Method and system for guaranteeing power supply of loads at different levels based on low-power-index area

Abstract

The invention discloses a power supply guarantee method and system for loads at all levels based on a low-power-index area. The method comprises the steps that whether a power grid incoming line switch exists in the low-power-index area or not is determined; if the power grid incoming line switch exists, determining whether the main bus is provided with a section switch; if yes, whether the section switch is in an opening state or not is determined; a power supply mode is selected according to the opening judgment result and the different load grades, the power supply mode comprises dual power supply, the dual power supply comprises a power grid and a micro-grid, and a power distribution switching box is connected between the power grid and the micro-grid and used for completing power switching between the power grid and the micro-grid. The method can effectively solve the problems that under the low construction cost, an independent power supply or a single-path large power grid power supply network is insufficient in reliability, and the power supply requirements of loads of all levels cannot be met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power supply guarantee, and particularly relates to a method and system for guaranteeing power supply of loads at all levels based on a region with low power index. BACKGROUND

[0002] The power index records the procedures, time and cost of an enterprise for obtaining permanent power connection. In addition to measuring the efficiency of power connection, new indexes are also applied to measure the reliability of power supply, transparency of electricity charges and prices. When a large power grid supplies power to loads by a single circuit, the reliability of power supply to loads is reduced due to faults, maintenance and the like, and the power supply of a single power supply local power grid also has the problems of low reliability or high price. Therefore, the power index obtained in a region with high cost of extension of the grid network frame, expansion of power equipment and power production is low. In order to improve the power index obtained in the region, in addition to strengthening the investment in power construction of the large power grid, it is also a means to invest in and construct a renewable energy local power grid or a regional energy autonomous power grid. However, due to the construction cost, the renewable energy local power grid also has the problems of low reliability of power supply or high price in the operation process, and the regional energy autonomous power grid has the problem of poor economy in the operation process. Loads can be divided into three levels according to the requirements for power supply reliability and the loss or influence degree caused by power interruption. The first level of load is supplied by double power sources, and the other power source should not be damaged when one power source fails. The external power supply line of the second level of load is preferably supplied by a 35kV, 20kV or 10kV double circuit. When the load is small or the power supply condition of the region is difficult, the second level of load can be supplied by a 35kV, 20kV or 10kV overhead line. The third level of load can be supplied by a single power source single circuit. The scheme for guaranteeing power supply to meet the power demand of loads at all levels in a region with low power index has the problem of high cost. SUMMARY

[0003] (I) Objectives of the Invention The present application aims to provide a method and system for guaranteeing power supply to loads at all levels based on a region with low power index, which effectively solves the problem that the reliability of a single power supply or a single circuit power supply network of the large power grid is insufficient and cannot meet the power supply demand of the first level of load under low construction cost.

[0004] (II) Technical Solutions To solve the above problems, the first aspect of the present application provides a method for guaranteeing power supply to loads at all levels based on a region with low power index, comprising: determining whether a grid line switch exists in the region with low power index; if the grid line switch exists, determining whether the main bus has a sectionalizing switch; If the sectionalizing switch is provided, it is determined whether the sectionalizing switch is in an open state; The power supply mode is selected in combination with the open state determination result and different load levels, and the power supply mode includes dual power supply, the dual power supply includes a power grid and a micro grid, a power distribution switch box is connected between the power grid and the micro grid, and the power distribution switch box is used to complete power switching between the power grid and the micro grid.

[0005] Preferably, the open state determination result includes that the main bus is provided with the sectionalizing switch and the sectionalizing switch is open, the main bus is provided with the sectionalizing switch and the sectionalizing switch is closed, and the main bus is not provided with the sectionalizing switch.

[0006] Preferably, if the open state determination result is that the main bus is provided with the sectionalizing switch and the sectionalizing switch is open, the main bus is divided into a first bus and a second bus, the second bus is provided with a micro grid and an on-site energy storage system, the on-site energy storage system provides power support for local power load, and the power supply mode of different load levels includes: If the power grid loses voltage and the first bus loses voltage, the second bus is switched to: For primary load, if the power supply switching action time meets the power supply preset interruption time, the primary load is switched to the micro grid for power supply through the power distribution switch box; For secondary load, the secondary load is directly switched to the micro grid through the power distribution switch box; For tertiary load, the tertiary load is first powered off and then determined whether to be powered according to the remaining capacity of the micro grid.

