Urban distribution network tie line optimization method and system based on two tie connection modes

Abstract

The present invention provides a method and system for optimizing the tie lines of an urban distribution network based on a two-tie connection wiring mode, wherein the maximum power allowed to be transmitted during normal operation of each radial line is determined according to the connection mode, and the single radial line layout is completed; on the basis of the single radial line, the line end nodes are connected in pairs to form a single tie connection, and during the connection process, it is necessary to avoid the connection between the line end nodes of two substations belonging to the same substation; on the single tie trunk line, the intermediate tie points are selected according to the principle of uniform load distribution, and then the intermediate tie points are connected in pairs to generate tie lines to form a two-tie connection wiring mode; based on the two-tie connection wiring mode, an optimization model for tie lines of an urban distribution network is established, and constraints related to the actual distribution network planning are constructed and solved. The present invention can efficiently make decisions to obtain the optimal tie line layout plan, and considers the actual street layout, the tie line is the shortest, and each load block is guaranteed to have power supply.

Description

Technical Field

[0001] The invention belongs to the technical field of power system distribution network planning, and in particular relates to a method and system for optimizing tie lines of an urban distribution network based on a two-tie connection mode. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The urban distribution network is an important part of the power system. All construction and renovation projects must be coordinated with the urban development plan. In recent years, cities have developed rapidly, the demand for electricity load has increased rapidly, and the requirements for power quality and power supply reliability have continued to increase. Relatively speaking, the construction and development of urban networks are relatively slow. At present, the construction of urban power grids cannot meet the needs of urban economic and social development very well. One of the important reasons is that the unreasonable structure of the power grid is one of the important reasons.

[0004] The ultimate goal of urban distribution network planning is to determine the corresponding optimal distribution network structure according to the load level and power supply planning during the planning period to meet the demand for reliable and economical power distribution. Pure radial lines are not recommended for use in urban medium-voltage distribution networks with high reliability requirements due to their poor reliability. Usually, the radial trunk lines are connected through tie switches in the middle to form a wiring mode with higher reliability. In a line with a connection, when a line fails, the faulty line section can be isolated, and the load on the normal line section can be transferred to other trunk lines through the tie line, so that the range of users affected by the power outage is smaller. Therefore, it is extremely necessary to consider the feeder wiring mode in the distribution network planning. In the current urban distribution network, the commonly used wiring methods are single radiation, single connection and three-segment two-connection wiring mode.

[0005] For the actual urban distribution network planning considering the wiring mode, due to the constraints of many practical engineering factors, many current technical methods are often not feasible for engineering, and it is very difficult to achieve automatic layout through computers, which greatly increases the difficulty of planners' work. Among them, the implementation of the two-connection wiring mode is the most difficult. Solving it through traditional mathematical optimization methods is the most direct and effective method, but the first problem to be solved by mathematical optimization methods is to establish a mathematical model, and the difficulty lies in how to analytically express the optimization objectives and constraints of the model and combine them with specific applications. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a method and system for optimizing the interconnection lines of an urban distribution network based on a two-interconnection wiring mode. The present invention can efficiently make decisions to obtain the optimal interconnection line layout plan, and considers the actual street layout, the interconnection line is the shortest, and each load block is guaranteed to have power supply.

[0007] According to some embodiments, the present invention adopts the following technical solutions:

[0008] A method for optimizing tie lines of an urban distribution network based on a two-tie connection mode comprises the following steps:

[0009] Model the actual street layout and convert graphic information into data information;

[0010] Determine the maximum power allowed to be transmitted during normal operation of each radial line according to the contact method, and complete the layout of the single radial line;

[0011] On the basis of a single radial line, the line end nodes are connected in pairs to form a single contact connection. During the connection process, it is necessary to avoid connecting the line end nodes of two lines belonging to the same substation to each other;

[0012] On the single contact trunk line, select the intermediate contact points according to the principle of uniform load distribution, and then connect the intermediate contact points in pairs to generate contact lines, forming a two-contact wiring mode;

[0013] Based on the two-interconnection wiring mode, an optimization model for the urban distribution network interconnection line is established, and constraints related to the actual distribution network planning are constructed;

[0014] The optimization model of the urban distribution network tie line is linearized and solved under constraints to obtain the final optimization solution for the urban distribution network tie line.

