A Power System Dispatching Method Based on Cascading Failure Prevention

Abstract

The present invention discloses a power system dispatching method based on cascading failure prevention, comprising the following steps: (1) establishing a power system cascading failure model based on power system topology, relevant line parameters and constraints through DC power flow calculation; (2) calculating line parameters in the power system that reflect the cascading failure correlation based on cascading failure accident chain data, and establishing corresponding power system operation constraints; (3) ensuring power quality and power safety based on power grid line and load data, and establishing a dispatching method model that meets all load consumption requirements with the lowest power generation cost or fuel consumption; (4) obtaining a power system safe operation optimization strategy with the lowest generator power generation cost and load shedding cost as the optimization goal. The present invention can optimize the power system operation with cascading failure prevention as the goal, improve the power system resilience and improve the power system safety while considering the power system economy.

Description

Technical Field

[0001] The present invention relates to a power system dispatching method, and in particular to a power system dispatching method based on cascading failure prevention. Background Art

[0002] A cascading failure in a power system refers to a series of failure events in which one or more initial faults act as a disturbance, triggering subsequent failures in other components of the system. Cascading failures can arise from factors within the power system, such as aging faults, protection misoperation, and human intervention, or from external factors, such as natural disasters and animal or plant contact with power lines. Historical analysis of power outages reveals that while large-scale power outages are extremely rare, they can cause significant damage and losses, and the risk of serious power outages remains significant. Therefore, relying solely on safety verification for a given set of anticipated faults is insufficient to effectively reduce the risk of cascading failures. In fact, after the initial triggering phase of a cascading failure, factors that exacerbate the propagation of the cascading process within the system primarily originate from within the system. These factors include, but are not limited to, line overloads caused by power flow transfers, protection misoperation or failure to operate, hidden faults, and system disconnection. Given the different mechanisms exhibited by cascading failures during the initial triggering and subsequent propagation phases, the analysis and treatment of faults in these two phases will differ.

[0003] In recent years, major power outages caused by natural disasters have become a frequent occurrence, attracting widespread attention from the international power industry. These incidents are primarily caused by natural disasters such as typhoons, hail, and lightning strikes, which can lead to component failures within the power transmission and distribution network. These failures cause widespread changes in the power system's network flow, leading to overloads and subsequent shutdowns of other line components. This rapidly propagates through the system like a chain reaction, ultimately causing a complete system collapse and resulting in a major power outage. Researching and analyzing the mechanisms by which these low-probability events trigger significant power outages is of great significance. Currently, power industry researchers both domestically and internationally have proposed various approaches to identifying critical links in power systems. For example, these approaches use topology and complex networks to identify critical links or nodes within the power system as a whole. However, these approaches lack the ability to directly determine the criticality of each identified link and the precise amount of load loss resulting from the failure; these approaches require simulation of cascading failures. There are also methods that directly analyze and calculate the critical circuits during the propagation of cascading failure simulations by analyzing relevant data from cascading failures. This method can produce relatively accurate and effective results, but for cascading failure simulations with high randomness and large volumes, this method is computationally intensive and places high demands on the simulation model. Alternatively, there are methods that continuously simulate power system cascading failure models to obtain the required cascading failure data, then process and analyze it using statistical methods to identify statistically significant critical circuits and paths. However, as a statistical method, this method also has issues such as reliance on data accuracy and sample size. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a dry-type high-frequency transformer and a processing technology that increases the heat dissipation area and insulation level.

[0005] Technical solution: The power system dispatching method of the present invention comprises the following steps:

[0006] S1, based on the power system topology, relevant line parameters and constraints, by calculating the DC power flow, a line overload type power system cascading failure model including hidden faults is established to obtain the cascading failure accident chain data;

[0007] S2, based on the cascading failure accident chain data, calculates the line parameters in the power system that reflect the correlation of the cascading failure, obtains the key links of the cascading failure in the power system, and establishes the power system operation constraints corresponding to the key links of the cascading failure;

[0008] S3, based on grid line and load data, regulates and dispatches power generation equipment and primary energy, maintaining the set power quality and ensuring power safety, and establishes a dispatching method model that meets all load consumption requirements at the lowest power generation cost or fuel consumption;

[0009] S4 takes the minimum generator power generation cost and load shedding cost as the optimization goal, combines the conventional safety constraints of the power system, and adds the safety constraints considering the prevention of cascading failures of the power system to obtain the optimization strategy for the safe operation of the power system.

