CN117650517A - Method and device for recovering faults and reconstructing network of micro-grid system - Google Patents

Abstract

The utility model relates to a method for fault recovery and network reconstruction of a micro-grid system, which comprises the steps of establishing a multi-objective optimization function of the micro-grid system, establishing a feasible topology structure from distributed energy sources to load nodes, establishing a fault retrieval sequence optimization strategy model, establishing an AC/DC line operation constraint condition of the micro-grid system based on the fault retrieval sequence optimization strategy model and the feasible topology structure, adopting mixed integer second order cone planning, and obtaining an optimal detection scheme through convex relaxation treatment and second order cone. According to the method and the device, when a plurality of faults occur to the micro-grid, a fault maintenance sequence optimization strategy is established, the faults are eliminated one by one according to the importance degree of the faults, so that the smoothness of a power supply line from a power supply to important loads is ensured, more important loads are ensured to be recovered, meanwhile, the reliability of the micro-grid is enhanced, the elasticity of the micro-grid is improved, and the resistance of the micro-grid in disasters is enhanced. The application also relates to a device, equipment and storage medium for recovering the faults of the micro-grid system and reconstructing the network.

Description

Method and device for recovering faults and reconstructing network of micro-grid system

Technical Field

The present disclosure relates to the field of power systems, and in particular, to a method and apparatus for fault recovery and network reconfiguration of a micro-grid system.

Background

Along with frequent disasters caused by extreme weather, the micro-grid is increasingly frequent in large-scale power failure accidents, so that huge economy is caused, and normal production and living of people are greatly disturbed. The micro-grid is quickly recovered after the fault occurs, and has great significance for normal life of people and normal production of society.

Compared with the traditional micro-grid, the novel micro-grid has the advantages that the renewable energy access proportion is greatly increased, the power is supplied in multiple modes, and along with the large-scale construction of the distributed power supply (DG) in the micro-grid, how to fully utilize the distributed power supply to recover power supply to a power failure area becomes a research hot spot of the micro-grid in recent years. At present, an artificial intelligent algorithm is generally adopted to solve the problem of fault recovery of a novel micro-grid, but the method is easy to sink into local optimum, has long time and is difficult to obtain a global optimum solution.

Disclosure of Invention

In order to solve the problem of fault recovery of a novel micro-grid, the application provides a method and a device for fault recovery and network reconstruction of a micro-grid system.

In a first aspect, the present application provides a method for recovering a fault and reconstructing a network of a micro grid system, where the method includes:

s1, based on information of load nodes in a micro-grid system, establishing a multi-objective optimization function of the micro-grid system;

s2, constructing a feasible topological structure from the distributed energy sources in the direct-current line to the load nodes in the micro-grid system by using a depth-first traversal algorithm;

s3, establishing a fault retrieval order optimization strategy model;

s4, based on the fault retrieval order optimization strategy model and the feasible topological structure, constructing an alternating current line operation constraint condition and a direct current line operation constraint condition of the micro-grid system;

s5, adopting mixed integer second order cone planning, and obtaining an optimal detection scheme based on the AC line operation constraint condition and the DC line operation constraint condition of the micro-grid system through convex relaxation treatment and second order cone to convert the fault retrieval sequence optimization strategy model.

In a second aspect, the present application further provides an apparatus for recovering from a fault and reconstructing a network of a micro grid system, where the apparatus includes:

the multi-objective optimization module is used for establishing a multi-objective optimization function of the micro-grid system based on information of load nodes in the micro-grid system;

The depth traversal module is used for constructing a feasible topological structure from the distributed energy sources in the direct-current line to the load nodes in the micro-grid system by utilizing a depth-first traversal algorithm;

the strategy model building module is used for building a fault retrieval order optimization strategy model;

the constraint condition constructing module is used for constructing an alternating current line operation constraint condition and a direct current line operation constraint condition of the micro-grid system based on the fault retrieval order optimization strategy model and the feasible topological structure;

the solving module is used for adopting mixed integer second order cone planning, and solving an optimal detection scheme after the fault retrieval sequence optimization strategy model is converted through convex relaxation treatment and second order cones based on the AC line operation constraint condition and the DC line operation constraint condition of the micro-grid system.

In a third aspect, the present application further provides a computer device, including a memory and a processor, where the memory stores a computer program, and the processor implements the method for recovering from a failure and reconstructing a network of the micro grid system according to any one of the first aspects when the processor executes the computer program.

In a fourth aspect, the present application further provides a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method for recovering from a failure and reconstructing a network of a microgrid system of any one of the first aspects.

The method for recovering faults and reconstructing the network of the micro-grid system comprises the steps of establishing a multi-objective optimization function of the micro-grid system based on information of load nodes in the micro-grid system; constructing a feasible topological structure from the distributed energy sources in the direct-current line to the load nodes in the micro-grid system by using a depth-first traversal algorithm; establishing a fault retrieval order optimization strategy model; optimizing a strategy model and a feasible topological structure based on a fault retrieval sequence, and constructing an alternating current line operation constraint condition and a direct current line operation constraint condition of the micro-grid system; and adopting mixed integer second order cone planning, and obtaining an optimal detection scheme based on alternating current line operation constraint conditions and direct current line operation constraint conditions of the micro-grid system through convex relaxation treatment and second order cone to optimize strategy model conversion of the fault retrieval sequence. According to the method, the AC-DC interconnection system is built in the micro-grid, all the connecting lines in the micro-grid adopt the DC lines, then a depth-first traversal strategy based on AC-DC interconnection is built, more feasible power supply paths containing the DC lines are ensured to be searched in the topological structure of the AC-DC interconnection system, and then a power supply recovery path scheme with small network loss and high stability is searched. According to the method and the device, when a plurality of faults occur in the micro-grid in the face of extreme disaster weather, the micro-grid is subjected to preliminary island division so as to maintain important loads of the grid and power supply of other loads, a fault maintenance sequence optimization strategy is established, the faults are eliminated one by one according to the importance degree of the faults, the smooth power supply line from a power supply to the important loads is ensured, and more important loads are ensured to be recovered. Island division is carried out through time-division dynamics, the whole fault recovery and reconstruction time interval is divided into a plurality of time segments, multi-time-segment dynamic island division is carried out, flexible and efficient utilization of energy sources in a system is guaranteed, and the system is cooperated with a depth-first traversal strategy, so that global optimal solutions are guaranteed to be found. And finally, converting the modeling type into a mixed integer second order cone planning model by using a second order cone technology to carry out global optimal solution. The reliability of the micro-grid is enhanced, the elasticity of the micro-grid is improved, and the resistance of the micro-grid in disasters is enhanced.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:

fig. 1 is a schematic flow chart of a method for recovering a fault and reconstructing a network of a micro-grid system according to an embodiment of the present application;

FIG. 2 is a schematic flow chart of a method for recovering from a fault and reconstructing a network of a micro grid system according to another embodiment of the present application;

FIG. 3 is an initial schematic diagram of a system in a method for recovering a fault and reconstructing a network of a micro grid system according to another embodiment of the present application;

fig. 4 is a schematic diagram of preliminary division after fault occurrence of a method for recovering a fault and reconstructing a network of a micro grid system according to another embodiment of the present application;

FIG. 5 is a schematic diagram of multi-period island division in a method for recovering a fault and reconstructing a network of a micro grid system according to another embodiment of the present application;

FIG. 6 is a schematic diagram showing the comparison of important load recovery amounts of two schemes under continuous time periods of a method for recovering faults and reconstructing a network of a micro grid system according to another embodiment of the present application;

FIG. 7 is a schematic diagram showing a comparison of network loss of two schemes during successive periods of time of a method for recovering from a fault and reconstructing a network of a micro grid system according to another embodiment of the present application;

Fig. 8 is a schematic block diagram of a method and an apparatus for recovering a fault and reconstructing a network of a micro grid system according to an embodiment of the present application.

Detailed Description

The invention will be described in detail below with reference to the drawings in connection with embodiments. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.

The following detailed description is exemplary and is intended to provide further details of the invention. Unless defined otherwise, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the invention.

Embodiment one:

the following describes in detail the method for recovering a fault and reconstructing a network of a micro-grid system according to an embodiment of the present application with reference to fig. 1, including the following steps:

s1, based on information of load nodes in a micro-grid system, establishing a multi-objective optimization function of the micro-grid system.