[0015] As an optional implementation method, the specific process of generating a tie line and forming two tie connection modes includes: for the intermediate tie points that are separated from the original distribution system, an additional virtual distribution system is established, that is, it is assumed that there is a virtual load point and a virtual substation at each intermediate tie point, and the matching of the intermediate tie points can be achieved through the connection between the virtual substations; the connection of the virtual substations can adopt the idea of ​​N-1 safety constraints, that is, all loads can still maintain normal power supply after a substation fails, and the two ends of the line are connected to two different substations respectively.

[0016] As an optional implementation method, the specific process of determining the optimization plan for the urban distribution network interconnection lines includes: exhaustively enumerating all the solutions for matching the intermediate interconnection points in pairs and generating an initial solution set, screening the initial solution set in turn according to the proposed constraints, retaining those that meet the constraints and discarding those that do not, until a interconnection point matching solution that meets all the constraint requirements is obtained, which is the best solution.

[0017] As an optional implementation, the urban distribution network tie line optimization model takes the shortest tie line path as the optimization goal.

[0018] As an optional implementation, the constraint conditions of the urban distribution network tie line optimization model include basic grid planning constraints, wiring mode constraints and node connection constraints.

[0019] As a further limited implementation method, the basic constraints of power grid planning include load power supply constraints, tie line capacity constraints, tie line construction constraints, node power balance constraints under normal circumstances, and substation output constraints under normal circumstances;

[0020] The wiring mode constraints include virtual substation outgoing line number constraints and virtual substation matching constraints;

[0021] The node connection constraints include line non-bifurcation constraints and corresponding constraints under single virtual substation failure; the constraints under fault scenarios include load power supply constraints, interconnection line capacity constraints, node power balance constraints, substation output constraints, and virtual substation matching constraints.

[0022] As an optional implementation, the specific process of linearizing the urban distribution network tie line optimization model includes: processing the nonlinear part of the model according to the linearization method and converting it into a mixed integer linear programming model.

[0023] An urban distribution network tie line optimization system based on two tie connection modes, comprising:

[0024] The urban distribution network modeling module is configured to model the actual street layout and convert the graphic information into data information;

[0025] The two-tie connection mode construction module is configured to establish the maximum power allowed to be transmitted when each radial line is operating normally according to the connection mode, and complete the single radial line layout; on the basis of the single radial line, the line end nodes are connected in pairs to form a single connection connection. During the connection process, it is necessary to avoid connecting the end nodes of two lines belonging to the same substation to each other; on the single connection trunk line, the intermediate connection points are selected according to the principle of uniform load distribution, and then the intermediate connection points are connected in pairs to generate a connection line, forming a two-tie connection mode;

[0026] The optimization model building module is configured to build an optimization model of the urban distribution network tie line based on the two tie connection modes, and to build constraints related to the actual distribution network planning;

[0027] The optimization solution module is configured to linearize the optimization model of the urban distribution network tie line, solve it under constraint conditions, and obtain the final optimization solution for the urban distribution network tie line.

[0028] An electronic device comprises a memory and a processor, and computer instructions stored in the memory and executed on the processor. When the computer instructions are executed by the processor, the steps in the above method are completed.

[0029] A computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, the steps in the above method are completed.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention takes into account the characteristics of actual urban distribution networks and is based on real street layouts. The optimization result has strong adaptability and high engineering reference value.

[0032] The present invention analyzes and considers a plurality of commonly used wiring modes, and designs a feasible and effective implementation method of two-connection wiring modes according to the characteristics of each wiring mode, which meets the requirements of actual urban distribution networks.

[0033] The present invention achieves analytical expression of multiple complex constraints, which is different from the existing optimization technology implemented by intelligent algorithms, establishes a rigorous and effective mathematical model, and can be implemented through traditional mathematical optimization methods.

[0034] The present invention adopts a mixed integer linear programming algorithm to improve the computer's solving ability by converting complex problems into relatively simple linear problems, thereby solving the problem that direct solving in existing methods may lead to memory exhaustion when considering complex constraints.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0037] Figure 1 is a schematic diagram of the process of this embodiment;

[0038] Figure 2 Schematic diagram of the system structure of this embodiment;

[0039] Figure 3 Schematic diagram of three wiring modes of this embodiment;

[0040] Figure 4 Schematic diagram of virtual load and virtual substation of this embodiment;

[0041] Figure 5This is a schematic diagram of the correct matching method of this embodiment;

[0042] 6(a) and (b) are schematic diagrams of the error matching mode of this embodiment. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0044] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0045] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0046] Embodiment 1:

[0047] like Figure 1 As shown, this embodiment provides a method for optimizing tie lines of an urban distribution network based on two tie connection modes, including:

[0048] S101: Design an optimization method for interconnection lines of an urban distribution network based on a two-interconnection connection mode.

