Dynamic reactive power supply site selection method based on voltage disturbance propagation capability sorting

Abstract

The invention discloses a dynamic reactive power supply site selection method based on voltage disturbance propagation capability sorting, and the method comprises the steps: firstly building an anticipated accident set of a power system, defining a short-term voltage stability index SVSI based on a voltage response track, carrying out the objective weighting of each node according to the topological information and prior information of the power system, and carrying out the selection of the power system anticipated accident set; calculating a first-stage voltage disturbance propagation capability evaluation value of each node, taking the calculated evaluation value and the occurrence probability of each key accident as weight factors, combining a short-term voltage stability evaluation index SVSI to form a weighted short-term voltage stability index WSVSI, sorting the WSVSI values, selecting a plurality of nodes with large values, and calculating the first-stage voltage disturbance propagation capability evaluation value of each node; the installation position is used for the dynamic reactive power supply. According to the dynamic reactive power supply site selection method based on voltage disturbance propagation capability sorting, the power system nodes which have great influence on cascading failure danger can be efficiently identified, and a necessary basis is provided for capacity planning of a follow-up reactive power compensation device.

Description

Technical Field

[0001] The invention relates to the field of reactive power site selection in an electric power system, and in particular to a dynamic reactive power site selection method based on voltage disturbance propagation capability ranking. Background Art

[0002] With the rapid growth of the global economy and the continuous increase in population, energy demand continues to rise. However, due to the limited traditional energy resources and the increasing environmental pollution problems, people are forced to turn to more sustainable and environmentally friendly power generation methods. New energy power generation has become one of the important ways to cope with climate change, reduce greenhouse gas emissions and ensure energy security.

[0003] Wind power generation plays an important role in renewable energy generation. However, when a grid fault causes a voltage drop, wind turbines may absorb reactive power from the grid, exacerbating voltage problems. During operation, wind turbines are susceptible to voltage disturbances caused by extreme weather or cascading failures, which can lead to deterioration of power system voltage stability and even large-scale power outages. In addition, as the inertia of wind power generation systems decreases and the complexity of system dynamics increases, the possibility of causing cascading failures is also increasing.

[0004] In order to deal with voltage problems and cascading failures, traditional capacitor banks have a slow response speed and can no longer meet the needs of the system after a fault. In contrast, dynamic reactive power compensation power supplies have a faster response speed and can effectively solve the voltage stability problem of wind power generation systems. However, due to the high investment cost, the application of dynamic reactive power compensation power supplies is greatly limited; secondly, the traditional site selection method only considers the voltage stability performance of a single node and fails to fully analyze the voltage disturbance propagation capacity of each node. In this process, according to whether the evaluation process considers the system topology, the traditional site selection method can be mainly divided into the following two categories: the first type of method does not consider the system topology, and is only based on the voltage stability evaluation of a single node (or the average value of the voltage stability evaluation of the entire power system), ignoring the structural characteristics of the node itself and the interconnection characteristics of the node in the operation of the power grid. When subjected to a large disturbance, the potential danger of cascading failures is difficult to reveal. Although the second type of method takes into account the system topology, it lacks consideration of factors such as the electrical quantity characteristics of a single node in the power grid (such as node load size, node voltage stability), and it is difficult to establish a model that conforms to the actual physical characteristics of the power grid, and the prediction accuracy of key nodes that are prone to cascading failures needs to be improved. In view of this, it is necessary to improve this technology. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a dynamic reactive power source site selection method based on voltage disturbance propagation capability ranking, so as to efficiently identify power system nodes with greater impact on the risk of cascading failures, and provide a necessary basis for subsequent capacity planning of reactive compensation devices.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A dynamic reactive power source site selection method based on voltage disturbance propagation capability ranking comprises the following steps:

[0008] S1. Establish a set of anticipated accidents in the power system;

[0009] S2, define the short-term voltage stability index SVSI based on the post-fault voltage response trajectory curve;

[0010] S3, using the power system topology information and prior information as weight factor inputs, evaluating the node disturbance propagation capability, and calculating the evaluation value of each node in the system;

[0011] S4, taking the assessment results and the probability of accident occurrence as weights, adding them to the SVSI to form the weighted short-term voltage stability index WSVSI;

[0012]

[0013] S5. Based on the established set of expected accidents, the WSVSI value of each node in the system after the fault is calculated to evaluate the node voltage disturbance propagation capability;

[0014] S6. Sort the calculated WSVSI values ​​of each node in the system, and preferentially select several nodes with larger values ​​as installation locations.

