Graph theory-based flexible resource screening method and system for line out-of-limit scene

Abstract

The invention discloses a graph theory-based flexible resource screening method and system for a line out-of-limit scene, and the method comprises the steps: constructing a graph structure of a power grid, calculating the correlation degree between nodes and branches, and constructing a line out-of-limit and flexible resource correlation matrix based on the correlation degree and a flexible resource type; calculating the sensitivity according to the change degree of the active power of each branch along with the flexible resource active power of each node, and calculating the priority of flexible resource access to each node of different branches according to the sensitivity and the adjustment cost; setting a target branch, and preliminarily screening candidate nodes according to a line out-of-limit and flexible resource incidence matrix; calculating the minimum variable quantity of the active power of the target branch in the set time period caused by flexible resource adjustment of the candidate nodes; and after the candidate nodes are sorted according to the priorities, the absolute values of the corresponding minimum variable quantities are sequentially accumulated, and when a set out-of-limit threshold value is exceeded, the accumulation is stopped. According to the invention, adjustment characteristic complementation among multiple flexible resources is realized, and the adjustment potential of the flexible resources is fully exerted.

Description

Technical Field

[0001] This invention belongs to the field of power grid dispatching technology, and more specifically, relates to a graph theory-based flexible resource selection method and system for line overrun scenarios. Background Technology

[0002] With the construction of new power systems, distributed renewable energy sources such as distributed photovoltaic and distributed wind power are being integrated into medium- and low-voltage power grids in large quantities. The output of distributed renewable energy is highly volatile due to factors such as weather conditions. Furthermore, new loads, such as electric vehicles and user-side energy storage, also exhibit volatile characteristics. The combined effect of these factors means that the amplitude and direction of the grid's net load can change rapidly, potentially leading to negative net loads at certain times, with users feeding excess power back to the upstream grid. Since there are limits to the transmission power of power lines, drastic fluctuations in net load can cause the transmission power to exceed these limits, resulting in line overload issues. If the transmission power along the traditional power supply direction exceeds the forward safety limit, a forward heavy overload will occur; if the transmission power along the reverse power supply direction exceeds the reverse safety limit, a reverse heavy overload will occur. The volatility of distributed renewable energy, coupled with the volatility of new loads, significantly increases the frequency of line overloads in medium- and low-voltage power grids, necessitating effective solutions.

[0003] In traditional power systems, line violations primarily occur in high-voltage grids and are resolved by deploying large generating units. However, in modern power systems, large generating units connected to high-voltage grids cannot independently resolve line violation issues in medium- and low-voltage grids. In contrast, diverse and flexible resources connected to medium- and low-voltage grids, possessing regulation capabilities, capable of stable dispatch, and used to maintain power system supply and demand balance, such as distributed renewable energy, energy storage, and electric vehicles, can be used to address line violation issues in medium- and low-voltage grids. However, some unresolved issues remain regarding the coordinated dispatch and control of these diverse and flexible resources.

[0004] Existing resource scheduling and control methods primarily rely on solving optimization problems to uniformly regulate all resources. However, given the large number and wide distribution of flexible resources, this uniform regulation approach results in an excessively large optimization space, increasing the complexity of the optimization problem and reducing its efficiency.

[0005] For specific line violation scenarios, not all resources are suitable for resolving the line violation problem. Traditional methods lack applicability assessments for different resources participating in specific line violation regulation. Before optimization, there is a lack of in-depth research on how to determine whether a resource is suitable for participating in specific line violation regulation based on its characteristics, and how to identify useless resources that cannot participate in specific line violation regulation.

[0006] Furthermore, various flexible resources differ significantly in their adjustment characteristics, such as adjustment capacity, adjustment cost, and adjustable time periods. Moreover, due to differences in location and type, their contribution to over-limit adjustment on different lines varies. Even within the set of flexible resources capable of participating in over-limit adjustment for a specific line, their cost-effectiveness in participating in over-limit adjustment, as well as the magnitude and direction of their contribution to the over-limit problem on that specific line, differ. A systematic method is still lacking for prioritizing the selection of more suitable resources from among the flexible resources capable of participating in over-limit adjustment for a specific line for optimization.

[0007] For simple radial networks, it is relatively easy to determine which resources can participate in over-limit regulation of specific lines. However, if the power grid contains ring networks, the relevant analysis becomes more complex. For complex networks, the analysis of whether flexible resources can participate in over-limit regulation of specific lines, and which flexible resources should be preferentially selected for participation in over-limit regulation of specific lines, remains insufficient. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a graph-based flexible resource selection method and system for line overrun scenarios.

[0009] The present invention adopts the following technical solution.

[0010] The first aspect of this invention proposes a graph-based flexible resource selection method for line overrun scenarios, comprising: Construct a graph structure for the power grid, and divide the graph structure into different subgraphs based on the topology type of the power grid; the topology types include radial network topology and ring network topology; Based on the subgraph to which each node and each branch belong, and the reachability of each node to the tail node on each branch, the correlation degree between the node and the branch is calculated. All correlation degrees form the correlation matrix between line overrun and access node. A flexible resource type matrix is ​​constructed according to the flexible resource type of the node. The correlation matrix between line overrun and access node and the flexible resource type matrix are multiplied to obtain the correlation matrix between line overrun and flexible resource. The flexible resource types include load and distributed new energy. Sensitivity is calculated based on the degree to which the active power of each branch changes with the active power of the flexible resources connected to each node. Priority for each node to access flexible resources for different branches is calculated based on the sensitivity and the adjustment cost of each node accessing flexible resources. Set a target branch, and based on the elements of the correlation matrix between line over-limit and flexible resources, the upward and downward adjustment capabilities of the flexible resources accessed by each node within a set time period, and the power of the target branch within a set time period, initially screen out nodes that will participate in the over-limit adjustment of the target branch as candidate nodes. Based on the sensitivity and the minimum adjustable capacity and minimum adjustable capacity of the flexible resources accessed by each candidate node within a set time period, calculate the minimum change in active power of the target branch within a set time period caused by the flexible resource adjustment of the candidate node. Candidate nodes are sorted in ascending order of priority. The absolute value of the minimum change in active power for each candidate node is accumulated sequentially according to the sort order. The process stops when the minimum change exceeds the set threshold. The flexible resources accessed by the corresponding candidate node are the flexible resources selected during the set time period.

