Power distribution network extension planning method and system with reliability constraint, medium and processor

Abstract

The invention discloses a power distribution network extension planning method and system with reliability constraint, a medium and a processor, and relates to the technical field of power distribution network extension planning. According to the method, a planning scheme is obtained by constructing and initializing a topological structure of the power distribution network, collecting historical operation data to obtain a reliability index, establishing electrical, investment and reliability constraints, setting an objective function and constructing a model. According to the method, reliability indexes can be directly and accurately considered, tie line arrangement and network reconstruction after faults are considered, system-level and node-level reliability accurate constraints are achieved, different load requirements are met, planning economy and reliability are improved, and the problems that an existing method is excessive in investment or insufficient in reliability, limited in flexibility and accuracy and the like are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of distribution network expansion planning, in particular to a distribution network expansion planning method with reliability constraints, a system, a medium and a processor. BACKGROUND

[0002] With the increasing demand for power supply reliability, distribution network reliability evaluation becomes more and more important. The reliability of the distribution network planning is one of the important means to improve the reliability of the distribution network. How to embed the results of the distribution network reliability evaluation (i.e. express and constrain various reliability indicators) into the distribution network planning model is a problem to be solved at present.

[0003] In recent years, some researchers have proposed reliability evaluation methods based on optimization models, trying to directly incorporate reliability evaluation into distribution network planning models. For example, Muñoz-Delgado et al. proposed a linear programming method in 2018 to describe the fault impact range by modeling virtual power flow. Although this method can embed reliability indicators in the planning model, it does not consider the supporting role of tie lines in load restoration, which may underestimate the actual reliability of the distribution network. There is currently no method that can simultaneously consider tie line planning and post-fault load restoration strategy for meshed distribution network planning, which may lead to over-investment or failure to meet reliability requirements, and existing methods are difficult to accurately express and constrain various reliability indicators in the planning model, limiting the flexibility and accuracy of planning.

[0004] In view of this, a distribution network expansion planning method with reliability constraints, a system, a medium and a processor are needed. SUMMARY

[0005] In view of the problems in the prior art that may lead to over-investment or failure to meet reliability requirements, limit the flexibility and accuracy of planning, etc., the present application provides a distribution network expansion planning method with reliability constraints, a system, a medium and a processor, which can directly and accurately consider reliability indicators in the planning process, and simultaneously consider the selection and arrangement of tie lines and post-fault network reconstruction strategies in the planning model to improve the economy and reliability of the planning, and realize accurate constraint of reliability indicators, including system-level and node-level reliability requirements to meet the individualized reliability requirements of different loads. The specific technical solutions are as follows: A distribution network expansion planning method with reliability constraints, comprising: S1: constructing a distribution network topology and initializing; S2: collecting historical operation data of the distribution network, and obtaining reliability indicators of the distribution network according to the distribution network topology; S3: Establishing electrical constraints, investment constraints and reliability constraints of the distribution network expansion planning; S4: Setting a target function of the distribution network expansion planning; S5: Building a distribution network expansion planning model with the constraints and the target function and solving the model to obtain a planning scheme.

[0006] Further, the step S1 comprises: S11: Counting and recording the number of nodes, branches, transformers and substations in the distribution network and the connection relationship therebetween.

[0007] S11: Establishing the topology structure of the distribution network according to the recorded data, and clearly defining the connection relationship between the existing nodes and the possible planning line path.

[0008] S13: Initializing the parameters of the distribution network, including the types of conductors and transformers, and setting the planning period and the life cycle parameters of the equipment to simulate the influence of equipment aging on the distribution network.

[0009] Further, in the step S2, the historical operation data of the distribution network are collected, and the reliability indicators of the distribution network are obtained according to the topology structure of the distribution network, comprising the following steps: S21: By collecting the historical failure data of the equipment of the distribution network, the failure rate of the branch is determined, and the influence of the failure on each node is analyzed, and finally the user outage frequency is obtained; S22: By counting the historical repair and switching operation time, the network reconstruction capability is analyzed, and the interruption duration of each node under different failure conditions is calculated to obtain the user outage duration; S23: Calculating the reliability indicators of the distribution network according to the user outage frequency and the user outage duration.

[0010] Further, the user outage frequency calculation formula is as follows: ; In the above formula, is the user outage frequency of node i in the tth stage; is the failure rate of branch xy in the tth stage; is a binary variable, whether the load of node i is affected by power outage under the failure scenario of branch xy in the tth stage; is the load node set in the tth stage.

