Power grid operation mode division and power balance method considering multiple types of states and related device

Abstract

The invention provides a power grid operation mode division and power balance method considering multiple types of states and a related device, and aims to solve the problems of complex structure, heavy load of a transformer, unbalanced load and the like in the operation of an AC / DC micro-grid group system. The method comprises the following steps: acquiring state parameters such as transformer heavy load, system critical power PC, storage battery SOC and the like; dividing five main modes and sub-modes based on fault types and state parameters; the VSC power is regulated and controlled through a load balancing strategy, so that the load rates of the transformers are equal to reduce the loss; mode switching is completed within 100 ms, and it is ensured that the load rate fluctuation is smaller than or equal to 5%. The device correspondingly comprises a state parameter acquisition module, a mode division module, a power regulation and control module and a switching module. According to the method, multi-dimensional dynamic regulation and control are realized, the system stability, economy and fault response speed are improved, and the method is suitable for an intelligent power distribution scene with high-proportion renewable energy access.

Description

Technical Field

[0001] This invention relates to the field of power grid technology, specifically a method and related apparatus for classifying power grid operation modes and achieving power balance considering multiple types of states. Background Technology

[0002] With the large-scale integration of renewable energy into the grid, microgrids, as the main platform for distributed energy, face challenges such as small capacity and weak disturbance resistance. AC / DC microgrid clusters have become an important solution for improving power supply reliability. However, these systems suffer from complex structures, transformer overload, and load imbalances, leading to risks of localized overload, voltage instability, and equipment damage. Existing technologies regulate power through flexible interconnection devices (such as voltage source converters, VSCs), but traditional methods only consider a single fault type, failing to incorporate multiple dimensions such as transformer overload, system critical power, and battery state of charge (SOC). This results in insufficient adaptability of the regulation strategy, hindering rapid response and economical operation under fault conditions.

[0003] Although domestic and international research has proposed multi-mode operation and control strategies (such as virtual synchronous machine technology and composite control strategies), the following shortcomings exist:

[0004] 1. Single mode classification: Based only on fault type (such as VSC fault, transformer fault), without integrating dynamic parameters such as transformer overload, power deficit / excess and energy storage status;

[0005] 2. Disjointed control logic: The lack of a linkage mechanism between "fault type - system status - power control" leads to delayed response during mode switching;

[0006] 3. Insufficient economic optimization: The role of load balancing in reducing transformer losses has not been mathematically proven, and the control targets lack theoretical support. Summary of the Invention

[0007] This invention provides a method and related device for classifying power grid operation modes and achieving power balance that considers multiple types of states. By integrating fault types and system dynamic parameters, it realizes adaptive mode switching and efficient power regulation.

[0008] A method for classifying power grid operation modes and balancing power supply considering multiple states includes the following steps:

[0009] Step 1: Obtain system status parameters: The system status parameters include transformer overload, system critical power (PC), and battery state of charge (SOC). bat ;

[0010] Step 2, Multi-dimensional mode classification: Based on the fault type and the system status parameters obtained in Step 1, the power grid operation mode is divided into 5 main modes and sub-modes;

[0011] Step 3, Power Regulation Based on Balanced Load: Based on the mode division results in Step 2, the control module calls the corresponding regulation formula to adjust the VSC power:

[0012] Step 4: Mode Switching and Dynamic Optimization

[0013] The transformer load rate is monitored in real time. When a mode switching condition is detected, the control module completes the switching of the control formula within 100ms to ensure that the transformer load rate fluctuation is ≤5% during the switching process.

[0014] Furthermore, in step 2, the multi-dimensional mode division is based on the fault type and the system state parameters obtained in step 1, dividing the power grid operation mode into 5 main modes and sub-modes, specifically including:

[0015] Mode 1 is the flexible interconnection mode: fault-free, based on the number of heavily loaded transformer areas, the system critical power PC, and the battery state of charge (SOC). bat It is further divided into 16 sub-patterns;

[0016] Mode 2 is the AC bus fault mode: all transformers in the distribution area are disconnected from the grid, distributed power sources prioritize supplying DC loads, and the remaining power is supplied to AC loads;

[0017] Mode 3 is the DC bus fault mode: there is no energy exchange between microgrids, and the AC load is jointly powered by the distribution network and distributed generation.

[0018] Mode 4 is the VSC failure mode: when one or two VSCs fail, the AC load in the faulty area is powered by the distribution network, and the load in the non-faulty areas is balanced by the VSC.

[0019] Mode 5 is the transformer fault mode: when one or two transformers fail, the AC load of the faulty transformer area is powered by the VSC of the non-faulty transformer area.

[0020] Furthermore, step 3, power regulation based on load balancing, specifically includes: power excess and SOC... bat ≤SOC max Prioritize transferring power from heavily loaded transformer stations to lightly loaded stations via VSC, while simultaneously charging and storing energy; power deficit and SOC bat >SOC min : Through joint regulation of energy storage discharge and VSC power transfer; where SOC min For battery charging threshold, SOC max This is the battery discharge threshold.

[0021] Furthermore, in step 3, when balancing the load, the loss of the load transformer is minimized. Minimizing the loss of the load transformer is achieved by setting the load rates of n transformers to be equal.

[0022] A power grid operation mode classification and power balancing device considering multiple types of states, comprising:

[0023] The system status parameter acquisition module is used to acquire system status parameters, including transformer overload, system critical power (PC), and battery state of charge (SOC). bat ;

[0024] The multi-dimensional mode division module is used to divide the power grid operation mode into 5 main modes and sub-modes based on the fault type and the acquired system state parameters.

[0025] The power regulation block based on load balancing is used by the control module to adjust the VSC power according to the mode division results and the corresponding regulation formula.

[0026] The mode switching and dynamic optimization module is used to monitor the transformer load rate in real time. When the mode switching condition is detected, the control module completes the switching of the control formula within 100ms to ensure that the transformer load rate fluctuation is ≤5% during the switching process.

[0027] Furthermore, the multi-dimensional mode division module, based on fault type and acquired system state parameters, divides the power grid operation mode into 5 main modes and sub-modes, specifically including:

[0028] Mode 1 is the flexible interconnection mode: fault-free, based on the number of heavily loaded transformer areas, the system critical power PC, and the battery state of charge (SOC). bat It is further divided into 16 sub-patterns;

[0029] Mode 2 is the AC bus fault mode: all transformers in the distribution area are disconnected from the grid, distributed power sources prioritize supplying DC loads, and the remaining power is supplied to AC loads;

[0030] Mode 3 is the DC bus fault mode: there is no energy exchange between microgrids, and the AC load is jointly powered by the distribution network and distributed generation.