[0015] In the above technical solution, in S2, the short-term voltage stability index is defined as follows:

[0016] Among them, B represents the set of all nodes; T c and T end Respectively represent the simulation end time and fault clearing time; N b Represents the number of nodes; V i,j,k and V i,0 They represent the static voltage amplitude of node i at time j after accident k and before the accident respectively; Δt j Represents the time step taken for the simulation.

[0017] In the above technical solution, in S2, f(V i,j,k ,V i,0 ) is the voltage deviation value of the i-th node at the j-th time in the k-th accident, which is defined as follows:

[0018]

[0019] Among them, δ is the threshold value.

[0020] In the above technical solution, in S3, the method for evaluating the node disturbance propagation capability comprises the following steps:

[0021] S31. The network adjacency matrix provides the topological information of the power system and will be used to create the augmented network matrix. As shown below:

[0022]

[0023] Wherein, A=(a ij ) N×N is the adjacency matrix of the power system network, a ij is an element in the adjacency matrix A;

[0024] S32. In order to offset the impact of adding ground nodes on the network topology and ensure the accuracy of node identification results, the node prior information matrix is ​​added below Node prior information matrix The diagonal elements of represent the prior information of node importance. The prior information of ground nodes is set to The node prior information matrix As shown below:

[0025]

[0026] S33, according to the obtained augmented network matrix and node prior information matrix Constructing the Iteration Matrix

[0027] S34, calculate the node algorithm score s, the iteration includes two operations, namely linear transformation and normalization, the denominator of the normalization method used is set to the sum of the scores of all nodes including the ground node, and the update iteration rule is:

[0028]

[0029] S35, through iteration, all nodes converge to a stable state s i =1(i=1,2,...,N); Finally, the importance score of the ground node s N+1 The number of nodes in the power system is evenly distributed to each node, and the importance score MR of each node excluding the ground node g is obtained:

[0030]

[0031] S36. All nodes are ranked according to the calculation results of the above evaluation method. The higher the score of the node, the greater its importance in the grid structure. When a chain failure occurs in the power system, the failure of a node with a large score is more likely to cause the accident to expand further, that is, the node has a greater possibility of expanding the accident than other nodes.

[0032] In the above technical solution, in S31, if nodes i and j are connected by an edge, then a ij = 1, if nodes i and j have no edge, then a ij =0; add the ground node g and set its corresponding element to 0. Obviously, the ground node has established edges with other nodes and is set to 1 in the matrix below.

[0033] In the above technical solution, in S33, the iteration matrix contains the prior information of the power system nodes. Initially, for ordinary nodes, the score is set to s i =1(i=1,2,...,N), and for ground nodes there are also s g =s N+1 =1, set the convergence condition as follows: the difference in s scores obtained in two iterations is less than a predetermined threshold;

[0034]

[0035] In the above technical solution, in S1, the set of anticipated accidents of the power system is generated by historical accident records and short-term voltage stability index evaluation.

[0036] In the above technical solution, the evaluation result of S3 and the probability of accident occurrence are used as weights in S4 and added to SVSI to form a weighted short-term voltage stability index WSVSI, which is defined as follows:

[0037] WSVSI i =∑ k∈K p k ×SVSI k ×MR i

[0038] Where: P k represents the probability of accident k occurring; K represents the set of accidents.

