Flexible interconnected power distribution network fault recovery method and system based on mobile energy storage cooperation

Abstract

The invention provides a flexible interconnected power distribution network fault recovery method and system based on mobile energy storage cooperation, and the method comprises the steps: obtaining a fault position of a flexible interconnected power distribution network, constructing a first-stage optimization model based on island division and network reconstruction, and carrying out the first-stage fault recovery of the power distribution network; and if the unrecovered load exists, carrying out optimization scheduling on the mobile energy storage, building a second-stage optimization model based on island division, network reconstruction and mobile energy storage collaboratively, and carrying out second-stage fault recovery on the power distribution network until the fault recovery of the place where the fault occurs is completed. By introducing mobile energy storage, staged power supply recovery is realized, and the recovery effect is improved; the relaxation operation simplifies the calculation and improves the solving efficiency, thereby effectively reducing the power loss load and network loss, enhancing the fault handling capacity of the power distribution network, guaranteeing the power supply reliability, and providing powerful support for the stable operation of a power system.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network fault recovery, and in particular to a flexible interconnected distribution network fault recovery method and system based on mobile energy storage collaboration. Background Art

[0002] The distribution system directly faces thousands of households, and its fault recovery ability directly affects the power supply reliability of users. With the rapid development of power electronics technology, as an innovative distribution network structure, the flexible interconnected distribution network breaks the physical limitations of the traditional distribution network through power electronics technology, realizes flexible power scheduling, power flow optimization and fault isolation between different regions, and is becoming an effective solution in the distribution network fault recovery strategy.

[0003] Due to its flexibility and portability, Mobile Energy Storage System (MESS) plays an increasingly important role in the modern energy system. In the flexible interconnected distribution network, the power of the mobile energy storage can be transmitted to the fault area through the flexible interconnection device, thus reducing the rescue time when it is difficult for the mobile energy storage vehicle to directly drive to the fault point for power supply in case of traffic obstruction caused by disasters, etc., and further reducing the power outage time.

[0004] The application of new devices such as flexible interconnection devices and mobile energy storage vehicles enriches the means of distribution network fault recovery. However, the differences in the working characteristics of different fault recovery devices increase the difficulty of fault recovery.

[0005] Most of the existing flexible interconnected AC / DC distribution network fault recovery strategies are solved based on island division and network reconfiguration. Although mobile energy storage is introduced for auxiliary recovery in some cases, phased fault recovery is not involved, and it is difficult to perform accurate and efficient recovery operations according to the characteristics of different fault stages, which affects the overall recovery efficiency and effect. At the same time, it is difficult to relax the constraint conditions, making the handling of relevant electrical parameter constraints less flexible and accurate. It may lead to the fact that the fault recovery scheme is difficult to meet the strict electrical constraint conditions during actual operation, reducing the safety and stability of the distribution network operation. In addition, most of the existing technologies currently use electric buses and electric taxis as mobile energy storage devices to participate in the distribution network fault recovery strategy, and often only consider a single strategy of network reconfiguration or mobile energy storage, ignoring the energy loss problem of these devices during the movement process. This not only reduces the utilization efficiency of the mobile energy storage device, but also further reduces the distribution network fault recovery ability. Summary of the Invention

[0006] To solve the above problems, the present invention proposes a flexible interconnected distribution network fault recovery method and system based on mobile energy storage collaboration, and gives a two-stage fault recovery strategy for the flexible interconnected distribution network based on island division, network reconfiguration and mobile energy storage collaboration: in the first stage, the load is quickly restored to power by using island division, network reconfiguration and the power of flexible interconnected devices; in the second stage, considering conditions such as the access location and deployment time of mobile energy storage vehicles, different access points of mobile energy storage vehicles are optimized, and through the coordinated cooperation of mobile energy storage vehicles and flexible interconnected devices, the fault recovery rate is improved.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a flexible interconnected distribution network fault recovery method based on mobile energy storage collaboration, including:

[0009] Obtain the fault location of the flexible interconnected distribution network, construct a first-stage optimization model based on island division and network reconfiguration, and perform the first-stage fault recovery on the distribution network;

[0010] If there is unrecovered load, through the optimal scheduling of mobile energy storage, construct a second-stage optimization model based on island division, network reconfiguration and mobile energy storage collaboration, and perform the second-stage fault recovery on the distribution network until the fault at the fault location is repaired.

[0011] Preferably, the obtaining of the fault location of the flexible interconnected distribution network is specifically: obtaining the parameters of the flexible interconnected distribution network, judging whether a fault occurs based on a preset threshold, and cutting off the fault to obtain the fault location.

[0012] Preferably, the first-stage optimization model takes the least lost load, the least total loss of the restored distribution network and the least number of switch actions as the recovery objectives, and sets the first constraint conditions for construction;

[0013] The first constraint conditions include system power flow constraints, system security constraints, distribution network network topology structure constraints, DG type and output constraints, island power balance constraints, and active power and capacity constraints of flexible interconnected devices.

