Active power distribution network power supply reliability evaluation method based on optimal power flow
By correcting the maintenance and isolation outage matrix using the minimum spanning tree algorithm and combining it with the dynamic line failure rate, an active distribution network power supply reliability assessment method based on optimal power flow is constructed. This solves the problems of insufficient network topology dynamic optimization and fault isolation logic in traditional assessment methods, and achieves accurate outage scope judgment and reliability assessment.
Patent Information
- Application Number
- CN202510848284.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-24
- Publication Date
- 2025-09-23
AI Technical Summary
Traditional power supply reliability assessment methods for active distribution networks fail to fully consider the dynamic optimization of network topology and fault isolation logic, resulting in errors in the judgment of power outage scope and inaccurate reliability assessment.
The minimum spanning tree algorithm is used to dynamically correct the maintenance outage matrix and the isolation outage matrix. Combined with the line dynamic failure rate matrix, an evaluation method based on optimal power flow is constructed to accurately quantify maintenance and fault isolation.
It significantly improves the accuracy of power outage type judgment and reliability assessment, and solves the problems of misjudgment of power outage scope and inaccurate reliability assessment caused by ignoring dynamic optimization of network topology and fault isolation logic in traditional assessment methods.
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Figure CN120688267A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of active distribution networks, and more particularly to a method for evaluating the power supply reliability of an active distribution network based on optimal power flow. Background Art
[0002] Due to the large-scale integration of distributed power sources (photovoltaic, wind power, energy storage, etc.), active distribution networks present significant characteristics such as multi-faceted interactions between "source-grid-load", bidirectional power flow, and dynamically changeable topology structures. With the high penetration of renewable energy and the participation of flexible loads on the user side, the operating state of the distribution network is increasingly complex due to the influence of intermittent power output fluctuations, time-varying load characteristics, and network reconstruction strategies. Traditional power supply reliability assessment frameworks based on unidirectional power flow and static topology are difficult to adapt to their dynamic operating requirements. In this context, the assessment method needs to transform from "static passive" to "dynamic active" to accurately reflect the topology optimization and adjustment process of the active distribution network in maintenance, fault and other scenarios, as well as the supporting role of distributed power sources in power restoration strategies.
[0003] Traditional distribution network reliability assessments are often based on historical statistical data and fixed network structures. They fail to fully account for the impact of distributed generation in active distribution networks on fault current distribution and protection device operation logic, and lack quantitative analysis of the coupling relationship between line load factor and dynamic fault rate. Furthermore, with the widespread adoption of intelligent switching and feeder automation technologies, the real-time and accuracy of fault isolation and power restoration have significantly improved. However, traditional assessment methods inadequately capture the dynamic fault isolation process and topology reconstruction strategies, resulting in reliability indicators that fail to truly reflect the actual operating characteristics of active distribution networks. Therefore, research on assessment methods that combine dynamic network topology optimization, fault isolation logic, and dynamic line fault rate has become a key technical direction for improving the accuracy and engineering applicability of active distribution network reliability assessments.
[0004] The existing technology has at least the following problems: The dynamic optimization process of the network topology is poorly considered, and the maintenance outage matrix and the isolation outage matrix cannot be dynamically corrected according to actual conditions. The fault isolation logic is ignored, and the isolation of the outage scope after a fault occurs is not accurately reflected. At the same time, the dynamic failure rate analysis of the line is not combined, resulting in deviations in the judgment of the outage scope and inaccurate reliability calculation results, making it difficult to comprehensively, dynamically and accurately assess the impact of power outages and the reliability level of the power grid.
[0005] In view of the above problems, the present invention proposes a solution. Summary of the Invention
[0006] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides an active distribution network power supply reliability assessment method based on optimal power flow, which dynamically corrects the maintenance outage matrix and the isolation outage matrix through the minimum spanning tree algorithm, and integrates the line dynamic failure rate matrix to solve the problems of misjudgment of power outage scope and inaccurate reliability assessment caused by ignoring the dynamic optimization of network topology and fault isolation logic in traditional assessment methods.