S2, constructing a feasible topological structure from the distributed energy sources in the direct-current line to the load nodes in the micro-grid system by using a depth-first traversal algorithm.

S3, establishing a fault retrieval order optimization strategy model.

And S4, optimizing a strategy model and a feasible topological structure based on the fault retrieval sequence, and constructing an alternating current line operation constraint condition and a direct current line operation constraint condition of the micro-grid system.

S5, adopting mixed integer second order cone planning, and obtaining an optimal detection scheme based on alternating current line operation constraint conditions and direct current line operation constraint conditions of the micro-grid system through convex relaxation treatment and second order cone-to-fault retrieval order optimization strategy model conversion.

Based on the above embodiment, specifically, step S1 includes:

establishing a multi-objective optimization function by using the maximum value of the sum of the weight coefficient products of all load nodes and all load nodes in the micro-grid system and the minimum value of network loss:

where k is the number of the load node in the micro-grid, V _Load Is the collection of load nodes in the micro-grid, beta _k Is the switch state value of the kth load node, Z _L,k Is the load carried by the kth load node, gamma _k Is the weight coefficient of the load carried by the kth load node, gamma _b Is the collection of vector lines formed by initial load nodes and final load nodes in a micro-grid system, r _ij Is the resistance value of the vector line ij from the initial load node i to the final load node j, Is the current value of the vector line ij from the initial load node j to the final load node j.

Based on the above embodiment, specifically, step S2 includes:

depth-first traversal algorithm E (G) is adopted, and distributed power supply set V based on micro-grid _DC Distributed power supply node to V _Load Searching the electric distance between the medium load nodes and the feasible paths from the distributed energy nodes to the load nodes to obtain the feasible topological structure from the distributed power nodes to the load nodes:

V _DC ＝{V _d1 ,V _d2 ,V _d3 ,…}

V _Load ＝{V _l1 ,V _l2 ,V _l3 ,…}

wherein V is _da Is V _DC A-th distributed power supply node of (V) _lb Is V _L The b-th load node in load, d (V _da ,V _lb ) Is V _DC A-th distributed power supply node to V _Load The electrical distance of the b-th load node in the system is more than or equal to 1, and b is more than or equal to 1.

It should be appreciated that the depth-first traversal algorithm is not particularly limited in this application, and existing depth-first traversal algorithms may be used.

Based on the above embodiment, specifically, step S3 includes:

based on the on-off state value of the vector line ij in the fault recovery t period, the number of lines overhauled at most in one overhauling period, the time consumed for overhauling one fault line, namely the overhauling period, and the number of overhauling periods included in the fault period, a fault overhauling sequence optimization strategy is established:

Wherein t is _n Is the last period of the fault recovery t period, t _m Is the next period of the fault recovery t period,vector line ij of final load node j of initial load node ij is at t _n Switch state value of time period->Vector line ij of final load node j of initial load node ij is at t _m Switch state value of time period->The switching state value of the vector line ij of the final load node j of the initial load node i in the period of fault recovery T is adopted, L is the set of all the fault vector lines, M is the number of lines which are overhauled at the same time at most in one overhauling period, T ₀ Is a maintenance period, N _T Is the number of service periods that the failure period includes.

Based on the above embodiment, specifically, step S4 includes:

s41, establishing distributed power supply constraint and energy storage constraint;

output minimum value of active power of distributed power supply based on kth load node in t periodOutput maximum value of active power of distributed power supply of kth load node in t period +.>Active power value +.>The distributed power supply of the kth load node is reactive in t period>Distributed power supply capacity of kth load node +.>Minimum operating power factor of the distributed power supply of the kth load node >Charging and discharging active power of battery at kth load node in t period +.>Charging and discharging reactive power of battery at kth load node in t period +.>Apparent power of battery at kth load node in t period +.>Maximum value of reactive power of battery at j-th load node +.>Normal battery operating loss power of battery at kth load node in t period +.>Loss rate of battery connection at kth load node +.>The ratio delta Y of the electric quantity loss of the battery to the off-grid electric energy of the battery, and the initial instantaneous state of charge value of the battery at the kth load node in the t period +.>The initial instantaneous state of charge value of the battery at the kth load node in the period t + deltat +.>Minimum state of charge of the battery at the kth load node +.>And the maximum value of the state of charge of the battery at the kth load node +.>The following constraints are established:

s42, constructing constraint conditions of a feasible topological structure of an alternating current region in the micro-grid system;

based on the feasible topology, the constraint conditions for establishing the feasible topology of the alternating current area are as follows:

wherein v is _ij Is the parent-child relationship of the initial load node i and the final load node i in the vector line ij, v _ji Is the parent-child relationship of the initial load node j and the final load node i in the vector line ji, i ₁ Is the only root node in the micro-grid system, gamma _a Is a node set which is all adjacent to the initial load node in the micro-grid system, and gamma _c Is a collection of nodes other than the root node within the micro-grid system.

S43, constructing a power flow constraint condition of an alternating current region of the micro-grid system based on the improved power flow model.

S44, constructing a power flow constraint condition of the direct current region of the micro-grid system based on the improved power flow model.

S45, constructing a voltage constraint condition and a current constraint condition of the micro-grid system.

S46, constructing a VSC model constraint of the voltage source converter station, wherein the specific constraint conditions are as follows:

Q _{VSC，ij，min} ≤Q _t，ij ≤Q _{VSC，ij，max}

R _{VSC，ij，min} ≤P _t，ij ≤R _{VSC，ij，max}

wherein Q is _VSC,ij,max Is the reactive power compensation upper limit value, Q, of the voltage source converter station VSC of the vector line ij _VSC,ij,min Is the reactive power compensation lower limit value Qt, i of the voltage source converter station VSC of the vector line ij _j Reactive power of voltage source converter station VSC of vector line ij in period t, P _VSC,ij,max Is the upper active power limit value, P, of the voltage source converter station VSC of the vector line ij _VSC,ij,min Is the active power lower limit value, P, of the voltage source converter station VSC of the vector line ij _t,ij Is the active power lower limit value of the voltage source converter station VSC of the vector line ij during the period t.

P _AC,t,ij Is the active power transmitted from AC node i to AC node j in period t, Q _AC,t,ij Is the reactive power transmitted from ac node I to ac node j in period t, I _VSC,t,ij Is the current value of the voltage source converter station VSC of the vector line ij in the period t, R _VSC,t,ij Is the voltage value, X, of the voltage source converter station VSC of the vector line ij during the period t _VSC,t,ij Reactance value, P, of voltage source converter station VSC of vector line ij in period t _DC,t,ij Active power of direct current side of voltage source converter station VSC of vector line ij in t period, Q _VSC,t,ij Is the reactive power of the voltage source converter station VSC of the vector line ij during period t.

The step S43 specifically includes:

determining a parent node set of alternating-current nodes in a feasibility topological structure and a child node set of alternating-current nodes in the feasibility topological structure, setting an outflow point of which the parent node is power and an inflow point of which the child node is power, wherein the child node is provided with a plurality of parent nodes, and establishing the following constraint:

where qac is the ac node, c (iac) is the parent node set of ac nodes iac in the feasibility topology, s (iac) is the child node set of ac nodes iac in the feasibility topology, c (jac) is the parent node set of ac nodes jac in the feasibility topology, and s (jac) is the child node set of ac nodes jac in the feasibility topology.

κ _t,iac-jac Is the switching variable, κ, of the vector line iac-jac from ac node iac to ac node jac over the period t _iac-jac Is the switching variable of the vector line iac-jac,is the current value from ac node iac to ac node jac in period t, U _AC,t,jac Is the amplitude of the voltage at ac node jac during time t, U _AC,t,iac Is the amplitude of the voltage at the ac node iac during the period t, R _iac-jac Is the resistance value of the vector circuit iac-jac, X _iac-jac Is the reactance value of the vector line iac-jac.