[0014] Preferably, based on the system power flow constraint, the big M method is introduced into the variant forms of Ohm's law and power definition, and variable equivalent substitution is performed on the voltage square term and the current square term, specifically:

[0015]

[0016] Among them, r ij 、x ij respectively represent the equivalent resistance and equivalent reactance of the distribution network line ij; P ij represents the active power flowing through the line ij; Qij Denote the reactive power flowing through line ij; I ij Denote the current flowing through line ij; U i , U j Denote the voltages at nodes i and j respectively; m ij Is an auxiliary variable in the big M method and is a very large integer; z ij Is a binary variable, taking 1 when the line switch is closed and 0 when it is open. That is, for a disconnected line z ij = 0, m ij Takes a very large value, the constraint term is relaxed, and the node voltages at both ends of the branch are uncorrelated. For a closed line z ij = 1, that is, ignoring the m ij Term in the constraint condition; Only when the line switch is closed, that is, z ij Takes 1, will there be a constraint on the terminal voltage.

[0017] Preferably, the second-order cone relaxation method is used to relax the power flow constraints of the system.

[0018] Preferably, the second-stage optimization model takes the shortest repair time and the least load outage time as the restoration objectives, and constructs with the second constraint conditions set;

[0019] The second constraint conditions include the first constraint condition and the mobile energy storage discharge and capacity constraints.

[0020] Preferably, the restoration objectives of the second-stage optimization model are specifically:

[0021]

[0022] Among them, P Loss,i Denote the lost load of M and N types of loads, T all Is the total time required for manual repair of the fault after the fault occurs; T s Is the load outage time when the load is not connected to the power outage area during the mobile energy storage scheduling process; The T s Includes the deployment time of the mobile energy storage vehicle

[0023]

[0024] Among them, D represents the distance between the mobile energy storage and the power outage area; α ME And λ s Represent the mobile speed coefficient and the correction coefficient respectively during the mobile energy storage scheduling process; α ME Is affected by the road traffic conditions, vehicle performance and road conditions during the mobile energy storage vehicle scheduling process, and λ s Is affected by weather conditions and the charge and discharge state factors of the mobile energy storage vehicle.

[0025] In a second aspect, the present invention provides a flexible interconnected distribution network fault recovery system based on mobile energy storage collaboration, including:

[0026] A first-stage recovery module configured to obtain the fault location of the flexible interconnected distribution network, construct a first-stage optimization model based on island division and network reconfiguration, and perform first-stage fault recovery on the distribution network;

[0027] A second-stage recovery module configured to, if there are unrecovered loads, optimize the scheduling of mobile energy storage, construct a second-stage optimization model based on the collaboration of island division, network reconfiguration and mobile energy storage, and perform second-stage fault recovery on the distribution network until the fault at the fault location is repaired.

[0028] In a third aspect, the present invention provides a computer-readable storage medium with a computer program stored thereon, and when the program is executed by a processor, the steps in a method for fault recovery of a flexible interconnected distribution network based on mobile energy storage collaboration described in the first aspect are implemented.

[0029] In a fourth aspect, the present invention provides a computer device including a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, the steps in a method for fault recovery of a flexible interconnected distribution network based on mobile energy storage collaboration described in the first aspect are implemented.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] The present invention realizes two-stage recovery by introducing mobile energy storage. In the first stage, island division and network reconfiguration are used in combination with the power of flexible interconnection devices to quickly restore power supply to some loads. When the restoration is not complete, in the second stage, mobile energy storage is used to further optimize the power supply. This phased recovery method effectively improves the fault recovery rate and is more flexible and comprehensive than traditional single strategies. At the same time, relaxation operations adopted in model construction, such as introducing the big M method into power flow constraints and performing second-order cone relaxation processing, can simplify the calculation process, transform the complex mixed-integer nonlinear programming model into a second-order cone programming model that can be efficiently solved, greatly improve the solution efficiency, reduce the consumption of computing resources, and provide a more efficient and accurate solution for distribution network fault recovery.

[0032] The present invention realizes the coordination of mobile energy storage with islanding division and network reconfiguration. In the initial stage of a fault, islanding division and network reconfiguration can quickly isolate the fault area, transfer power using flexible interconnection devices, and reduce the load loss of power outage. However, relying solely on this, the recovery ability is limited, and the addition of mobile energy storage can make up for the deficiency. Considering the flexible deployment characteristics of mobile energy storage, it can be scheduled to the power outage area according to the actual situation. After islanding division, if the power in the island is insufficient, mobile energy storage can be used as a supplementary power source to ensure the stable operation of the island; during the process of network reconfiguration, mobile energy storage can also assist in adjusting the power distribution to enable the distribution network to return to the normal operation state faster. This coordination method greatly improves the fault recovery rate, effectively responds to complex faults, enhances the toughness and reliability of the distribution network, reduces the power outage time and losses of users, and provides strong support for improving the overall operation efficiency and power supply quality of the distribution network.

[0033] Advantages of additional aspects of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute a limitation to the present invention.