[0007] Preferably, if the open state determination result is that the main bus is provided with the sectionalizing switch and the sectionalizing switch is open, the power supply mode of different load levels further includes: For primary load, if the power supply switching action time does not meet the power supply interruption time requirement, the power supply of the power grid is first cut off, and then the on-site energy storage system is used for power supply.

[0008] Preferably, if the open state determination result is that the main bus is provided with the sectionalizing switch and the sectionalizing switch is closed and the main bus is not provided with the sectionalizing switch, the main bus is provided with a micro grid and an on-site energy storage system, and the power supply mode of different load levels includes: If the power grid loses voltage: For primary load, the centralized energy storage system is first switched from a power source mode to a voltage source mode, and the power supply of the power grid is cut off, and then the primary load is matched according to different requirements of the primary load on the power supply interruption time, and the centralized energy storage system provides power support for the main bus load; For secondary load, the secondary load switch is first opened, and then the secondary load switch is closed after the main bus is restored to normal voltage by the centralized energy storage system, and the power supply of the secondary load is restored by the main bus; For the third level load, first power failure exits operation, and then whether to supply power to the third level load is determined according to the remaining capacity of the centralized energy storage system or the micro-grid.

[0009] Preferably, the matching according to different requirements of the power supply interruption time of the first level load comprises: If the centralized energy storage system switching time meets the power supply interruption time requirement, the main busbar is continuously used for power supply; If the centralized energy storage system switching time does not meet the power supply interruption time requirement, the local energy storage system is used for power supply.

[0010] Preferably, the method further comprises: if there is no grid incoming line switch, the main busbar is provided with a cold standby power supply and a local energy storage system; If the grid voltage fails: For the first level load, the grid power supply is cut off and the local energy storage system is used for power supply; For the second level load, whether to start the cold standby power supply is determined according to the fault reason; For the third level load, first power failure exits operation, and then whether to supply power to the third level load is determined according to the remaining capacity of the centralized energy storage system or the micro-grid.

[0011] In addition, the second aspect of the present application provides a power supply guarantee system for loads of different levels in a low power index area, comprising: A first judgment module is used to determine whether there is a grid incoming line switch in the low power index area; A second judgment module is used to determine whether the main busbar is provided with a sectionalizing switch if there is a grid incoming line switch; A third judgment module is used to determine whether the sectionalizing switch is in an open state if the sectionalizing switch is provided; A power supply mode selection module is used to select a power supply mode in combination with the open determination result and different load levels, wherein the power supply mode comprises double power supply, the double power supply comprises a grid and a micro-grid, a distribution switch box is connected between the grid and the micro-grid, and the distribution switch box is used to complete power switching between the grid and the micro-grid.

[0012] Preferably, the power supply mode selection module is used to: If the open determination result is that the main busbar is provided with a sectionalizing switch and the sectionalizing switch is open, the main busbar is divided into a first busbar and a second busbar, the second busbar is provided with a micro-grid and a local energy storage system, the local energy storage system provides power support for local power load, and the power supply mode of different load levels comprises: If the grid voltage fails and the first busbar voltage fails, the second busbar is switched to: For the first level load, if the power supply switching action time meets the preset power supply interruption time, the first level load is switched to the micro-grid for power supply through the distribution switch box; For the secondary load, switch to the micro-grid directly through the distribution switch box; For the tertiary load, first exit operation after power failure, and then determine whether to supply power to the tertiary load according to the remaining capacity of the micro-grid.

[0013] Preferably, the power supply mode selection module is used for: If the switching-off determination result is that the main bus has a section switch and the section switch is open, the power supply mode of different load levels further includes: For the primary load, if the power supply switching action time does not meet the power supply interruption time requirement, first cut off the power grid power supply, and then use the local energy storage system for power supply.