P _AC,t,iac-jac Is the active power transmitted from ac node iac to ac node jac during period t, Q _AC,t,iac-jac Is the reactive power transferred from ac node iac to ac node jac during period t, P _AC,t,jac Is the active power flowing in by the alternating current node iac in the t period, Q _AC,t,jac The representation is the reactive power flowing in by the ac node jac during the t period。

Is the input value of the active power of the distributed power supply at ac node jac during the t period,Is the input value of the reactive power of the distributed power supply at ac node jac during the t period,Is the output value of active power in an alternating current node iac energy storage battery in the t period,/->Is the output value, P, of the reactive power in the alternating current node jac energy storage battery in the t period _{AC,t,jac,load} Is the load power consumed by active power on the ac node jac during the t period, Q _AC,t,j,load Is the load power that reactive power consumes on ac node jac during the t period.

The step S44 specifically includes:

determining a father node set of the direct current nodes in the feasibility topological structure, setting an outflow point of which the father node is power, allowing the father nodes to have a plurality of father nodes, and establishing the following constraint:

where qdc is a dc node, c (idc) is a parent node set of dc nodes idc in the feasibility topology, s (idc) is a child node set of dc nodes idc in the feasibility topology, c (jdc) is a parent node set of dc nodes jdc in the feasibility topology, s (jdc) is a child node set of dc nodes jdc in the feasibility topology; p (P) _DC,t,jdc Is the active power that the ac node jdc flows into during the t period,is the current value flowing from the dc node idc to the dc node jdc in the t period, U _DC,t,jdc Is the voltage amplitude of the DC node jdc during the t period, U _DC,t,idc Is the voltage amplitude of the DC node idc in the t period, P _DC,t,idc-jdc Active power transmitted by DC node idc to DC node jdc during period t, Q _DC,t,idc-jdc Reactive power transmitted by dc node idc to dc node jdc during period t,/->The active power of the distributed power supply in the t period is input value of the direct current node jdc, +. >Is the input value of the reactive power of the distributed power supply at the dc node jdc during the t period,/->Is the output value of active power in the direct current node jdc energy storage battery in the t period,/->Is the output value of the active power in the direct current node jdc energy storage battery in the period t, P _{DC,t,jdc,load} Is consumed by active power on the DC node jdc during the t periodLoad power, Q _{DC,t,jdc,load} Is the load power consumed by reactive power on the DC node jdc during the t period, R _idc-jdc Is the resistance value of the vector line idc-jdc, kappa _idc-jdc Is the switching variable of vector line idc-jdc.

The step S45 specifically includes:

s451, constructing voltage constraint of an alternating current node in an alternating current region of the micro-grid system:

wherein U is _AC,kac,min Is the minimum voltage of the alternating current node kac, U _AC,kac,max Is the maximum voltage of the alternating current node kac, U _AC,t,kac Is the voltage value of the ac node kac at time t;

s452, constructing voltage constraint of a direct current node in a direct current region of the micro-grid system.

Wherein U is _DC Kdc, min is the voltage minimum of the DC node kac, U _DC,i,max Is the voltage minimum of the direct current node kdc, U _DC,t,kac Is the voltage value of the dc node kdc at time t;

and D453, constructing current constraint of an alternating current circuit of an alternating current region in the micro-grid system.

Wherein I is _{AC,iac-jac,max} Is the maximum value of the current from the AC node iac to the AC node jac in the AC circuit iac-jac, I _{AC,iac-jac,min} Is the minimum value of the current from the alternating current node iac to the alternating current node jac in the alternating current circuit iac-jac, I _AC,t,iac-jac Is the current value of ac node iac to ac node jac in ac circuit iac-jac for the period t.

And D453, constructing current constraint of a direct current circuit of a direct current region in the micro-grid system:

wherein I is _{DC,idc-jdc,max} Is the maximum value of the current from the DC node idc to the DC node jdc in the DC circuit idc-jdc, I _{DC,idc-jdc,min} Is the minimum value of the current from the DC node idc to the DC node jdc in the DC circuit idc-jdc, I _DC,t,idc-jdc Is the current value of dc node idc to dc node jdc in dc circuit idc-jdc for the period t.

Based on the above embodiment, step S5 specifically includes adopting a second order cone relaxation process as follows:

-κ _ij M ₁ ≤P _ij，t ≤κ _ij M ₁

-κ _ij M ₂ ≤Q _ij，t ≤κ _ij M ₂

-κ _ij M ₃ ≤I _ij，t ≤κ _ij M ₃

wherein M is ₁ ～M ₄ The values of (a) are particularly large positive numbers.

Through second order cone conversion and solving:

further conversion to mixed integer second order cone constraints are as follows:

through the second order cone conversion step, the mixed integer nonlinear programming problem which is difficult to solve rapidly and accurately is converted into the mixed integer second order cone programming problem based on the fault retrieval order optimization strategy model, the subsequent solution can be programmed through YAMIP, and finally the final result is obtained on CPLEX software.

According to the method for recovering faults and reconstructing the network of the micro-grid system, when the micro-grid is subjected to multiple faults in the face of extreme disaster weather, the micro-grid is subjected to preliminary island division so as to maintain important loads and other load power supply of the grid, a fault maintenance sequence optimization strategy is established, the faults are eliminated one by one according to the importance degree of the faults, the smooth power supply line from a power supply to the important loads is ensured, and more important loads are ensured to be recovered. Island division is carried out through time-division dynamics, the whole fault recovery and reconstruction time interval is divided into a plurality of time segments, multi-time-segment dynamic island division is carried out, flexible and efficient utilization of energy sources in a system is guaranteed, and the system is cooperated with a depth-first traversal strategy, so that global optimal solutions are guaranteed to be found. And finally, converting the modeling type into a mixed integer second order cone planning model by using a second order cone technology to carry out global optimal solution. The reliability of the micro-grid is enhanced, the elasticity of the micro-grid is improved, and the resistance of the micro-grid in disasters is enhanced.

Embodiment two:

the following will describe in detail the use of the method for recovering a fault and reconstructing a network of a micro grid system according to the embodiments of the present application in an actual environment with reference to fig. 2 to 7, and specifically includes the following steps:

110. and establishing a microgrid optimization target.

120. And establishing a depth-first traversal strategy of the direct current line.

130. And establishing a fault maintenance sequence optimization strategy model.

140. And establishing AC/DC operation constraint of the micro-grid system.

It should be understood that, in this embodiment, an ac/dc interconnection system is first built in a micro-grid, so that all the connecting lines in the micro-grid adopt dc lines, and then a depth-first traversal strategy based on ac/dc interconnection is built, so that more feasible power supply paths including dc lines are ensured to be searched in the topology structure of the ac/dc interconnection system, and then a power supply restoration path scheme with small network loss and high stability is searched. When a plurality of faults occur in the micro-grid, the micro-grid performs preliminary island division so as to maintain important loads and other loads of the power grid to supply power, then a fault overhaul sequence optimization strategy is established, the faults are eliminated one by one according to the importance degree of the faults, so that the power supply line from a power supply to the important loads is ensured to be smooth, more important loads are ensured to be recovered, the whole fault recovery and reconstruction time interval is divided into a plurality of time periods, the multi-period dynamic island division is performed, the flexible and efficient utilization of energy sources in the system is ensured, and the overall optimal solution is ensured to be found in cooperation with the depth-first traversal strategy. And finally, converting the modeling type into a mixed integer second order cone planning model by using a second order cone technology to carry out global optimal solution. The reliability of the micro-grid is enhanced, the elasticity of the micro-grid is improved, and the resistance of the micro-grid in disasters is enhanced.

Step 110, establishing multi-objective optimization by using the maximum sum of the weight coefficient products of all loads and the load grades where the loads are in and the minimum network loss, and establishing an objective function as follows:

where k is the number of the load node in the micro-grid, V _Load Is the collection of load nodes in the micro-grid, beta _k The value is 1, which represents the switch closing, namely the load input carried by the switch node, and the value is 0, which represents the opening, namely the load carried by the switch node is not input; z is Z _L,k Is the load carried by the kth load node, gamma _k The weight coefficient of the load carried by the kth load node can be valued according to actual conditions, the weight coefficient of the first-stage load is 10, the weight coefficient of the second-stage load is 5, and the weight coefficient of the third-stage load is 1; gamma ray _b Is the collection of vector lines formed by initial load nodes and final load nodes in a micro-grid system, r _ij Is the resistance value of the vector line ij from the initial load node i to the final load node j,is the current value of the vector line ij from the initial load node i to the final load node j.