[0011] Further, the user outage duration calculation formula is as follows: ; In the above formula, is the user outage duration of node i in the tth stage; The switching operation time after a fault in branch XY; The repair time after a fault in branch XY; Let be a binary variable, representing whether the load of node i has been restored to power supply after network reconstruction in the case of a fault in branch xy at stage t.

[0012] Furthermore, the reliability index is calculated using the following formula: ; ; ; In the above formula, The average power outage frequency index of the system in stage t; Let i be the number of users at node i in stage t. The index of the average power outage duration in stage t; The expected energy supply for stage t is not yet complete. A set of load level scenarios; The duration of the b-th load scenario; Let the load rate be for load scenario b. Let be the peak load of node i in stage t.

[0013] Furthermore, in step S4, the objective function is as follows: ; ; ; ; in, To expand the total cost of the plan; For investment costs; For reliability costs, This is the reliability cost coefficient; For maintenance costs; t is the stage of the extended planning; T is the total number of stages in the extended planning; Let be the present value factor of the investment cost in stage t; Let be the present value factor of the maintenance cost in stage t; This represents the number of years preceding stage t; It is the interest rate calculated in finance; This represents the number of years preceding stage t; As an alternative branch conductor for the power distribution network system; A set of alternative branch conductors for a power distribution network system; , These are the alternative branch wires. Investment and maintenance costs; As a backup transformer for the power distribution network system; A set of alternative transformers for the power distribution network system; These are the alternative transformers Investment and maintenance costs; They are nodes The investment and maintenance costs of the substation; Let be the set of all nodes s; ( ), and They represent the stages respectively. At the beginning, is it on a branch? Install alternative branch wires at the location Is it on the feeder? Install alternative transformer b at the location and whether it is at the node A substation was built at the location; For the set of branch lines; j and j are the nodes at both ends of the branch, respectively; For feeders; For feeder set; It is the transpose of a unit vector; , , and These are the wires and the transformer. (0) Predefined aging vector for stage.

[0014] A distribution network expansion planning system with reliability constraints, applied to the aforementioned distribution network expansion planning method with reliability constraints, includes: The topology module is used to construct and initialize the distribution network topology. The reliability module is used to collect historical operating data of the distribution network and obtain the reliability indicators of the distribution network based on the distribution network topology. The constraint module is used to establish electrical constraints, investment constraints, and reliability constraints for distribution network expansion planning; The target module is used to set the objective function for the distribution network expansion plan; The planning module is used to construct an extended planning model of the distribution network based on constraints and objective functions, and then solve it to obtain the planning scheme.

[0015] A computer-readable storage medium includes a stored program, wherein, when the program is executed, it controls the device where the computer-readable storage medium is located to perform the above-described distribution network expansion planning method with reliability constraints.

[0016] A processor for running a program, wherein the program performs the power distribution network expansion planning method with reliability constraints as described above when running.

[0017] Compared with the prior art, the application has the following beneficial effects: 1. The application provides a power distribution network expansion planning method with reliability constraints, which can directly and accurately consider reliability indexes in the planning process, and simultaneously considers the selection and arrangement of tie lines and the network reconfiguration strategy after failure in the planning model, so as to improve the economy and reliability of the planning, realize accurate constraint of the reliability indexes, and meet the individualized reliability requirements of different loads. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the specific embodiments or prior art description will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale.

[0019] Figure 1 Fig. 1 is a flowchart of a power distribution network expansion planning method with reliability constraints; Figure 2 Fig. 2 is a structural diagram of a power distribution network expansion planning system with reliability constraints; Figure 3 Fig. 3 is a single-line diagram of a 54-node system; Figure 4 Fig. 4 is an investment planning view of the model of the present application when the system is in normal state; Fig. 5 is an investment planning view of the traditional planning model when the system is in normal state. Figure 5 Fig. 6 is an investment planning view of the model of the present application when the system is in failure state; Fig. 7 is an investment planning view of the traditional planning model when the system is in failure state. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0021] It should be understood that, when used in the present application, the terms "comprise" and "include" indicate the existence of the described features, integers, steps, operations, elements and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components and / or sets thereof.

[0022] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0023] It should also be further understood that the term “and / or” as used in this application refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0024] Example 1 like Figure 1 The diagram shows a flowchart of a distribution network expansion planning method with reliability constraints, which includes the following steps: S1: Construct and initialize the power distribution network topology.

[0025] S11: Count and record the number of nodes, branches, transformers and substations in the distribution network and their interconnections.

[0026] S11: Based on the recorded data, the topology of the distribution network was established, and the connection relationships between existing nodes and possible planned route paths were clarified.

[0027] S13: Initialize distribution network parameters, including the number of conductor and transformer types, and set the planning period and equipment life cycle parameters to simulate the impact of equipment aging on the distribution network.