[0014] (Three) beneficial effects The above technical scheme of the present application has the following beneficial technical effects: the present application provides a method and system for guaranteeing power supply of loads at all levels based on a region with low power indicators, which can reduce the construction and operation cost of guaranteeing power supply of loads at all levels in a region with low power indicators, and effectively improve the power indicators obtained, the specific method being as follows: according to whether there is a grid incoming line switch, a section switch, whether the section switch is in the switching-off state and other conditions in the region with low power indicators, it is determined according to the switching-off determination result and different load levels whether dual power supply is needed, and power switching between the grid and the micro-grid is completed through the distribution switch box. The present application uses a network frame structure with flexible switching capability of multiple operation modes, selects an adaptive power supply mode according to the difference between the power load level and the power supply interruption time, controls the construction cost, effectively solves the problem of insufficient reliability of the power supply network and difficulty in meeting the power supply demand of loads at all levels, improves the system economy, and provides a feasible path for realizing fine planning of power supply of loads at all levels with consideration of economy and reliability in the region with low power indicators. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a flowchart of the method for guaranteeing power supply of loads at all levels based on a region with low power indicators of the present application; Figure 2 is a schematic diagram of the system for guaranteeing power supply of loads at all levels based on a region with low power indicators of the present application; Figure 3 is a schematic diagram of the electrical structure of the power network of the specific embodiment of the present application; Figure 4 is a control flowchart of the power supply guarantee scheme of loads at all levels of the specific embodiment of the present application. DETAILED DESCRIPTION

[0016] In order to make the objects, technical solutions and advantages of the present application clearer, further detailed description will be made to the present application with reference to the specific embodiments and the accompanying drawings. It should be understood that the description is only exemplary and is not intended to limit the scope of the present application. In addition, in the following description, the description of the known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0017] As shown in Figure 1 The first aspect of the present application provides a method for power supply guarantee of loads at different levels based on low power index area. The present application is applied to power supply network for power demand of loads at different levels corresponding to power supply of a large power grid. The network frame structure supports flexible switching between on-grid and off-grid operation modes. The dual power supply is composed of a large power grid and a micro-grid operating independently. The power supply network contains at least one voltage source capable of independent operation (off-grid), multiple controllable switches, and power electronic devices with multiple switchable operation modes. The network can be split into the smallest unit for operation. In the area where the large power grid network frame does not extend, when constructing a power supply network to meet the power demand of loads at different levels corresponding to the position far away from the power system, the network frame structure supporting flexible switching of multiple operation modes is adopted, which contains the following characteristics: multi-voltage source support, at least two independent voltage sources; multiple controllable switches, independent controllable switches for loads at different levels, independent controllable switches for power sources with different functions, and sectional switches for busbars; power electronic devices with multiple switchable operation modes, such as current source operation mode, voltage source operation mode, maximum power tracking operation mode, and limited power operation mode; network can be split into the smallest unit for operation, supporting independent voltage source with one level of load independent operation, combined with Figure 4 As shown in S1, determining whether there is a grid incoming line switch in the low power index area; S2, if there is a grid incoming line switch, determining whether the main bus has a sectional switch; S3, if the sectional switch is provided, determining whether the sectional switch is in the open state; S4, combining the sectional switch determination result and the power supply mode selection for different load levels, the power supply mode including dual power supply, the dual power supply including a power grid (first power source) and a micro-grid (second power source), and a power distribution switch box connected between the power grid and the micro-grid, the power distribution switch box being used for completing power switching between the power grid and the micro-grid. The sectional switch determination result includes: the main bus has a sectional switch and the sectional switch is open, the main bus has a sectional switch and the sectional switch is closed, and the main bus does not have a sectional switch.