[0011] Preferably, the step of dividing the power grid graph structure into different subgraphs according to the power grid topology type specifically involves: For a radial network topology, the graph structure is divided into main paths and sub-paths. The main path is the path with the most nodes starting from the main power source, and the sub-path is the path that extends from the nodes on the main path. The nodes that extend the path are called branch points. For a ring network topology, the graph is divided into leading paths, main paths, and sub-paths. The leading path is the path from the main power source to the starting point of the ring network. The starting point of the ring network is a node on the ring network from which multiple currents flow. The main path is the ring network itself. Sub-paths are paths that extend from nodes on the main path or leading path. Nodes from which paths extend are called branch points.

[0012] Preferably, after dividing the power grid graph structure into different subgraphs according to the power grid topology, the nodes and branches of the power grid graph structure are renumbered. The power flow direction from the main power source to the power grid is used as the reference direction, and the node connected to the main power source is designated as node 1. For radial network topology, the nodes are numbered sequentially in the order of main path first and then sub-path, with the node number increasing along the reference direction. For ring network topology, the nodes are numbered sequentially in the order of leading path, main path, and sub-path, with the node number increasing along the reference direction. For the connection in the first The node and the first Branches between nodes, among which , define the first The node and the first Each node represents the first and last node of the branch. Sort the branches in ascending order of their first nodes. If the first nodes of the branches are the same, sort them in ascending order of their last nodes. After sorting, number them sequentially.

[0013] Preferably, for a radial network topology, if the j-th node belongs to the set of upstream nodes of the tail node of the i-th branch... If the correlation between the i-th branch and the j-th node is 0, then the correlation between the i-th branch and the j-th node is 0. The j-th node is either the tail node of the i-th branch or a set of downstream nodes belonging to the tail node of the i-th branch. If the degree of association between the i-th branch and the j-th node is equal to the reachability between the tail node of the i-th branch and the j-th node; The reachability between the tail node of the i-th branch and the j-th node is as follows: if the tail node of the i-th branch is reachable from the j-th node along the positive direction of active power flow, the reachability is 1; otherwise, it is 0. The set of upstream nodes of the tail node of the i-th branch for: If the i-th branch belongs to the main path, the power flow direction from the main power source to the radial network is used as the reference direction. Includes all main path nodes traversed when current flows to the tail node of the i-th branch; if the main path node is a branch point, It also includes all nodes on the sub-paths derived from that branch point; If the i-th branch is a sub-path Its branch point is x, with the power flow direction from the main power source to this radial network as the reference direction. Includes all main path nodes, except for the sub-paths of the i-th branch. All nodes on the outer sub-path and the sub-path through which current flows from the branch point x of the i-th branch to the tail node of the i-th branch. All nodes on; The set of downstream nodes of the tail node of the i-th branch for: If the i-th branch belongs to the main path, the power flow direction from the main power source to the radial network is used as the reference direction. Includes all main path nodes that the current flows through after exiting this node, and the tail node of the i-th branch itself; if the main path node is a branch point, It also includes all nodes on the sub-paths derived from that branch point; If the i-th branch is a sub-path Its branch point is x, with the power flow direction from the main power source to this radial network as the reference direction. Includes the sub-paths traversed after the current flows out from the tail node of the i-th branch. The nodes on the i-th branch and the tail node of the i-th branch itself.

[0014] Preferably, for a ring network topology, if the i-th branch is a leading path or a sub-path, then the correlation between the i-th branch and the j-th node is equal to the reachability between the tail node of the i-th branch and the j-th node. If the i-th branch belongs to the main path, and the j-th node belongs to... Or, the j-th node belongs to the sub-path and the branch point of the sub-path belongs to If the degree of association between the i-th branch and the j-th node is equal to the reachability between the tail node of the i-th branch and the j-th node; The set of nodes in the main path that starts from the ring network starting point and moves along the reverse reference direction to the tail node of the i-th branch. Excluding the starting point of the ring network; If the i-th branch belongs to the main path, and the j-th node belongs to... Or, the j-th node belongs to the sub-path and the branch point of the sub-path belongs to If the degree of association between the i-th branch and the j-th node is equal to the negative of the reachability between the tail node of the i-th branch and the j-th node; The nodes in the main path that start from the ring network starting point and follow the reference direction to reach the first node of the i-th branch are... Including the starting point of the ring network; If the i-th branch is a main path and the j-th node is a preceding path, then the correlation between the i-th branch and the j-th node is 0.

[0015] Preferably, a flexible resource type matrix is ​​constructed based on the flexible resource access type of the node. The correlation matrix between line over-limit and access node and the flexible resource type matrix are multiplied to obtain the correlation matrix between line over-limit and flexible resource access, specifically: The flexible resource type matrix is ​​a column vector, and the j-th element of the flexible resource type matrix... This represents the flexible resource type of the j-th node. If the j-th node receives a load, then... If the j-th node is connected to a distributed renewable energy source, then If the j-th node is not connected to the flexible resource, then .