[0007] To achieve the above object, the present invention provides the following technical solutions: A method for evaluating the power supply reliability of an active distribution network based on optimal power flow comprises the following steps: obtaining a first matrix and a second matrix of the distribution network, solving an objective function and a circuit constraint in parallel to obtain a third matrix, wherein the objective function is constructed by taking the minimum active power loss on all lines of the distribution network within a cycle as a goal, and the circuit constraint is constructed based on circuit principles; constructing a fourth matrix and a fifth matrix, and correcting the fourth matrix and the fifth matrix based on a minimum spanning tree algorithm; correcting a historical average failure rate according to the rated capacity of the line and the average load within the cycle to obtain a sixth matrix; and obtaining reliability data within the cycle based on the first matrix, the second matrix, the fourth matrix, the fifth matrix, and the sixth matrix.
[0008] In a preferred embodiment, the circuit constraints include ohmic constraints, power balance constraints, node voltage constraints, line current constraints and network structure constraints; the first matrix includes a line length matrix, the second matrix includes a node power outage number matrix, the third matrix includes a line connectivity relationship matrix, the fourth matrix includes a maintenance power outage matrix, the fifth matrix includes an isolation power outage matrix, and the sixth matrix includes a line dynamic failure rate matrix; the fault data includes the number of line power outages.
[0009] In a preferred embodiment, the first matrix is obtained by obtaining line data and node data of the distribution network, marking the lines according to the first and last nodes, and obtaining the length of each line; the second matrix is obtained by recording the number of power outages at each node within a cycle.
[0010] In a preferred embodiment, the fourth matrix and the fifth matrix are corrected based on the minimum spanning tree algorithm, specifically as follows: a line set consisting of all lines is obtained, and combined with the third matrix, a distribution network line set within the period is obtained; an undirected graph within the distribution network period is constructed based on the distribution network line set and the obtained distribution network node set; based on the undirected graph, a first minimum tree between the main power supply node and each node is generated by the minimum spanning tree algorithm; the fourth matrix is corrected based on the first minimum tree; a non-minimum tree set of each node is constructed based on the difference set of the minimum spanning tree of each node and the distribution network line set within the period; all lines in the non-minimum tree set of each node are traversed to generate a second minimum tree between the main power supply node and the end node of the line; based on the second minimum tree, if there is no switching device at the head end of the line, the fourth matrix is corrected; if there is a non-circuit breaker switch at the head end of the line and there is a switch at the head end of at least one line, the fifth matrix is corrected.
[0011] In a preferred embodiment, the method for obtaining the historical average failure rate is specifically as follows: obtaining historical failure data of each line in the distribution network, and combining it with a preset average failure rate formula to obtain the historical average failure rate of the distribution network.
[0012] In a preferred embodiment, the power balance constraint includes a line balance constraint and a node balance constraint.
[0013] In a preferred embodiment, the intra-cycle reliability data includes the number of node power outages within the cycle.
[0014] The technical effects and advantages of the present invention's method for evaluating the reliability of power supply of an active distribution network based on optimal power flow are as follows: The present invention solves the line connectivity matrix by constructing basic data such as the line length matrix and the node power outage number matrix, combined with the optimal power flow model with the goal of minimizing active power loss. The core innovation lies in using the minimum spanning tree algorithm to dynamically correct the maintenance power outage matrix and the isolation power outage matrix: first, based on the distribution network topology, a first minimum tree is generated from the main power supply to each node, and the maintenance impact range in the fourth matrix is corrected; secondly, by calculating the node non-minimum tree, for the line fault scenario in the non-minimum tree, a second minimum tree is generated in combination with the switch type, and the fourth matrix and the fifth matrix are differentially corrected. The accuracy of the power outage type judgment is significantly improved, and the dynamic failure rate of the line is integrated to achieve reliability assessment. At the same time, the minimum spanning tree is combined with the switch logic to accurately quantify maintenance and fault isolation, effectively solving the problems of misjudgment of the power outage range and inaccurate reliability assessment caused by ignoring the dynamic optimization of the network topology and fault isolation logic in traditional evaluation methods. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 A schematic flow chart of a method for evaluating power supply reliability of an active distribution network based on optimal power flow is provided in an embodiment of the present invention. DETAILED DESCRIPTION
[0016] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.