[0018] Preferably, in the S4 step, if the opening determination result is that the main bus has sectional switches and the sectional switches are open, the main bus is divided into a first bus and a second bus, the second bus is provided with a microgrid and a local energy storage system, the local energy storage system provides power support for local power load, and the power supply modes for different load levels include: if the power grid loses voltage and the first bus loses voltage, the second bus is switched to: (1) For primary load, if the power supply switching action time meets the power supply preset interruption time, the primary load is switched to the microgrid for power supply through the distribution switching box; if the power supply switching action time does not meet the power supply interruption time requirement, the power supply is first cut off, and then the local energy storage system is used for power supply. In a power supply network with one large power grid power supply, a microgrid capable of independent operation is constructed as a second power source according to the power size of the primary and secondary load. When the main bus of the distribution station has sectional switches and the sectional switches are open, a power source switchable end distribution box is arranged at the primary load access point, and a voltage source operating mode energy storage system is arranged to connect the primary load distribution bus. When the large power grid power supply network loses voltage, for the primary load whose power supply switching action time can meet the power supply interruption time requirement, the second power source (microgrid) can be switched by the distribution box for continuous power supply. For the primary load with strict power supply interruption time requirement, the local energy storage system with network type energy storage control mode is used, the power supply box incoming line switch is opened, the power supply is continued, and the minimum power supply unit is operated to a set time length. Whether to be connected to the second power supply network is selected according to the state of charge of the local energy storage system battery.

[0019] (2) For secondary load, the secondary load is directly switched to the microgrid through the distribution switching box. When the large power grid power supply network loses voltage, the secondary load is switched to the second power supply network for power supply through the power source.

[0020] (3) For tertiary load, the tertiary load is first lost and exited from operation, and then whether to supply power to the tertiary load is determined according to the remaining capacity of the microgrid. The tertiary load supplied by a single power source single loop loses voltage and exits from operation when the large power grid power supply network loses voltage, and then the sectional switch parallel operation is restored according to the system capacity.

[0021] The microgrid capable of independent operation is used as an effective supplement to the large power grid single loop for load power supply in the area with low power index, the control strategies preset for different levels of load are triggered through electrical quantity criteria, the power supply switching is completed when the large power grid fails, the power supply reliability is improved, the uninterrupted power supply of the primary load is ensured, the investment in large power grid network construction is saved, and an application scenario for distributed energy consumption is added.

[0022] Preferably, in the S4 step, if the switching-off determination result is that the main bus is provided with a sectionalizer and the sectionalizer is closed and the main bus is not provided with a sectionalizer, the main bus is provided with a micro-grid and an on-site energy storage system, and the power supply modes for different load levels include: if the power grid loses voltage: (1) For a first-level load, the centralized energy storage system is switched from a power source mode to a voltage source mode, and the power grid supply is cut off, and then the first-level load is matched according to different requirements for power supply interruption time, and the centralized energy storage system provides power support for the main bus load; the matching according to different requirements for power supply interruption time of the first-level load specifically includes: if the centralized energy storage system switching time meets the power supply interruption time requirement, the main bus continues to supply power; if the centralized energy storage system switching time does not meet the power supply interruption time requirement, the on-site energy storage system supplies power. When the main bus of the distribution station does not have a sectionalizer or the sectionalizer is closed, all devices are operated in parallel under normal working conditions. When the large power grid supply network loses voltage, the working mode of the energy storage system connected to the main bus of the distribution station is switched from a power source mode to a voltage source mode, and the grid-connected feeder switch is tripped, and the local power supply network is operated in an off-grid mode. For the first-level load whose centralized energy storage system working mode switching time meets the power supply interruption time requirement, the original circuit can be used to continue to supply power (the terminal distribution box (if any) does not switch the power source because the second power source is interlocked with the sectionalizer). For the first-level load with strict power supply interruption time requirement, the on-site energy storage system with network-forming energy storage control mode is used, the feeder switch of the supply box is disconnected, power supply is continued, and the minimum power supply unit formed operates to a set time length, and then it is selected according to the state of charge of the battery of the on-site energy storage system whether to be connected to the distribution station bus restored by the centralized energy storage.

[0023] (2) For a second-level load, the second-level load switch is first disconnected, the main bus is restored to normal voltage through the centralized energy storage system, and then the second-level load switch is closed to restore the power supply of the second-level load through the main bus. When the large power grid supply network loses voltage, the second-level load switch is first disconnected, the voltage is restored through the centralized energy storage system of the main bus of the distribution station, and then the switch is closed to continue to supply power. For the power supply network with a long power failure time of the first power source, the second power source can be provided with a controllable and non-random power output generating device, such as a diesel generator, a gas unit, or a fuel cell.