[0016] Preferably, the calculation of the priority for each node to access flexible resources in different branches based on sensitivity and the adjustment cost of each node accessing flexible resources specifically involves: If the j-th node is not connected to the flexible resource, then the sensitivity of the j-th node to the flexible resource adjustment for all branches is 0. If the j-th node accesses flexible resources, then the j-th node adjusts the sensitivity of the flexible resources to the i-th branch. Let be: the partial derivative of the active power of the i-th branch with respect to the active power of the flexible resources connected to the j-th node; For the i-th branch, the priority of the j-th node is the adjustment cost of the j-th node accessing flexible resources divided by the sensitivity. The absolute value of.

[0017] Preferably, the preliminary screening of nodes participating in the target branch's over-limit adjustment as candidate nodes specifically involves: If the power of the target branch is greater than the set positive risk value within the set time period, the line over-limit logic is 1; if the power of the target branch is less than the set reverse risk value within the set time period, the line over-limit logic is -1; if the power of the target branch is less than or equal to the set positive risk value and greater than or equal to the set reverse risk value within the set time period, the line over-limit logic is 0. If the flexible resources accessed by the j-th node have the ability to be increased within a set time period, and the product of the element corresponding to the line limit and flexible resource association matrix of the j-th node and the target branch and the line limit logic is -1, then the corresponding node is a candidate node for increase. If the flexible resources accessed by the j-th node have the ability to be downgraded within a set time period, and the product of the element corresponding to the line over-limit and flexible resource association matrix of the j-th node and the target branch and the line over-limit logic is 1, then the corresponding node is a candidate node for downgrading. Preferably, the minimum change in active power of the target branch within a set time period caused by the flexible resource adjustment of the candidate nodes is specifically as follows: For the candidate node that is adjusted upwards, the minimum change in active power of the target branch within the set time period is the minimum adjustable capacity within the corresponding set time period multiplied by the sensitivity of the candidate node to the target branch for flexible resource adjustment. For a candidate node that is downgraded, the minimum change in active power of the target branch within a set time period is the minimum adjustable capacity within the corresponding set time period multiplied by the sensitivity of the candidate node to flexible resource adjustment of the target branch, where the minimum adjustable capacity is a negative value.

[0018] Preferably, if the line over-limit logic is 1, then the set over-limit threshold is: the difference between the set positive risk value and the power of the target branch within the set time period, the absolute value of the difference multiplied by 1 and the sum of the set margin. If the line over-limit logic is -1, then the set over-limit threshold is: calculate the difference between the set reverse risk value and the power of the target branch within the set time period, multiply the difference by 1 and sum with the set margin.

[0019] The second aspect of this invention proposes a graph-based flexible resource selection system for line overrun scenarios, based on the method described in the first aspect of this invention. The system includes a graph structure construction module, a line overrun and flexible resource association matrix construction module, a priority calculation module, a candidate node selection module, a minimum change in active power calculation module, and a flexible resource selection module. Specifically: Graph Structure Construction Module: Constructs the graph structure of the power grid, and divides the graph structure into different subgraphs according to the topology type of the power grid; the topology types include radial network topology and ring network topology; The module for constructing the correlation matrix between line overruns and flexible resources calculates the correlation degree between nodes and branches based on the subgraph to which each node and each branch belong, and the reachability of each node to the tail nodes on each branch. All correlation degrees form the correlation matrix between line overruns and access nodes. A flexible resource type matrix is ​​constructed based on the flexible resource type of the node's access. The correlation matrix between line overruns and access nodes and the flexible resource type matrix are multiplied to obtain the correlation matrix between line overruns and flexible resources. The flexible resource types include load and distributed renewable energy. Priority calculation module: Calculates sensitivity based on the degree of change of active power of each branch with the active power of flexible resources accessed by each node, and calculates the priority of each node accessing flexible resources for different branches based on the sensitivity and the adjustment cost of each node accessing flexible resources. Candidate Node Screening Module: Set a target branch, and based on the elements of the correlation matrix between line over-limit and flexible resources, the upward and downward adjustment capabilities of the flexible resources accessed by each node within a set time period, and the power of the target branch within a set time period, initially screen out nodes that will participate in the over-limit adjustment of the target branch as candidate nodes. The minimum change in active power calculation module calculates the minimum change in active power of the target branch within a set time period caused by the flexible resource adjustment of the candidate node, based on the sensitivity and the minimum adjustable capacity and minimum adjustable capacity of the flexible resources connected to each candidate node within a set time period. Flexible resource filtering module: Sort candidate nodes according to their priority from smallest to largest, and accumulate the absolute value of the minimum change in active power for each candidate node in order of sorting. Stop when the limit is exceeded. The flexible resources accessed by the corresponding candidate node are the flexible resources selected in the set time period.

[0020] The beneficial effects of this invention are as follows: Compared with existing technologies, this invention generates different subgraphs for radial and ring network subgraphs and performs different subsequent processing, improving its applicability to complex power grid scenarios; by calculating the correlation and sensitivity of nodes and branches, and combining flexible resource types and costs, it can effectively address line over-limit problems; this invention optimizes the economy of resource scheduling by combining scheduling cost calculation priority, and ultimately selects the most economical set of flexible resources from a massive pool of flexible resources that can effectively solve line over-limit problems, improving the matching degree between candidate flexible resources and line over-limit demands, and avoiding the scheduling of inefficient or ineffective resources. The flexible resource set selected by this invention can be further optimized and solved in subsequent steps. The selection by this invention reduces the dimensionality of subsequent optimization problems, increases the solution speed, improves the cost-effectiveness of over-limit regulation, and demonstrates its application potential in large-scale power systems. This invention achieves complementary regulation characteristics among multiple flexible resources, fully leveraging the regulation potential of multiple flexible resources. Attached Figure Description

