconducting current limiter fails or needs maintenance, the connecting switch between the two superconducting switch station ring networks is disconnected to cut off the power supply to the superconducting current limiter, so that the two superconducting switch stations and their outgoing lines can still operate normally.

11. The method for operating a petal-type power distribution network based on a superconducting switch station according to claim 10, characterized in that: The superconducting reactor realizes segmented adjustment of compensation capacity through a tap changer.

12. The petal-type power distribution network based on superconducting switch stations according to claim 7, characterized in that: The superconducting cable cold box is equipped with a refrigerator. The cold box of the superconducting cable and the cold box of the superconducting power conversion equipment are respectively provided with a first coil heat exchanger and a second coil heat exchanger. The superconducting power conversion equipment includes a superconducting reactor and a superconducting current limiter. The first coil heat exchanger is filled with first liquid nitrogen, which is connected to the liquid nitrogen inside the superconducting cable. The first coil heat exchanger is filled with second liquid nitrogen outside. The cold head of the refrigerator is immersed in the second liquid nitrogen. The interior of the second coil heat exchanger is filled with third liquid nitrogen, which is connected to the liquid nitrogen inside the superconducting power conversion equipment, and the exterior of the second coil heat exchanger is filled with fourth liquid nitrogen; The outlet of the first coil heat exchanger is connected to the inlet of a superconducting power conversion equipment cold box, and the outlet of the superconducting power conversion equipment cold box is connected to the liquid nitrogen inlet of the superconducting cable.

13. A method for operating a shared refrigerator in a superconducting switch station, applied to a petal-type power distribution network based on a superconducting switch station as claimed in claim 12, characterized in that: The refrigerator provides cold energy to the cold box of the superconducting cable to maintain the low temperature of the second liquid nitrogen. The second liquid nitrogen transfers the cold energy to the first liquid nitrogen through the first coil heat exchanger. The first liquid nitrogen flows between the first coil heat exchanger and the superconducting cable to transfer the cold energy to the superconducting cable, ensuring that the superconducting cable is maintained in a low-temperature superconducting state. The first liquid nitrogen also transfers cold energy to the fourth liquid nitrogen through flow, and the fourth liquid nitrogen transfers cold energy to the third liquid nitrogen through the second coil heat exchanger. The third liquid nitrogen flows between the second coil heat exchanger and the superconducting power conversion equipment, thereby transferring cold energy to the superconducting power conversion equipment, ensuring that the superconducting power conversion equipment is maintained in a low-temperature superconducting state.

14. The petal-type power distribution network based on superconducting switch stations according to claim 7, characterized in that: The superconducting cable cold box is equipped with a refrigerator. The superconducting cable cold box and the thermostat of the superconducting power conversion equipment are respectively provided with a first coil heat exchanger and a second coil heat exchanger. The superconducting power conversion equipment includes a superconducting reactor and a superconducting current limiter. The first coil heat exchanger is filled with first liquid nitrogen, which is connected to the liquid nitrogen inside the superconducting cable. The first coil heat exchanger is filled with second liquid nitrogen outside. The cold head of the refrigerator is immersed in the second liquid nitrogen. The inlet of the second coil heat exchanger is connected to the outlet of the first coil heat exchanger, and the outlet of the second coil heat exchanger is connected to the liquid nitrogen inlet of the superconducting cable.

15. A method for operating a shared refrigerator in a superconducting switch station, applied to a petal-type power distribution network based on a superconducting switch station as claimed in claim 14, characterized in that: The refrigerator provides cold energy to the cold box of the superconducting cable to maintain the low temperature of the second liquid nitrogen. The second liquid nitrogen transfers the cold energy to the first liquid nitrogen through the first coil heat exchanger. The first liquid nitrogen flows between the first coil heat exchanger and the superconducting cable to transfer the cold energy to the superconducting cable, ensuring that the superconducting cable is maintained in a low-temperature superconducting state. The first liquid nitrogen also transfers cold energy to the second coil heat exchanger through flow, ensuring that the thermostat of the superconducting power conversion equipment is maintained in a low-temperature superconducting state.

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