[0024] (3) For a third-level load, the third-level load is first lost and exited from operation, and then it is determined whether to supply power to the third-level load according to the remaining capacity of the centralized energy storage system or the micro-grid. The third-level load supplied by a single power source single circuit loses voltage and exits from operation when the large power grid supply network loses voltage, and then it can be put into operation again according to the centralized energy storage capacity of the system.

[0025] Preferably, the method further includes: if there is no grid feeder switch, the main bus is provided with a cold standby power source and an on-site energy storage system, and if the power grid loses voltage: (1) For the first level load, cut off the power supply of the power grid and use the local energy storage system to supply power; for the power supply network without the support of the large power grid in the position far away from the power system, a cold standby power system with a faster start-up time is constructed. When the power supply network loses voltage, for the first level load, the local energy storage system adopting the network type energy storage control mode disconnects the supply box incoming line switch, continues to supply power, and forms a minimum power supply unit that operates to the set time length and then selects whether to merge into the main bus of the distribution station restored by the standby power supply according to the state of charge of the local energy storage system battery; the local energy storage system that guarantees seamless switching of power supply for the first level load adopts the network type energy storage control strategy, and can use the corresponding power output value change to participate in the battery state of charge adjustment and the economic optimization of the whole system when the standard frequency is used.

[0026] (2) For the second level load, determine whether to start the cold standby power supply according to the fault reason. When the power supply network loses voltage, for the second level load, the voltage loss caused by internal power supply line failure can be continued by power supply switching of the distribution box, the voltage loss caused by power failure can be restored by the cold standby power system connected to the main bus of the distribution station, and the voltage loss caused by bus failure can be switched to the second bus operation by the distribution box if there is bus segmentation, and if there is no segmentation, the power supply needs to be restored after the fault is eliminated.

[0027] (3) For the third level load, first lose power and exit operation, and then determine whether to supply power to the third level load according to the local energy storage system or the cold standby power supply. The third level load supplied by a single power supply single loop loses power and exits operation when the power supply network loses voltage, and can be put into operation according to the system power capacity.

[0028] As shown in Figure 2 The second aspect of the present application provides a power supply guarantee system for loads in a low power index area, which comprises: A first judgment module 21 is used to determine whether there is a power grid incoming line switch in the low power index area; A second judgment module 22 is used to determine whether the main bus is provided with a sectionalizing switch if there is a power grid incoming line switch; A third judgment module 23 is used to determine whether the sectionalizing switch is in the open state if the sectionalizing switch is provided; Power supply mode selection module 24 is used to select the power supply mode based on the tripping determination result and different load levels. The power supply mode includes dual power supply, which includes the power grid and a microgrid. A distribution switching box is connected between the power grid and the microgrid to complete the power switching between the power grid and the microgrid. The power supply mode selection module 24 is used to: if the tripping determination result is that the main bus has a sectionalizing switch and the sectionalizing switch is open, then divide the main bus into a first bus and a second bus. The second bus is equipped with a microgrid and a local energy storage system. The local energy storage system provides power to local electrical loads. Power supply support includes different power supply methods for different load levels: If the grid loses power and the first bus loses power, the power supply will switch to the second bus; for primary loads, if the power switching action time meets the preset power interruption time, the primary load will be switched to microgrid power supply through the distribution switching box; for primary loads, if the power switching action time does not meet the power interruption time requirement, the grid power supply will be cut off first, and then the local energy storage system will be used for power supply; for secondary loads, the power supply will be switched directly to the microgrid through the distribution switching box; for tertiary loads, the power supply will be cut off first, and then the remaining capacity of the microgrid will be used to determine whether to supply power to the tertiary load.

[0029] The following is in conjunction with the appendix Figure 3 The invention will be further illustrated by examples and implementation cases. A power distribution network with a single power grid supply line is shown in the attached example. Figure 3 As shown, a single busbar segmented electrical main wiring is adopted. During normal operation, the two busbars operate separately. The primary and secondary loads are powered by the first section of the distribution busbar (the primary power source), while the second section of the busbar operates with some tertiary loads.

[0030] The following steps are used: Step 1: Real-time sensing of switch status, determining the operating mode based on switch position.