[0017] Example 1, Figure 1 The present invention provides a method for evaluating the reliability of power supply of an active distribution network based on optimal power flow, comprising the following steps: S1, obtaining a first matrix and a second matrix of the distribution network, and solving them in parallel with an objective function and a circuit constraint to obtain a third matrix, wherein the objective function is constructed by minimizing the active power loss on all lines of the distribution network within a cycle, and the circuit constraint is constructed based on circuit principles; S2, constructing a fourth matrix and a fifth matrix, and modifying the fourth matrix and the fifth matrix based on a minimum spanning tree algorithm; S3, based on the line rated capacity and the average load within the period, correct the historical average failure rate to obtain the sixth matrix; S4, obtaining intra-cycle reliability data according to the first matrix, the second matrix, the fourth matrix, the fifth matrix and the sixth matrix.
[0018] This embodiment constructs basic data such as the line length matrix and the node outage number matrix, and solves the line connectivity relationship matrix in combination with the optimal power flow model with the goal of minimizing active power loss. The core innovation lies in using the minimum spanning tree algorithm to dynamically correct the maintenance outage matrix and the isolation outage matrix: first, based on the distribution network topology, a first minimum tree is generated from the main power supply to each node, and the maintenance impact range in the fourth matrix is corrected; secondly, by calculating the node non-minimum tree, for the line fault scenario in the non-minimum tree, a second minimum tree is generated in combination with the switch type, and the fourth matrix and the fifth matrix are differentially corrected. The accuracy of the outage type judgment is significantly improved, and the dynamic failure rate of the line is integrated to achieve reliability assessment. At the same time, the minimum spanning tree is combined with the switch logic to accurately quantify maintenance and fault isolation, effectively solving the problem of misjudgment of the outage range and inaccurate reliability assessment caused by ignoring the dynamic optimization of the network topology and fault isolation logic in traditional evaluation methods.
[0019] S1, obtain the first matrix and the second matrix of the distribution network, and solve them in parallel with the objective function and the circuit constraint to obtain the third matrix. The objective function is constructed by minimizing the active power loss on all lines of the distribution network within a cycle, and the circuit constraint is constructed based on the circuit principle.
[0020] In this embodiment, the circuit constraints include ohmic constraints, power balance constraints, node voltage constraints, line current constraints, and network structure constraints; The first matrix includes a line length matrix, the second matrix includes a node outage number matrix, the third matrix includes a line connectivity relationship matrix, the fourth matrix includes a maintenance outage matrix, the fifth matrix includes an isolation outage matrix, and the sixth matrix includes a line dynamic failure rate matrix; The fault data includes the number of line power outages.
[0021] In this embodiment, the first matrix is obtained by obtaining line data and node data of the distribution network, marking the lines according to the first and last nodes, and obtaining the length of each line; The second matrix is obtained by recording the number of power outages of each node within a cycle.
[0022] S2: construct a fourth matrix and a fifth matrix, and modify the fourth matrix and the fifth matrix based on a minimum spanning tree algorithm.
[0023] In this embodiment, the fourth matrix and the fifth matrix are modified based on the minimum spanning tree algorithm, specifically: Obtain the line set consisting of all lines, and combine it with the third matrix to obtain the distribution network line set within the period; According to the distribution network line set and the obtained distribution network node set, an undirected graph within the distribution network cycle is constructed; Based on the undirected graph, the first minimum tree between the main power node and each node is generated by the minimum spanning tree algorithm; Modifying the fourth matrix according to the first minimum tree; According to the difference set of the minimum spanning tree of each node and the set of distribution network lines in the period, a non-minimum tree set of each node is constructed; Traverse all lines in the non-minimum tree set of each node to generate the second minimum tree between the main power node and the line end node; According to the second minimum tree, if there is no switch device at the line head end, the fourth matrix is modified; if there is a non-circuit breaker switch at the line head end and at least one line head end has a switch, the fifth matrix is modified.
[0024] It should be noted that the main power supply node refers to the common point where the distribution network is connected to the large power grid.
[0025] S3, based on the line rated capacity and the average load within the period, correct the historical average failure rate to obtain the sixth matrix.