[0031] Mode 4 is the VSC failure mode: when one or two VSCs fail, the AC load in the faulty area is powered by the distribution network, and the load in the non-faulty areas is balanced by the VSC.

[0032] Mode 5 is the transformer fault mode: when one or two transformers fail, the AC load of the faulty transformer area is powered by the VSC of the non-faulty transformer area.

[0033] Furthermore, the power regulation block based on balanced load adjusts the VSC power according to the mode division result, and the control module calls the corresponding regulation formula to adjust the VSC power, specifically including: power excess and SOC bat ≤SOC maxPrioritize transferring power from heavily loaded transformer stations to lightly loaded stations via VSC, while simultaneously charging and storing energy; power deficit and SOC bat >SOC min : Through joint regulation of energy storage discharge and VSC power transfer; where SOC min For battery charging threshold, SOC max This is the battery discharge threshold.

[0034] Furthermore, during load balancing, the load transformer loss is minimized. Minimizing load transformer loss is achieved by setting the load rates of n transformers to be equal.

[0035] A power grid operation mode classification and power balance system considering multiple types of states includes: a computer-readable storage medium and a processor;

[0036] The computer-readable storage medium is used to store executable instructions;

[0037] The processor is used to read executable instructions stored in the computer-readable storage medium and execute the power grid operation mode division and power balance method that considers multiple types of states.

[0038] A non-transitory computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned method for classifying power grid operation modes and balancing power supply considering multiple types of states.

[0039] The present invention has the following beneficial effects:

[0040] 1. Multi-dimensional dynamic mode division: Combining fault types (such as VSC fault, transformer fault) and system dynamic parameters (transformer overload, critical power PC, battery SOC), the power grid is divided into 5 main modes and sub-modes, which solves the problem of single mode division and insufficient adaptability in traditional mode division, realizes the linkage mechanism of "fault type-system state-power regulation", and improves the regulation flexibility under complex operating conditions.

[0041] 2. Balanced load and economical operation: Through mathematical proof, the total copper loss is minimized when the load rates of n transformers are equal. Based on this, a power regulation strategy is designed to prioritize the transfer of power from heavily loaded transformer areas through flexible interconnection devices (VSC). Combined with energy storage charging and discharging optimization, this effectively reduces transformer losses, improves the economic efficiency of system operation, and extends equipment life.

[0042] 3. Fast mode switching and improved stability: Real-time monitoring of transformer load rate and completion of mode switching within 100ms ensure that load rate fluctuation is ≤5% during the switching process. This solves the problem of delayed response of traditional control, enhances the system's ability to respond quickly to disturbances and faults, and ensures voltage stability and power supply continuity. Attached Figure Description

[0043] Figure 1 This is a diagram of the collaborative and mutually supportive model of the AC / DC microgrid group system according to an embodiment of the present invention;

[0044] Figure 2 This is a power flow diagram of the flexible interconnection mode according to an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of the fault locations in modes 2 to 5 of this embodiment of the invention;

[0046] Figure 4 This is a schematic diagram of the partitioning result of mode i in an embodiment of the present invention;

[0047] Figure 5 This is a schematic diagram of the partitioning result of Mode 2 in embodiment 2 of the present invention;

[0048] Figure 6 This is a schematic diagram of the partitioning result of Mode 4 in embodiment 4 of the present invention;

[0049] Figure 7 This is a schematic diagram of the partitioning result of Mode 5 in embodiment 5 of the present invention;

[0050] Figure 8 This is a schematic diagram of the simulation results of Mode 1 of the present invention;

[0051] Figure 9 This is a schematic diagram of the simulation results of Mode 2 of the present invention;

[0052] Figure 10 This is a schematic diagram of the simulation results of Mode 3 of the present invention;

[0053] Figure 11 This is a schematic diagram of the simulation results when Mode 4VSC3 fails according to an embodiment of the present invention;

[0054] Figure 12 This is a schematic diagram of the simulation results when both VSC3 and VSC4 fail simultaneously in mode 4 of this invention.

[0055] Figure 13 This is a schematic diagram of the simulation results when transformer 3 fails in mode 5 of the present invention;

[0056] Figure 14 This is a schematic diagram of the faults of transformer 3 and transformer 4 in embodiment 5 of the present invention;

[0057] Figure 15 This is a flowchart of a power grid operation mode division and power balance method considering multiple states according to an embodiment of the present invention. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] The basic structure of the AC / DC microgrid group system collaborative model mainly includes an AC bus, transformer, AC primary and secondary standard interfaces for energy storage vehicles, a flexible low-voltage DC interconnection device (Voltage Source Converter, VSC), distributed power sources such as photovoltaics, energy storage systems, DC buses, AC loads, and DC loads. Under the condition of not considering faults, the AC port adopts a three-phase three-wire bridge topology, and the DC port uses a photovoltaic DC grid-connected converter to connect distributed power sources such as photovoltaics, while simultaneously using an energy storage converter to connect battery energy storage devices. Its topology is as follows: Figure 1 As shown. The AC / DC microgrid group collaborative mutual assistance system studied in this invention constructs flexible low-voltage DC interconnection devices on the low-voltage side of 5 microgrids, and the 5 microgrids are interconnected in parallel through AC buses, and AC / DC connection is achieved within the microgrids through VSC.

[0060] System failures can be categorized into the following five modes.

[0061] Mode 1: Flexible Interconnection Mode. In this mode, all VSCs operate in parallel with the grid. All feeders can achieve flexible interconnection through VSCs, and feeder power can flow bidirectionally through the VSCs. Power flow regulation can balance the transformer load. The power flow direction in flexible interconnection mode is as follows: Figure 2 As shown.

[0062] Mode 2: AC bus fault mode. In this mode, all AC port transformers are disconnected from the grid. Distributed power sources prioritize supplying DC loads. AC loads are supplied by distributed power sources only after the DC load demand has been met.

[0063] Mode 3: DC bus fault mode. In this mode, there is no energy exchange between microgrids. Distributed power sources prioritize supplying DC loads. AC loads are supplied through the distribution network and through distributed power sources while simultaneously meeting the DC load demand.

[0064] Mode 4: VSC Fault Mode. In this mode, the AC load corresponding to the faulty VSC is powered by the distribution network. Distribution areas without VSC faults can achieve transformer load balancing through power flow regulation.

[0065] Mode 5: Transformer Failure Mode. In this mode, some AC port transformers are disconnected from the grid. Power needs to be supplied to the AC loads of the transformer-failed microgrid via VSC. Power flow regulation can achieve transformer load balancing in areas where no transformer failure has occurred.