[0021] Figure 1 This is a flowchart of the present invention; Figure 2 This is a simulation system topology diagram in the simulation examples listed in this invention; Figure 3 The following is a topology diagram of the simulation system listed in the simulation examples of this invention; Figure 4 This is a flowchart of the calculation of each matrix in this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0023] like Figure 1 As shown, Embodiment 1 of the present invention proposes a flexible resource selection method based on graph theory for line overrun scenarios, including: S1. Construct the graph structure of the power grid, and divide the graph structure of the power grid into different subgraphs according to the topology type of the power grid; the topology type includes radial network topology and ring network topology; S1.1 Constructing the graph structure of the power grid ,in, The graph structure of the power grid. For a graph structure, the set of nodes The set of branches in a graph structure; S1.2. Based on the topology type of the power grid, the graph structure of the power grid is divided into different subgraphs, specifically as follows: For radial network topology, the graph structure Classified as main path and sub-path , The graph structure represents the main path of the radial network topology. This is the set of nodes for the main path of the radial network topology. This is the set of branches of the main path in the radial network topology; This is a graph structure representing the subpaths of a radial network topology. Let be the set of nodes for the subpaths of the radial network topology. This is the set of branches of the sub-paths in a radial network topology. The main path of the radial network topology is the path with the most nodes originating from the main power source. Sub-paths are paths branching off from nodes on the main path. The nodes that branch off are called branch points. Sub-paths are further divided into different subgraphs based on the branch points. ;in, The first sub-path partition of the radial network topology x Graph structure of subgraphs, The first sub-path partition of the radial network topology x The set of nodes in a subgraph The first sub-path partition of the radial network topology x The set of branches in a subgraph; For ring network topology, the graph structure Divided into leading paths , main path and sub-path ,in, This is the graph structure of the leading paths in a ring network topology. For a ring network topology, the set of nodes in the leading path. This is the set of branches of the leading path in a ring network topology; This is the graph structure of the main path in a ring network topology. This is the set of nodes along the main path of the ring network topology. This is the set of branches of the main path in a ring network topology; This is a graph structure representing the subpaths of a ring network topology. Let be the set of nodes for the sub-paths of the ring network topology. This is the set of branches of the sub-paths in a ring network topology. The leading path is the path from the main power source to the starting point of the ring network. The starting point of the ring network is a node on the ring network from which multiple currents flow. The main path is the ring network itself. Sub-paths are paths leading out from nodes on the main path or the leading path. The nodes from which paths lead are called branch points. Sub-paths are further divided into different subgraphs based on the branch points. ,in, The first sub-path division for the ring network topology x Graph structure of subgraphs, The first sub-path division for the ring network topology x The set of nodes in a subgraph The first sub-path division for the ring network topology x The set of branches of a subgraph.

[0024] S1.3. After dividing the power grid graph structure into different subgraphs according to the power grid topology, renumber each node and branch of the power grid graph structure. The power flow direction from the main power source to the power grid is used as the reference direction. The node connected to the main power source is designated as node 1. For radial network topologies, nodes are numbered sequentially in the order of main path first, then subpath, with the node number increasing along the reference direction. For ring network topologies, nodes are numbered sequentially in the order of leader path, main path, and subpath, with the node number increasing along the reference direction. The order of subpath numbering is not strictly defined; for nodes connected to the first subpath... The node and the first Branches between nodes, among which , define the first The node and the first Each node represents the first and last node of the branch. Sort the branches in ascending order of their first nodes. If the first nodes of the branches are the same, sort them in ascending order of their last nodes. After sorting, number them sequentially.

[0025] S1.4 Define the reference direction and upstream and downstream directions. Define the active power flow reference direction: for connections at nodes , ( For a branch between nodes, the positive direction of the active power flow is the first node of the branch. Flowing to the end node of the branch ; Node injection power reference direction: When a node connects to distributed renewable energy, the node injection power is negative; when it connects to load, the node injection power is positive. Flexible resource adjustment direction: If the distributed renewable energy generation increases or the load power consumption increases, the adjustment will be upward; otherwise, the adjustment will be downward. The correlation between flexible resources and the active power of the line: when flexible resources are adjusted upward, the active power of the branch increases or when flexible resources are adjusted downward, the active power of the branch decreases, which is a positive correlation, and vice versa. Upstream and downstream of a radial network node; for a radial network topology, with the power flow direction of the main power source supplying power to the network as the reference direction, for a certain node, the direction of current flowing to the node is defined as the upstream of the node, and the direction of current flowing out of the node is defined as the downstream of the node.

[0026] S2. Based on the subgraph to which each node and each branch belong, and the reachability of each node to the tail node on each branch, calculate the correlation degree between the node and the branch. All correlation degrees form the correlation matrix between line limit violation and access node. Construct a flexible resource type matrix according to the flexible resource type of the node. Multiply the correlation matrix between line limit violation and access node and the flexible resource type matrix to obtain the correlation matrix between line limit violation and flexible resource. The flexible resource type includes load and distributed new energy. S2.1 Establish a global positive reachability matrix : The global positive reachability matrix represents the reachability of one node to another along the positive direction of active power flow. The first in q Line number j Column elements For: If the first q The node to the first j If a node is reachable along the positive direction of the active power flow, its reachability is 1; otherwise, it is 0. The formula is:

[0027] S2.2 Establish a correlation matrix between line over-limit and access node : Line over-limit and access node correlation matrix The i Line number j Column elements For the first i branch road and the first j The degree of correlation between nodes; S2.2.1, For the radial network topology: If the first... i The branch road belongs to the main path, and the first branch road is the main path. j The node belongs to the node in the main path. i The set of upstream nodes of the tail node of a branch Then the first i branch road and the first j The correlation degree of each node is equal to 0; If the first i The branch road belongs to the main path, and the first branch road is the main path. j The node is the _th i The tail node of the branch path or the first node in the main path i The set of downstream nodes of the tail node of a branch. Then the first i branch road and the first j The correlation degree of the nth node is equal to that of the nth node. i The tail node of the branch and the first j The reachability between nodes is expressed by the formula:

[0028] in, For the first i A side road; For the first i a side road The tail node, For the first i The tail node of the branch and the first jReachability between nodes.