[0049] In step S101, the method for implementing the two-connection wiring mode is divided into three steps: input of basic planning data, including load power supply data, street layout data, etc.

[0050] According to the characteristics that distribution network lines are usually laid out along streets, the streets in the planning area are taken as candidate branches. Since urban streets are intertwined, the small blocks surrounded by multiple streets are called blocks, the section of streets surrounding the blocks is called segments, and the place where the segments are connected is called a junction.

[0051] In addition, the following explanations are required for the three commonly used wiring modes mentioned: Figure 3 As shown. A single tie line is formed by connecting two single radial lines through a tie switch; a two-tie wiring mode unit is formed by connecting two single tie lines through a tie switch. The tie line generated by the connection process has two intermediate tie points (virtual substation nodes) at its start and end, and its layout may pass through multiple sections.

[0052] Specifically, three steps to achieve optimization of the urban distribution network tie lines based on the two-tie connection mode are as follows.

[0053] The first step is to determine the maximum power allowed to be transmitted when each radial line is in normal operation according to the contact method, and complete the single radial line layout. It should be noted that the maximum transmission capacity P max-load The following formula should be satisfied:

[0054]

[0055] In the formula, m represents the maximum number of interconnected lines for each radial line, that is, the m-interconnection wiring mode.

[0056] The second step is to connect the line end nodes in pairs on the basis of the single radial line to form a single liaison connection. During the connection process, it is necessary to avoid connecting the line end nodes of two lines belonging to the same substation to each other.

[0057] In the third step, according to the principle of uniform load distribution, the intermediate contact points are selected on the single contact trunk line obtained in step 2, and then the intermediate contact points are connected in pairs to generate contact lines, forming a two-contact wiring mode. Among them, the key to the third step is only how to achieve the matching between the two nodes, so each intermediate contact point can be separated from the original distribution system and considered separately. For this purpose, an additional virtual distribution system is established. It is assumed that there is a virtual load point and a virtual substation at each intermediate contact point. The matching of the intermediate contact points can be achieved through the connection between the virtual substations. In order to facilitate implementation, the size of the virtual load needs to be specially set. When two load points are located on the same single contact line, the sizes of the two loads are set to be equal; otherwise, the sizes are different. In addition, it is assumed that the capacity of the virtual substation is sufficient. The description of the virtual load and virtual substation is as follows Figure 4 shown.

[0058] S102: Taking the shortest tie line path as the optimization goal, relevant constraints that need to be considered in the actual distribution network planning project are introduced to obtain a tie line self-optimization model based on the two tie connection modes that meets various constraints.

[0059] The objective function of the optimization model of the urban distribution network tie line based on the two-tie connection mode is expressed as:

[0060]

[0061] Among them, L s , N S and N L are the length of the branch to be selected, the total number of road sections and the total number of planned contact lines. Decision variable b s,l Indicates whether to build route l on road section s. s,lWhen the value is 1, it means that line l is built on section s; when the value is 0, no line is built.

[0062] The basic constraints of power grid planning include load power supply constraints, tie line capacity constraints, tie line construction constraints, node power balance constraints under normal circumstances, and substation output constraints under normal circumstances;

[0063] The wiring mode constraints include virtual substation outgoing line number constraints and virtual substation matching constraints;

[0064] The node connection constraints include line non-bifurcation constraints and corresponding constraints under single virtual substation failure. Constraints under fault scenarios include load power supply constraints, interconnection line capacity constraints, node power balance constraints, substation output constraints, and virtual substation matching constraints.

[0065] Specifically, the constraints of the objective function are:

[0066] 1) Load power supply constraints

[0067] In the model, each load located at the node is powered by the planned tie line, and the constraints are as follows:

[0068]

[0069] Among them, NG vir , and D j,l They represent the virtual substation node, the virtual load on node j and the power supply of the tie line l to the load on node j respectively.

[0070] 2) Substation output constraints

[0071]

[0072]

[0073] In the above formula, if node j is not a substation node, there is no substation output at this point. The value of is 0; if node j is a virtual substation node, the sum of the power in the outgoing lines of each virtual substation should be less than the maximum output allowed by the substation

[0074] 3) Node power balance constraints

[0075]

[0076] Among them, P s,lrepresents the power flowing through line l on section s; right(s) and left(s) represent the right and left nodes of section s, respectively. For each node j, the power flowing into the tie line at that point should be equal to the power flowing out.