[0031] Step 2: Voltage loss was detected in section I of the distribution bus, while voltage return was detected in section II of the distribution bus.

[0032] Step 3: The local energy storage PCS disconnects K when the I-section busbar loses voltage. 31 The system is running under a Level 1 load with an interruption time requirement in the millisecond range.

[0033] Step 4: When Section I loses voltage and Section II gains voltage, the voltage switching action of the primary load terminal distribution box is activated. The interruption time requirement is in the second range. Primary load 2 is switched to be powered by the Section II bus.

[0034] Step 5: When Section I loses voltage and Section II gains voltage, the voltage switching action of the secondary load terminal distribution box is activated, and the secondary load is switched to be powered by the Section II bus.

[0035] Step 6: Section I pressure loss, Level 3 load exits operation.

[0036] Step seven: when the system capacity is sufficient and the energy storage state of charge is high, issue a remote control order to close the disconnection switch to restore the three-level load power supply.

[0037] Step eight: the incoming line switch of the I-section bus has voltage, the disconnection switch is opened, and the incoming line switch is closed.

[0038] Step nine: the I-section has voltage, the second-level load terminal distribution box voltage switching action, and the second-level load restores the first power supply.

[0039] Step ten: the I-section has voltage, the first-level load 2 terminal distribution box voltage switching action, and the first-level load 2 restores the first power supply.

[0040] Step eleven: the I-section has voltage, the first-level load 1 local PCS load synchronization grid connection, K 31 is closed, and the first-level load 1 restores the first power supply.

[0041] Specifically, the sectional switch can be interlocked with the first power supply of the distribution box.

[0042] Specifically, if the large power grid loses power for a long time, the hydrogen fuel cell can be started.

[0043] Specifically, if the local energy storage state of charge is low during the loss of power of the large power grid, the II-section bus can be powered by a control order.

[0044] It should be understood that the above specific embodiments of the present application are only used for illustrative or explanatory purposes, and do not constitute a limitation on the present application. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present application shall be included in the protection scope of the present application. In addition, the appended claims of the present application are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

[0045] It should be understood that the above specific embodiments of the present application are only used for illustrative or explanatory purposes, and do not constitute a limitation on the present application. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present application shall be included in the protection scope of the present application. In addition, the appended claims of the present application are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries. These computer program instructions can also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer readable memory produce a manufactured product including instruction devices, which realize the flow Figure 1one or more processes and / or blocks Figure 1 Those skilled in the art can understand that all or part of the steps in the above-mentioned method embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, the program includes the flow of the above-mentioned method embodiments. The storage medium can be a magnetic disc, an optical disc, a read-only memory (ROM) or a random access memory (RAM), etc. The steps in the method embodiments of the present application can be adjusted, combined and deleted in sequence according to actual needs. The modules in the system embodiments of the present application can be combined, divided and deleted according to actual needs.

Claims

1. A method for power supply guarantee of loads at different levels based on low power index area, characterized in that, The method comprises the following steps: determining whether there is a grid incoming line switch in the low power index area; if there is a grid incoming line switch, determining whether the main bus has a sectionalizing switch; if the main bus has a sectionalizing switch, determining whether the sectionalizing switch is in an open state; combining the open state determination result and the different load levels to select a power supply mode, wherein the power supply mode comprises a dual power supply, the dual power supply comprises a grid and a microgrid, a distribution switch box is connected between the grid and the microgrid, and the distribution switch box is used to complete power switching between the grid and the microgrid.

2. The method according to claim 1, wherein, The open state determination result comprises that the main bus has a sectionalizing switch and the sectionalizing switch is open, the main bus has a sectionalizing switch and the sectionalizing switch is closed, and the main bus does not have a sectionalizing switch.

3. The method according to claim 2, wherein If the open state determination result is that the main bus has a sectionalizing switch and the sectionalizing switch is open, the main bus is divided into a first bus and a second bus, the second bus is provided with a microgrid and an on-site energy storage system, the on-site energy storage system provides power support for local power load, and the power supply mode of different load levels comprises: if the grid loses voltage and the first bus loses voltage, switching to the second bus: for a first load, if the power supply switching action time meets the power supply preset interruption time, switching the first load to the microgrid through the distribution switch box; for a second load, directly switching to the microgrid through the distribution switch box; for a third load, first exiting operation after losing power, and then determining whether to supply power to the third load according to the remaining capacity of the microgrid.