[0029] S2.2.2, For a ring network topology: If the first i If a branch is a leading path or a sub-path, then the first branch... i branch road and the first j The correlation degree of the nth node is equal to that of the nth node. i The tail node of the branch and the first j Reachability between nodes; If the first i The branch road belongs to the main path, and the first branch road is the main path. j Each node belongs to , or the j Each node belongs to a subpath and the branch points of the subpath belong to Then the first i branch road and the first j The correlation degree of the nth node is equal to that of the nth node. i The tail node of the branch and the first j Reachability between nodes; In the main path, starting from the beginning of the ring network and moving along the reverse reference direction to reach the first... i The set of nodes within the tail node of a branch. Excluding the starting point of the ring network; If the first i The branch road belongs to the main path, and the first branch road is the main path. j Each node belongs to , or the j Each node belongs to a subpath and the branch points of the subpath belong to Then the first i branch road and the first j The correlation degree of the nth node is equal to that of the nth node. i The tail node of the branch and the first j Negative numbers for reachability between nodes; In the main path, starting from the starting point of the ring network and following the reference direction to reach the first... i The nodes within the first node of each branch path, Including the starting point of the ring network; If the first i The branch road belongs to the main path, and the first branch road is the main path. j If the nth node belongs to the preceding path, then the nth node... i branch road and the first j The correlation degree of a node is equal to 0, and the formula is:

[0030] in, The total number of nodes. The first sub-path division for the ring network topology x Sub-image The branch point.

[0031] S2.3 Construct a flexible resource type matrix based on the flexible resource access types of the nodes. : Flexible Resource Type Matrix As a column vector, a flexible resource type matrix The j element Indicates the first j Flexible resource types for the nth node, if the nth node... j If each node connects to the load, then If the first j If each node is connected to the distributed new energy source, then If the first j If a node is not connected to flexible resources, then .

[0032] S2.4 Multiply the correlation matrix between line over-limit and access node and the flexible resource type matrix to obtain the correlation matrix between line over-limit and flexible resource. Specifically: Flexible resource association matrix No. i Line number j Column elements Specifically:

[0033] in, This represents the total number of branch roads. S3. Calculate the sensitivity based on the degree of change of the active power of each branch with the active power of the flexible resources connected to each node, and calculate the priority of each node connecting to flexible resources for different branches based on the sensitivity and the adjustment cost of each node connecting to flexible resources. S3.1 Establish a flexible resource adjustment sensitivity matrix : The first of the flexible resource adjustment sensitivity matrix i Line number j Column elements For the first j The node can flexibly adjust resources to support the first... i The sensitivity of each branch; If the first j If the first node is not connected to the flexible resource, then the second node... j Each node can flexibly adjust resources, and the sensitivity of all branches is 0. If the first j If the first node accesses flexible resources, then the second node... j The node can flexibly adjust resources to support the first... i Sensitivity of the branch For: thei The active power of the branch circuit is related to the first j The partial derivative of the active power of the flexible resources accessed by each node; the formula is:

[0034] in, Indicates the first i a side road active power, Indicates the first j The active power of flexible resources accessed by each node. express about The partial derivatives of .

[0035] S3.2 Establish a flexible resource adjustment cost matrix , its first j element Indicates the first j The adjustment cost of flexible resources for node access; if the first node... j For flexible resources where no node is connected, then .

[0036] S3.3 Establish a flexible resource adjustment priority matrix : Establish a flexible resource adjustment priority matrix. The i Line number j Column elements For the corresponding priority, for the first i branch road, no. j The priority of the node is the first j The adjustment cost of each node accessing flexible resources divided by sensitivity. The absolute value of is given by the formula:

[0037] S4. Set the target branch. The target branch is the first... k a side road Based on the elements of the correlation matrix between line over-limit and flexible resources, the upward and downward adjustment capabilities of the flexible resources accessed by each node within a set time period, and the power of the target branch within a set time period, nodes participating in the over-limit adjustment of the target branch are initially selected as candidate nodes. S4.1 Constructing a line over-limit logic matrix: Line over-limit logic matrix The t element For the first tLine over-limit logic within a time period. If the power of the target branch is greater than the set positive risk value within the set time period, the line over-limit logic is 1; if the power of the target branch is less than the set reverse risk value within the set time period, the line over-limit logic is -1; if the power of the target branch is less than or equal to the set positive risk value and greater than or equal to the set reverse risk value within the set time period, the line over-limit logic is 0. S4.2 Construct a logical matrix of resource adjustment capabilities , its first t Line number j Column elements The definition is as follows: If the first j The resources accessed by the node in the first... t The adjustment can be made either upwards or downwards within a given time period (i.e., it has the ability to both increase and decrease). If only upward adjustment is possible, then If only downward adjustment is possible, then If it cannot be adjusted, then .

[0038] S4.3, if the first j The flexible resources accessed by each node have the ability to be increased within a set time period, and the first node... j The elements corresponding to the path violation and flexible resource association matrix of the node and the target branch are related to the first node and the target branch. t The product of the line over-limit logic in each time period is -1, then the corresponding node in the th t Each time period is a candidate node for upward adjustment; If the first j The flexible resources accessed by each node have the ability to be reduced within a set time period, and the first node... j If the product of the element corresponding to the line limit violation and flexible resource association matrix of a node and the target branch and the line limit violation logic is 1, then the corresponding node is a candidate node for downgrading. The formula for selecting candidate nodes is:

[0039]

[0040]

[0041] in, The set of all candidate nodes; This is the set of candidate nodes to be upgraded; This is the set of candidate nodes to be downgraded; The first part of the correlation matrix between line over-limit and flexible resources k Line number j The elements of the column.