[0026] In this embodiment, the method for obtaining the historical average failure rate is specifically as follows: Obtain historical fault data for each line in the distribution network, and combine it with the preset average failure rate formula to obtain the historical average failure rate of the distribution network.
[0027] In this embodiment, the sixth matrix has the following specific formula:
[0028]
[0029] Where, is the dynamic failure rate of line x, is the historical average failure rate of the distribution network, is the average load of line x in period T, is the rated capacity of line x, is the correction factor, is the total number of distribution network lines.
[0030] In this embodiment, the specific formula of the objective function is:
[0031] Where, The line within the operating cycle T binary decision variables for input states, For the line resistance; The number of times the line passes through at time t within the operating cycle T The current, The line set consisting of all lines.
[0032] In this embodiment, the power balance constraint includes a line balance constraint and a node balance constraint; The specific formula of the node balance constraint is:
[0033] Where, and are the net injected active power and net injected reactive power of node j at time t, is the set of lines with node j as the starting node, and They are the lines starting from node j at time t The active power transmitted and the reactive power injected, represents the set of lines ending at node j, is a node set, For the line resistance; is the number of times the line passes through at time t within period T. The current on.
[0034] In this embodiment, the average failure rate formula is specifically as follows:
[0035] Where, is the historical average failure rate of the distribution network, Y is the historical number of years, is the number of failures that occurred on line x in the historical Y years, is the length of line x, is the total number of distribution network lines.
[0036] S4, obtaining intra-cycle reliability data according to the first matrix, the second matrix, the fourth matrix, the fifth matrix and the sixth matrix.
[0037] In this embodiment, the intra-cycle reliability data includes the number of node power outages within the cycle; The specific formula for the number of node power outages within the cycle is:
[0038] Where, is the matrix of node power outage times within a cycle, is the second matrix of the previous cycle, .* is the matrix dot multiplication, is the first matrix, is the sixth matrix, EL and OL are the fourth matrix and the fifth matrix respectively.
[0039] Example 2 comprises the following steps: Step 1: Based on the information of the distribution network lines and nodes, the objective function of the network optimization operation of the distribution network in a certain mode is constructed, the constraints of the network optimization of the distribution network within the operation cycle are set, and the connection relationship matrix of each line and the line set of the distribution network within the operation cycle T are obtained through optimization calculation; Step 2: Establish and initialize the maintenance outage matrix EL and the isolation outage matrix OL, and use the minimum tree algorithm to modify the matrix; Step 3: Correct the historical average failure rate based on the line parameters and, combined with the known data from Step 1, calculate the number of power outages within the operating cycle T. As the distribution network's operating mode changes, reassess the reliability of the distribution network under the new operating mode until all possible operating modes are exhausted, resulting in a comprehensive reliability estimate for the distribution network under each operating mode.
[0040] In this embodiment, step 1 specifically includes: Step 101: Obtain basic information of the distribution network and initialize the reliability index that needs to be evaluated for the distribution network.
[0041] Obtain information about lines and nodes in the distribution network and form an undirected graph of the distribution network. nodes, define the node set as Assume that the first and last nodes of the line in the distribution network are i and j respectively, then the line is named , the set of all lines is ,have Established.
[0042] Get the length of each line of the line to form a line length matrix ,in: is the length of line x; is the number of lines in the distribution network.
[0043] Define a node outage count vector to record the number of power outages each node experiences within a specified time period , and initialize it, assigning 0 to all elements in the matrix.
[0044]
[0045] in: is the number of power outages at node i.
[0046] According to the historical fault statistics of each line in the distribution network, the historical average failure rate of the distribution network is calculated. , as follows:
[0047] in: is the historical average failure rate of the distribution network, Y is the historical number of years, is the number of failures that occurred on line x in the historical Y years, is the length of line x, is the total number of distribution network lines.
[0048] Step 102: Construct the objective function of the distribution network under a certain mode of network optimization operation. Assume that the operation period of the distribution network is T, and the line is optimized. Operational status , so that the active power loss of all lines in the distribution network is minimized during the operation cycle, and the objective function of network optimization is given as follows:
[0049] in: The line within the operating cycle T Input state 0-1 variable, if , then it means that the line in the operation cycle T Put into operation. If , it means the line Not put into operation; For the line resistance; The number of times the line passes through at time t within the operating cycle T The current on.