[0028] S2: Collect historical operating data of the distribution network and obtain the reliability indicators of the distribution network based on the distribution network topology.

[0029] S21: By collecting historical fault data of distribution network equipment, the fault rate of the branch is determined, and the impact of faults on each node is analyzed to finally obtain the user outage frequency (CIF). The calculation formula is as follows: ; In the above formula, Let be the power outage frequency (times / year) of node i in stage t, which measures the number of power outages at node i in this stage; Let xy be the failure rate (times / year·unit length) of branch xy in stage t, reflecting the probability of branch failure; is a binary variable representing whether the load of node i is affected by the power outage in the xy fault scenario of branch in stage t (1 indicates that it is affected, 0 indicates that it is not affected). Let be the set of load nodes in stage t.

[0030] S22: By counting the historical repair and switching operation time, analyze the network reconfiguration capability, calculate the outage duration of each node under different fault conditions to obtain the customer interruption duration (CID), the calculation formula is as follows: ; In the above formula, is the customer interruption duration of node i in the tth stage (hours / year), which measures the cumulative outage time of node i in this stage. is the switching operation time after branch xy failure (hours), that is, the time consumption of fault isolation and network reconfiguration. is the repair time after branch xy failure (hours), that is, the total time consumption of completely repairing the fault branch. is a binary variable, whether the load of node i is restored after network reconfiguration under the tth stage branch xy failure scenario (1 represents restoration, and 0 represents non-restoration).

[0031] S23: Calculate the reliability indicators of the distribution network according to the customer interruption frequency (CIF) and the customer interruption duration (CID), which are used to evaluate the reliability of the distribution network and the effectiveness of the planning scheme.

[0032] ; ; ; In the above formula, is the system average interruption frequency index in the tth stage (times / house / year), which reflects the average number of times that users in the system experience power outages. is the number of users of node i in the tth stage (house), which is used to calculate the system-level indicators. is the system average interruption duration index in the tth stage (hours / house / year), which reflects the average outage time of users in the system. is the expected energy not supplied in the tth stage (MWh / year), which measures the total energy loss of the system due to power outages. is a set of load level scenarios (such as peak, flat, and low valley loads). is the duration of the bth load scenario (hours / year), for example, the peak load lasts for 2000 hours per year. is the load rate of the bth load scenario (dimensionless), that is, the ratio of actual load to peak load. is the peak load of node i in the tth stage (MWh), which is used to calculate energy loss.

[0033] S3: Establish the electrical constraints, investment constraints and reliability constraints of the distribution network expansion planning.

[0034] S31: Establish the corresponding electrical constraints to ensure that the node power balance, line power flow and node voltage are within the normal operating range, and meet the corresponding capacity limit. The specific electrical constraints include: (I) Distflow constraint equation from normal operation and branch fault, including the following: 1. Power flow constraint ignoring loss term as follows: ; (6) ; (7) ; (8) ; (9) In the above formula, is the scene identifier, when , it represents the normal scene of branch , and the corresponding variable is the value under the normal operation scene, when , it represents the power failure scene caused by branch fault; represents whether branch ij is connected due to network reconfiguration after branch xy fault (or normal operation condition) at stage t, 1 represents connected, and 0 represents disconnected; is a large enough number; , represents the active power and reactive power of branch ij at scene xy and stage t; , represents the active power and reactive power of node i at scene xy and stage t; represents the voltage square value of node i at scene xy and stage t; is the voltage of transformer node; is the set of transformer nodes; parameters and represent the resistance of branch ij at stage t and the reactance of branch ij at stage t, respectively; represents the set of all nodes of the distribution network.

[0035] 2. The node voltage constraint is as follows formula (10): ; (10) In the above formula, , represent the lower limit and upper limit of the node voltage.

[0036] 3. The branch in scene , the connection status of phase t is determined by a binary variable , and is limited by the power flow constraint (11) of branch , which is formulated as follows: ; (11) In the above equation, denotes the set of all branches.

[0037] 4. The linearized conductor available capacity constraint of branch i j is obtained from the quadratic capacity limit, which is formulated as follows: ; (12) ; (13) ; (14) ; (15) In the above equations, denotes the maximum limit power of branch i j at phase t; , denote the active power and reactive power of transformer e at scenario x y and phase t, respectively; denotes the branches connected to transformer e; , denote the active power and reactive power of the branches connected to transformer e at scenario x y and phase t, respectively.

[0038] 5. The capacity constraint of transformer e is formulated as follows: ; (16) ; (17) denotes the maximum limit power of transformer e at phase t.

[0039] 6. Constraint (18) states that when branch i j has no conductor connection at phase t, the connection status = 0, which is formulated as follows: ; (18) .