As shown in fig. 3, according to the ac/dc interconnection condition of the power distribution network system, a depth-first traversal policy model of the dc line in step 120 is established:

In order to fully exert the advantages of interconnection and intercommunication and energy complementation of the direct current lines, a feasible topology searching strategy based on the prior traversal of the direct current lines is adopted. The strategy searches feasible paths from different types of distributed energy sources to load nodes based on a depth-first traversal algorithm, and obtains a feasible topological structure for connecting the different types of distributed energy sources to the load nodes in the searching process.

V _DC ＝{V _d1 ,V _d2 ,V _d3 ,…}

V _Load ＝{V _l1 ,V _l2 ,V _l3 ,…}

Wherein V is _DC Is a microgrid distributed power supply set; v (V) _Load Is a micro-grid load node set; v _ds1 ,v _ds2 ,v _ds3 … are respectively set V _DC A distributed power node in (a); v _l1 ,v _l2 ,v _l3 … are respectively set V _Load A load node in (a); d (v) _ds1 ,v _l1 ) For set V _DC Medium v _ds1 Node to set V _Load Medium v _l1 The electrical distance of the node.

Step 130 is implemented by preferentially overhauling the faults between two adjacent islands with the most important loads in the disaster, and the model is as follows:

wherein t is _n Is the last period of the fault recovery t period, t _m Is the next period of the fault recovery t period,vector line ij of final load node j of initial load node ij is at t _n Switch state value of time period->Vector line ij of final load node j of initial load node ij is at t _m Switch state value of time period->The method is characterized in that a switching state value of a vector line ij of a final load node j of a starting load node i in a fault recovery T period is used for indicating that a fault line is disconnected when the value is 0, and indicating that the fault line is communicated when the value is 1, L is a set of all fault vector lines, M is the number of lines which are overhauled at the most in one overhauling period at the same time, and T ₀ Is a maintenance period, N _T Is the number of service periods that the failure period includes.

As shown in fig. 4 to 5, the ac/dc operation constraint and the second order cone planning process of the micro grid system established in the step 4 are implemented in a specific manner.

(1) And the constraint of the distributed power supply and the energy storage is established, and for the distributed power supply such as the energy storage, the constraint of the charging and discharging power is ensured, and the state of charge of the distributed power supply is ensured to be within the interval of the upper limit and the lower limit.

Wherein,is the output minimum value of active power of the distributed power supply of the kth load node in the period t,is the maximum output value of active power of the distributed power supply of the kth load node in the period t,/for the active power of the distributed power supply of the kth load node in the period t>Active power value of distributed power supply which is kth load node in t period,/->The distributed power supply which is the kth load node is reactive in the period t, and is +.>Distributed power supply capacity of kth load node,/->Is the lowest operating power factor of the distributed power supply of the kth load node, +.>Is the charging and discharging active power of the battery at the kth load node in the t period, +.>Is the charge-discharge reactive power of the battery at the kth load node in the t period,/for the time period>Is the apparent power of the battery at the kth load node during period t,/for the period t >Is the maximum value of the reactive power of the battery at the kth load node, for example>Is the normal operating power loss of the battery at the kth load node in the period t,/for the battery at the kth load node>Is the loss rate of battery connection at the kth load node, deltay is the ratio of the battery power loss to the battery off-grid power, +.>Is the initial instantaneous state of charge value of the battery at the kth load node at time t,is the initial instantaneous state of charge value of the battery at the kth load node during the period t + deltat, #>Is the minimum state of charge of the battery at the kth load node,/for the battery at the kth load node>Is the maximum state of charge of the battery at the kth load node.

(2) The topological constraint conditions for establishing the micro-grid alternating current region are as follows:

wherein v is _ij Is the initial load node i and the final load node in the vector line ijParent-child relationship of point i, v _ji Is the parent-child relationship of the initial load node j and the final load node i in the vector line ji.

If node i is a child node of node j, then v _ij Has a value of 1, v _ji The value of (2) is 0.

Otherwise v _ij Has a value of 0, v _ji The value of (2) is 1.

If nodes i and j are not connected, u _ij Has a value of 0, v _ij Has a value of 0, v _ji The value of (2) is 0.

i ₁ Is the only root node in the micro-grid system, gamma _a Is a node set which is all adjacent to the initial load node in the micro-grid system, and gamma _c Is a set of nodes other than the root node in the micro-grid system; the second one indicates that all nodes except the root node have only one parent node, and the third one indicates that the root node has no parent node.

(3) Establishing a tide constraint condition of an alternating current region of a micro-grid

In view of the dynamic transformation characteristics of the micro-grid system in disaster, in a traditional radial micro-grid, each load node-to-root node approach is generally considered to be unique, namely, node i has a unique parent node j, and many child nodes can exist. Because the micro-grid is changed to have a ring structure due to the connection of the connecting lines, the power supply paths of some nodes are changed due to the dynamic change of the topological structure of the micro-grid system, and the father node of the node i is changed along with the time-division island division. Therefore, in the time-division island division process, the traditional Disflow module is not applicable in the dynamic change process of the micro-grid system. Based on this, an extended Distflow flow model is adopted herein, which is suitable for the flow calculation of a radial micro-grid system of dynamic transformation, defines the power reference direction of each line in the micro-grid, defines the parent node as the outflow point of power, defines the child node as the inflow point of power based on the reference direction, allows one child node to have a plurality of parent nodes, and increases the switching variable k of one line _t,ij The traditional Distflow tide model is improved and improved to obtain the method suitable forThe Distflow flow constraint of the AC/DC interconnected micro-grid fault recovery and network reconstruction strategy is as follows:

where qac is an ac node, c (iac) is a parent node set of ac nodes iac in the feasibility topology, s (iac) is a child node set of ac nodes iac in the feasibility topology, c (jac) is a parent node set of ac nodes jac in the feasibility topology, and s (jac) is a child node set of ac nodes jac in the feasibility topology;

κ _t,iac-jac is the switching variable, κ, of the vector line iac-jac from ac node ia ≡to ac node jac over the period t _iac-jac Is the switching variable of the vector line iac-jac,is the current value from ac node iac to ac node jac in period t, U _AC,t,jac Is in the t periodThe amplitude of the internal voltage at ac node jac, U _AC,t,iac Is the amplitude of the voltage at the ac node iac during the period t, R _iac-jac Is the resistance value of the vector circuit iac-jac, X _iac-jac Is the reactance value of the vector line iac-jac;

P _AC,t,iac-jac is the active power transmitted from ac node iac to ac node jac during period t, Q _AC,t,iac-jac Is the reactive power transferred from ac node iac to ac node jac during period t, P _AC,t,jac Is the active power flowing in by the alternating current node iac in the t period, Q _AC,t,jac The representation is the reactive power flowing in by the ac node jac during the t period;

is the input value of the active power of the distributed power supply at ac node jac during the t period,Is the input value of the reactive power of the distributed power supply at ac node jac during the t period,Is the output value of active power in the alternating current node jac energy storage battery in the t period,/->Is the output value, P, of the reactive power in the alternating current node jac energy storage battery in the t period _{AC,t,jac,load} Is the load power consumed by active power on the ac node jac during the t period, Q _AC,t,j,load Is the load power that reactive power consumes on ac node jac during the t period;

(4) Establishing a tide constraint condition of a direct current region of a micro-grid

According to the current modeling method of the micro-grid alternating current region, a current model of the direct current region can be obtained, and the constraint is as follows:

where qdc is a dc node, c (idc) is a parent node set of dc nodes idc in the feasibility topology, s (idc) is a child node set of dc nodes idc in the feasibility topology, c (jdc) is a parent node set of dc nodes jdc in the feasibility topology, s (jdc) is a child node set of dc nodes jdc in the feasibility topology; p (P) _DC,t,jdc Is the active power that the ac node jdc flows into during the t period,is the current value flowing from the dc node idc to the dc node jdc in the t period, U _DC,t,jdc Is the voltage amplitude of the DC node jdc during the t period, U _DC,t,idc Is the voltage amplitude of the DC node idc in the t period, P _DC,t,idc-jdc Active power transmitted by DC node idc to DC node jdc during period t, Q _DC,t,idc-jdc Reactive power transmitted by dc node idc to dc node jdc during period t,/->The active power of the distributed power supply in the t period is input value of the direct current node jdc, +.>Is the input value of the reactive power of the distributed power supply at the dc node jdc during the t period,/->Is the output value of active power in the DC node idc energy storage battery in t period,The output value of active power in the dc node idc energy storage battery in the period of t, P _{DC,t,jdc,load} Is the load power consumed by active power on a DC node idc in a period t, Q _{DC,t,jdc,load} Is the load power consumed by reactive power on the DC node idc in the t period, R _idc-jdc Is the resistance value of the vector line idc-idc, κ _idc-jdc Is the switching variable of vector line idc-jdc.