[0042] S5. Based on the sensitivity and the minimum adjustable capacity and minimum adjustable capacity of the flexible resources accessed by each candidate node within a set time period, calculate the minimum change in active power of the target branch within a set time period caused by the flexible resource adjustment of the candidate node, specifically: For the candidate node that is adjusted upwards, the minimum change in active power of the target branch within the set time period is the minimum adjustable capacity within the corresponding set time period multiplied by the sensitivity of the candidate node to the target branch for flexible resource adjustment. For a candidate node that is downgraded, the minimum change in active power of the target branch within a set time period is the minimum adjustable capacity within the corresponding set time period multiplied by the sensitivity of the candidate node to flexible resource adjustment of the target branch, where the minimum adjustable capacity is a negative value.

[0043] Minimum change in active power The formula is:

[0044] in, , respectively in the t Within the time period, the first j The minimum adjustable capacity and minimum adjustable capacity of each node are used to form a numerical matrix of resource upscaling capability. All the minimum adjustable capacities constitute a numerical matrix of resource reduction capabilities. ; For the first j Each node can flexibly adjust resources for the target branch. Sensitivity.

[0045] S6. Sort the candidate nodes according to their priority from smallest to largest. Then, sum up the absolute values ​​of the minimum change in active power for each candidate node in order of priority. The selected flexible resource must satisfy the following:

[0046] The simplified formula is:

[0047] in, , … These are the 1st, 2nd, ... , ... of the candidate nodes after being sorted by their respective priorities from smallest to largest. -1 node; , … They are respectively , … The target branch caused by flexible resource adjustment is in the first t The minimum change in active power within a given time period; The absolute value is the set threshold value for exceeding the limit; As a margin, this embodiment sets it to 10%. For the first t For each time period, if the line over-limit logic is 1, the over-limit value is the difference between the set positive risk value and the power of the target branch within the set time period, and the over-limit value is negative; if the line over-limit logic is -1, the over-limit value is the difference between the calculated set reverse risk value and the power of the target branch within the set time period. When the line over-limit logic is 1, the over-limit value and , … Since all values ​​are negative, the flexible resource selection process is as follows: candidate nodes are sorted from lowest to highest priority, and the absolute value of the minimum change in active power for each candidate node is accumulated sequentially according to the sorting. The process stops when the minimum change exceeds the set threshold. The flexible resource accessed by the corresponding candidate node is the flexible resource selected within the set time period.

[0048] Specifically, this embodiment uses a 43-node system in a certain location for simulation verification. The topology of the 43-node system and its flexible resource access are as follows: Figure 2 As shown, the topology diagram of the 43-node system is as follows: Figure 3 As shown in the figure. The subgraph partitioning results are shown in Table 1.

[0049] Table 1. Subgraph partitioning results of the 43-node system

[0050] The target branch selected in this embodiment is a branch. The control cycle is divided into 8 time periods. The flexible resource sets selected for each time period are shown in Table 2.

[0051] Table 2 Flexible resource sets selected for each time period

[0052] Embodiment 2 of the present invention proposes a graph-based flexible resource selection system for line overrun scenarios based on the method described in Embodiment 1 of the present invention. The system includes a graph structure construction module, a line overrun and flexible resource association matrix construction module, a priority calculation module, a candidate node selection module, a minimum change in active power calculation module, and a flexible resource selection module. Specifically: Graph Structure Construction Module: Constructs the graph structure of the power grid, and divides the graph structure into different subgraphs according to the topology type of the power grid; the topology types include radial network topology and ring network topology; The module for constructing the correlation matrix between line overruns and flexible resources calculates the correlation degree between nodes and branches based on the subgraph to which each node and each branch belong, and the reachability of each node to the tail nodes on each branch. All correlation degrees form the correlation matrix between line overruns and access nodes. A flexible resource type matrix is ​​constructed based on the flexible resource type of the node's access. The correlation matrix between line overruns and access nodes and the flexible resource type matrix are multiplied to obtain the correlation matrix between line overruns and flexible resources. The flexible resource types include load and distributed renewable energy. Priority calculation module: Calculates sensitivity based on the degree of change of active power of each branch with the active power of flexible resources accessed by each node, and calculates the priority of each node accessing flexible resources for different branches based on the sensitivity and the adjustment cost of each node accessing flexible resources. Candidate Node Screening Module: Set a target branch, and based on the elements of the correlation matrix between line over-limit and flexible resources, the upward and downward adjustment capabilities of the flexible resources accessed by each node within a set time period, and the power of the target branch within a set time period, initially screen out nodes that will participate in the over-limit adjustment of the target branch as candidate nodes. The minimum change in active power calculation module calculates the minimum change in active power of the target branch within a set time period caused by the flexible resource adjustment of the candidate node, based on the sensitivity and the minimum adjustable capacity and minimum adjustable capacity of the flexible resources connected to each candidate node within a set time period. Flexible resource filtering module: Sort candidate nodes according to their priority from smallest to largest, and accumulate the absolute value of the minimum change in active power for each candidate node in order of sorting. Stop when the limit is exceeded. The flexible resources accessed by the corresponding candidate node are the flexible resources selected in the set time period.