[0040] denotes that for all scenarios x y consisting of set Y and the special scenario “NO”, the equations (or constraints) numbered from (6) to (18) are all satisfied and take effect; ​where 1 means yes and 0 means no; Y represents the main part of the scenario set, such as a set of basic scenarios including normal operation, fault, etc., and stores a number of preset scenario categories.

[0041] (ii) The constraint of identifying the influence of branch outage and load recovery on the node.

[0042] In this part, two key binary variables are defined for the node and , which represent whether the load of the node is affected by the outage of the branch and the supply condition of the network after the reconfiguration after the fault. The load demand of the node will be affected by the outage of the branch at stage if and only if . After the reconfiguration of the network after the fault, the load of the node can be normally supplied if and only if .

[0043] 1. The following constraint (19) shows that in the current scenario , the branch fails and is isolated: ; (19); 2. The nodes belonging to the same feeder attribute variable as the fault branch , which means that under the normal operation condition at stage , these nodes belong to the same feeder as the branch , will be affected by the outage caused by the upstream circuit breaker tripping, as shown in constraint (20): ; (20) In the above formula, represents whether the load of node i is affected by the outage of branch xy at scenario xy and stage t, 1 means affected, and 0 means not affected; , represents whether node i and branch belong to feeder f under the normal operation condition at stage t, 1 means yes, and 0 means no; represents the set of all feeders; represents the set of load nodes at stage t.

[0044] After the circuit breaker tripping and switching interruption duration , the fault branch ​The switches on both sides are opened to isolate the fault. The system topology is then reconfigured by operating the switches and circuit breakers to restore the maximum outage power requirement, as shown in approximately (21)-(24): ; ; ; ; ; In the above formula, This indicates whether the load of node i is affected by the disconnection of branch xy in scenario xy and stage t, with 1 indicating that it is affected and 0 indicating that it is not affected; This indicates whether the load of node i can be powered normally after the network reconstruction following a fault, in scenario xy and stage t. 1 indicates yes, and 0 indicates no. This represents the actual active power of node i in scenario xy and stage t. This represents the original active power demand of node i at stage t, i.e., the active power of node i without considering the impact of faults. This represents the actual reactive power of node i under scenario xy and stage t; This represents the initial reactive power demand of node i at stage t.

[0045] For nodes unaffected by the power outage, their demands should not be affected after the network reconfiguration following the fault, as constrained by constraint (21) (thus avoiding...). and (Case 0). In this invention, it is assumed that only all power can be restored after reconfiguration (case 0). ) load or cut off all ( 0) Load, as constrained by (22) and (23). Radial operation constraints of the reconfigured distribution network are shown in (24).

[0046] (III) Constraints arise from the assignment of nodes and branches to feeders under normal operating conditions. Referring to the recovery steps described in Part II, nodes on the same feeder as the faulty branch will be affected by the power outage. For example, if a node belongs to a feeder... branch road A persistent fault occurred, caused by the feeder. The power supply nodes will inevitably be affected, and correspondingly... , Therefore, this invention utilizes attribution variables. and to characterize the nodes and branches whether they belong to a feeder under normal operating conditions at stage These variables are continuously defined but only take binary values, as indicated by constraints (27)-(34).

[0047] ; ; ; ; ; ; ; ; ; In the above equations, represents the actual active power at node i at stage t under normal operating scenario (NO); represents the original active power demand at node i at stage t, i.e. the active power at node i without considering the impact of the fault; represents the actual reactive power at node i at stage t under normal operating scenario (NO); represents the original reactive power demand at node i at stage t, i.e. the reactive power at node i without considering the impact of the fault. represents whether branch ij is on at stage t under normal operating scenario (NO), 1 means on, 0 means off. (Analogous meaning when subscript is j) represents whether node i belongs to feeder f under normal operating conditions at stage t, 1 means yes, 0 means no (although continuously defined, only takes binary values). represents whether branch ij belongs to feeder f under normal operating conditions at stage t, 1 means yes, 0 means no (although continuously defined, only takes binary values). represents whether branch connected with transformer under normal operating conditions at stage t belongs to feeder f, 1 means yes, 0 means no (although continuously defined, only takes binary values). Whether it belongs to feeder f, 1 indicates yes, 0 indicates no (although it is a continuous definition, only binary numbers are taken). This indicates that in the normal operation scenario (NO), at stage t, the relationship with the transformer... Connecting branches (i.e.) Whether the connection is active or disconnected: 1 indicates active, 0 indicates disconnected.