(5) Security constraints for micro-grid systems

Constructing voltage constraint of alternating current nodes in an alternating current region of a micro-grid system:

wherein U is _AC,kac,min Is the minimum voltage of the alternating current node kac, U _AC,kac,max Is the maximum voltage of the alternating current node kac, U _AC,t,kac Is the voltage value of the ac node kac at time t.

Constructing voltage constraint of a direct current node in a direct current region of the micro-grid system:

wherein U is _DC,kdc,min Is the voltage minimum of the direct current node kdc, U _DC,i,max Is the voltage minimum of the direct current node kdc, U _DC,t,kac Is the voltage value of the dc node kdc at time t.

Current constraint of an alternating current circuit of an alternating current region in a micro-grid system is constructed:

wherein I is _{AC,iac-jac,max} Is the maximum value of the current from the AC node iac to the AC node jac in the AC circuit iac-jac, I _{AC,iac-jac,min} Is the minimum value of the current from the alternating current node iac to the alternating current node jac in the alternating current circuit iac-jac, I _AC,t,iac-jac Is the current value of ac node iac to ac node jac in ac circuit iac-jac for the period t.

Current constraint of a direct current circuit of a direct current region in a micro-grid system is constructed:

wherein I is _{DC,idc-jdc,max} Is the maximum value of the current from the DC node idc to the DC node jdc in the DC circuit idc-jdc, I _{DC,idc-jdc,min} Is the minimum value of the current from the DC node idc to the DC node jdc in the DC circuit idc-jdc, I _DC,t,idc-jdc Is the current value of dc node idc to dc node jdc in dc circuit idc-jdc for the period t.

(6) VSC converter station model constraints

The VSC converter station model may be considered to consist of an equivalent impedance and an ideal VSC, with the converter losses being equivalent in terms of power consumption by the equivalent resistors. The constraints are as follows:

Q _{VSC，ij，min} ≤Q _t，ij ≤Q _{VSC，ij，max}

R _{VSC，ij，min} ≤P _t，ij ≤R _{VSC，ij，max}

Wherein Q is _VSC,ij,max Is the reactive power compensation upper limit value, Q, of the voltage source converter station VSC of the vector line ij _VSC,ij,min Is the reactive power compensation lower limit value, Q, of the voltage source converter station VSC of the vector line ij _t,ij Is a vector lineReactive power, P of voltage source converter station VSC of circuit ij in t period _VSC,ij,max Is the upper active power limit value, P, of the voltage source converter station VSC of the vector line ij _VSC,ij,min Is the active power lower limit value, P, of the voltage source converter station VSC of the vector line ij _t,ij Is the active power lower limit value of the voltage source converter station VSC of the vector line ij in the period t;

P _AC,t,ij is the active power transmitted from AC node i to AC node j in period t, Q _AC,t,ij Is the reactive power transmitted from ac node I to ac node j in period t, I _VSC,t,ij Is the current value of the voltage source converter station VSC of the vector line ij in the period t, R _VSC,t,ij Is the voltage value, X, of the voltage source converter station VSC of the vector line ij during the period t _VSC,t,ij Reactance value, P, of voltage source converter station VSC of vector line ij in period t _DC,t,ij Active power of direct current side of voltage source converter station VSC of vector line ij in t period, Q _VSC,t,ij Is the reactive power of the voltage source converter station VSC of the vector line ij during period t.

Based on the above embodiment, further, step 150 is included.

Step 150 specifically includes: the second order cone relaxation treatment is adopted as follows:

-κ _ij M ₁ ≤P _ij,t ≤κ _ij M ₁

-κ _ij M ₂ ≤Q _ij，t ≤κ _ij M ₂

-κ _ij M ₃ ≤I _ij，t ≤κ _ij M ₃

Wherein M is ₁ ～M ₄ The values of (a) are particularly large positive numbers.

Through second order cone conversion and solving:

further conversion to mixed integer second order cone constraints are as follows:

through the second order cone conversion step, the mixed integer nonlinear programming problem which is difficult to solve rapidly and accurately is converted into the mixed integer second order cone programming problem based on the fault retrieval order optimization strategy model, the subsequent solution can be programmed through YAMIP, and finally the final result is obtained on CPLEX software.

In addition, in order to verify the effectiveness of the method, experiments were performed in which the ieee33 node micro grid was modified as shown in fig. 3 to 5 as a micro grid system topology diagram, and if a thunderstorm extreme disaster weather occurred, the micro grid lines 24-25, 2-19, 21-22, 6-7, 12-13, and 32-33 failed, the system was disconnected from the main grid, the disaster duration was 3 hours, and the disaster occurrence time period was 15:00 to 18:00, and the following two experimental schemes were adopted.

Experimental scheme 1: by using the AC/DC interconnection-based micro-grid fault recovery and network reconstruction strategy, when typhoon extreme disaster weather occurs, an AC/DC interconnection system is firstly built in the micro-grid, so that all connecting lines in the micro-grid adopt DC lines, then a depth-first traversal strategy based on AC/DC interconnection is built, more feasible power supply paths containing the DC lines are ensured to be searched in the topological structure of the AC/DC interconnection system, and then a power supply recovery path scheme with small network loss and high stability is searched. When a plurality of faults occur in the micro-grid, the micro-grid performs preliminary island division so as to maintain important loads and other loads of the power grid to supply power, then a fault overhaul sequence optimization strategy is established, the faults are eliminated one by one according to the importance degree of the faults, so that the power supply line from a power supply to the important loads is ensured to be smooth, more important loads are ensured to be recovered, the whole fault recovery and reconstruction time interval is divided into a plurality of time periods, the multi-period dynamic island division is performed, the flexible and efficient utilization of energy sources in the system is ensured, and the overall optimal solution is ensured to be found in cooperation with the depth-first traversal strategy. And finally, converting the modeling type into a mixed integer second order cone planning model by using a second order cone technology to carry out global optimal solution.

Experimental scheme 2: the method is not used, a direct current interconnection line is not adopted in a network, a depth-first traversal strategy based on alternating current-direct current interconnection is not constructed, and when thunderstorm extreme disaster weather occurs, the micro-grid system is normally isolated and divided according to fault information, and then fault elimination is normally and randomly carried out.

Analysis of the example graph: as can be seen from fig. 6 to 7, the recovery amount of the important load is greater in experiment scheme 1 than in experiment scheme 2, and the network loss is smaller in experiment scheme 1 than in experiment scheme 2. Therefore, the AC/DC interconnection-based micro-grid fault recovery and network reconstruction strategy provided by the application can be obtained, the power supply capacity to important loads in a disaster can be improved, the power supply of the important loads in each island in the disaster is ensured, the network loss is reduced, and the elasticity of the micro-grid in the disaster is improved.

According to the method, the AC-DC interconnection system is built in the micro-grid, all the connecting lines in the micro-grid adopt the DC lines, then a depth-first traversal strategy based on AC-DC interconnection is built, more feasible power supply paths containing the DC lines are ensured to be searched in the topological structure of the AC-DC interconnection system, and then a power supply recovery path scheme with small network loss and high stability is searched.

According to the method, when a plurality of faults occur to the micro-grid in the face of extreme disaster weather, the micro-grid is subjected to preliminary island division so as to maintain important loads of the grid and power supply of other loads, then a fault overhaul sequence optimization strategy is established, the faults are eliminated one by one according to the importance degree of the faults, the smooth power supply line from a power supply to the important loads is ensured, and more important loads are ensured to be recovered.