[0077] 4) Interconnection line capacity constraints

[0078]

[0079] in, The above formula indicates that the power flowing through line l cannot exceed the maximum transmission capacity allowed by the line.

[0080] 5) Tie line construction constraints

[0081]

[0082] Constraint (8) indicates that if the power flow on a section s is not zero, then at least one line must be built on the section. s,l |Linearization is required, and absolute value linearization is used. The method is as follows:

[0083]

[0084] 6) Wiring mode constraints

[0085] A key point of this model is how to analytically express the mutual matching of two single-tie trunk lines and meet the requirements of the two-tie wiring mode at the same time, so as to achieve Figure 5 The matching results shown avoid the erroneous matching modes of self-matching shown in FIG6 (a) and multiple matching shown in (b).

[0086] To achieve the above objectives, the following constraints need to be satisfied:

[0087] a) Constraints on the number of outgoing lines from virtual substations

[0088] In the two-tie connection mode, each intermediate contact point needs to be connected to another intermediate contact point through a tie line, and there will not be a phenomenon where an intermediate contact point is connected to multiple intermediate contact points at the same time, as shown in Figure 6(a). In order to make each intermediate contact point match only one intermediate contact point, it is defined that each virtual substation has only one outgoing line, and the analytical expression is as follows:

[0089]

[0090] Constraint (10) indicates that only one tie line is constructed on all sections connected to the virtual substation, that is, the number of outgoing lines from the substation is 1.

[0091] b) Virtual substation matching constraints

[0092] A two-tie connection mode unit includes two single-tie trunk lines. Therefore, when the virtual substations are matched with each other, the two intermediate tie points on the same single-tie trunk line must be matched with the other two intermediate tie points on the other single-tie trunk line at the same time. Figure 5 In order to avoid the incorrect matching method shown in Figure 6(b), the output of the two virtual substations on the same single tie line is defined to be equal, and the analytical expression is as follows:

[0093]

[0094] Among them, i f ,j f represents the single tie line to which nodes i and j belong. Constraint (11) indicates that when nodes i and j belong to two intermediate tie points on the same single tie line, the total output of the virtual substations on these two nodes is equal.

[0095] 7) Node connection constraints

[0096] In this model, the connection between two nodes is another key point. In order to express the node connection constraints analytically, the node association and N-1 safety criteria are used. The specific constraints are as follows:

[0097] a) Tie line non-bifurcation constraint

[0098] In the two-tie connection mode, the tie line is not allowed to bifurcate, and the mathematical expression is as follows:

[0099]

[0100] The above formula indicates that the correlation degree of each node on each tie line does not exceed 2. The endpoint correlation degree of the tie line is 1, indicating that only one tie line (a segment of a complete tie line) is connected to the point; the correlation degree of other nodes on the tie line is 2, indicating that two tie lines (two adjacent segments of a complete tie line) are connected to the point.

[0101] b) Virtual substation connection constraints

[0102]

[0103]

[0104]

[0105]

[0106]

[0107] Constraints (13)-(17) are single substation failure scenario constraints, the purpose of which is to connect two virtual substations to generate a tie line. When a virtual substation fails, all virtual loads are required to maintain normal power supply without power outages. Obviously, the closed-loop network structure can realize load transfer, which means that the two endpoints of the tie line must be two different virtual substations. The subscript w in the constraint represents the faulty substation, and the 0 / 1 parameter represents the logical relationship between the faulty substation w, node j and the single contact trunk line f. If node j is a normal substation node and belongs to the same single contact trunk line as the faulty substation w, parameter The value is 0; if node j and the faulty substation w do not belong to the same single contact line, or node j is not a substation node, then the parameter The value is 1. Constraint (13) represents the load power supply constraint under the fault scenario. Constraint (14) indicates that when node j is a substation node and is not a faulty substation, the substation output at the node cannot exceed its allowed capacity limit. Constraint (15) indicates that if node j is a substation node and a fault occurs, or node j is not a substation node, the substation output at this point is 0. Constraint (16) indicates that the power flowing into each node is equal to the power flowing out. Add parameter It is then stated that if the faulty substation and the normal substation belong to the same single tie line, the output of the normal substation is forced to become 0, again avoiding the problem of multiple matching of the single tie line. Constraint (17) is the virtual substation matching constraint under the fault scenario, and its purpose is the same as constraint (11).

[0108] S103: According to the linearization processing method, the nonlinear part in the model is processed and converted into a mixed integer linear programming model, and then the model is solved by the CPLEX solver.