[0066] The location of the fault in modes 2 to 5 is as follows: Figure 3 As shown.

[0067] Please see Figure 15 The first aspect of this invention provides a method for classifying power grid operation modes and achieving power balance considering multiple types of states, comprising the following steps:

[0068] Step 1: Obtain system status parameters: The system status parameters include transformer overload, system critical power (PC), and battery state of charge (SOC). bat ;

[0069] (1) Transformer overload

[0070] The AC load exceeding 80% of the transformer's rated capacity is defined as a heavy load condition.

[38] All transformers in the five distribution areas may experience heavy load conditions. To maintain economical system operation, it is necessary to transfer power flow to the heavily loaded main transformers to remove them from the heavy load. If a transformer in a distribution area becomes heavily loaded, it is necessary to control the VSC power to remove it from the heavy load.

[0071] (2) System critical power

[0072] Define the critical power P of the system C Used to measure the maximum load that the system can handle. When P C ≥0 indicates that the system has excess critical power, P C <0 indicates a critical power deficit in the system.

[0073] The system critical power corresponding to the five modes is as follows: .

[0074]

[0075] In the formula P C1 To P C5— System critical power under 5 modes.

[0076] R — Set of transformer area sequences, R={1,2,3,4,5}.

[0077] q,b — represent the station area number, q∈R.

[0078] S T— Rated capacity of transformer (kVA).

[0079] P pvq— Power generation of a single microgrid q photovoltaic array (kW).

[0080] P alq— AC load power (kW) of the transformer area q.

[0081] P dlq— DC load power (kW) of the transformer area.

[0082] Where m and n represent the station area numbers that experienced a fault, and i is the number of stations that did not experience a fault. m, n ∈ R and m ≠ n. In mode 4, if VSC m If damaged, then i=4, b∈R{m}. If VSC m and VSC n If all are damaged, then i=3, b∈R{m,n}. In mode 5, if transformer T m If damaged, then i=4. If transformer T... m and T n If all are damaged, then i=3.

[0083] (3) Battery state of charge

[0084] This invention employs a battery energy storage device to prevent overcharging, over-discharging, and frequent charging and discharging of the battery, thereby extending its service life. It introduces the concept of the battery's State of Charge (SOC).

[39] Its value is expressed as follows: .

[0085]

[0086] In the formula, SOC bat— Battery state of charge.

[0087] Q remain— The remaining charge in the battery.

[0088] Q rated— The rated charge capacity of the battery.

[0089] Assuming the initial SOC of the battery is 100%, and its charge / discharge thresholds are set to 20% and 80% respectively, i.e., SOC min =20%, SOC max =80%.

[0090] Batteries should avoid frequent charging and discharging to ensure their lifespan. When system power is excessive, if the state of charge (SOC) is low... bat <SOC max The battery will charge if necessary, otherwise it will remain in standby mode; when the system power is insufficient, if the SOC... bat ≤SOCmin The battery will then be in standby mode; otherwise, it will discharge.

[0091] Step 2, Multi-dimensional Mode Classification: Based on the fault type and the system state parameters obtained in Step 1, the power grid operation mode is divided into 5 main modes and sub-modes:

[0092] Step 3: Power regulation based on balanced load: According to the mode division results in Step 2, the control module calls the corresponding regulation formula to adjust the VSC power.

[0093] Step 4: Mode Switching and Dynamic Optimization

[0094] The transformer load rate is monitored in real time. When a mode switching condition is detected, the control module completes the switching of the control formula within 100ms to ensure that the transformer load rate fluctuation is ≤5% during the switching process.

[0095] This invention employs a load balancing control strategy. In power systems where multiple transformers operate in parallel, using a load balancing distribution strategy can significantly reduce total system losses and improve economic efficiency.

[0096] The copper loss of each transformer increases proportionally to the square of its load rate. When multiple transformers share the total load, uneven load distribution will cause some transformers to bear a higher load rate, resulting in a sharp increase in their copper losses due to the square relationship. The reduction in losses of lightly loaded transformers cannot offset this non-linear increase, leading to an increase in the overall copper loss of the system. Conversely, if a load balancing strategy is used to make the load rates of all transformers uniform, the copper losses of all transformers will be at the same and lower level. At this point, the overall system loss reaches its minimum.

[0097] From an economic perspective, load balancing not only directly reduces power loss and saves operating costs, but also prevents some transformers from accelerating insulation aging due to long-term overload, extending equipment life and reducing maintenance and replacement costs.

[0098] Assuming the total load is represented by S, and the transformer short-circuit loss is represented by P. d All transformers have the same load power factor. Under the condition of unbalanced loads on the transformers, assume the load factors of transformers 1, 2, ..., n are β1, β2, ..., βn, respectively. n The output power of each transformer is S1, S2, ..., S... n The sum of the output power values ​​of n transformers is S, as shown in the following formula. As shown.

[0099]

[0100] At this time, the total copper loss P of the n transformers cu1 As shown in the following formula As shown.

[0101]

[0102] When n transformers have the same load rate, the output power of each transformer is S. b The load factor β of each transformer b As shown in the formula As shown.

[0103]

[0104] At this time, the total copper loss P of n transformers cu2 As shown in the following formula .

[0105]

[0106] The difference ΔP between equations (2-4) and (2-6) cu The following formula is used: .

[0107]

[0108] In the formula In the case where β1=β2=……=β n =β p Then ΔP cu =0, if β1, β2,...,β n If not all are equal, then ΔP cu >0.

[0109] Therefore, if the load rates of n transformers are equal, the total copper loss of the transformers will be minimized, the transformer losses will be smaller, and the economy will be greater.

[0110] Taking into account fault modes, critical power, battery state of charge, and transformer overload, the following modes can be identified. To reduce the number of modes, a maximum of two transformers will be considered simultaneously under overload, or two distribution areas will experience VSC faults or transformer faults simultaneously.

[0111] The division between Mode 1 and Mode 3 is as follows: Figure 4 As shown, i represents the mode number, i∈{1,3}. j, k represent the station area numbers, j,k∈R, and j≠k.

[0112] The partitioning results of Mode 2 are as follows Figure 5 As shown.

[0113] The partitioning results of Mode 4 are as follows Figure 6As shown, m and n represent the station area numbers, m and n ∈ R, and m ≠ n.

[0114] The partitioning results of Mode 5 are as follows Figure 7 As shown, m and n represent the station area numbers, m and n ∈ R, and m ≠ n.