[0048] Constraints (25) and (26) represent the load of a node under normal operating conditions. The membership variables of the virtual power flow are defined by constraints (27)-(30), where constraint (29) represents the source of the virtual power flow, and constraints (27)-(28) indicate if the branch Under normal operating conditions ( The virtual power flow will pass through this branch. Constraints (31) and (32) indicate that a node or branch can only be powered by one feeder.

[0049] (iv) This constraint stems from the availability of the equipment.

[0050] binary variables and Representing branches and transformer The current state. Constraints (35)-(38) describe the branch. The current state ( ),capacity( ),resistance( ), reactance ( ) and failure rate ( The relationship between the transformer and conductor selection. Constraints (40) and (41) respectively show the transformer's... The current state and capacity of the transformer. The logical constraints between transformer installation and substation existence are shown in constraints (42) and (43).

[0051] ; ; ; ; ; In the above formula, denotes whether there is a conductor connection at branch ij at stage t (1 means yes, 0 means no); is the transpose of the unit vector (all elements are 0 except the t-th element which is 1); a is an alternative branch conductor of the distribution system; is the set of alternative branch conductors of the distribution system; is a binary variable denoting whether the alternative branch conductor a is installed at branch ij at the beginning of stage t (1 means installed, 0 means not installed); is the aging vector of conductor a at stage t (used to model the impact of equipment aging on the distribution system); is a binary variable denoting whether the alternative branch conductor a is installed at branch ij in the initial state (before the planning starts) (1 means installed, 0 means not installed); is the initial aging vector of conductor a (denotes the remaining usage period of the existing conductor); denotes the maximum limit power (capacity constraint) of branch ij at stage t; is the rated capacity of alternative branch conductor a; is the length of branch ij; denotes the resistance of branch ij at stage t; is the unit length resistance of alternative branch conductor a. denotes the reactance of branch ij at stage t. is the unit length reactance of alternative branch conductor a; denotes the failure rate of branch xy at stage t; denotes the length of branch xy; is the unit length failure rate of alternative branch conductor a. denotes the existing state of transformer e at stage t (1 means exists, 0 means does not exist); is a binary variable denoting whether the alternative transformer e is installed at feeder f at the beginning of stage t (1 means installed, 0 means not installed); denotes the transformer at stage t; is a binary variable denoting whether the alternative transformer is installed at feeder f in the initial state (before the planning starts) (1 means installed, 0 means not installed); denotes the transformer at stage t; is the initial aging vector of transformer (denotes the remaining usage period of the existing transformer); denotes the maximum limit power (capacity constraint) of transformer at stage t; is the set of transformers at node s; denotes the state of transformer at stage τ (1 means existing, 0 means not existing); is a binary variable, which denotes whether substation is built at node s at the beginning of stage τ (1 means built, 0 means not built); is a binary variable, which denotes whether substation exists at node s at the initial state (before the planning starts) (1 means existing, 0 means not existing); is the set of substation nodes.

[0052] In order to consider the aging of conductor a and transformer e, the aging vectors , , and are defined as: where, is the number of stage of the remaining service life of existing alternative branch conductor a, is the number of stage of the remaining service life of existing alternative branch conductor a, is the number of stage of the life cycle of transformer replacement scheme , is the number of stage of the remaining service life of existing transformer replacement scheme . Taking constraint (35) as an example, denotes the existence of conductor on branch in the entire planning period (stage ), as a dimensional vector, which is obtained by multiplying the unit vector to obtain the existence of conductor on branch at stage .

[0053] S32: Determine the equipment investment constraint to ensure that the annual investment does not exceed the budget and reasonably arrange the equipment replacement timing.

[0054] In the above formula, is the investment cost of the tth stage, is the upper limit of the budget of the tth stage, is the total budget of the planning period; ( ) is the replacement interval of conductor a (transformer b), ( ) is the life cycle thereof. is the latest replacement stage of the initial conductor a, is the remaining life cycle thereof; is the state of installing the transformer b for the feeder f of the tth stage, is the state of constructing the substation for the (initial) node s of the tth stage; is the state of installing the conductor a for the branch ij of the tth stage; is the maximum allowed difference of investment cost between adjacent stages.

[0055] S33: In order to ensure the feasibility of the planning scheme, corresponding reliability constraints are defined to meet the reliability requirements of the system and important users.