The island division is carried out through the time-division dynamics, the whole fault recovery and reconstruction time interval is divided into a plurality of time segments, the multi-time-segment dynamic island division is carried out, the flexible and efficient utilization of energy sources in the system is ensured, and the overall optimal solution is ensured to be found in cooperation with the depth-first traversal strategy. And finally, converting the modeling type into a mixed integer second order cone planning model by utilizing a second order cone technology to carry out overall optimal solution, enhancing the reliability of the micro-grid, improving the elasticity of the micro-grid, and enhancing the resistance of the micro-grid in disasters.

Embodiment III:

the following will describe in detail the device for recovering a fault and reconstructing a network of a micro grid system according to an embodiment of the present application with reference to fig. 8, where the device includes:

the multi-objective optimization module is used for establishing a multi-objective optimization function of the micro-grid system based on information of load nodes in the micro-grid system.

The depth traversal module is used for constructing a feasible topological structure from the distributed energy sources in the direct-current line to the load nodes in the micro-grid system by utilizing a depth-first traversal algorithm.

And the strategy model building module is used for building a fault retrieval order optimization strategy model.

And the constraint condition constructing module is used for optimizing a strategy model and a feasible topological structure based on the fault retrieval sequence and constructing an alternating current line operation constraint condition and a direct current line operation constraint condition of the micro-grid system.

The solving module is used for solving an optimal detection scheme based on alternating current line operation constraint conditions and direct current line operation constraint conditions of the micro-grid system by adopting mixed integer second order cone planning and through convex relaxation treatment and conversion of a second order cone to fault retrieval order optimization strategy model.

Based on the above embodiment, further, the multi-objective optimization module is specifically configured to establish a multi-objective optimization function with a maximum sum of weight coefficient products of all load nodes and each load node in the micro-grid system and a minimum network loss:

where k is the number of the load node in the micro-grid, V _Load Is the collection of load nodes in the micro-grid, beta _k Is the switch state value of the kth load node, Z _L,k Is the load carried by the kth load node, gamma _k Is the weight coefficient of the load carried by the kth load node, gamma _b Is the collection of vector lines formed by initial load nodes and final load nodes in a micro-grid system, r _ij Is the resistance value of the vector line ij from the initial load node i to the final load node j,is the current value of the vector line ij from the initial load node i to the final load node j.

Based on the above embodiment, further, the depth traversal module is specifically configured to use a depth-first traversal algorithm E (G), and based on the microgrid distributed power supply set V _DC Distributed power supply node to V _Load Electrical distance of medium load node, distributed energy node to loadSearching the feasible paths of the nodes to obtain a feasible topological structure from the distributed power supply node to the load node:

V _DC ＝{V _d1 ,V _d2 ,V _d3 ,…}

V _Load ＝{V _l1 ,V _l2 ,V _l3 ,…}

wherein V is _da Is V _DC A-th distributed power supply node of (V) _lb Is V _L The b-th load node in load, d (V _da ,V _lb ) Is V _DC A-th distributed power supply node to V _Load The electrical distance of the b-th load node in the system is more than or equal to 1, and b is more than or equal to 1.

Based on the above embodiment, further, a policy model module is established, and is specifically configured to establish a fault maintenance order optimization policy based on the on-off state value of the vector line ij in the fault recovery t period, the number of lines that are simultaneously maintained in one maintenance period, the time consumed for maintaining one fault line, that is, the maintenance period, and the number of maintenance periods included in the fault period:

Wherein t is _n Is the last period of the fault recovery t period, t _m Is the next period of the fault recovery t period,vector line ij of final load node j of initial load node ij is at t _n Switch state value of time period->Vector line ij of final load node j of initial load node ij is at t _m Switch state value of time period->The switching state value of the vector line ij of the final load node j of the initial load node i in the period of fault recovery T is adopted, L is the set of all the fault vector lines, M is the number of lines which are overhauled at the same time at most in one overhauling period, T ₀ Is a maintenance period, N _T Is the number of service periods that the failure period includes.

The constraint condition construction module comprises a first constraint construction unit, a second constraint construction unit, a third constraint construction unit, a fourth constraint construction unit, a fifth constraint construction unit and a sixth constraint construction unit;

the first constraint construction unit is specifically used for establishing distributed power supply constraint and energy storage constraint;

output minimum value of active power of distributed power supply based on kth load node in t periodOutput maximum value of active power of distributed power supply of kth load node in t period +.>Active power value +. >The distributed power supply of the kth load node is reactive in t period>Distributed power supply capacity of kth load node +.>Minimum operating power factor of the distributed power supply of the kth load node>Charging and discharging active power of battery at kth load node in t period +.>Charging and discharging reactive power of battery at kth load node in t period +.>Apparent power of battery at kth load node in t period +.>Maximum value of the reactive power of the battery at the kth load node +.>Normal battery operating loss power of battery at kth load node in t period +.>Loss rate of battery connection at kth load node +.>The ratio delta Y of the electric quantity loss of the battery to the off-grid electric energy of the battery, and the initial instantaneous state of charge value of the battery at the kth load node in the t period +.>The initial instantaneous state of charge value of the battery at the kth load node in the period t + deltat +.>Minimum state of charge of the battery at the kth load node +.>And the maximum value of the state of charge of the battery at the kth load node +.>The following constraints are established:

the second constraint construction unit is specifically used for constructing constraint conditions of a feasible topological structure of the alternating current region in the micro-grid system;

based on the feasible topology, the constraint conditions for establishing the feasible topology of the alternating current area are as follows:

Wherein v is _ij Is the parent-child relationship of the initial load node i and the final load node i in the vector line ij, v _ji Is the parent-child relationship of the initial load node j and the final load node i in the vector line ji, i ₁ Is the only root node in the micro-grid system, gamma _a Is a node set which is all adjacent to the initial load node in the micro-grid system, and gamma _c Is a set of nodes other than the root node in the micro-grid system;

the third constraint construction unit is used for constructing a power flow constraint condition of an alternating current region of the micro-grid system based on the improved power flow model;

a fourth constraint construction unit, configured to construct a power flow constraint condition of the direct current region of the micro-grid system based on the improved power flow model;

the fifth constraint construction unit is specifically used for constructing a voltage constraint condition and a current constraint condition of the micro-grid system;

the sixth constraint construction unit is specifically configured to construct a VSC model constraint of the voltage source converter station, where specific constraint conditions are as follows:

Q _VSC,ij,min ≤Q _t，ij ≤Q _VSC,ij,max

R _VSC,ij,min ≤P _t，ij ≤R _VSC,ij,max

wherein Q is _VSC,ij,max Is the reactive power compensation upper limit value, Q, of the voltage source converter station VSC of the vector line ij _VSC,ij,min Reactive power compensation lower limit value of voltage source converter station VSC of vector line ij，Q _t, i _j Reactive power of voltage source converter station VSC of vector line ij in period t, P _VSC,ij,max Is the upper active power limit value, P, of the voltage source converter station VSC of the vector line ij _VSC,ij,min Is the active power lower limit value, P, of the voltage source converter station VSC of the vector line ij _t,ij Is the active power lower limit value of the voltage source converter station VSC of the vector line ij in the period t;

P _AC,t,ij is the active power transmitted from AC node i to AC node j in period t, Q _AC,t,ij Is the reactive power transmitted from ac node I to ac node j in period t, I _VSC,t,ij Is the current value of the voltage source converter station VSC of the vector line ij in the period t, R _VSC,t,ij Is the voltage value, X, of the voltage source converter station VSC of the vector line ij during the period t _VSC,t,ij Reactance value, P, of voltage source converter station VSC of vector line ij in period t _DC,t,ij Active power of direct current side of voltage source converter station VSC of vector line ij in t period, Q _VSC,t,ij Is the reactive power of the voltage source converter station VSC of the vector line ij during period t.