[0115] The system's basic control strategy is a load balancing control strategy to reduce overall losses and achieve economical operation. vsc This represents the power flowing through VSC. When P vsc When the signal is positive, the DC microgrid supplies power to the AC load through the VSC; conversely, when the signal is negative, the AC microgrid supplies power to the DC microgrid. z and q represent the transformer substation numbers. z ∈ R{j,k}, q ∈ R. P batq This indicates the charging and discharging power (kW) of the battery in the q-zone.

[0116] (1) Mode 1 power transfer analysis

[0117] At this point, the system is in a flexible interconnection state.

[0118] Mode 1-1: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0119] Modes 1-2: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0120] Modes 1-3: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0121] Modes 1-4: System power excess, SOC bat ≤SOC max P acj ≤0.8S T Pack ≤0.8S T P acz ≤0.8S T .

[0122] The specific adjustments for modes 1-1 to 1-4 are as follows: As shown.

[0123]

[0124] Modes 1-5: System power excess, SOC bat SOC max P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0125] Modes 1-6: System power excess, SOC bat SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0126] Modes 1-7: System power excess, SOC bat SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0127] Modes 1-8: System power excess, SOC bat SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T

[0128] The specific adjustments for modes 1-5 to 1-8 are as follows: As shown.

[0129]

[0130] Modes 1-9: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0131]

[0132] Modes 1-10: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0133]

[0134] In the formula, b represents the microgrid sequence number, b∈R\{j}.

[0135] Modes 1-11: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0136]

[0137] In the formula, b represents the microgrid sequence number, b∈R\{k}.

[0138] Modes 1-12: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0139]

[0140] Modes 1-13: System power deficit, SOC bat SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0141]

[0142] Modes 1-14: System power deficit, SOC bat SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0143]

[0144] In the formula, b represents the microgrid sequence number, b∈R\{j}.

[0145] Modes 1-15: System power deficit, SOC bat SOC min P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0146]

[0147] In the formula, b represents the microgrid sequence number, b∈R\{k}.

[0148] Modes 1-16: System power deficit, SOC bat SOC min P acj ≤0.8ST P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0149]

[0150] (2) Mode 2 power transfer analysis

[0151] At this time, the system is in an AC bus fault state, P acq =0.

[0152] Mode 2-1: System power excess, SOC bat ≤SOC max The specific control of this mode is as follows: As shown.

[0153]

[0154] Mode 2-2: System power excess, SOC bat SOC max The specific control of this mode is as follows: As shown.

[0155]

[0156] Modes 2-3: System power deficit, SOC bat ≤SOC min The specific control of this mode is as follows: As shown.

[0157]

[0158] Modes 2-4: System power deficit, SOC bat SOC min The specific control of this mode is as follows: As shown.

[0159]

[0160] (3) Mode 3 power transfer analysis

[0161] The system is currently in a DC bus fault state.

[0162] Mode 3-1: System power excess, SOC bat ≤SOCmax P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0163] Mode 3-2: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0164] Mode 3-3: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0165] Modes 3-4: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0166] The specific adjustments from Mode 3-1 to Mode 3-4 are as follows: As shown.

[0167]

[0168] Modes 3-5: System power excess, SOC bat SOC max P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0169] Modes 3-6: System power excess, SOC bat SOC max P acj>0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0170] Modes 3-7: System power excess, SOC bat SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0171] Modes 3-8: System power excess, SOC bat SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0172] The specific adjustments from Mode 3-5 to Mode 3-8 are as follows: As shown.

[0173]

[0174] Modes 3-9: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0175] Mode 3-10: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0176] Mode 3-11: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T Pack >0.8S T P acz ≤0.8S T .

[0177] Mode 3-12: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0178] The specific adjustments from Mode 3-9 to Mode 3-12 are as follows: As shown.

[0179]

[0180] Mode 3-13: System power deficit, SOC bat SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0181] Mode 3-14: System power deficit, SOC bat SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0182] Mode 3-15: System power deficit, SOC bat SOC min P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0183] Mode 3-16: System power deficit, SOC bat SOC min P acj ≤0.8S T P ack ≤0.8ST P acz ≤0.8S T .

[0184] The specific adjustments from Mode 3-13 to Mode 3-16 are as follows: As shown.

[0185]

[0186] (4) Mode 4 power transfer analysis

[0187] The system is currently in a VSC fault state.

[0188] 1) When there is one VSC failure, P VSCm =0.

[0189] Mode 4-1: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0190] Mode 4-2: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0191] Mode 4-3: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0192] Mode 4-4: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0193] The specific adjustments from Mode 4-1 to Mode 4-4 are as follows: As shown.

[0194]

[0195] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0196] Modes 4-5: System power excess, SOC bat SOC max P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0197] Modes 4-6: System power excess, SOC bat SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0198] Modes 4-7: System power excess, SOC bat SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0199] Modes 4-8: System power excess, SOC bat SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0200] The specific adjustments from Mode 4-7 to Mode 4-8 are as follows: As shown.

[0201]

[0202] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0203] Modes 4-9: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0204] If m≠j≠k, then the specific control of this mode is as follows: As shown.

[0205]

[0206] In the formula, b represents the microgrid sequence number, b∈R\{m,j,k}.

[0207] If m=j, then the specific control of this mode is as follows: As shown.

[0208]

[0209] In the formula, b represents the microgrid sequence number, b∈R\{m,k}.

[0210] If m=k, then the specific control of this mode is as follows: As shown.

[0211]

[0212] In the formula, b represents the microgrid sequence number, and b∈R\{m,j}.

[0213] Mode 4-10: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0214] If m=j, then the specific control of this mode is as follows: As shown.

[0215]

[0216] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0217] If m≠j, then the specific control of this mode is as follows: As shown.

[0218]

[0219] In the formula, b represents the microgrid sequence number, and b∈R\{m,j}.

[0220] Mode 4-11: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0221] If m=k, then the specific control of this mode is as follows: As shown.

[0222]

[0223] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0224] If m≠k, then the specific control of this mode is as follows: As shown.

[0225]

[0226] In the formula, b represents the microgrid sequence number, b∈R\{m,k}.

[0227] Mode 4-12: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0228]

[0229] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0230] Mode 4-13: System power deficit, SOC bat ≤SOC min P acj >0.8S T Pack >0.8S T P acz ≤0.8S T .

[0231] If m≠j≠k, then the specific control of this mode is as follows: As shown.

[0232]

[0233] In the formula, b represents the microgrid sequence number, b∈R\{m,j,k}.

[0234] If m=j, then the specific control of this mode is as follows: As shown.

[0235]

[0236] In the formula, b represents the microgrid sequence number, b∈R\{m,k}.

[0237] If m=k, then the specific control of this mode is as follows: As shown.