[0053] The flowcharts for each matrix calculation in this embodiment are as follows: Figure 4 As shown.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A graph-based flexible resource selection method for line over-limit scenarios, characterized in that, include: Construct a graph structure for the power grid, and divide the graph structure into different subgraphs based on the topology type of the power grid; the topology types include radial network topology and ring network topology; Based on the subgraph to which each node and each branch belong, and the reachability of each node to the tail node on each branch, the correlation degree between the node and the branch is calculated. All correlation degrees form the correlation matrix between line overrun and access node. A flexible resource type matrix is ​​constructed according to the flexible resource type of the node. The correlation matrix between line overrun and access node and the flexible resource type matrix are multiplied to obtain the correlation matrix between line overrun and flexible resource. The flexible resource types include load and distributed new energy. Sensitivity is calculated based on the degree to which the active power of each branch changes with the active power of the flexible resources connected to each node. Priority for each node to access flexible resources for different branches is calculated based on the sensitivity and the adjustment cost of each node accessing flexible resources. Set a target branch, and based on the elements of the correlation matrix between line over-limit and flexible resources, the upward and downward adjustment capabilities of the flexible resources accessed by each node within a set time period, and the power of the target branch within a set time period, initially screen out nodes that will participate in the over-limit adjustment of the target branch as candidate nodes. Based on the sensitivity and the minimum adjustable capacity and minimum adjustable capacity of the flexible resources accessed by each candidate node within a set time period, calculate the minimum change in active power of the target branch within a set time period caused by the flexible resource adjustment of the candidate node. Candidate nodes are sorted in ascending order of priority. The absolute value of the minimum change in active power for each candidate node is accumulated sequentially according to the sort order. The process stops when the minimum change exceeds the set threshold. The flexible resources accessed by the corresponding candidate node are the flexible resources selected during the set time period.

2. The graph-based flexible resource selection method for line over-limit scenarios according to claim 1, characterized in that, include: The process of dividing the power grid graph structure into different subgraphs based on the power grid topology is as follows: For a radial network topology, the graph structure is divided into main paths and sub-paths. The main path is the path with the most nodes starting from the main power source, and the sub-path is the path that extends from the nodes on the main path. The nodes that extend the path are called branch points. For a ring network topology, the graph is divided into leading paths, main paths, and sub-paths. The leading path is the path from the main power source to the starting point of the ring network. The starting point of the ring network is a node on the ring network from which multiple currents flow. The main path is the ring network itself. Sub-paths are paths that extend from nodes on the main path or leading path. Nodes from which paths extend are called branch points.

3. The graph-based flexible resource selection method for line over-limit scenarios according to claim 2, characterized in that, include: After dividing the power grid graph structure into different subgraphs according to the power grid topology, the nodes and branches of the power grid graph structure are renumbered. The power flow direction from the main power source to the power grid is used as the reference direction, and the node connected to the main power source is designated as node 1. For radial network topology, the nodes are numbered sequentially in the order of main path first and then sub-path, with the node number increasing along the reference direction. For ring network topology, the nodes are numbered sequentially in the order of leading path, main path, and sub-path, with the node number increasing along the reference direction. For the connection in the first The node and the first Branches between nodes, among which , define the first The node and the first Each node represents the first and last node of the branch. Sort the branches in ascending order of their first nodes. If the first nodes of the branches are the same, sort them in ascending order of their last nodes. After sorting, number them sequentially.

4. The graph-based flexible resource selection method for line over-limit scenarios according to claim 3, characterized in that, include: For a radial network topology, if the j-th node belongs to the set of upstream nodes of the tail node of the i-th branch... If the correlation between the i-th branch and the j-th node is 0, then the correlation between the i-th branch and the j-th node is 0. The j-th node is either the tail node of the i-th branch or a set of downstream nodes belonging to the tail node of the i-th branch. If the degree of association between the i-th branch and the j-th node is equal to the reachability between the tail node of the i-th branch and the j-th node; The reachability between the tail node of the i-th branch and the j-th node is as follows: if the tail node of the i-th branch is reachable from the j-th node along the positive direction of active power flow, the reachability is 1; otherwise, it is 0. The set of upstream nodes of the tail node of the i-th branch for: If the i-th branch belongs to the main path, the power flow direction from the main power source to the radial network is used as the reference direction. Includes all main path nodes traversed when current flows to the tail node of the i-th branch; if the main path node is a branch point, It also includes all nodes on the sub-paths derived from that branch point; If the i-th branch is a sub-path Its branch point is x, with the power flow direction from the main power source to this radial network as the reference direction. Includes all main path nodes, except for the sub-paths of the i-th branch. All nodes on the outer sub-path and the sub-path through which current flows from the branch point x of the i-th branch to the tail node of the i-th branch. All nodes on; The set of downstream nodes of the tail node of the i-th branch for: If the i-th branch belongs to the main path, the power flow direction from the main power source to the radial network is used as the reference direction. Includes all main path nodes that the current flows through after exiting this node, and the tail node of the i-th branch itself; if the main path node is a branch point, It also includes all nodes on the sub-paths derived from that branch point; If the i-th branch is a sub-path Its branch point is x, with the power flow direction from the main power source to this radial network as the reference direction. Includes the sub-paths traversed after the current flows out from the tail node of the i-th branch. The nodes on the i-th branch and the tail node of the i-th branch itself.

5. The graph-based flexible resource selection method for line over-limit scenarios according to claim 3, characterized in that, include: For a ring network topology, if the i-th branch is a leading path or a sub-path, then the affinity between the i-th branch and the j-th node is equal to the reachability between the tail node of the i-th branch and the j-th node. If the i-th branch belongs to the main path, and the j-th node belongs to... Or, the j-th node belongs to the sub-path and the branch point of the sub-path belongs to If the degree of association between the i-th branch and the j-th node is equal to the reachability between the tail node of the i-th branch and the j-th node; The set of nodes in the main path that starts from the ring network starting point and moves along the reverse reference direction to the tail node of the i-th branch. Excluding the starting point of the ring network; If the i-th branch belongs to the main path, and the j-th node belongs to... Or, the j-th node belongs to the sub-path and the branch point of the sub-path belongs to If the degree of association between the i-th branch and the j-th node is equal to the negative of the reachability between the tail node of the i-th branch and the j-th node; The nodes in the main path that start from the ring network starting point and follow the reference direction to reach the first node of the i-th branch are... Including the starting point of the ring network; If the i-th branch is a main path and the j-th node is a preceding path, then the correlation between the i-th branch and the j-th node is 0.