[0039] In the above technical solution, in S5, a simulation model is built in a software platform that supports electromechanical transient modeling and simulation, and simulation is performed according to the set of anticipated accidents of the power system established in S1, and the voltage response trajectory curve of each node after the fault is cleared is recorded. Based on the weighted short-term voltage stability index WSVSI described in S4, the WSVSI value of the system under the action of the anticipated accident k is calculated to evaluate the node voltage disturbance propagation capability.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The dynamic reactive power source site selection method based on voltage disturbance propagation capability ranking of the present invention evaluates the node disturbance propagation capability and further obtains the node voltage disturbance propagation capability ranking result, which can effectively identify the key nodes that are likely to affect the system voltage stability and cause cascading failures, and can be used to guide the selection of dynamic reactive power source installation locations to alleviate the risk of cascading failures faced by high-penetration wind power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 It is a flow chart of the dynamic reactive power source site selection method based on voltage disturbance propagation capability ranking of the present invention;

[0044] Figure 2 It is a comparison chart of the calculation results of the dynamic reactive power source site selection method based on voltage disturbance propagation capability ranking of the present invention and PageRank and Adaptive LeaderRank algorithms;

[0045] Figure 3 The present invention is a flowchart of a method for evaluating node disturbance propagation capability in a dynamic reactive power source site selection method based on voltage disturbance propagation capability ranking. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0047] Please refer to Figures 1 to 3As shown, the present invention discloses a dynamic reactive power source site selection method based on voltage disturbance propagation capability ranking. First, a power system expected accident set is established. In this embodiment, the power system expected accident set is generated by historical accident records and short-term voltage stability index evaluation. In the specific implementation process, the expected accident set is composed of n faults, among which The faults are selected from the faults that can have a greater impact on the power grid in the historical accident records. The faults are generated by the evaluation results of the short-term voltage stability index proposed in the present invention, and the node faults with larger evaluation results are selected as another part of the expected accident set, and the probability of accident occurrence P is recorded. k The accident set in this example includes 10 different anticipated critical faults. To preserve generality, the probability of each anticipated critical accident is 10%.

[0048] Secondly, a short-term voltage stability index SVSI is defined based on the post-fault voltage response trajectory curve. Specifically, in this embodiment, a short-term voltage stability index (Short-term Voltage Stability Index, SVSI) is defined as shown in the following formula:

[0049]

[0050] Among them, B represents the set of all nodes; T c and T end Respectively represent the simulation end time and fault clearing time; N b Represents the number of nodes; V i,j,k and V i,0 They represent the static voltage amplitude of node i at time j after accident k and before the accident respectively; Δt j Represents the time step taken for the simulation.

[0051] And f(V i,j,k ,V i,0 ) is the voltage deviation value of the i-th node at the j-th time in the k-th accident, which is defined as follows:

[0052]

[0053] Wherein, δ is a threshold value, and in this embodiment, 0.1 pu is taken as the threshold value.

[0054] The power system topology information and prior information are used as weight factor inputs to evaluate the node disturbance propagation capability and calculate the evaluation value of each node in the system.

[0055] In this embodiment, the topology information of the IEEE39 node system model is used, and the prior information (node ​​load size) is added as input. Among them, the topology information clarifies the specific topological connection relationship of each node in the system, and the prior information is a detailed description of the electrical characteristics of the power system and other information. The above information is used as the input of the node disturbance propagation capability evaluation index of the first stage of the present invention, and the corresponding evaluation value can be obtained by calculation.

[0056] Please refer to Figure 3 As shown, the method for evaluating the node disturbance propagation capability includes the following steps:

[0057] First, the network adjacency matrix provides the topological information of the power system, which will be used to create the augmented network matrix As shown below:

[0058]

[0059] Wherein, A=(a ij ) N×N is the adjacency matrix of the power system network, a ij is an element in the adjacency matrix A; if nodes i and j have an edge, then a ij = 1, if nodes i and j have no edge, then a ij =0; add the ground node g and set its corresponding element to 0. Obviously, the ground node has established edges with other nodes and is set to 1 in the matrix below.