[0238]

[0239] In the formula, b represents the microgrid sequence number, and b∈R\{m,j}.

[0240] Mode 4-14: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0241] If m=j, then the specific control of this mode is as follows: As shown.

[0242]

[0243] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0244] If m≠j, then the specific control of this mode is as follows: As shown.

[0245]

[0246] In the formula, b represents the microgrid sequence number, and b∈R\{m,j}.

[0247] Mode 4-15: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0248] If m=k, then the specific control of this mode is as follows: As shown.

[0249]

[0250] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0251] If m≠k, then the specific control of this mode is as follows: As shown.

[0252]

[0253] In the formula, b represents the microgrid sequence number, b∈R\{m,k}.

[0254] Mode 4-16: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0255]

[0256] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0257] 2) When there are two VSC failures, P VSCm =0, P VSCn =0.

[0258] Mode 4-17: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack >0.8ST P acz ≤0.8S T .

[0259] Mode 4-18: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0260] Mode 4-19: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0261] Mode 4-20: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0262] The specific adjustments from Mode 4-19 to Mode 4-20 are as follows: As shown.

[0263]

[0264] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0265] Mode 4-21: System power excess, SOC bat SOC max P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0266] Mode 4-22: System power excess, SOC bat SOC max P acj >0.8S TP ack ≤0.8S T P acz ≤0.8S T .

[0267] Mode 4-23: System power excess, SOC bat SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0268] Mode 4-24: System power excess, SOC bat SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0269] The specific adjustments from Mode 4-21 to Mode 4-24 are as follows: As shown.

[0270]

[0271] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0272] Mode 4-25: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0273] If m≠n≠j≠k, the specific control of this mode is as follows: As shown.

[0274]

[0275] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j,k}.

[0276] If m=j, n=k or m=k, n=j, then the specific control of this mode is as follows: As shown.

[0277]

[0278] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0279] If m=j, n≠k or m≠k, n=j, then the specific control of this mode is as follows: As shown.

[0280]

[0281] In the formula, b represents the microgrid sequence number, b∈R\{m,n,k}.

[0282] If m≠j, n=k or m=k, n≠j, the specific control of this mode is as follows: As shown.

[0283]

[0284] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j}.

[0285] Mode 4-26: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0286] If j=m or j=n, then the specific control of this mode is as follows: As shown.

[0287]

[0288] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0289] If j≠m≠n, then the specific control of this mode is as follows: As shown.

[0290]

[0291] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j}.

[0292] Mode 4-27: System power deficit, SOC bat ≤SOC min P acj≤0.8S T P ack >0.8S T P acz ≤0.8S T Let R = {1, 2, 3, 4, 5}, and j, k, z, b represent the microgrid sequence numbers, where j, k, z, b ∈ R and j ≠ k. z ∈ R\{j, k}.

[0293] If k=m or k=n, then the specific control of this mode is as follows: As shown.

[0294]

[0295] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0296] If k≠m≠n, then the specific control of this mode is as follows: As shown.

[0297]

[0298] In the formula, b represents the microgrid sequence number, b∈R\{m,n,k}.

[0299] Mode 4-28: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0300]

[0301] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0302] Mode 4-29: System power deficit, SOC bat SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0303] If m≠n≠j≠k, the specific control of this mode is as follows: As shown.

[0304]

[0305] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j,k}.

[0306] If m=j, n=k or m=k, n=j, then the specific control of this mode is as follows: As shown.

[0307]

[0308] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0309] If m=j, n≠k or m≠k, then the specific control of this mode is as follows: As shown.

[0310]

[0311] In the formula, b represents the microgrid sequence number, b∈R\{m,n,k}.

[0312] If m≠j, n=k or m=k, n≠j, then the specific control of this mode is as follows: As shown.

[0313]

[0314] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j}.

[0315] Mode 4-30: System power deficit, SOC bat SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0316] If j=m or j=n, then the specific control of this mode is as follows: As shown.

[0317]

[0318] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0319] If j≠m≠n, then the specific control of this mode is as follows: As shown.

[0320]

[0321] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j}.

[0322] Mode 4-31: System power deficit, SOC bat SOC min P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0323] If k=m or k=n, then the specific control of this mode is as follows: As shown.

[0324]

[0325] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0326] If k≠m≠n, then the specific control of this mode is as follows: As shown.

[0327]

[0328] In the formula, b represents the microgrid sequence number, b∈R\{m,n,k}.

[0329] Mode 4-32: System power deficit, SOC bat SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0330]

[0331] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0332] (5) Mode 5 power transfer analysis

[0333] The system is currently in a transformer fault state.

[0334] 1) When one transformer fails, P VSCm =0.

[0335] Mode 5-1: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0336] Mode 5-2: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0337] Mode 5-3: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0338] Mode 5-4: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0339] The specific adjustments for modes 5-1 to 5-4 are as follows: As shown.

[0340]

[0341] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0342] Mode 5-5: System power excess, SOC bat SOC max P acj >0.8S T P ack >0.8ST P acz ≤0.8S T .

[0343] Modes 5-6: System power excess, SOC bat SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0344] Modes 5-7: System power excess, SOC bat SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0345] Modes 5-8: System power excess, SOC bat SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0346] The specific adjustments from Mode 5-5 to Mode 5-8 are as follows: As shown

[0347]

[0348] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0349] Modes 5-9: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0350] If m≠j≠k, then the specific control of this mode is as follows: As shown.

[0351]

[0352] In the formula, b represents the microgrid sequence number, b∈R\{m,j,k}.

[0353] If m=j, then the specific control of this mode is as follows: As shown.

[0354]

[0355] In the formula, b represents the microgrid sequence number, b∈R\{m,k}.

[0356] If m=k, then the specific control of this mode is as follows: As shown.

[0357]

[0358] In the formula, b represents the microgrid sequence number, and b∈R\{m,j}.

[0359] Modes 5-10: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0360] If m=j, then the specific control of this mode is as follows: As shown.

[0361]

[0362] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0363] If m≠j, then the specific control of this mode is as follows: As shown.

[0364]

[0365] In the formula, b represents the microgrid sequence number, and b∈R\{m,j}.

[0366] Modes 5-11: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack >0.8S T P acz≤0.8S T .

[0367] If m=k, then the specific control of this mode is as follows: As shown.

[0368]

[0369] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0370] If m≠k, then the specific control of this mode is as follows: As shown.

[0371]

[0372] In the formula, b represents the microgrid sequence number, b∈R\{m,k}.

[0373] Modes 5-12: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0374]

[0375] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0376] Mode 5-13: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0377] If m≠j≠k, then the specific control of this mode is as shown in the formula.