Based on the above embodiment, further, the third constraint construction unit is specifically configured to determine a parent node set of the ac node in the feasibility topology structure and a child node set of the ac node in the feasibility topology structure, set an outflow point where the parent node is power, set an inflow point where the child node is power, and set a plurality of parent nodes in the child node, and establish the following constraint:

Where qac is an ac node, c (iac) is a parent node set of ac nodes iac in the feasibility topology, s (iac) is a child node set of ac nodes iac in the feasibility topology, c (jac) is a parent node set of ac nodes jac in the feasibility topology, s (jac) is a child node set of ac nodes jac in the feasibility topology;

κ _t,iac-jac is the switching variable, κ, of the vector line iac-jac from ac node iac to ac node jac over the period t _iac-jac Is the switching variable of the vector line iac-jac,is the current value from ac node iac to ac node jac in period t, U _AC,t,jac Is the amplitude of the voltage at ac node jac during time t, U _AC,t,iac Is the amplitude of the voltage at the ac node iac during the period t, R _iac-jac Is the resistance value of the vector circuit iac-jac, X _iac-jac Is the reactance value of the vector line iac-jac;

P _AC,t,iac-jac is the active power transmitted from ac node iac to ac node jac during period t, Q _AC,t,iac-jac Is the reactive power transferred from ac node iac to ac node jac during period t, P _AC,t,jac Is the active power flowing in by the alternating current node iac in the t period, Q _AC,t,jac The representation is the reactive power flowing in by the ac node jac during the t period;

is the input value of the active power of the distributed power supply at ac node jac during the t period,/ >Is the input value of the reactive power of the distributed power supply at ac node jac during the t period,Is the output value of active power in the alternating current node jac energy storage battery in the t period,/->Is the output value, P, of the reactive power in the alternating current node jac energy storage battery in the t period _{AC,t,jac,load} Is the load power consumed by active power on the ac node jac during the t period, Q _AC,t,j,load Is the load power that reactive power consumes on ac node jac during the t period;

according to the micro-grid system fault recovery and network reconstruction strategy provided by the third embodiment of the application, when a plurality of faults occur to the micro-grid in the face of extreme disaster weather, the micro-grid is subjected to preliminary island division so as to maintain important loads and other load power supply of the grid, a fault maintenance sequence optimization strategy is established, the faults are eliminated one by one according to the importance degree of the faults, the smooth power supply line from a power supply to the important loads is ensured, and more important loads are ensured to be recovered. Island division is carried out through time-division dynamics, the whole fault recovery and reconstruction time interval is divided into a plurality of time segments, multi-time-segment dynamic island division is carried out, flexible and efficient utilization of energy sources in a system is guaranteed, and the system is cooperated with a depth-first traversal strategy, so that global optimal solutions are guaranteed to be found. And finally, converting the modeling type into a mixed integer second order cone planning model by using a second order cone technology to carry out global optimal solution. The reliability of the micro-grid is enhanced, the elasticity of the micro-grid is improved, and the resistance of the micro-grid in disasters is enhanced.

In addition, the embodiment of the application comprises a computer device, and the computer device comprises a memory and a processor, wherein the memory stores a computer program, and the processor realizes the method for recovering the fault and reconstructing the network of the micro-grid system according to any one of the technical schemes when executing the computer program.

The embodiment of the application further comprises a computer readable storage medium, wherein a computer program is stored on the computer readable storage medium, and the computer program realizes the method for recovering the faults and reconstructing the network of the micro grid system in any of the technical schemes when being executed by a processor.

It will be appreciated by those skilled in the art that the present invention can be carried out in other embodiments without departing from the spirit or essential characteristics thereof. Accordingly, the above disclosed embodiments are illustrative in all respects, and not exclusive. All changes that come within the scope of the invention or equivalents thereto are intended to be embraced therein.

Claims (10)

1. A method for fault recovery and network reconfiguration of a micro-grid system, the method comprising:

s1, based on information of load nodes in a micro-grid system, establishing a multi-objective optimization function of the micro-grid system;

S2, constructing a feasible topological structure from the distributed energy sources in the direct-current line to the load nodes in the micro-grid system by using a depth-first traversal algorithm;

s3, establishing a fault retrieval order optimization strategy model;

s4, based on the fault retrieval order optimization strategy model and the feasible topological structure, constructing an alternating current line operation constraint condition and a direct current line operation constraint condition of the micro-grid system;

s5, adopting mixed integer second order cone planning, and obtaining an optimal detection scheme based on the AC line operation constraint condition and the DC line operation constraint condition of the micro-grid system through convex relaxation treatment and second order cone to convert the fault retrieval sequence optimization strategy model.

2. The method according to claim 1, wherein the step S1 specifically comprises:

establishing a multi-objective optimization function by using the maximum sum of the weight coefficient products of all load nodes and all load nodes in the micro-grid system and the minimum network loss:

wherein k is the number of the load node in the micro-grid, V _Load Is the collection of load nodes in the micro-grid, beta _k Is the switch state value of the kth load node, Z _L,k Is the load carried by the kth load node, gamma _k Is the weight coefficient of the load carried by the kth load node, gamma _b Is the set of vector lines formed by initial load nodes and final load nodes in the micro-grid system, r _ij Is the resistance value of the vector line ij from the initial load node i to the final load node j,is the current value of the vector line ij from the initial load node i to the final load node j.

3. The method according to claim 1, wherein the step S2 specifically comprises:

based on the microgrid distributed power supply set V by adopting a depth-first traversal algorithm E (G) _DC To the V _Load And searching the feasible paths from the distributed energy nodes to the load nodes by using the electric distance of the medium load nodes to obtain the feasible topological structure from the distributed energy nodes to the load nodes:

V _DC ＝{V _d1 ,V _d2 ,V _d3 ,…}

V _Load ＝{V _l1 ,V _l2 ,V _l3 ,…}

wherein V is _da Is said V _DC A-th distributed power supply node of (V) _lb Is said V _Load The b-th load node, d (V _da ,V _lb ) Is said V _DC From the a-th distributed power supply node to the V _Load The electrical distance of the b-th load node in the system is more than or equal to 1, and b is more than or equal to 1.

4. A method according to claim 3, wherein said step S3 comprises:

based on the on-off state value of the vector line ij in the fault recovery t period, the number of lines overhauled at most in one overhauling period, the time consumed for overhauling one fault line, namely the overhauling period, and the number of overhauling periods included in the fault period, a fault overhauling sequence optimization strategy is established:

Wherein t is _n Is the last period of the fault recovery t period, t _m Is the next period of the fault recovery t period,vector line ij of final load node j of initial load node ij is at t _n Switch state value of time period->Is based on initial load nodeVector line ij of i final load node j is at t _m Switch state value of time period->The switching state value of the vector line ij of the final load node j of the initial load node i in the period of fault recovery T is adopted, L is the set of all the fault vector lines, M is the number of lines which are overhauled at the same time at most in one overhauling period, T ₀ Is a maintenance period, N _T Is the number of service periods that the failure period includes.

5. The method according to claim 2, wherein the step S4 specifically includes:

s41, establishing distributed power supply constraint and energy storage constraint;

output minimum value of active power of distributed power supply based on kth load node in t periodOutput maximum value of active power of distributed power supply of kth load node in t period +.>Active power value +.>The distributed power supply of the kth load node is reactive in t period>Distributed power supply capacity of kth load node +.>Minimum operating power factor of the distributed power supply of the kth load node >Charging and discharging active power of battery at kth load node in t period +.>Charging and discharging reactive power of battery at kth load node in t period +.>Apparent power of battery at kth load node in t period +.>Maximum value of the reactive power of the battery at the kth load node +.>Normal battery operating loss power of battery at kth load node in t period +.>Loss rate of battery connection at kth load node +.>The ratio delta Y of the electric quantity loss of the battery to the off-grid electric energy of the battery, and the initial instantaneous state of charge value of the battery at the kth load node in the t period +.>The initial instantaneous state of charge value of the battery at the kth load node in the period t + deltat +.>Minimum state of charge of the battery at the kth load node +.>And a state of charge maximum of the battery at the kth load nodeThe following constraints are established:

s42, constructing constraint conditions of a feasible topological structure of an alternating current region in the micro-grid system;

based on the feasible topology, the constraint conditions for establishing the feasible topology of the alternating current area are as follows:

wherein v is _ij Is the parent-child relationship of the initial load node i and the final load node i in the vector line ij, v _ji Is the parent-child relationship of the initial load node j and the final load node i in the vector line ji, i ₁ Is the only root node in the micro-grid system, gamma _a Is a node set which is all adjacent to the initial load node in the micro-grid system, and gamma _c Is a set of nodes other than the root node in the micro-grid system;

s43, constructing a power flow constraint condition of an alternating current region of the micro-grid system based on the improved power flow model;

s44, constructing a power flow constraint condition of a direct current region of the micro-grid system based on the improved power flow model;

s45, constructing a voltage constraint condition and a current constraint condition of the micro-grid system;

s46, constructing a VSC model constraint of the voltage source converter station, wherein the specific constraint conditions are as follows:

Q _{VSC，ij，min} ≤Q _t，ij ≤Q _{VSC，ij，max}

P _{VSC，ij，min} ≤P _t，ij ≤P _{VSC，ij，max}

wherein Q is _{VSC，ij，max} Is the reactive power compensation upper limit value, Q, of the voltage source converter station VSC of the vector line ij _{VSC，ij，min} Is the reactive power compensation lower limit value, Q, of the voltage source converter station VSC of the vector line ij _t，ij Is the voltage of vector line ijReactive power of source converter station VSC in period t, P _{VSC，ij，max} Is the upper active power limit value, P, of the voltage source converter station VSC of the vector line ij _{VSC，ij，min} Is the active power lower limit value, P, of the voltage source converter station VSC of the vector line ij _t，ij Is the active power lower limit value of the voltage source converter station VSC of the vector line ij in the period t;

P _AC，t，ij is the active power transmitted from AC node i to AC node j in period t, Q _AC，t，ij Is the reactive power transferred from ac node I to ac node j in period f, I _VSC，t，ij Is the current value of the voltage source converter station VSC of the vector line ij in the period t, R _VSC，t，ij Is the voltage value, X, of the voltage source converter station VSC of the vector line ij during the period t _VSC，t，ij Reactance value, P, of voltage source converter station VSC of vector line ij in period t _DC，t，ij Active power of direct current side of voltage source converter station VSC of vector line ij in t period, Q _VSC，t，ij Is the reactive power of the voltage source converter station VSC of the vector line ij during period t.

6. The method of claim 5, wherein the step of determining the position of the probe is performed,

the step S43 specifically includes:

determining a father node set of alternating-current nodes in the feasibility topological structure and a child node set of alternating-current nodes in the feasibility topological structure, setting an outflow point of which the father node is power and an inflow point of which the child node is power, wherein the child node is provided with a plurality of father nodes, and establishing the following constraint:

where qac is an ac node, c (iac) is a parent node set of ac nodes iac in the feasibility topology, s (iac) is a child node set of ac nodes iac in the feasibility topology, c (jac) is a parent node set of ac nodes jac in the feasibility topology, s (jac) is a child node set of ac nodes jac in the feasibility topology;

κ _t,iac-jac Is the switching variable, κ, of the vector line iac-jac from ac node iac to ac node jac over the period t _iac-jac Is the switching variable of the vector line iac-jac,is the current value from ac node iac to ac node jac in period t, U _AC,t,jac Is the amplitude of the voltage at ac node jac during time t, U _AC,t,iac Is the amplitude of the voltage at the ac node iac during the period t, R _iac-jac Is the resistance value of the vector circuit iac-jac, X _iac-jac Is the reactance value of the vector line iac-jac;

P _AC,t,iac-jac is the active power transmitted from ac node iac to ac node jac during period t, Q _AC,t,iac-jac Is the reactive power transferred from ac node iac to ac node jac during period t, P _AC,t,jac Is an alternating current node in t periodActive power of iac inflow, Q _AC,t,jac The representation is the reactive power flowing in by the ac node jac during the t period;

is the input value of the active power of the distributed power supply at ac node jac during the t period,Is the input value of the reactive power of the distributed power supply at ac node jac during the t period,Is the output value of active power in the alternating current node jac energy storage battery in the t period,/->Is the output value, P, of the reactive power in the alternating current node jac energy storage battery in the t period _{AC,t,jac,load} Is the load power consumed by active power on the ac node jac during the t period, Q _AC,t,j,load Is the load power that reactive power consumes on ac node jac during the t period;

the step S44 specifically includes:

determining a father node set of the direct current nodes in the feasibility topological structure, setting an outflow point of which the father node is power, allowing the father nodes to have a plurality of father nodes, and establishing the following constraint:

where qdc is a direct current node, c (idc) is a parent node set of direct current nodes idc in the feasibility topology, s (idc) is a child node set of direct current nodes idc in the feasibility topology, c (jdc) is a parent node set of direct current nodes jdc in the feasibility topology, s (jdc) is a child node set of direct current nodes jdc in the feasibility topology; p (P) _DC,t,jdc Is the active power that the ac node jdc flows into during the t period,is the current value flowing from the dc node idc to the dc node jdc in the t period, U _DC,t,jdc Is the voltage amplitude of the DC node jdc during the t period, U _DC,t,idc Is the voltage amplitude of the DC node idc in the t period, P _DC,t,idc-jdc Active power transmitted by DC node idc to DC node jdc during period t, Q _DC,t,idc-jdc Reactive power transmitted by the dc node idc to the dc node jdc during the t period, The active power of the distributed power supply in the t period is input value of the direct current node jdc, +.>Is the input value of the reactive power of the distributed power supply at the dc node jdc during the t period,/->Is an energy storage battery with active power at a direct current node jdc in t periodForce output value of->Is the output value of the active power in the direct current node jdc energy storage battery in the period t, P _{DC,t,jdc,load} Is the load power consumed by active power on the DC node jdc during the t period, Q _{DC,t,jdc,load} Is the load power consumed by reactive power on the DC node jdc during the t period, R _idc-jdc Is the resistance value, κ, of the vector line jdc-jdc _idc-jdc Is the switching variable of vector line idc-jdc.

7. The method according to claim 5, wherein the step S45 specifically includes:

s451, constructing voltage constraint of an alternating current node in an alternating current region of the micro-grid system:

wherein U is _AC,kac,min Is the minimum voltage of the alternating current node kac, U _AC,kac,max Is the maximum voltage of the alternating current node kac, U _AC,t,kac Is the voltage value of the ac node kac at time t;

s452, constructing voltage constraint of a direct current node in a direct current region of the micro-grid system:

wherein U is _DC,kdc,min Is the voltage minimum of the direct current node kac, U _DC,i,max Is the voltage minimum of the direct current node kdc, U _DC,t,kac Is the voltage value of the dc node kdc at time t;

and D453, constructing current constraint of an alternating current circuit of an alternating current region in the micro-grid system:

wherein I is _{AC,iac-jac,max} Is the maximum value of the current from the AC node iac to the AC node jac in the AC circuit iac-jac, I _{AC,iac-jac,min} Is the minimum value of the current from the alternating current node iac to the alternating current node jac in the alternating current circuit iac-jac, I _AC,t,iac-jac Is the current value from the ac node iac to the ac node jac in the ac circuit iac-jac in the period t;

and D453, constructing current constraint of a direct current circuit of a direct current region in the micro-grid system:

wherein I is _{DC,idc-jdc,max} Is the maximum value of the current from DC node idc to DC node jdc in DC circuits jdc-jdc, I _{DC,idc-jdc,min} Is the minimum value of the current from the DC node idc to the DC node jdc in the DC circuit idc-jdc, I _DC,t,idc-jdc Is the current value of the dc node idc to dc node jdc in the dc circuit idc-jdc during the period t.

8. An apparatus for recovering a fault and reconstructing a network of a micro-grid system, the apparatus comprising:

the multi-objective optimization module is used for establishing a multi-objective optimization function of the micro-grid system based on information of load nodes in the micro-grid system;

the depth traversal module is used for constructing a feasible topological structure from the distributed energy sources in the direct-current line to the load nodes in the micro-grid system by utilizing a depth-first traversal algorithm;

The strategy model building module is used for building a fault retrieval order optimization strategy model;

the constraint condition constructing module is used for constructing an alternating current line operation constraint condition and a direct current line operation constraint condition of the micro-grid system based on the fault retrieval order optimization strategy model and the feasible topological structure;

the solving module is used for adopting mixed integer second order cone planning, and solving an optimal detection scheme after the fault retrieval sequence optimization strategy model is converted through convex relaxation treatment and second order cones based on the AC line operation constraint condition and the DC line operation constraint condition of the micro-grid system.

9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the method of micro grid system fault recovery and network reconstruction of any one of claims 1 to 7.

10. A computer readable storage medium having stored thereon a computer program, which when executed by a processor implements the method of micro grid system fault recovery and network reconfiguration of any one of claims 1 to 7.