[0060] In order to offset the impact of adding ground nodes on the network topology and ensure the accuracy of node identification results, the node prior information matrix is ​​added below The diagonal matrix of the node's prior information The diagonal elements of represent the prior information of node importance (including information such as node load size). The prior information of ground nodes is set to The node prior information matrix As shown below:

[0061]

[0062] Then according to the obtained augmented network matrix and node prior information matrix Constructing the Iteration Matrix

[0063] Iteration Matrix contains the prior information of the power system nodes. Initially, for ordinary nodes, the score is set to s i =1(i=1,2,...,N), and for ground nodes there are also s g =sN+1 =1, set the convergence condition as follows: the difference in s scores obtained in two iterations is less than a predetermined threshold;

[0064]

[0065] Calculate the node algorithm score s. The iteration includes two operations, namely linear transformation and normalization. The denominator of the normalization method used is set to the sum of the scores of all nodes including the ground node. The update iteration rule is:

[0066]

[0067] Through iteration, all nodes converge to a stable state s i =1(i=1,2,...,N); Finally, the importance score of the ground node s N+1 The number of nodes in the power system is evenly distributed to each node, and the importance score MR of each node excluding the ground node g is obtained:

[0068]

[0069] Finally, all nodes are ranked according to the calculation results of the above evaluation method. The higher the score of the node, the greater its importance in the grid structure. When a chain failure occurs in the power system, the failure of a node with a high score is more likely to cause the accident to expand further, that is, the node has a greater possibility of expanding the accident than other nodes.

[0070] Please refer to Figure 2 As shown in the figure, the method for evaluating the node disturbance propagation capability is an improved method based on algorithms such as PageRank and Adaptive LeaderRank, which is more in line with the actual physical characteristics model of the power grid and can effectively identify key nodes that are prone to cascading failures. Specifically, identifying key nodes in the power system helps system planners to effectively deploy dynamic reactive power compensation devices, which is a method to improve voltage stability under large disturbances. When an unexpected fault event occurs at a node, the key node can be identified by evaluating the possibility of the faulty node initiating a cascading fault, thereby guiding the installation location of the dynamic reactive power source and improving the voltage stability of the power system.

[0071] For a power system network consisting of N nodes, add a ground node g to connect with the ordinary node i. The connection here is a bidirectional connection between the ground node g and the original node i, turning the original network into a fully connected network of N+1 nodes. The SR score of node i is proportional to the SR score of its neighbor node j. The more neighbor nodes j of node i, the higher the score of node i, and the more important the corresponding node i is.

[0072] The evaluation results and the probability of an accident are used as weights and added to the SVSI to form a weighted short-term voltage stability index WSVSI. In this embodiment, the evaluation values ​​of each node in the above system and the probability of an accident are used as weights and added to the SVSI to form a weighted short-term voltage stability index WSVSI, which is defined as follows:

[0073] WSVSI i =∑ k∈K p k ×SVSI k ×MR i

[0074] Where: P k represents the probability of accident k occurring; K represents the set of accidents.

[0075] Specifically, in this process, the short-term voltage stability index is defined based on the post-fault voltage response trajectory curve, and the probability of the accident and the importance score MR of each node in the system are calculated. i The weighted values ​​are added to form the weighted short-term voltage stability index WSVSI.

[0076] In this embodiment, the evaluation index not only considers the degree and duration of voltage deviation, but also evaluates the comprehensive process of voltage dynamic response after disturbance. i , to distinguish the differences in structure and propagation importance of each node in the power system, thereby further improving the accuracy of transient voltage stability assessment results and the system's defense capabilities against potential cascading failures.