[0378]

[0379] In the formula, b represents the microgrid sequence number, b∈R\{m,j,k}.

[0380] If m=j, then the specific control of this mode is as follows: As shown.

[0381]

[0382] In the formula, b represents the microgrid sequence number, b∈R\{m,k}.

[0383] If m=k, then the specific control of this mode is as follows: As shown.

[0384]

[0385] In the formula, b represents the microgrid sequence number, and b∈R\{m,j}.

[0386] Mode 5-14: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0387] If m≠j, then the specific control of this mode is as follows: As shown.

[0388]

[0389] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0390] If m≠j, then the specific control of this mode is as follows: As shown.

[0391]

[0392] In the formula, b represents the microgrid sequence number, and b∈R\{m,j}.

[0393] Modes 5-15: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0394] If m=k, then the specific control of this mode is as follows: As shown.

[0395]

[0396] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0397] If m≠k, then the specific control of this mode is as follows: As shown.

[0398]

[0399] In the formula, b represents the microgrid sequence number, b∈R\{m,k}.

[0400] Modes 5-16: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0401]

[0402] In the formula, b represents the microgrid sequence number, and b∈R{m}.

[0403] 2) When two transformers fail, P VSCm =0, P VSCn =0.

[0404] Mode 5-17: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0405] Mode 5-18: System power excess, SOC bat ≤SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0406] Mode 5-19: System power excess, SOC bat ≤SOCmax P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0407] Mode 5-20: System power excess, SOC bat ≤SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0408] The specific adjustments from Mode 5-17 to Mode 5-20 are as follows: As shown.

[0409]

[0410] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0411] Mode 5-21: System power excess, SOC bat SOC max P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0412] Mode 5-22: System power excess, SOC bat SOC max P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0413] Mode 5-23: System power excess, SOC bat SOC max P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0414] Mode 5-24: System power excess, SOC bat SOC max P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0415] The specific adjustments from Mode 5-21 to Mode 5-24 are as follows: As shown.

[0416]

[0417] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0418] Mode 4-25: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0419] If m≠n≠j≠k, then the specific regulation of this mode is as follows: As shown.

[0420]

[0421] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j,k}.

[0422] If m=j, n=k or m=k, n=j, then the specific control of this mode is as follows: As shown.

[0423]

[0424] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0425] If m=j, n≠k or m≠k, n=j, then the specific control of this mode is as follows: As shown.

[0426]

[0427] In the formula, b represents the microgrid sequence number, b∈R\{m,n,k}.

[0428] If m≠j and n=k, or m=k and n≠j, then the specific control of this mode is as follows: As shown.

[0429]

[0430] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j}.

[0431] Mode 4-26: System power deficit, SOC bat ≤SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0432] If j=m or j=n, then the specific control of this mode is as follows: As shown.

[0433]

[0434] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0435] If j≠m≠n, then the specific control of this mode is as follows: As shown.

[0436]

[0437] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j}.

[0438] Mode 4-27: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0439] If k=m or k=n, then the specific control of this mode is as follows: As shown.

[0440]

[0441] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0442] If k≠m≠n, then the specific control of this mode is as follows: As shown.

[0443]

[0444] In the formula, b represents the microgrid sequence number, b∈R\{m,n,k}.

[0445] Mode 4-28: System power deficit, SOC bat ≤SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown.

[0446]

[0447] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0448] Mode 4-29: System power deficit, SOC bat SOC min P acj >0.8S T P ack >0.8S T P acz ≤0.8S T .

[0449] If m≠n≠j≠k, then the specific regulation of this mode is as follows: As shown.

[0450]

[0451] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j,k}.

[0452] If m=j, n=k or m=k, n=j, then the specific control of this mode is as follows: As shown

[0453]

[0454] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0455] If m=j, n≠khuo, m≠k, n=j, then the specific control of this mode is as follows: As shown.

[0456]

[0457] In the formula, b represents the microgrid sequence number, b∈R\{m,n,k}.

[0458] If m≠j and n=k, or m=k and n≠j, then the specific control of this mode is as follows: As shown.

[0459]

[0460] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j}.

[0461] Mode 4-30: System power deficit, SOC bat SOC min P acj >0.8S T P ack ≤0.8S T P acz ≤0.8S T .

[0462] If j=m or j=n, then the specific control of this mode is as follows: As shown.

[0463]

[0464] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0465] If j≠m≠n, then the specific control of this mode is as follows: As shown.

[0466]

[0467] In the formula, b represents the microgrid sequence number, b∈R\{m,n,j}.

[0468] Mode 4-31: System power deficit, SOC bat SOC min P acj ≤0.8S T P ack >0.8S T P acz ≤0.8S T .

[0469] If k=m or k=n, then the specific control of this mode is as follows: As shown.

[0470]

[0471] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0472] If k≠m≠n, then the specific control of this mode is as follows: As shown

[0473]

[0474] In the formula, b represents the microgrid sequence number, b∈R\{m,n,k}.

[0475] Mode 4-32: System power deficit, SOC bat SOC min P acj ≤0.8S T P ack ≤0.8S T P acz ≤0.8S T The specific control of this mode is as follows: As shown

[0476]

[0477] In the formula, b represents the microgrid sequence number, b∈R\{m,n}.

[0478] Simulation verification:

[0479] 3.1 Parameter Settings

[0480] Simulation parameters were designed to verify the rationality and effectiveness of the proposed control strategy. The system voltage level, transformer rated capacity, VSC capacity, converter capacity, renewable photovoltaic output, and DC load are shown in Table 1 below.

[0481] Table 1 Simulation Parameters

[0482]

[0483] 3.2 Simulation Verification

[0484] (1) Mode 1

[0485] When P is set to [0.2, 1)s, al1 =70kW, P al2 =100kW, P al3=120kW, P al4 =130kW, P al5 =150kW, the control method proposed in this invention was not used during this stage; at [1,2)s, the control method proposed in this invention was used, and the transformer T1 to T5 was normally loaded; at [2,3)s, P al1 The load is increased to 200kW, T1 is under heavy load, and transformers T2 to T5 are under normal load; at [3,4]s, P al2 The load was increased to 200kW, with transformers T1 and T2 simultaneously under heavy load, while transformers T3 through T5 operated under normal load. The power changes for each unit are shown in Table 2. Simulation results are as follows: Figure 8 As shown.

[0486] Table 2 Power variations of various components under flexible interconnection mode

[0487]

[0488] It can be seen that the control method proposed in this invention was not used in the range [0.2, 1)s. In the range [1, 2)s, the system adopted the control method of this invention, achieving transformer load balancing. In the ranges [2, 3)s and [2, 3)s, the system had excess power; when the AC load in the distribution area was too high, the transformer could be unloaded and transformer load balancing could be achieved.