[0035] Figure 1 It is a main flowchart of a flexible interconnected distribution network fault recovery method based on mobile energy storage coordination provided by an embodiment of the present invention;

[0036] Figure 2 It is a schematic diagram of the scheduling of mobile energy storage MESS provided by an embodiment of the present invention;

[0037] Figure 3 It is a flowchart of a fault recovery strategy provided by an embodiment of the present invention;

[0038] Figure 4 It is the power supply states and their time relationships of three types of loads during fault recovery provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] Embodiment 1

[0041] As Figure 1 shown, this embodiment discloses a flexible interconnected distribution network fault recovery method based on mobile energy storage coordination, including the following steps:

[0042] S1: Obtain the fault location of the flexible interconnected distribution network, construct a first-stage optimization model based on islanding division and network reconfiguration, and perform the first-stage fault recovery on the distribution network;

[0043] S2: If there is un-restored load, through the optimal scheduling of mobile energy storage, a second-stage optimization model is constructed based on the coordination of island division, network reconfiguration, and mobile energy storage to perform the second-stage fault restoration of the distribution network until the fault at the fault location is repaired.

[0044] Next, combined with Figure 1 , a flexible interconnected distribution network fault restoration method based on the coordination of mobile energy storage disclosed in this embodiment will be described in detail.

[0045] (1) Fault strategy analysis of the distribution network with mobile energy storage and flexible interconnection devices

[0046] 1. Analysis of the role of the flexible interconnection device FID in the fault restoration process

[0047] As a flexible interconnection device widely used in the current distribution network, the intelligent soft switch SOP can expand the power supply restoration range on the fault side and provide effective voltage support when restoring power supply.

[0048] Under normal circumstances, the distribution network supplies power to users according to the established operation mode. However, when a fault occurs, different regions of the distribution network will appear in different states. Among them, the normal power supply area is the area that is not affected by the fault and has always maintained the normal power supply state. Its power equipment operates normally and can continuously supply power to the connected users; the fault area is the area where the fault actually occurs, and internal electrical equipment such as lines and transformers have faults such as short circuits and groundings, which is the source of power outages and distribution network abnormalities; the non-fault power outage area itself has normal equipment, but due to faults in other areas of the distribution network, this area has a power outage.

[0049] At this time, the intelligent soft switch SOP can flexibly deliver the electric energy in the non-fault area to the fault side by quickly adjusting its own operation state and changing the power flow direction and magnitude, thereby expanding the power supply restoration range on the fault side. At the same time, since the fault may cause voltage fluctuations, the SOP can provide voltage support for the fault area by adjusting the reactive power to ensure the normal operation of the equipment.

[0050] For the dual-terminal soft switch SOP, the control modes in its normal and fault operation states will be switched. That is, the operation mode in the normal operation state is the PQ-U dc Q control mode. When a fault occurs and is removed, the port connecting to the non-fault power outage area is switched to the V f control mode to support the voltage and load.

[0051] Among them, during normal operation, PQ-U dcThe Q control mode is mainly used to achieve precise control of active power, reactive power, and DC-side voltage to ensure the stable operation of the distribution network and power quality. When a fault occurs, the ports connecting the non-faulty power-loss areas switch to the V f control mode, which mainly realizes voltage support and load restoration for the power-loss areas by controlling the voltage V f to ensure that the equipment in this area can restart and operate at an appropriate voltage level.

[0052] When performing steady-state analysis of the power supply restoration of the distribution network, the non-faulty side U dc Q control can be equivalently processed as PQ control.

[0053] After a fault occurs in the distribution network, in order to restore power supply as soon as possible, the power-loss areas are usually isolated to form multiple islands. Island division is a key operation. It divides the distribution network into relatively independent parts according to the different regional states formed after fault location and fault isolation. In these islands, the access position and operating state of the flexible interconnection device SOP will have an important impact on the island division and fault recovery strategy. By equivalently processing the SOP under different access scenarios, the power balance and power supply restoration plan in the island can be analyzed and planned more accurately, improving the efficiency and reliability of the distribution network fault recovery.

[0054] Therefore, during the island division process of this embodiment, according to the power-loss areas formed after fault location and fault isolation in the distribution network, it can be divided into 3 scenarios based on the access position of its flexible interconnection device to obtain the equivalent processing method of the flexible interconnection device SOP during fault island division, so as to carry out the fault recovery strategy of the flexible distribution network in the strategy of this embodiment. The scenarios are as follows:

[0055] ① Both ends of the intelligent soft switch are outside the power-loss area;

[0056] ② One end of the intelligent soft switch is inside the power-loss area and the other end is outside the power-loss area;

[0057] ③ Both ends of the intelligent soft switch are inside the power-loss area.

[0058] According to the access situation of its flexible interconnection device during the fault, the processing of the SOP during the fault recovery island division needs to adopt different processing methods according to different situations. For scenarios ① and ③, the intelligent soft switch can be regarded as a line with limited power transmission. For scenario ②, if the power on the power supply side of the intelligent soft switch is sufficient, it can be regarded as a power source with the rated power of the intelligent soft switch inside the power-loss area. At this time, island division can be carried out at the access node of the intelligent soft switch.

[0059] This method of dividing and processing different scenarios according to the access location of the flexible interconnection device enables more reasonable utilization of the flexible interconnection device during the fault recovery process, optimizes power distribution and power flow direction, improves the adaptability and recovery ability of the distribution network under different fault conditions, and solves the problem of the lack of a flexible response mechanism in traditional distribution networks when facing faults.