[0056] As shown in (53)-(57), different reliability indicators need to be applied to different nodes and different stages: In the above formula, is the maximum allowed value of user outage frequency (times / year) for the node i of the tth stage, which is a preset reliability constraint threshold for ensuring that the outage frequency of the node does not exceed the specified upper limit. is the maximum allowed value of user outage duration (hours / year) for the node i of the tth stage, which is a preset reliability constraint threshold for limiting the cumulative outage duration of the node. is the maximum allowed value of system average outage frequency index (times / house・year) for the tth stage, which is a system-level reliability constraint threshold for ensuring that the average outage frequency of the overall users meets the requirements. is the maximum allowed value of system average outage duration index (hours / house・year) for the tth stage, which is a system-level reliability constraint threshold for controlling the average outage duration of the overall users. is the maximum allowed value of expected energy not supplied (MWh / year) for the tth stage, which is a system-level reliability constraint threshold for limiting the total energy loss caused by outages.

[0057] S4: Set the objective function of the distribution network expansion planning.

[0058] Specifically, the total cost of the expansion planning is minimized as the objective function, the total cost The calculation formula is as follows:​​​​ ; wherein, is the total cost of the expansion planning; is the investment cost; is the reliability cost, wherein is the reliability cost coefficient; is the maintenance cost; t is the stage of the expansion planning; the duration of the expansion planning is divided into T stages of known duration, all variables in the model are associated with each stage; is the present value coefficient of the investment cost in the t-th stage; is the present value coefficient of the maintenance cost in the t-th stage.

[0059] Further, the present value coefficient of the investment cost in the t-th stage is calculated as follows: ; Further, the present value coefficient of the maintenance cost in the t-th stage is calculated as follows: ; In the above equations, represents the number of years before the t-th stage; to denotes the number of years between the t-th stage and the -th stage minus one year. is the typical rate symbol in financial calculations, used to discount future costs to present value.

[0060] Further, the investment cost is calculated as follows: ; Further, the maintenance cost is calculated as follows: In the above equations, is the candidate branch conductor of the distribution network system; is the set of candidate branch conductors of the distribution network system; , are the investment cost and the maintenance cost, respectively, of the candidate branch conductor ; is the candidate transformer of the distribution network system; is the set of candidate transformers of the distribution network system; are the investment cost and the maintenance cost, respectively, of the candidate transformer ; are the nodes The investment cost and the maintenance cost of the substation; is the set of all nodes s; binary number represent whether to install an alternative branch conductor at branch , whether to install an alternative transformer b at feeder , and whether to build a substation at node , respectively, at the beginning of phase ; is the set of branch lines; , j the nodes at both ends of the branch line; is the feeder; is the set of feeders; is the unit vector transpose, i.e., excluding the element equal to 1, the remaining elements are all equal to zero; in addition, , , and are the predefined aging vectors of conductors and transformers at phase (0), respectively. Further, the maintenance cost includes periodic (preventive) maintenance cost and repair maintenance cost. In actual cases, the reliability of power equipment is affected by the level of maintenance. The more meticulous and solid the maintenance work is, the higher the reliability of the equipment is. At the same time, the maintenance cost of each device is predefined to keep its outage rate constant.

[0061] Further, the maintenance cost includes periodic (preventive) maintenance cost and repair maintenance cost. In actual cases, the reliability of power equipment is affected by the level of maintenance. The more meticulous and solid the maintenance work is, the higher the reliability of the equipment is. At the same time, the maintenance cost of each device is predefined to keep its outage rate constant.

[0062] S5: Construct a distribution network expansion planning model with constraint conditions and objective functions and solve the planning scheme.

[0063] S51: Set the convergence condition, and construct a distribution network expansion planning model combining the constraint condition and the objective function.

[0064] The distribution network expansion planning model can be expressed as: minimize the objective function (1), subject to constraints (2)-(57), .

[0065] The distribution network expansion planning model proposed in this scheme adopts a mixed integer linear programming (MILP) form, which can be solved by existing commercial software. In the model, the number of nodes, branches, transformers and substations in the distribution network is respectively set to , , and ​​​​​​Most of the variables and their dimensions are listed in Table 1. The number of conductor and transformer types are 3 and 2, respectively and .

[0066] Table 1: Decision variables and their dimensions S52: Select a suitable commercial solver to solve the distribution network expansion planning model, and output the detailed planning scheme.

[0067] S6: Analyze the solution results.

[0068] According to the detailed planning scheme, the improvement effect of system reliability indicators is evaluated, the power supply reliability of important users is analyzed, and the reliability between regions is compared to ensure the technical feasibility and economy of the planning scheme.