[0109] CPLEX is an optimization engine from IBM. This optimization engine is used to solve four basic problems: linear programming (LP), quadratic programming (QP), constrained quadratic programming (QCQP), second-order cone programming (SOCP), and the corresponding mixed integer programming (MIP) problems. CPLEX has the following advantages: (1) It can solve some very difficult industry problems; (2) It solves very quickly; (3) It sometimes provides the advantage of super linear acceleration.

[0110] This embodiment constructs a mixed integer linear programming model for optimizing distribution network tie lines, which can be used for planning under the conditions of considering street layout and fault scenarios. The simulation operation is more comprehensive, and the optimization results are more reliable and comprehensive, which improves the engineering application value of distribution network planning.

[0111] This embodiment takes into account street layout, wiring mode and node connection modeling issues, and can effectively adapt to the new situation of current power grid development.

[0112] This embodiment constructs an optimization model for the urban distribution network tie line based on the two-tie connection mode, and makes rigorous analytical expressions for various practical needs, so that the optimization results are more accurate and more practical. In addition, the nonlinear optimization problem is converted into a complete linear optimization problem, so that a mixed integer linear programming algorithm can be used for solution, which improves the efficiency and reliability of the model solution.

[0113] In other embodiments, since the location information and quantity information of each intermediate contact point are known, all the solutions for matching the intermediate contact points can be directly enumerated and an initial solution set can be generated. Then, the initial solution set is screened in sequence according to the proposed constraint conditions, and those that meet the requirements are retained, and those that do not meet the requirements are discarded, until a contact point matching solution that meets all constraint requirements is obtained, which is the best solution. Finally, with the shortest path as the goal, the contact line layout of the best matching solution is determined.

[0114] Embodiment 2:

[0115] An urban distribution network tie line optimization system based on two tie connection modes, comprising:

[0116] The urban distribution network modeling module is configured to model the actual street layout and convert the graphic information into data information;

[0117] The two-tie connection mode construction module is configured to establish the maximum power allowed to be transmitted when each radial line is operating normally according to the connection mode, and complete the single radial line layout; on the basis of the single radial line, the line end nodes are connected in pairs to form a single connection connection. During the connection process, it is necessary to avoid connecting the end nodes of two lines belonging to the same substation to each other; on the single connection trunk line, the intermediate connection points are selected according to the principle of uniform load distribution, and then the intermediate connection points are connected in pairs to generate a connection line, forming a two-tie connection mode;

[0118] The optimization model building module is configured to build an optimization model of the urban distribution network tie line based on the two tie connection modes, and to build constraints related to the actual distribution network planning;

[0119] The optimization solution module is configured to linearize the optimization model of the urban distribution network tie line, solve it under constraint conditions, and obtain the final optimization solution for the urban distribution network tie line.

[0120] Embodiment three:

[0121] An electronic device includes a memory and a processor, and computer instructions stored in the memory and executed on the processor. When the computer instructions are executed by the processor, the steps in the method of the first embodiment are completed.

[0122] Embodiment 4:

[0123] A computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by a processor, the steps in the method of the first embodiment are completed.

[0124] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0125] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0126] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0127] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0128] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for optimizing tie lines of an urban distribution network based on a two-tie connection mode, characterized in that: The following steps are involved: Model the actual street layout and convert graphic information into data information; Determine the maximum power allowed to be transmitted during normal operation of each radial line according to the contact method, and complete the layout of the single radial line; On the basis of a single radial line, the line end nodes are connected in pairs to form a single contact connection. During the connection process, it is necessary to avoid connecting the line end nodes of two lines belonging to the same substation to each other; On the single contact trunk line, select the intermediate contact points according to the principle of uniform load distribution, and then connect the intermediate contact points in pairs to generate contact lines, forming a two-contact wiring mode; The specific process of generating a tie line and forming a two-tie connection mode includes: for the intermediate ties that are separated from the original distribution system, an additional virtual distribution system is established, and there is a virtual load point and a virtual substation at each intermediate ties. The matching of the intermediate ties is achieved through the ties between the virtual substations; the ties between the virtual substations adopt the idea of ​​N-1 safety constraints, and all loads can still maintain normal power supply after a substation fails. The two ends of the line are connected to two different substations respectively; Based on the two-tie connection mode, an optimization model of the urban distribution network tie line is established, and constraints related to the actual distribution network planning are constructed; the constraints of the urban distribution network tie line optimization model include basic grid planning constraints, connection mode constraints and node connection constraints; the objective function of the urban distribution network tie line optimization model is expressed as: Among them, L s , N S and N L are the length of the branch to be selected, the total number of road sections and the total number of planned contact lines; the decision variable b s,l Indicates whether to build line l on section s; when variable b s,l When the value is 1, it means that line l is built on section s; when the value is 0, no line is built; The optimization model for the tie line of the urban distribution network takes the shortest tie line path as the optimization goal; The urban distribution network interconnection line optimization model is linearized and solved under constraints to obtain the final urban distribution network interconnection line optimization plan; the specific determination process of the urban distribution network interconnection line optimization plan includes: exhaustively enumerating all the solutions for matching the intermediate interconnection points in pairs and generating an initial solution set, screening the initial solution set in turn according to the proposed constraints, retaining those that meet the constraints and discarding those that do not, until the interconnection point matching solution that meets all the constraint requirements is obtained as the best solution.