[0050] Step 103: Provide the constraints for network optimization of the distribution network within the operation period T, as follows: 1) The two directly connected nodes i and j in the distribution network must satisfy Ohm's law. At the same time, the phase angles of each variable are relaxed, and the following equation holds:
[0051] in: and The lines passing through at time t are Active power and reactive power; For the line reactance; and are the voltages of nodes i and j at time t respectively.
[0052] But if the line disconnect, and Will be forced to 0, then the failure rate calculation formula is invalid, and the lines are forced to be disconnected It is unreasonable to have the same voltage amplitude at both ends. Therefore, the Big M method is introduced to rewrite the failure rate calculation formula as follows:
[0053] Wherein: M is a larger value.
[0054] 2) The lines in the distribution network must meet the power balance constraint. For example, the power balance constraint is:
[0055] 3) Nodes in the distribution network must satisfy power balance constraints. Taking node j as an example, its power balance constraint is:
[0056] in: and are the net injected active power and net injected reactive power of node j at time t respectively; represents the set of lines with node j as the starting node; and They represent the lines starting from node j at time t. Active power transmitted and reactive power injected; represents the set of lines ending at node j; In the above formula, the net injected active power and net injected reactive power of node j are and is defined as follows: According to the output characteristics of the distributed power source, the time-series output power of each node in the operating cycle T can be obtained. Assume that the output characteristics of the distributed power source at node j in the operating cycle T are:
[0057] in: and are the active output and reactive output sequences of the distributed generation at node j in the operation period T; and are the active power output and reactive power output of node j at time t in the operation cycle T. If node j has no distributed power generation, then .
[0058] Similarly, according to the load output characteristics, the load time series power demand of each node in the operation period T can be obtained. Assume that the load power demand characteristics of node j are:
[0059] in: and are respectively the active power demand and reactive power demand of the load at node j in the operation period T; and are respectively the active power demand and reactive power demand of node j at time t within the operation period T. If node j has no load, then .
[0060] From the above analysis, we can see that the net injected active power of node j is and net injected reactive power It can be expressed as:
[0061] in: and are the net injected active power and net injected reactive power of node j at time t within the operation period T, and the following equation is established:
[0062] 4) To ensure the voltage quality of the power grid, the node voltage must be controlled within a certain range. To ensure the safety of the line, the current on the line also has an upper limit. For example, the node voltage constraints and line current constraints are listed as follows:
[0063] in: and are the maximum and minimum voltage values of node i respectively; For the line The upper limit of the current transmitted.
[0064] 5) In order to protect the setting and reduce the short-circuit current, the distribution network must operate in a radial manner, that is, there is no ring network topology in the network. Therefore, the line input state variable that can reflect the distribution network structure must satisfy the following formula:
[0065] in: It is a 0-1 variable, and 0 indicates a line Disconnected, equal to 1 means the line Closed; NN represents the total number of nodes.
[0066] By combining the above formulas and using optimization software, we can obtain the matrix that reflects the connectivity relationship of each line within the operation cycle T. , and then get the line set of the distribution network within the operation period T .
[0067] In this embodiment, step 2 specifically includes: Step 201: Form and initialize a maintenance outage matrix EL. Assume there are Nd nodes and Nl lines in the distribution network, then the maintenance outage matrix EL is as follows:
[0068] Among them, the elements in the matrix are all 0-1 variables.
[0069] It should be noted that when When , it means that the maintenance of line a fault will cause power outage at node b, otherwise it means that the maintenance of line a fault will not cause power outage at node b.
[0070] Initialize the matrix and initialize all its elements to 0.
[0071] Step 202: Form and initialize the isolated power outage matrix OL. Since there are Nd nodes and Nl lines in the distribution network, the isolated power outage matrix OL is as follows:
[0072] Among them, the elements in the matrix are all 0-1 variables.
[0073] It should be noted that when When , it means that the isolation of line a fault will cause power outage at node b, otherwise it means that the isolation of line a fault will not cause power outage at node b.