[0069] Specific example analysis This application uses a 54-node system as a test system, as shown in Figure 3 . The test system includes 50 load nodes, 4 substation nodes and 63 branches, with the power and voltage reference values being 1 MVA and 13.5 kV, respectively, and the currency unit used being $. And this application considers two transformer replacement schemes and three conductor replacement schemes. The failure rate of the feeder is set to 0.1 times per year per kilometer, and the interruption duration of repair-switching and switching-only is set to 3 hours and 0.5 hours, respectively. The load demand is simulated by three load levels, and the load factors are equal to 70% (2,000 hours / year), 83% (5,760 hours / year) and 100% (1,000 hours / year) of the corresponding peak demand, respectively. The planning period for investment decision is 10 years, and is divided into 5 sub-stages, each with a time of two years. And the interest rate in the model is set to 10%, and the unit reliability of EENS is set to 10$ / MWh. The life of the conductor and transformer is set to 20 years.

[0070] In this example analysis, . To verify the effectiveness of the model proposed in this paper, the planning results are compared with the planning model based on the traditional reliability evaluation method in the first section. Figure 4 and Figure 5 show the comparison results of the planning schemes of the two models, respectively.

[0071] In Figure 4 ​In the diagram, three tie lines are planned between nodes 24 and 25, nodes 37 and 43, and nodes 42 and 48. As can be seen from the diagram, after load restoration following a fault, the load demand of downstream nodes of the out-of-power branch can be effectively transferred to another feeder via the tie lines, thereby improving system reliability. Figure 5 In the traditional planning model, an additional substation and two transformers are built at node 53 to meet reliability requirements. Figure 5 In the proposed network, a radial structure is formed, with three independent parts separated from each other. Table 2 lists detailed data such as planning cost, reliability index, and computation time.

[0072] Table 2: Comparison of Results As shown in Table 2, under the same reliability requirements, the planning results obtained by the model proposed in this invention are more economical (costing approximately one-quarter of that of traditional planning models). This is achieved by employing a network reconstruction strategy. Figure 4 The proposed planning scheme, under the condition of low investment cost, has a reliability index that is similar to... Figure 5 The high-cost solutions shown are comparable. Therefore, it is crucial to consider tie lines in reliability assessments and planning models.

[0073] Example 2 like Figure 2 As shown, a distribution network expansion planning system with reliability constraints, applied to the aforementioned distribution network expansion planning method with reliability constraints, includes: The topology module is used to construct and initialize the distribution network topology. The reliability module is used to collect historical operating data of the distribution network and obtain the reliability indicators of the distribution network based on the distribution network topology. The constraint module is used to establish electrical constraints, investment constraints, and reliability constraints for distribution network expansion planning; The target module is used to set the objective function for the distribution network expansion plan; The planning module is used to construct an extended planning model of the distribution network based on constraints and objective functions, and then solve it to obtain the planning scheme.

[0074] Example 3 A computer-readable storage medium includes a stored program, wherein, when the program is executed, it controls the device where the computer-readable storage medium is located to perform the above-described distribution network expansion planning method with reliability constraints.

[0075] Example 4 A processor for running a program, wherein the program performs the power distribution network expansion planning method with reliability constraints as described above when running.

[0076] The application discloses a power distribution network expansion planning method with reliability constraints, a system, a medium and a processor, and relates to the technical field of power distribution network expansion planning. The method comprises the following steps: constructing a power distribution network topology structure and initializing, collecting historical operation data to obtain reliability indexes, establishing electrical, investment and reliability constraints, setting a target function, and constructing a model to obtain a planning scheme. The method can directly and accurately consider the reliability indexes, takes into account the layout of tie lines and network reconfiguration after a fault, realizes accurate constraints of system-level and node-level reliability, meets different load demands, improves planning economy and reliability, and solves problems such as excessive investment or insufficient reliability, limited flexibility and accuracy of existing methods.

[0077] Those skilled in the art can understand that the units of the examples described in combination with the embodiments disclosed herein can be realized in electronic hardware, computer software or a combination of both, and the components of the examples have been described in the above description in general terms in terms of functions in order to clearly illustrate the interchangeability of hardware and software. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0078] In the embodiments provided in the present application, it should be understood that the division of units is only a logical functional division, and actual implementation can have another division manner, for example, multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored, etc.

[0079] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0080] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or say the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server or a network device, etc.) to execute all or part of the steps of the method described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a mobile hard disk, a magnetic disk or an optical disk, and various media that can store program codes.

[0081] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the present application.

Claims

1. A distribution network expansion planning method with reliability constraints, characterized in that, include: S1: Construct and initialize the power distribution network topology; S2: Collect historical operating data of the distribution network and obtain the reliability indicators of the distribution network based on the distribution network topology; S3: Establish electrical constraints, investment constraints, and reliability constraints for distribution network expansion planning; S4: Define the objective function for the distribution network expansion plan; S5: Construct an extended planning model for the distribution network based on constraints and objective functions, and solve it to obtain the planning scheme.