[0060] 2. Optimal Scheduling for Fault Recovery with Mobile Energy Storage MESS Participation

[0061] In this embodiment, the optimal scheduling strategy for mobile energy storage to participate in fault recovery mainly focuses on the optimization of its spatio-temporal dynamic scheduling. As Figure 2 shown, for the power outage area after the fault of the flexible interconnected distribution network, combined with different access points of the mobile energy storage MESS, according to the scheduling time and traffic distance of the mobile energy storage MESS, through the optimal scheduling of the mobile energy storage in this area, the best access point and the optimal scheduling scheme of the mobile energy storage MESS are obtained, so that the fault of the distribution network can be most effectively restored.

[0062] 3. Fault Recovery Strategy for Flexible Interconnected Distribution Network with MESS Participation

[0063] Since relying solely on distribution network reconfiguration and islanding often results in low efficiency of fault recovery, the main process of the multi-stage recovery strategy for the fault of the flexible interconnected distribution network based on islanding, network reconfiguration and mobile energy storage collaboration proposed in this embodiment is as Figure 3 shown, specifically:

[0064] ① Obtain the fault location, first perform islanding and network reconfiguration on the flexible interconnected distribution network, and with the cooperation of the flexible interconnection device, restore the power supply of the distribution network.

[0065] ② If the load in the distribution network fails to be fully restored, optimize the scheduling of the local MESS to make it reach the fault recovery location for further power supply restoration.

[0066] ③ After the MESS arrives, perform islanding and network reconfiguration of the distribution network again to generate advanced islands and further restore power supply until the fault repair at the fault location is completed.

[0067] Under the condition of meeting the objectives of each fault recovery strategy, the objective function that the entire recovery process needs to meet is:

[0068]

[0069] In the formula, P Loss,i corresponds to Figure 4 the power outage load of the M and N types of loads in all ; T sIt is the power outage time of the load that is not connected to the power outage area during the mobile energy storage dispatching process.

[0070] Its objective function is to minimize the product of the power outage time in the fault power outage area and the power loss after restoration. It is necessary to consider both the dispatching time of the mobile energy storage and the fault recovery amount after the mobile energy storage arrives and the distribution network re-divides the island and reconstructs the network, so as to minimize the total power outage of the load.

[0071] Define three types of loads M, N, and G during the fault recovery process, where M is the set of loads that have not been restored during the entire fault recovery process, N is the set of loads restored during the second-stage fault recovery with the participation of mobile energy storage, and G is the set of loads that have been restored to power in the first stage. The relationship between various loads is as Figure 4 shown. Combined with Figure 2 the distribution network shown, assume that a fault occurs on the secondary side of transformer T2. After the first stage of loads 1 and 2, the fault recovery is completed. At the same time, by dispatching the MESS to supply power to node 4, nodes 3, 4, and 5 are restored to power, and node 6 fails to be restored. Then M = {6}, N = {3, 4, 5}, and G = {1, 2}.

[0072] (2) Flexible interconnected distribution network fault recovery model with the participation of mobile energy storage

[0073] 1. First-stage fault recovery model

[0074] In the first stage of fault recovery, load rapid power restoration is achieved by island division, network reconstruction, and flexible interconnection device power transfer. At this time, the mobile energy storage device does not participate in fault recovery.

[0075] (1) Objective function

[0076] During the distribution network fault recovery process, the core objective is to minimize the power outage load in the non-fault area, while also preventing an increase in network losses due to changes in the network structure. In addition, consider the life and operating costs of the operating switches. Therefore, the fault recovery model selects the minimum power outage load, the minimum total loss of the restored distribution network, and the minimum number of switch operations as the recovery objectives during the flexible interconnected distribution network fault reconstruction and island division process.

[0077]

[0078]

[0079] In the formula, P LOAD,i is the active power consumed by the load at node i; α i is the load recovery coefficient of node i; Ω iis the importance coefficient of the load of node i; N is the set of all nodes; B is the set of all branches, r ij is the equivalent resistance of the distribution network line ij, I ij is the current flowing through the line ij, P SOP,L,i is the converter loss connected to node i; The opening of the switch is represented by K i where K i = 0, K i = 1 represent that the switch is in the open state and the closed state respectively; S and T represent the sets of line tie switches and sectional switches respectively.

[0080] The weight value is solved by constructing a judgment matrix, and the constructed judgment matrix J is as follows.

[0081]

[0082] The objective function obtained by geometric mean method calculation is:

[0083] f d1 = 0.8182f 1 + 0.0909f 2 + 0.0909βf 3 (6)

[0084] In the formula, in order to keep the objective function at the same order of magnitude during the solution process, a coefficient β is introduced.

[0085] The setting of this objective function closely focuses on key aspects such as reducing the power outage load, reducing network losses, and protecting switches, providing a clear optimization direction for the fault recovery in the first stage, and effectively ensuring the stable recovery of the distribution network in the initial stage of the fault.