[0489] (2) Mode 2

[0490] When the time interval is set to [0.2, 1) s, using the control method proposed in this invention, transformers T1 to T5 operate under normal load and balanced load, and the system operates in mode 1; when the time interval is [1, 2) s, an AC bus fault occurs, and the system switches to mode 2. The microgrid prioritizes supplying power to DC loads, and then supplies power to AC loads. The power changes of each part when switching from mode 1 to mode 2 are shown in Table 3. Simulation results are as follows: Figure 9 As shown.

[0491] Table 3 Power changes during the switch from Mode 1 to Mode 2

[0492]

[0493] It can be seen that when the AC bus fails at [1,2)s, the distributed generation prioritizes supplying power to the DC load. The AC load is then powered by the distributed generation after the DC load demand is met.

[0494] (3) Mode 3

[0495] When the time is set to [0.2, 1) s, the system operates in mode 1; when the time is [1, 2) s, a DC bus fault occurs, and the system switches to mode 3; when the time is [2, 3) s, P al1 The load is increased to 200kW, T1 is under heavy load, and transformers T2 to T5 are under normal load; at [3,4]s, Pal2 The load is increased to 200kW, with transformers T1 and T2 simultaneously under heavy load, while transformers T3 through T5 operate under normal load. The microgrid prioritizes supplying power to the DC load, followed by the AC load. Power variations for each component are shown in Table 4. Simulation results are as follows: Figure 10 As shown.

[0496] Table 4 Power Changes During the Switch from Mode 1 to Mode 3

[0497]

[0498] It can be seen that at [1,2)s, a DC bus fault occurs, and distributed power sources prioritize supplying DC loads. AC loads are supplied through the distribution network, and distributed power sources also supply power while meeting the DC load demand. At [2,3)s, there is a power shortage in transformer area 1. To avoid overloaded operation of the transformer, some loads need to be disconnected or energy storage power supply needs to be activated. At [3,4)s, there are power shortages in transformer areas 1 and 2. To avoid overloaded operation of the transformer, some loads need to be disconnected or energy storage power supply needs to be activated.

[0499] (4) Mode 4

[0500] 1) VSC3 fault setting. At [0.2, 1)s, the system operates in mode 1; at [1, 2)s, VSC3 fault occurs, and the system switches to mode 4; at [2, 3)s, P... al1 The load is increased to 200kW, T1 is under heavy load, and transformers T2, T4, and T5 are under normal load; at [3,4]s, P al2 The load was increased to 200kW, with transformers T1 and T2 simultaneously under heavy load, while transformers T4 and T5 operated under normal load. The power changes for each component are shown in Table 5. Simulation results are as follows: Figure 11 As shown.

[0501] Table 5 Power Variation of Each Component under Flexible Interconnection Mode

[0502]

[0503] As can be seen, at [1,2)s, VSC3 fails, and the AC load of transformer area 3 needs to be powered through the distribution network. At [2,3)s, the load of transformer area 1 is too large. The control strategy proposed in this invention can achieve transformer load balancing and avoid transformer overload operation. At [3,4)s, the loads of transformer areas 1 and 2 are too large. The control strategy proposed in this invention can achieve transformer load balancing and avoid transformer overload operation.

[0504] 2) Both VSC3 and VSC4 fail simultaneously. When set to [0.2, 1) s, the system operates in mode 1; when set to [1, 2) s, VSC3 and VSC4 fail, and the system switches to mode 4; when set to [2, 3) s, P... al1The load is increased to 200kW, T1 is under heavy load, and transformers T2 and T5 are under normal load; at [3,4]s, P al2 The load is increased to 200kW, with transformers T1 and T2 simultaneously under heavy load, while transformer T5 operates under normal load. The power changes for each component are shown in Table 6. Simulation results are as follows: Figure 12 As shown.

[0505] Table 6 Power Variation of Each Component under Flexible Interconnection Mode

[0506]

[0507] It can be seen that at [1,2)s, VSC3 and VSC4 fail, and the AC loads of transformer substations 3 and 4 need to be powered through the distribution network. At [2,3)s, the load on transformer substation 1 is too high. The control strategy proposed in this invention can achieve transformer load balancing and avoid transformer overload operation. At [3,4)s, the loads on transformer substations 1 and 2 are too high. The control strategy proposed in this invention can achieve transformer load balancing and avoid transformer overload operation.

[0508] (5) Mode 5

[0509] 1) Transformer 3 fault. When set to [0.2, 1) s, the system operates in mode 1; when set to [1, 2) s, T3 fault occurs, and the system switches to mode 5; when set to [2, 3) s, P... al1 The load is increased to 200kW, T1 is under heavy load, and transformers T2, T4, and T5 are under normal load; at [3,4]s, P al2 The load was increased to 200kW, with transformers T1 and T2 simultaneously under heavy load, while transformers T4 and T5 operated under normal load. The power changes for each component are shown in Table 7. Simulation results are as follows: Figure 13 As shown.

[0510] Table 7 Power Variation of Each Component under Flexible Interconnection Mode

[0511]

[0512] As can be seen, at [1,2)s, T3 fails, and the AC load of transformer area 3 needs to be powered through VSC. At [2,3)s, the load of transformer area 1 is too large. The control strategy proposed in this invention can achieve transformer load balancing and avoid transformer overload operation. At [3,4)s, the loads of transformer areas 1 and 2 are too large, and the system power is insufficient. To avoid transformer overload operation, it is necessary to disconnect part of the load or start energy storage power supply.

[0513] 2) Transformer 3 and Transformer 4 malfunction. When set to [0.2, 1) s, the system operates in mode 1; when set to [1, 2) s, T3 and T4 malfunction, and the system switches to mode 5; when set to [2, 3) s, P... al1The load is increased to 200kW, T1 is under heavy load, and transformers T2 to T5 are under normal load; at [3,4]s, P al2 The load was increased to 200kW, with transformers T1 and T2 simultaneously under heavy load, while transformers T3 through T5 operated under normal load. The power changes for each component are shown in Table 8. Simulation results are as follows: Figure 14 As shown.

[0514] Table 8 Power Variation of Each Component under Flexible Interconnection Mode

[0515]

[0516] It can be seen that at [1,2)s, T3 and T4 are faulty, and the AC loads in areas 3 and 4 need to be powered through VSC. At [2,3)s, the load in area 1 is too large, and the system power is insufficient. To avoid the transformer from operating under heavy load, it is necessary to disconnect part of the load or start energy storage power supply. At [3,4)s, the loads in areas 1 and 2 are too large, and the system power is insufficient. To avoid the transformer from operating under heavy load, it is necessary to disconnect part of the load or start energy storage power supply.