[0077] Based on the established expected accident set, the WSVSI value of each node in the system after the fault is calculated, and the node voltage disturbance propagation capability is evaluated. In this embodiment, a simulation system model is built in a software platform that supports electromechanical transient modeling and simulation (such as DSA; PowerFactory; PSS / E, etc., which are widely used in the academic and industrial circles of power systems), and simulation is performed according to the established power system expected accident set. The expected accidents are set, and the voltage response trajectory curve of each node is recorded after the fault line is removed. According to the weighted short-term voltage stability index WSVSI, the WSVSI index value of the system under the action of the expected accident k is calculated to realize the evaluation of the node voltage disturbance propagation capability.

[0078] Then, the calculated WSVSI values ​​of each node of the system are sorted, and several nodes with larger values ​​are preferentially selected as installation locations. In this embodiment, the WSVSI values ​​of each node of the system are sorted according to the calculated weighted short-term voltage stability index WSVSI value, and several nodes with the largest WSVSI value are selected as the installation locations of the dynamic reactive power supply.

[0079] Before capacity planning, it is necessary to optimize the location of reactive power sources to improve the economy and efficiency of dynamic reactive power sources and effectively deal with the risk of cascading failures caused by voltage disturbances. The dynamic reactive power source site selection method based on the voltage disturbance propagation capability ranking of the present invention first establishes an expected set of key accidents, and then defines the short-term voltage stability index SVSI based on the voltage response trajectory. Each node is objectively weighted according to the power system topology information and prior information, and the first-stage voltage disturbance propagation capability evaluation value MR of each node is calculated. The calculated MR evaluation value and the probability of occurrence of each key accident are used as weight factors, combined with the short-term voltage stability evaluation index SVSI, and finally a weighted short-term voltage stability index WSVSI is formed. Finally, based on the key accident set, the second-stage WSVSI evaluation value of each node in the system after the fault line is removed is calculated. The WSVSI values ​​are sorted and the 10 nodes with the largest values ​​are selected as the installation locations of the dynamic reactive power source. The present invention calculates objective weights based on the voltage disturbance propagation capability and uses them to weight each node, which can efficiently identify power system nodes with greater impact on the risk of cascading failures and provide a necessary basis for subsequent capacity planning of reactive power compensation devices.

[0080] In summary, the dynamic reactive power site selection method based on voltage disturbance propagation capability ranking of the present invention can effectively identify key nodes that are likely to affect system voltage stability and cause cascading failures by evaluating the node disturbance propagation capability, and can be used to guide the selection of dynamic reactive power installation locations. In addition, during the implementation process, on the one hand, the network topology characteristics of the power system and their mutual correlation are considered, and on the other hand, the electrical quantity node prior information (such as node load size) is added to establish a model that is more in line with actual physical characteristics, which can effectively identify key nodes that are likely to cause cascading failures, and is used to guide the selection of dynamic reactive power installation locations, so as to alleviate the chain failure risks faced by high-penetration wind power systems.

[0081] The above-described embodiments are merely descriptions of preferred implementations of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made by ordinary persons in the art to the technical solution of the present invention should fall within the protection scope of the present invention, and the technical contents for which protection is sought in the present invention have been fully recorded in the claims.

Claims

1. A dynamic reactive power source site selection method based on voltage disturbance propagation capability ranking, characterized in that: The following steps are involved: S1. Establish a set of anticipated accidents in the power system; S2, define the short-term voltage stability index SVSI based on the post-fault voltage response trajectory curve; S3, using the power system topology information and prior information as weight factor inputs, evaluating the node disturbance propagation capability, and calculating the evaluation value of each node in the system; S4, taking the assessment results and the probability of accident occurrence as weights, adding them to the SVSI to form the weighted short-term voltage stability index WSVSI; S5. Based on the established set of expected accidents, the WSVSI value of each node in the system after the fault is calculated to evaluate the node voltage disturbance propagation capability; S6. Sort the calculated WSVSI values ​​of each node in the system, and preferentially select several nodes with larger values ​​as installation locations.

2. The method for dynamic reactive power source site selection based on voltage disturbance propagation capability ranking according to claim 1, characterized in that: In S2, the short-term voltage stability index is defined as follows: Among them, B represents the set of all nodes; T c and T end Respectively represent the simulation end time and fault clearing time; N b Represents the number of nodes; V i,j,k and V i,0 They represent the static voltage amplitude of node i at time j after accident k and before the accident respectively; Δt j Represents the time step taken for the simulation.