6. The graph-based flexible resource selection method for line over-limit scenarios according to claim 3, characterized in that, include: A flexible resource type matrix is ​​constructed based on the flexible resource access type of the nodes. The correlation matrix between line over-limit and access nodes and the flexible resource type matrix are multiplied together to obtain the correlation matrix between line over-limit and flexible resources, specifically: The flexible resource type matrix is ​​a column vector, and the j-th element of the flexible resource type matrix... This represents the flexible resource type of the j-th node. If the j-th node receives a load, then... ; If the j-th node is connected to the distributed renewable energy source, then ; If the j-th node is not connected to the flexible resource, then .

7. The graph-based flexible resource selection method for line over-limit scenarios according to claim 3, characterized in that, include: The calculation of the priority for each node to access flexible resources in different branches based on sensitivity and the adjustment cost of each node accessing flexible resources is as follows: If the j-th node is not connected to the flexible resource, then the sensitivity of the j-th node to the flexible resource adjustment for all branches is 0. If the j-th node accesses flexible resources, then the j-th node adjusts the sensitivity of the flexible resources to the i-th branch. Let be: the partial derivative of the active power of the i-th branch with respect to the active power of the flexible resources connected to the j-th node; For the i-th branch, the priority of the j-th node is the adjustment cost of the j-th node accessing flexible resources divided by the sensitivity. The absolute value of.

8. The graph theory-based flexible resource selection method for line over-limit scenarios according to claim 7, characterized in that, include: The initial screening of nodes participating in the target branch's over-limit adjustment as candidate nodes specifically involves: If the power of the target branch is greater than the set positive risk value within the set time period, the line over-limit logic is 1; if the power of the target branch is less than the set reverse risk value within the set time period, the line over-limit logic is -1; if the power of the target branch is less than or equal to the set positive risk value and greater than or equal to the set reverse risk value within the set time period, the line over-limit logic is 0. If the flexible resources accessed by the j-th node have the ability to be increased within a set time period, and the product of the element corresponding to the line limit and flexible resource association matrix of the j-th node and the target branch and the line limit logic is -1, then the corresponding node is a candidate node for increase. If the flexible resources accessed by the j-th node have the ability to be downgraded within a set time period, and the product of the element corresponding to the line over-limit and flexible resource association matrix of the j-th node and the target branch and the line over-limit logic is 1, then the corresponding node is a candidate node for downgrading.

9. The graph theory-based flexible resource selection method for line over-limit scenarios according to claim 8, characterized in that, include: The minimum change in active power of the target branch within a set time period caused by the flexible resource adjustment of the candidate nodes is specifically defined as follows: For the candidate node that is adjusted upwards, the minimum change in active power of the target branch within the set time period is the minimum adjustable capacity within the corresponding set time period multiplied by the sensitivity of the candidate node to the target branch for flexible resource adjustment. For a candidate node that is downgraded, the minimum change in active power of the target branch within a set time period is the minimum adjustable capacity within the corresponding set time period multiplied by the sensitivity of the candidate node to flexible resource adjustment of the target branch, where the minimum adjustable capacity is a negative value.

10. The graph-based flexible resource selection method for line over-limit scenarios according to claim 1, characterized in that, include: If the line over-limit logic is 1, then the set over-limit threshold is: the difference between the set positive risk value and the power of the target branch within the set time period, the absolute value of the difference multiplied by 1 and the sum of the set margin. If the line over-limit logic is -1, then the set over-limit threshold is: calculate the difference between the set reverse risk value and the power of the target branch within the set time period, multiply the difference by 1 and sum with the set margin.

11. A graph-based flexible resource selection system for line overrun scenarios based on the method according to any one of claims 1-10, comprising a graph structure construction module, a line overrun and flexible resource association matrix construction module, a priority calculation module, a candidate node selection module, a minimum change in active power calculation module, and a flexible resource selection module, characterized in that: Graph Structure Construction Module: Constructs the graph structure of the power grid, and divides the graph structure into different subgraphs according to the topology type of the power grid; the topology types include radial network topology and ring network topology; The module for constructing the correlation matrix between line overruns and flexible resources calculates the correlation degree between nodes and branches based on the subgraph to which each node and each branch belong, and the reachability of each node to the tail nodes on each branch. All correlation degrees form the correlation matrix between line overruns and access nodes. A flexible resource type matrix is ​​constructed based on the flexible resource type of the node's access. The correlation matrix between line overruns and access nodes and the flexible resource type matrix are multiplied to obtain the correlation matrix between line overruns and flexible resources. The flexible resource types include load and distributed renewable energy. Priority calculation module: Calculates sensitivity based on the degree of change of active power of each branch with the active power of flexible resources accessed by each node, and calculates the priority of each node accessing flexible resources for different branches based on the sensitivity and the adjustment cost of each node accessing flexible resources. Candidate Node Screening Module: Set a target branch, and based on the elements of the correlation matrix between line over-limit and flexible resources, the upward and downward adjustment capabilities of the flexible resources accessed by each node within a set time period, and the power of the target branch within a set time period, initially screen out nodes that will participate in the over-limit adjustment of the target branch as candidate nodes. The minimum change in active power calculation module calculates the minimum change in active power of the target branch within a set time period caused by the flexible resource adjustment of the candidate node, based on the sensitivity and the minimum adjustable capacity and minimum adjustable capacity of the flexible resources connected to each candidate node within a set time period. Flexible resource filtering module: Sort candidate nodes according to their priority from smallest to largest, and accumulate the absolute value of the minimum change in active power for each candidate node in order of sorting. Stop when the limit is exceeded. The flexible resources accessed by the corresponding candidate node are the flexible resources selected in the set time period.

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