[0086] (2) Constraint conditions

[0087] ① System power flow constraint

[0088] Compared with the traditional power flow calculation method based on node power, the Disflow power flow calculation model is more suitable for the power flow calculation of radial distribution systems. Its power flow constraint equation is:

[0089]

[0090] In the formula, r ij , x ij respectively represent the equivalent resistance and equivalent reactance of the distribution network line ij; P ij represents the active power flowing through the line ij; Q ij represents the reactive power flowing through the line ij; I ij represents the current flowing through the line ij; U i 、U jrespectively represent the voltages at node i and node j; P j represents the equivalent active power flowing into the distribution network from the outside through node j; Q j represents the equivalent reactive power flowing into the distribution network from the outside through node j; P jk and Q jk respectively represent the active power and reactive power in the branch flowing from node j to node k; P DG,j and Q DG,j represent the active and reactive power outputs of the distributed power source at node j; P FID,j and Q FID,j respectively represent the active and reactive powers provided by the flexible interconnection device; P LOAD,j and Q LOAD,j respectively are the active power and reactive power consumed by the load at node j; α j is the load recovery coefficient of node j.

[0091] Meanwhile, for the line voltage drop balance equation, the big M method is introduced into the transformed forms of Ohm's law and power definition, and variable equivalent substitution is performed on the voltage square term and the current square term. The formula is as follows:

[0092]

[0093]

[0094] In the formula, m ij is the auxiliary variable in the big M method, which is a very large integer; z ij is a binary variable, which takes 1 when the line switch is closed and 0 when it is open. That is, for the line open, when z ij = 0, m ij takes a very large value, the constraint term is relaxed, and the node voltages at both ends of the branch are not related. For the line closed, when z ij = 1, the m ij term in the constraint condition can be ignored. Thus, it is obtained that only when the line switch is closed, that is, when z ij takes 1, will it impose a constraint on the terminal voltage.

[0095] This embodiment adopts the Disflow power flow calculation model and combines the big M method for variable equivalent substitution, improving the applicability and flexibility of the power flow calculation, being able to better handle the power flow constraints in the distribution network fault recovery process, and solving the problem that the traditional power flow calculation method is difficult to accurately apply in the case of faults. At the same time, the treatment of the voltage and current square terms makes the constraint conditions easier to solve, laying a foundation for the subsequent model optimization.

[0096] ② System security constraints

[0097] Both the node voltage and branch current need to satisfy safety constraints, which are as follows:

[0098]

[0099] In the formula, the upper and lower limit values of the voltage of node i are represented by U imin and U imax ; the maximum allowable current flowing through line ij is represented by I ijmax ; v i represents the square term of the voltage of node i, and μ ij represents the square term of the current of line ij.

[0100] The setting of system safety constraints ensures the electrical safety of the distribution network during the fault recovery process, prevents equipment damage or secondary faults caused by voltage or current exceeding the safety range, and can guarantee the stable operation of the distribution network.

[0101] ③ Distribution network network topology structure constraint

[0102] The entire network fault reconstruction and the divided islands should all satisfy the principle of radial operation. Its specific expression is:

[0103]

[0104] In the formula, Ω b is the set of all lines in the distribution network; Ω n is the set of all nodes in the system; Ω 0 is the set of source nodes in the distribution network. Under the premise of a single power source, there is one and only one; α t,ij is the operating state of branch ij at time t. Among them, α t,ij =0 means disconnected, and α t,ij =1 means operating; β t,ij is the subordinate relationship between nodes i and j at time t. Generally, it is defined in the form of a parent node. Among them, β t,ij =1 means that node i is the parent node of j at time t, that is, the power flows from node i to j, and β t,ij =0 means that node i is not the parent node of j at time t.

[0105] The distribution network network topology structure constraint ensures the rationality of the network structure after fault reconstruction and island division, maintains the normal operation logic of the distribution network, and helps to improve the efficiency and reliability of fault recovery.

[0106] ④ DG type and output constraint

[0107] The black start of the island needs DGs that can act as balancing nodes, that is, the island should contain DGs with droop control mode or V / f control mode.

[0108] 0 ≤ P Gi ≤ P Gi max (12)

[0109] Wherein, P Gi,max is the upper limit of the active power output of the i-th DG.

[0110] The DG type and output constraints provide necessary conditions for the stable operation of the island, ensuring that the distributed power supply can function properly in the island state, guaranteeing the power supply to the loads in the island, and improving the overall power supply capacity of the distribution network under fault conditions.

[0111] ⑤ Island power balance constraint

[0112] To ensure the stable operation of the system in the island state, the island needs to meet the power balance constraint.

[0113]

[0114] Where: P G is the active power of the i-th DG in the island; P D is the active power of the load; N g is the total number of DGs connected to the island; N A is the total number of loads incorporated into the island.

[0115] The island power balance constraint is the key to the stable operation of the island. By ensuring the balance between power supply and demand, it prevents voltage fluctuations or equipment failures caused by power imbalance in the island, and further enhances the recovery ability and stability of the distribution network after a fault.

[0116] ⑥ Active power and capacity constraints of the flexible interconnection device

[0117] Taking the two-terminal soft-switching SOP as an example, illustrate the transmission active power constraint and capacity constraint that it needs to meet.