4. The method according to claim 3, wherein, If the open state determination result is that the main bus has a sectionalizing switch and the sectionalizing switch is open, the power supply mode of different load levels further comprises: for a first load, if the power supply switching action time does not meet the power supply interruption time requirement, first cutting off the grid power supply, and then using the on-site energy storage system to supply power.

5. The method according to claim 3, wherein, If the open state determination result is that the main bus has a sectionalizing switch and the sectionalizing switch is closed, and the main bus does not have a sectionalizing switch, the main bus is provided with a microgrid and an on-site energy storage system, and the power supply mode of different load levels comprises: if the grid loses voltage: for a first load, first switching the centralized energy storage system from a power source mode to a voltage source mode, cutting off the grid power supply, and then matching different requirements of the first load on the power supply interruption time, wherein the centralized energy storage system provides power support for the main bus load; for a second load, first opening the second load switch, and then closing the second load switch after the main bus is restored to normal voltage by the centralized energy storage system, so as to restore the power supply of the second load by the main bus; for a third load, first exiting operation after losing power, and then determining whether to supply power to the third load according to the remaining capacity of the centralized energy storage system or the microgrid.

6. The method according to claim 3, wherein, The matching of different requirements of the first load on the power supply interruption time comprises: if the centralized energy storage system switching time meets the power supply interruption time requirement, continuing to use the main bus to supply power; if the centralized energy storage system switching time does not meet the power supply interruption time requirement, using the on-site energy storage system to supply power.

7. The method according to claim 3, wherein, The method further comprises that if there is no grid incoming line switch, the main bus is provided with a cold standby power supply and an on-site energy storage system; if the grid loses voltage: for a first load, cutting off the grid power supply and using the on-site energy storage system to supply power; for a second load, determining whether to start the cold standby power supply according to the fault reason; For the third level load, the power supply is first lost and then the on-site energy storage system or the cold standby power source is used to determine whether to supply power to the third level load.

8. A power supply guarantee system for each level of load based on a low power index area, characterized by, The method comprises the following steps: The first determining module is configured to determine whether there is a grid incoming line switch in the low power index area. The second determining module is configured to determine whether the main bus is provided with a sectionalizing switch if there is a grid incoming line switch. The third determining module is configured to determine whether the sectionalizing switch is in an open state if the main bus is provided with the sectionalizing switch. The power supply mode selection module is configured to select a power supply mode in combination with the open determination result and different load levels, wherein the power supply mode comprises double power supply, the double power supply comprises a grid and a microgrid, a distribution switch box is connected between the grid and the microgrid, and the distribution switch box is used to complete power switching between the grid and the microgrid.

9. The power index low area based level load power supply guarantee system according to claim 8, characterized in that, The power supply mode selection module is configured to: If the open determination result is that the main bus is provided with the sectionalizing switch and the sectionalizing switch is open, the main bus is divided into a first bus and a second bus, the second bus is provided with a microgrid and an on-site energy storage system, the on-site energy storage system provides power support for local power consumption loads, and the power supply mode of different load levels comprises: If the grid loses voltage and the first bus loses voltage, the second bus is switched to; For the first level load, if the power supply switching action time meets the power supply preset interruption time, the first level load is switched to the microgrid for power supply through the distribution switch box; For the second level load, the second level load is directly switched to the microgrid through the distribution switch box; For the third level load, the power supply is first lost and then the remaining capacity of the microgrid is used to determine whether to supply power to the third level load.

10. The power index low area based multi-level load power supply guarantee system according to claim 8, characterized in that, The power supply mode selection module is configured to: If the open determination result is that the main bus is provided with the sectionalizing switch and the sectionalizing switch is open, the power supply mode of different load levels further comprises: For the first level load, if the power supply switching action time does not meet the power supply interruption time requirement, the grid power supply is first cut off and then the on-site energy storage system is used for power supply.

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