[0074] Step 203: The line set of the distribution network within the operation period T obtained in step 103 , combined with the node set of the distribution network in step 101 , generate the undirected graph G of the distribution network in the operation cycle T, expressed as Generate the minimum spanning tree between the main power node (the common point connecting the distribution network and the large power grid, the main power node can be regarded as a node with infinite capacity) and each node. Taking node j as an example, the minimum spanning tree between the main power node and node j is recorded as , is the set of all lines from the main power node to node j. For the elements in the maintenance outage matrix EL Make corrections as shown below:
[0075] Among them, the elements in the matrix is a 0-1 variable. k is the minimum spanning tree When When , it means that the maintenance of line k fault will cause power outage at node j, otherwise it means that the maintenance of line k fault will not cause power outage at node j.
[0076] Step 204: The minimum spanning tree of node j obtained in step 203 , combined with the line set obtained in step 103 , take the difference between the two as the non-minimum tree of node j , as shown below:
[0077] Traversal For all lines in , forming the minimum spanning tree between the main power node and the end node of the line, recorded as ; At the same time , Represents a line set that stores the minimum spanning tree of line x minus the minimum spanning tree of node j Overlapping lines.
[0078] Step 205: Obtain a non-minimum tree from the network structure Middle line x head end switch type , set its value to be limited to 0, 1 and 2. When , it indicates that there is no switch at the beginning of line x; when When , it indicates that the switch type at the head end of line x is a circuit breaker; when When , it indicates that the switch at the head end of line x is a type of switchgear other than a circuit breaker. Are all the switch types of the first end of the lines in the set 0? When the maintenance outage matrix .
[0079] Step 206: Determine Whether the switch type at the head end of the lines in the set meets the following conditions: .Right now The head end switch type of any line in the set cannot be 1 and At least one line in the set has a switchgear installed. If the above conditions are met, the element in the outage matrix is isolated .
[0080] In this embodiment, step 3 specifically includes: Step 301: Based on the rated capacity of line x and its average load during the operating cycle T , the historical average failure rate Correction is performed to calculate the dynamic failure rate of line x within the operating period T. , the specific expression is as follows:
[0081] in: is the dynamic failure rate of line x, is the historical average failure rate of the distribution network, is the average load of line x in the operating period T, is the rated capacity of line x, is the correction factor, is the total number of distribution network lines.
[0082] Traverse and calculate the dynamic failure rate of all lines to form the line dynamic failure rate matrix within the operation period T , and there are .
[0083] Step 302: Based on the line length matrix in step 101 And the line dynamic failure rate matrix in step 301 , calculate the number of power outages of the node within the operation cycle T, as follows:
[0084] Where: is the matrix of node power outage times in period T, is the matrix of node power outage times in the previous cycle, and * represents matrix dot product; is the line length matrix; is the line dynamic failure rate matrix within the operation period T; EL and OL represent the maintenance outage matrix and isolation outage matrix respectively.
[0085] Step 303: When the operation mode of the distribution network changes, return to step 102 to re-evaluate the reliability of the distribution network under the new operation mode until all possible operation modes are traversed to obtain the comprehensive reliability of the distribution network under various operation modes.
[0086] The above formulas are all dimensionless and numerical calculations. The formulas are obtained by collecting a large amount of data and performing software simulation to obtain the most recent real situation. The preset parameters in the formulas are set by technicians in this field according to actual conditions.
[0087] The above embodiments may be implemented in whole or in part through software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments may be implemented in whole or in part in the form of a computer program product.
[0088] Those skilled in the art will appreciate that the modules and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.
[0089] In addition, each functional module in each embodiment of the present application may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.
[0090] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.
[0091] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for evaluating the reliability of power supply of an active distribution network based on optimal power flow, characterized in that: The following steps are involved: Obtaining a first matrix and a second matrix of the distribution network, and solving them in parallel with an objective function and a circuit constraint to obtain a third matrix, wherein the objective function is constructed by minimizing the active power loss on all lines of the distribution network within a cycle, and the circuit constraint is constructed based on circuit principles; constructing a fourth matrix and a fifth matrix, and modifying the fourth matrix and the fifth matrix based on a minimum spanning tree algorithm; According to the line rated capacity and the average load in the period, the historical average failure rate is corrected to obtain the sixth matrix; Intra-cycle reliability data is obtained according to the first matrix, the second matrix, the fourth matrix, the fifth matrix, and the sixth matrix.