[0118] The transmission active power constraint is:

[0119] P FID,i + P FID,j + P FID,L,i + P FID,L,j =0 (14)

[0120]

[0121]

[0122] Capacity constraint:

[0123]

[0124] Wherein, P FID,i 、PFID,j respectively represent the active power transmitted by the converters connected at nodes i and j; Q FID,i and Q FID,j respectively represent the reactive power transmitted by the converters connected at nodes i and j; P FID,L,i and P FID,L,j respectively represent the active power losses generated by the multi-terminal FID at nodes i and j; A FID,L,i and A FID,L,j represent the loss coefficients of the VSCs of the converters at nodes i and j; S FID,i and S FID,j respectively are the access capacities of the VSCs of the converters connected at nodes i and j.

[0125] The setting of the active power and capacity constraints of the flexible interconnection device ensures the safe and stable operation of the flexible interconnection device during the fault recovery process, enabling it to play a role within a reasonable power and capacity range, and avoiding affecting the fault recovery effect due to overload or insufficient performance.

[0126] (3) Second-order cone relaxation processing

[0127] Based on the substitution using the square terms of voltage and current above, further relaxation processing is performed on the constraint conditions in the power flow constraints, and its standard second-order cone constraint form can be obtained.

[0128]

[0129] At the same time, by converting the constraint conditions of the two-terminal SOP through the rotation cone constraint, the formula form of the second-order cone constraint that can be effectively solved can be obtained.

[0130]

[0131] The system power flow constraints involve complex electrical quantity relationships such as power, voltage, and current. In the calculation process, these quantities are coupled, and in actual operation, they are affected by various factors, with extremely high complexity; moreover, it is in a core position and directly determines the power transmission path and distribution. It is the key to the normal and fault recovery operation of the distribution network. Reasonable control of the power flow is crucial for the power supply recovery of non-fault areas and the stable operation of the island. At the same time, its influence range is extensive. Changes in the power flow distribution will affect many aspects such as node voltage, line current, and network loss. Unreasonable distribution will cause equipment operation problems and safety hazards.

[0132] This embodiment focuses on relaxing the system power flow constraints, which can concentrate on key problems. The second-order cone relaxation transforms complex constraint conditions into a form that can be efficiently solved, greatly reducing the difficulty of model solving and improving the calculation efficiency. More importantly, based on the accurate power flow distribution, power distribution and network reconstruction can be optimized during fault recovery, and relevant equipment can be used to restore power supply more accurately, improving the recovery rate and reliability and reducing power outage losses.

[0133] In this embodiment, during the first stage of fault recovery, island division and network reconstruction are carried out, which can quickly isolate the fault area, transfer power through the flexible interconnection device, effectively reduce the power loss load in the non-fault area, prevent the increase of network loss due to the change of network structure, and at the same time take into account the service life and operation cost of the operating switch, greatly improving the recovery efficiency in the initial stage of the fault, enhancing the emergency response ability of the distribution network during the sudden fault, and solving the problems of slow recovery speed and lack of systematic recovery strategy in the traditional method in the initial stage of the fault.

[0134] 2. Optimal scheduling model for mobile energy storage participating in fault recovery

[0135] Considering the situation that relying solely on the fault reconstruction and island division of the flexible interconnected distribution network may not fully recover the fault power loss load, in the second stage of fault recovery, considering conditions such as the access location of the mobile energy storage vehicle and the scheduling time, the different access points of the mobile energy storage vehicle are optimized, and through the coordinated cooperation of the mobile energy storage vehicle and the flexible interconnection device, the fault recovery rate is improved.

[0136] (1) Fault recovery objective function in the second stage

[0137] The objective function of the optimization scheme for distribution network reconstruction and island division with the participation of energy storage MESS is shown in formula (1) under the condition of considering formula (6).

[0138] (2) Calculation of MESS deployment time

[0139] The traffic conditions of the road usually appear congested or slippery due to the influence of extreme weather or human factors, which will affect the moving time of the mobile energy storage MESS to the destination. The moving time of the mobile energy storage m to the destination in the nth scheduling scheme is:

[0140]

[0141] In the formula, D represents the distance between the mobile energy storage and the power loss area; α ME and λ s respectively represent the moving speed coefficient and correction coefficient in the process of mobile energy storage scheduling. Among them, α ME is affected by the road traffic conditions, vehicle performance and road conditions during the MESS scheduling process, while λ sIt is affected by factors such as weather conditions and the charge-discharge state of MESS.

[0142] In this embodiment, by accurately calculating the deployment time of MESS and fully considering the influence of actual traffic and environmental factors on mobile energy storage scheduling, the arrival time of mobile energy storage can be more accurately predicted when formulating a fault recovery plan, the scheduling plan can be reasonably arranged, the recovery delay caused by inaccurate time estimation can be avoided, and the timeliness and reliability of fault recovery are improved.

[0143] (3) Constraints for distribution network fault recovery with MESS participation

[0144] ① Discharge and capacity constraints of mobile energy storage

[0145] When the mobile energy storage reaches the location where power supply is required, its discharge power and capacity need to meet the following constraints.

[0146]

[0147] In the formula: are the active charging power, active and reactive discharge powers of the mobile energy storage respectively; are the charging and discharging efficiencies of the mobile energy storage respectively; is the capacity of the mobile energy storage at time t.