3. The method for dynamic reactive power source site selection based on voltage disturbance propagation capability ranking according to claim 2, characterized in that: In S2, f(V i,j,k ,V i,0 ) is the voltage deviation value of the i-th node at the j-th time in the k-th accident, which is defined as follows: Among them, δ is the threshold value.

4. The method for dynamic reactive power source site selection based on voltage disturbance propagation capability ranking according to claim 1, characterized in that: In S3, the method for evaluating the node disturbance propagation capability comprises the following steps: S31. The network adjacency matrix provides the topological information of the power system and will be used to create the augmented network matrix. As shown below: Wherein, A=(a ij ) N×N is the adjacency matrix of the power system network, a ij is an element in the adjacency matrix A; S32. In order to offset the impact of adding ground nodes on the network topology and ensure the accuracy of node identification results, a node prior information matrix is ​​added Node prior information matrix The diagonal elements of represent the prior information of node importance. The prior information of ground nodes is set to The node prior information matrix As shown below: S33, according to the obtained augmented network matrix and node prior information matrix Constructing the Iteration Matrix S34, calculate the node algorithm score s, the iteration includes two operations, namely linear transformation and normalization, the denominator of the normalization method used is set to the sum of the scores of all nodes including the ground node, and the update iteration rule is: S35, through iteration, all nodes converge to a stable state s i =1(i=1,2,...,N); Finally, the importance score of the ground node s N+1 The number of nodes in the power system is evenly distributed to each node, and the importance score MR of each node excluding the ground node g is obtained: S36. All nodes are ranked according to the calculation results of the above evaluation method. The higher the score of the node, the greater its importance in the grid structure. When a chain failure occurs in the power system, the failure of a node with a large score is more likely to cause the accident to expand further, that is, the node has a greater possibility of expanding the accident than other nodes.

5. The method for dynamic reactive power source site selection based on voltage disturbance propagation capability ranking according to claim 4, characterized in that: In S31, if nodes i and j are connected by an edge, then a ij = 1, if nodes i and j have no edge, then a ij =0; add the ground node g and set its corresponding element to 0. Obviously, the ground node has established edges with other nodes and is set to 1 in the matrix below.

6. The method for dynamic reactive power source site selection based on voltage disturbance propagation capability ranking according to claim 4, characterized in that: In S33, the iteration matrix contains the prior information of the power system nodes. Initially, for ordinary nodes, the score is set to s i =1(i=1,2,...,N), and for ground nodes there are also s g =s N+1 =1, set the convergence condition as follows: the difference in s scores obtained in two iterations is less than a predetermined threshold; 7. The method for dynamic reactive power source site selection based on voltage disturbance propagation capability ranking according to claim 1, characterized in that: In S1, the set of anticipated accidents of the power system is generated by historical accident records and short-term voltage stability index evaluation.

8. The method for dynamic reactive power source site selection based on voltage disturbance propagation capability ranking according to claim 4, characterized in that: In S4, the evaluation result of S3 and the probability of accident occurrence are used as weights and added to SVSI to form a weighted short-term voltage stability index WSVSI, which is defined as follows: WSVSI i =∑ k∈K p k ×SVSI k ×MR i Where: P k represents the probability of accident k occurring; K represents the set of accidents.

9. The method for dynamic reactive power source site selection based on voltage disturbance propagation capability ranking according to claim 1, characterized in that: In S5, a simulation model is built in a software platform that supports electromechanical transient modeling and simulation, and simulation is performed according to the set of anticipated accidents of the power system established in S1. The voltage response trajectory curve of each node after the fault is cleared is recorded, and based on the weighted short-term voltage stability index WSVSI described in S4, the WSVSI value of the system under the action of the anticipated accident k is calculated to evaluate the node voltage disturbance propagation capability.

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