2. The method for evaluating power supply reliability of active distribution network based on optimal power flow according to claim 1, characterized in that: The circuit constraints include ohmic constraints, power balance constraints, node voltage constraints, line current constraints and network structure constraints; The first matrix includes a line length matrix, the second matrix includes a node outage number matrix, the third matrix includes a line connectivity relationship matrix, the fourth matrix includes a maintenance outage matrix, the fifth matrix includes an isolation outage matrix, and the sixth matrix includes a line dynamic failure rate matrix; The fault data includes the number of line power outages.
3. The method for evaluating power supply reliability of active distribution network based on optimal power flow according to claim 2, characterized in that: The first matrix is obtained by obtaining line data and node data of the distribution network, marking the lines according to the first and last nodes, and obtaining the length of each line; The second matrix is obtained by recording the number of power outages of each node within a cycle.
4. The method for evaluating power supply reliability of active distribution network based on optimal power flow according to claim 3, characterized in that: The fourth matrix and the fifth matrix are modified based on the minimum spanning tree algorithm, specifically: Obtain the line set consisting of all lines, and combine it with the third matrix to obtain the distribution network line set within the period; According to the distribution network line set and the obtained distribution network node set, an undirected graph within the distribution network cycle is constructed; Based on the undirected graph, the first minimum tree between the main power node and each node is generated by the minimum spanning tree algorithm; Modifying the fourth matrix according to the first minimum tree; According to the difference set of the minimum spanning tree of each node and the set of distribution network lines in the period, a non-minimum tree set of each node is constructed; Traverse all lines in the non-minimum tree set of each node to generate the second minimum tree between the main power node and the line end node; According to the second minimum tree, if there is no switch device at the line head end, the fourth matrix is modified; if there is a non-circuit breaker switch at the line head end and at least one line head end has a switch, the fifth matrix is modified.
5. The method for evaluating power supply reliability of active distribution network based on optimal power flow according to claim 4, characterized in that: The method for obtaining the historical average failure rate is specifically as follows: Obtain historical fault data for each line in the distribution network, and combine it with the preset average failure rate formula to obtain the historical average failure rate of the distribution network.
6. The method for evaluating power supply reliability of active distribution network based on optimal power flow according to claim 5, characterized in that: The specific formula of the sixth matrix is: Where, is the dynamic failure rate of line x, is the historical average failure rate of the distribution network, is the average load of line x in period T, is the rated capacity of line x, is the correction factor, is the total number of distribution network lines.
7. The method for evaluating power supply reliability of active distribution network based on optimal power flow according to claim 6, characterized in that: The specific formula of the objective function is: Where, The line within the operating cycle T binary decision variables for input states, For the line The resistance, The number of times the line passes through at time t within the operating cycle T The current, The line set consisting of all lines.
8. The method for evaluating power supply reliability of active distribution network based on optimal power flow according to claim 7, characterized in that: The power balance constraint includes a line balance constraint and a node balance constraint; The specific formula of the node balance constraint is: Where, and are the net injected active power and net injected reactive power of node j at time t, is the set of lines with node j as the starting node, and They are the lines starting from node j at time t The active power transmitted and the reactive power injected, represents the set of lines ending at node j, is a node set, For the line resistance; is the number of times the line passes through at time t within period T. The current on.
9. The method for evaluating power supply reliability of active distribution network based on optimal power flow according to claim 8, characterized in that: The average failure rate formula is specifically as follows: Where, is the historical average failure rate of the distribution network, Y is the historical number of years, is the number of failures that occurred on line x in the historical Y years, is the length of line x, is the total number of distribution network lines.
10. The method for evaluating power supply reliability of active distribution network based on optimal power flow according to claim 9, characterized in that: The intra-cycle reliability data includes the number of node power outages within the cycle; The specific formula for the number of node power outages within the cycle is: Where, is the matrix of node power outage times within a cycle, is the second matrix of the previous cycle, .* is the matrix dot multiplication, is the first matrix, is the sixth matrix, EL and OL are the fourth matrix and the fifth matrix respectively.