[0148] The discharge and capacity constraints of the mobile energy storage ensure the safety and stability of the mobile energy storage during the power supply process, prevent overcharging and over-discharging, protect the mobile energy storage equipment, and at the same time ensure that it can continuously and effectively provide support for the distribution network, improving the utilization efficiency of the mobile energy storage in fault recovery.

[0149] ② Other constraints

[0150] The goal and its constraints of the flexible interconnected distribution network recovery with mobile energy storage participation are the same as those in the first-stage fault recovery model.

[0151] Keeping some of the constraints in the first stage the same ensures the coherence and consistency of the entire fault recovery process, enables the operations and optimizations in different stages to be coordinated with each other, jointly promotes the fault recovery of the distribution network, avoids chaos and conflicts caused by excessive differences in constraint conditions, improves the overall effect of the fault recovery strategy, and solves the problem of inconsistent constraint conditions in the multi-stage recovery process.

[0152] (4) Solution algorithm for MESS participating in fault recovery

[0153] After the above steps, the problem of distribution network reconfiguration and islanding involving FID and MESS is transformed from a mixed-integer non-linear programming model that is difficult to solve efficiently into a second-order cone programming model. Existing mature mathematical optimization tools such as CPLEX and MOSEK can be called for solution. For the problem of distribution network system operation optimization, it has been proven that when the objective function is a strictly increasing function of branch current or node injection power, the second-order cone relaxation is accurate. To verify the accuracy of Equation (19) at the optimum after relaxation, the relaxation deviation calculation formula is:

[0154]

[0155] When the gap is small enough, it can be considered that the second-order cone relaxation meets the calculation accuracy requirements.

[0156] (5) Solution steps for MESS to participate in fault recovery

[0157] The process of solving for fault recovery with MESS participation is as follows:

[0158] ① According to the distribution network fault reconfiguration and islanding situation, obtain the power-off load nodes, and thus obtain the scheduling plan for MESS.

[0159] ② Calculate each scheduling plan to obtain its scheduling time and the power-off load situation of the distribution network fault recovery, so as to determine the value of the objective function for each plan.

[0160] ③ Determine the scheduling plan and fault recovery strategy for this stage from the scheduling plan corresponding to the minimum value among the objective function values of the fault recovery plans determined by each scheduling plan.

[0161] When the load cannot be fully restored in the first stage, in the second stage of this embodiment, mobile energy storage is introduced for optimal scheduling. By considering conditions such as the access location and deployment time of mobile energy storage vehicles, the flexibility of mobile energy storage is fully utilized, further improving the fault recovery rate, making up for the deficiencies of relying solely on network reconfiguration and islanding, effectively coping with complex fault situations, ensuring that more loads can be restored to power, enhancing the overall power supply reliability of the distribution network, and solving the problem of limited recovery ability of the existing technology in the face of complex faults.

[0162] By introducing mobile energy storage to participate in the load recovery of the distribution network, the present invention fully utilizes its flexibility, makes up for the deficiencies of relying solely on network reconfiguration and islanding, and enhances the ability to cope with complex faults. The relaxation operation improves the difficulty of model solution, making the calculation process smoother without affecting the accuracy. This not only improves the speed of fault recovery but also better balances various indicators in the recovery process, such as reducing the power-off load and network loss. Overall, it enhances the power supply reliability of the flexible interconnected distribution network after a fault and ensures the power consumption quality of users.

[0163] Through the coordination of mobile energy storage with islanding division and network reconfiguration, the present invention effectively addresses the deficiencies of traditional restoration methods. In the initial stage of a fault, islanding division and network reconfiguration quickly isolate the fault area, transfer power using flexible interconnection devices, and reduce the load of power outages. However, relying solely on this, the restoration ability is limited, and mobile energy storage joins in for coordination at this time. It is dispatched to the power outage area according to the actual situation. After islanding division, if the power within the island is insufficient, it can serve as a supplementary power source to ensure stable operation; during the process of network reconfiguration, it assists in adjusting the power distribution. This phased coordinated restoration method formulates precise strategies according to the characteristics of different fault stages. In the first stage, part of the load is quickly restored, and in the second stage, the power supply is further optimized with the help of mobile energy storage, greatly improving the fault restoration rate, enhancing the resilience and reliability of the distribution network, effectively coping with complex faults, and improving the overall restoration efficiency and effect.

[0164] Embodiment 2

[0165] This embodiment provides a flexible interconnected distribution network fault restoration system based on the coordination of mobile energy storage, including:

[0166] A first-stage restoration module, configured to obtain the fault location of the flexible interconnected distribution network, construct a first-stage optimization model based on islanding division and network reconfiguration, and perform first-stage fault restoration on the distribution network;

[0167] A second-stage restoration module, configured to, if there are unrecovered loads, through the optimal scheduling of mobile energy storage, construct a second-stage optimization model based on the coordination of islanding division, network reconfiguration, and mobile energy storage, and perform second-stage fault restoration on the distribution network until the fault at the fault location is repaired.

[0168] Embodiment 3

[0169] This embodiment provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the steps in a method for restoring a flexible interconnected distribution network fault based on the coordination of mobile energy storage as described in Embodiment 1 above.