2. The distribution network expansion planning method with reliability constraints according to claim 1, characterized in that, Step S1 includes: S11: Count and record the number of nodes, branches, transformers and substations in the distribution network and their interconnections. S11: Based on the recorded data, the topology of the distribution network was established, and the connection relationships between existing nodes and possible planned route paths were clarified. S13: Initialize distribution network parameters, including the number of conductor and transformer types, and set the planning period and equipment life cycle parameters to simulate the impact of equipment aging on the distribution network.

3. The distribution network expansion planning method with reliability constraints according to claim 1, characterized in that, In step S2, collecting historical operating data of the distribution network and obtaining reliability indicators of the distribution network based on the distribution network topology includes the following steps: S21: By collecting historical fault data of distribution network equipment, determine the fault rate of the branch, analyze the impact of faults on each node, and finally obtain the user power outage frequency; S22: By statistically analyzing historical repair and switching operation times, the network reconstruction capability is analyzed, and the interruption duration of each node under different fault conditions is calculated to obtain the user power outage duration. S23: Calculate the reliability index of the distribution network based on the user power outage frequency and the user power outage duration.

4. The distribution network expansion planning method with reliability constraints according to claim 3, characterized in that, The formula for calculating the frequency of user power outages is as follows: ； In the above formula, Let i be the user power outage frequency at node i in stage t. Let xy be the failure rate of branch xy in stage t; Let be a binary variable, representing whether the load of node i is affected by the power outage in the xy fault scenario of branch in stage t. Let be the set of load nodes in stage t.

5. The distribution network expansion planning method with reliability constraints according to claim 4, characterized in that, The formula for calculating the duration of the user power outage is as follows: ； In the above formula, Let be the duration of the power outage for user i at stage t. The switching operation time after a fault in branch XY; The repair time after a fault in branch XY; Let be a binary variable, representing whether the load of node i has been restored to power supply after network reconstruction in the case of a fault in branch xy at stage t.

6. The distribution network expansion planning method with reliability constraints according to claim 5, characterized in that, The formula for calculating the reliability index is as follows: ； ； ； In the above formula, The average power outage frequency index of the system in stage t; Let i be the number of users at node i in stage t. The index of the average power outage duration in stage t; The expected energy supply for stage t is not yet complete. A set of load level scenarios; The duration of the b-th load scenario; Let the load rate be for load scenario b. Let be the peak load of node i in stage t.

7. The distribution network expansion planning method with reliability constraints according to claim 6, characterized in that, In step S4, the objective function is as follows: ； ； ； ； in, To expand the total cost of the plan; For investment costs; For reliability costs, This is the reliability cost coefficient; For maintenance costs; t is the stage of the extended planning; T is the total number of stages in the extended planning; Let be the present value factor of the investment cost in stage t; Let be the present value factor of the maintenance cost in stage t; This represents the number of years preceding stage t; It is the interest rate calculated in finance; This represents the number of years preceding stage t; As an alternative branch conductor for the power distribution network system; A set of alternative branch conductors for a power distribution network system; , These are the alternative branch wires. Investment and maintenance costs; As a backup transformer for the power distribution network system; A set of alternative transformers for the power distribution network system; These are the alternative transformers Investment and maintenance costs; They are nodes The investment and maintenance costs of the substation; Let be the set of all nodes s; , and They represent the stages respectively. At the beginning, is it on a branch? Install alternative branch wires at the location Is it on the feeder? Install alternative transformer b at the location and whether it is at the node A substation was built at the location; For the set of branch lines; j and j are the nodes at both ends of the branch, respectively; For feeders; For feeder set; It is the transpose of a unit vector; , , and These are the wires and the transformer. (0) Predefined aging vector for stage.

8. A distribution network expansion planning system with reliability constraints, characterized in that, The distribution network expansion planning method with reliability constraints, applied to any one of claims 1 to 7, includes: The topology module is used to construct and initialize the distribution network topology. The reliability module is used to collect historical operating data of the distribution network and obtain the reliability indicators of the distribution network based on the distribution network topology. The constraint module is used to establish electrical constraints, investment constraints, and reliability constraints for distribution network expansion planning; The target module is used to set the objective function for the distribution network expansion plan; The planning module is used to construct an extended planning model of the distribution network based on constraints and objective functions, and then solve it to obtain the planning scheme.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored program, wherein, when the program is executed, it controls the device containing the computer-readable storage medium to perform the distribution network expansion planning method with reliability constraints as described in any one of claims 1 to 7.

10. A processor, characterized in that, The processor is used to run a program, wherein the program executes the distribution network expansion planning method with reliability constraints as described in any one of claims 1 to 7.

Images