[0517] A second aspect of the present invention provides a power grid operation mode classification and power balancing device considering multiple types of states, comprising:

[0518] The system status parameter acquisition module is used to acquire system status parameters, including transformer overload, system critical power (PC), and battery state of charge (SOC). bat ;

[0519] The multi-dimensional mode division module is used to divide the power grid operation mode into 5 main modes and sub-modes based on the fault type and the acquired system state parameters.

[0520] The power regulation block based on load balancing is used by the control module to adjust the VSC power according to the mode division results and the corresponding regulation formula.

[0521] The mode switching and dynamic optimization module is used to monitor the transformer load rate in real time. When the mode switching condition is detected, the control module completes the switching of the control formula within 100ms to ensure that the transformer load rate fluctuation is ≤5% during the switching process.

[0522] Another aspect of the present invention provides a power grid operation mode division and power balance system that considers multiple types of states, including: a computer-readable storage medium and a processor;

[0523] The computer-readable storage medium is used to store executable instructions;

[0524] The processor is used to read executable instructions stored in the computer-readable storage medium and execute the grid operation mode division and power balance method considering multiple states as described in the first aspect.

[0525] In another aspect, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the grid operation mode division and power balance method considering multiple types of states described in the first aspect.

[0526] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0527] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0528] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0529] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0530] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A power grid operation mode partitioning and power balancing method considering multiple types of states, characterized in that, The method comprises the following steps: Step 1, obtaining system state parameters: the system state parameters include transformer overload, system critical power PC, battery state of charge SOC bat ; Step 2, multi-dimensional mode division: based on the fault type and the system state parameters obtained in step 1, the power grid operation mode is divided into five main modes and sub-modes; Step 3, power regulation based on balanced load: according to the mode division result of step 2, the control module calls the corresponding regulation formula to adjust the VSC power: Step 4: mode switching and dynamic optimization real-time monitoring transformer load rate, when the mode switching condition is detected, the control module completes the regulation formula switching within 100ms, ensuring that the transformer load rate fluctuation is less than or equal to 5% during the switching process.

2. The method of claim 1, wherein: In the step 2, the multi-dimensional mode division, based on the fault type and the system state parameters obtained in step 1, the power grid operation mode is divided into five main modes and sub-modes, specifically including: Mode 1, flexible interconnection mode: no fault, according to the number of heavy load area, system critical power PC and battery state of charge SOC bat Subdivided into 16 sub-modes; Mode 2 is an AC bus fault mode: all substation transformers are off-grid, distributed power supplies priority to DC load, and the remaining power to AC load; Mode 3 is a DC bus fault mode: no energy exchange between microgrids, AC load is jointly supplied by distribution network and distributed power supply; Mode 4 is a VSC fault mode: 1 or 2 VSCs are faulty, the AC load of the faulty substation is supplied by the distribution network, and the non-faulty substation balances the load through VSC; Mode 5 is a transformer fault mode: 1 or 2 transformers are faulty, the AC load of the faulty substation is supplied by the non-faulty substation VSC.

3. The method of claim 1, wherein: The step 3 specifically comprises: when power is excessive and SOC bat ≤ SOC max , preferentially transferring power of the heavy-load area to the light-load area through the VSC, and charging the energy storage; when power is insufficient and SOC bat > SOC min , jointly regulating through discharging of the energy storage and power transfer of the VSC; wherein SOC min is a charging threshold of the battery, and SOC max is a discharging threshold of the battery.

4. The method of claim 3, wherein: In step 3, the load transformer loss is minimized when the load is balanced, and the load transformer loss is minimized by setting n transformer load rates to be equal.

5. A power grid operation mode partitioning and power balancing device considering multiple types of states, characterized in that, It comprises: The system state parameter acquisition module is configured to acquire system state parameters, wherein the system state parameters include transformer overload, system critical power PC, and battery state of charge SOC bat ; A multi-dimensional mode division module for dividing the power grid operation mode into five main modes and sub-modes based on the fault type and the obtained system state parameters; A power regulation block based on balanced load for adjusting the VSC power according to the mode division result by calling the corresponding regulation formula by the control module: A mode switching and dynamic optimization module for real-time monitoring of transformer load rate, when the mode switching condition is detected, the control module completes the regulation formula switching within 100ms, ensuring that the transformer load rate fluctuation is less than or equal to 5% during the switching process.

6. The apparatus of claim 5, wherein: The multi-dimensional mode division module divides the power grid operation mode into five main modes and sub-modes based on the fault type and the obtained system state parameters, specifically including: Mode 1, flexible interconnection mode: no fault, according to the number of heavy load area, system critical power PC and battery state of charge SOC bat Subdivided into 16 sub-modes; Mode 2 is an AC bus fault mode: all substation transformers are off-grid, distributed power supplies priority to DC load, and the remaining power to AC load; Mode 3 is a DC bus fault mode: no energy exchange between microgrids, AC load is jointly supplied by distribution network and distributed power supply; Mode 4 is a VSC fault mode: 1 or 2 VSCs are faulty, the AC load of the faulty substation is supplied by the distribution network, and the non-faulty substation balances the load through VSC; Mode 5 is a transformer fault mode: 1 or 2 transformers are faulty, the AC load of the faulty substation is supplied by the non-faulty substation VSC.

7. The apparatus of claim 5, wherein: The power regulation block based on balanced load controls the module to call the corresponding regulation formula to adjust the VSC power according to the mode division result, specifically including: power surplus and SOC bat ≤ SOC max : preferentially transfer the heavy load area power to the light load area through the VSC, and charge the energy storage; power shortage and SOC bat > SOC min : joint regulation through energy storage discharge and VSC power transfer; wherein SOC min is the battery charging threshold, and SOC max is the battery discharge threshold.

8. The apparatus of claim 7, wherein: When the load is balanced, the load transformer loss is minimized, and the load transformer loss is minimized by setting n transformer load rates to be equal.

9. A power grid operation mode partitioning and power balancing system considering multiple types of states, comprising: A computer readable storage medium and a processor; The computer readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer readable storage medium, and execute the power grid operation mode partitioning and power balancing method considering multiple types of states according to any one of claims 1-4. 10.A non-transitory computer readable storage medium having stored thereon a computer program, the computer program being executed by a processor to implement the power grid operation mode partitioning and power balancing method considering multiple types of states according to any one of claims 1-4.

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