[0170] Embodiment 4

[0171] This embodiment provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the steps in a method for restoring a flexible interconnected distribution network fault based on the coordination of mobile energy storage as described in Embodiment 1 above.

[0172] The steps or modules involved in the second to fourth embodiments above correspond to those in the first embodiment. For specific implementation manners, reference may be made to the relevant description part of the first embodiment. The term "computer-readable storage medium" should be understood to include a single medium or multiple media including one or more instruction sets; it should also be understood to include any medium that can store, encode, or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0173] The foregoing are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for recovering a flexible interconnected distribution network fault based on mobile energy storage collaboration, characterized in that: include: Obtain the fault location of the flexible interconnected distribution network, build the first-stage optimization model based on island division and network reconstruction, and perform the first-stage fault recovery of the distribution network; If there is an unrestored load, the mobile energy storage is optimized and dispatched, and a second-stage optimization model is constructed based on island division, network reconstruction and mobile energy storage to perform second-stage fault recovery on the distribution network until the fault is repaired at the fault location.

2. A method for recovering a flexible interconnected distribution network fault based on mobile energy storage collaboration as claimed in claim 1, characterized in that: The obtaining of the fault location of the flexible interconnected distribution network specifically includes: obtaining parameters of the flexible interconnected distribution network, determining whether a fault occurs based on a preset threshold, removing the fault, and obtaining the fault location.

3. A method for recovering a flexible interconnected distribution network fault based on mobile energy storage collaboration as claimed in claim 1, characterized in that: The first stage optimization model takes the minimum power loss load, the minimum total loss of the distribution network after restoration, and the minimum number of switch actions as the restoration objectives, and sets the first constraint condition for construction; The first constraint conditions include system flow constraints, system safety constraints, distribution network topology constraints, DG type and output constraints, island power balance constraints and flexible interconnection device active power and capacity constraints.

4. A method for recovering a flexible interconnected distribution network fault based on mobile energy storage collaboration as claimed in claim 3, characterized in that: Based on the system power flow constraints, the large M method is introduced into the variant form of Ohm's law and power definition, and the squared voltage term and the squared current term are replaced by equivalent variables, specifically: Among them, r ij 、x ij They represent the equivalent resistance and equivalent reactance of the distribution network line ij respectively; P ij Indicates the active power flowing through line ij; Q ij Represents the reactive power flowing through line ij; I ij Indicates the current flowing through line ij; U i , U j Respectively represent the voltage at node i and node j; m ij is the auxiliary variable in the Big M method, which is a very large integer; z ij is a binary variable, which takes 1 when the circuit breaker is closed and takes 0 when it is open. ij = 0, m ij Take it very large, the constraint term is relaxed, the node voltages at both ends of the branch are unrelated, and for the line closed z ij = 1, that is, m in the constraint condition is ignored ij Item; Only when the circuit breaker is closed, that is, z ij When it is 1, the terminal voltage will be constrained.

5. A method for recovering a flexible interconnected distribution network fault based on mobile energy storage collaboration as claimed in claim 3, characterized in that: The second-order cone relaxation method is used to relax the power flow constraints of the system.

6. A method for recovering a flexible interconnected distribution network fault based on mobile energy storage collaboration as claimed in claim 1, characterized in that: The second-stage optimization model takes the shortest repair time and the shortest load outage time as the recovery objectives and sets the second constraint condition for construction; The second constraint condition includes the first constraint condition and the mobile energy storage discharge and capacity constraint.

7. A method for recovering a flexible interconnected distribution network fault based on mobile energy storage collaboration as claimed in claim 6, characterized in that: The specific recovery objectives of the second-stage optimization model are: Among them, P Loss,i Indicates the power-off load of M and N type loads, T all T is the total time required for manual repair of a fault after it occurs; s is the load power outage time when the load is not connected to the power outage area for power supply during the mobile energy storage dispatch process; s Including the deployment time of mobile energy storage vehicles Where D represents the distance between the mobile energy storage and the power failure area; α ME and λ s Respectively represent the moving speed coefficient and correction coefficient in the mobile energy storage dispatch process; α ME Affected by the road traffic conditions, vehicle performance and road conditions during the dispatch of mobile energy storage vehicles, λ s Affected by weather conditions and the charging and discharging status of the mobile energy storage vehicle.

8. A flexible interconnected distribution network fault recovery system based on mobile energy storage collaboration, characterized in that: include: The first-stage restoration module is configured to obtain the fault location of the flexible interconnected distribution network, build a first-stage optimization model based on island division and network reconstruction, and perform first-stage fault restoration on the distribution network; The second-stage recovery module is configured to perform second-stage fault recovery on the distribution network by optimizing the scheduling of mobile energy storage if there is an unrestored load, and collaboratively constructing a second-stage optimization model based on island division, network reconstruction and mobile energy storage, until the fault at the fault location is repaired.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by the processor, the steps in the flexible interconnected distribution network fault recovery method based on mobile energy storage collaboration as described in any one of claims 1-7 are implemented.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps in the flexible interconnected distribution network fault recovery method based on mobile energy storage collaboration as described in any one of claims 1-7 are implemented.

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