2. A method for optimizing tie lines of an urban distribution network based on two tie connection modes as claimed in claim 1, characterized in that: The basic constraints of power grid planning include load power supply constraints, tie line capacity constraints, tie line construction constraints, node power balance constraints under normal circumstances, and substation output constraints under normal circumstances; The wiring mode constraints include virtual substation outgoing line number constraints and virtual substation matching constraints; The node connection constraints include line non-bifurcation constraints and corresponding constraints under single virtual substation failure; the constraints under fault scenarios include load power supply constraints, interconnection line capacity constraints, node power balance constraints, substation output constraints, and virtual substation matching constraints.

3. A method for optimizing tie lines of an urban distribution network based on two tie connection modes as claimed in claim 1, characterized in that: The specific process of linearizing the optimization model of the urban distribution network tie line includes: according to the linearization method, the nonlinear part in the model is processed and converted into a mixed integer linear programming model.

4. An urban distribution network tie line optimization system based on two tie connection modes, characterized in that: include: The urban distribution network modeling module is configured to model the actual street layout and convert the graphic information into data information; The two contact wiring mode building modules are configured to establish a maximum power allowed to be transmitted when each radial line is in normal operation according to the contact mode, and complete the single radial line layout; On the basis of a single radial line, the line end nodes are connected in pairs to form a single contact connection. During the connection process, it is necessary to avoid connecting the line end nodes of two lines belonging to the same substation to each other; on the single contact trunk line, the intermediate contact points are selected according to the principle of uniform load distribution, and then the intermediate contact points are connected in pairs to generate contact lines, forming a two-contact connection mode; The specific process of generating a tie line and forming a two-tie connection mode includes: for the intermediate ties that are separated from the original distribution system, an additional virtual distribution system is established, and there is a virtual load point and a virtual substation at each intermediate ties. The matching of the intermediate ties is achieved through the ties between the virtual substations; the ties between the virtual substations adopt the idea of ​​N-1 safety constraints, and all loads can still maintain normal power supply after a substation fails. The two ends of the line are connected to two different substations respectively; The optimization model construction module is configured to construct an optimization model of the urban distribution network tie line based on the two tie connection modes, and to construct constraints related to the actual distribution network planning; the constraints of the urban distribution network tie line optimization model include basic constraints of power grid planning, wiring mode constraints and node connection constraints; the objective function of the urban distribution network tie line optimization model is expressed as: Among them, L s , N S and N L are the length of the branch to be selected, the total number of road sections and the total number of planned contact lines; the decision variable b s,l Indicates whether to build line l on section s; when variable b s,l When the value is 1, it means that line l is built on section s; when the value is 0, no line is built; The optimization model for the tie line of the urban distribution network takes the shortest tie line path as the optimization goal; The optimization solution module is configured to linearize the optimization model of the urban distribution network interconnection line, solve it under the constraints, and obtain the final optimization plan for the urban distribution network interconnection line; the specific determination process of the optimization plan for the urban distribution network interconnection line includes: exhaustively enumerating all the solutions for matching the intermediate interconnection points in pairs and generating an initial solution set, screening the initial solution set in turn according to the proposed constraints, retaining those that meet the constraints and discarding those that do not meet the constraints, until the interconnection point matching solution that meets all the constraint requirements is obtained as the best solution.

5. An electronic device, characterized in that: The method comprises a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the steps in the method according to any one of claims 1 to 3 are completed.

6. A computer-readable storage medium, characterized in that: Used to store computer instructions, which, when executed by a processor, complete the steps of the method according to any one of claims 1 to 3.

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