[0010] In step S1, multiple cascading failure accident chains are simulated to obtain accident chain data based on the parameters of the power system network model, specifically:

[0011] S11, initializing power system network related parameters according to power system model data;

[0012] S12, sampling line faults caused by severe weather and setting them as system initial faults;

[0013] S13, determine whether there is an island in the detection system. If no island is generated, continue sampling the fault line; if there is only one island, proceed to step S14; if the number of islands is greater than or equal to two, proceed to step S16;

[0014] S14: Calculate the power flow based on the new system topology and determine whether each line is overloaded. For overloaded lines, calculate their fault probability based on the following fault probability model and update the line status information:

[0015]

[0016] in, is the failure probability of line l, p l is the current load factor of line l, is the rated load factor of line l, is the maximum load rate of line 1; if a new line overload fault occurs, the number of islands is determined. If it is still one, step S14 is repeated. If the number of islands is greater than or equal to two, step S16 is entered; if no new line overload fault occurs, step S15 is entered;

[0017] S15: Line hidden fault sampling is performed to check whether hidden faults have occurred in the lines adjacent to the previously faulted line. If a new hidden fault has occurred, the process proceeds to step S14. If no hidden fault has occurred, the process proceeds to the optimal load shedding model. The goal of the optimal load shedding model is to minimize the total load shedding of the system under the constraints of power balance and line power flow overload. The cascading fault simulation ends, the number of simulations is incremented, and the process proceeds to step S17.

[0018] S16: For each island, determine its island type, perform load shedding based on the number and type of nodes in each island, and calculate and record the total load loss. This cascading failure simulation ends, and the simulation count is incremented by one, proceeding to step S17.

[0019] S17, if the number of simulations is less than the maximum number of simulations, then go to step S12, otherwise, the simulation is completed, and relevant data such as the fault line, the number of disconnected machines and the amount of load loss for each simulation are calculated and recorded.

[0020] In step S2, the method for identifying the key links of the power system is:

[0021] S21, for n lines in the power system The N fault chains {L1, L2, ..., L N The propagation relationship of} is represented by an undirected graph express:

[0022]

[0023] Among them, l h represents the propagation line, l a Indicates a fragile line, l h →l a Represents the propagation relationship, i.e. l h Line fault caused a Line failure, Represents the propagation line set, whose elements are all lines with out-degree O>0 in the fault chain, represents the fragile fault set, whose elements are all lines with in-degree I>0 in the fault chain, is an undirected graph The set of edges in , whose elements are all the propagation relations in the fault chain;

[0024] S22, find the vector and The dimension of can be used to find the number of propagation lines n1 and the number of vulnerable lines n2; calculate the proportion of each propagation relationship in the total fault chain and obtain the propagation probability matrix, then the undirected graph Middle h Failure caused by a The probability of failure is expressed as:

[0025]

[0026] in, is the propagation probability matrix, Indicates l h →l a The number of times this propagation relationship appears in all faults, N is the total number of fault chains;

[0027] S23, perform row normalization and column normalization on the propagation probability matrix to obtain the corresponding row normalization matrix and column-normalized matrices

[0028] On this basis, the propagation value coefficient matrix is ​​obtained And the fragility coefficient matrix

[0029]

[0030] S24, the obtained vulnerability coefficient matrix It can reflect the correlation of vulnerable lines during the propagation of cascading faults; The value of i and fragile lines j In terms of the probability that both are affected by the same propagation line and fail, The larger the value of , the greater the probability of failure due to simultaneous influence;

[0031] Therefore, the correlation index of cascading failure vulnerable lines is obtained

[0032]

[0033] Among them, i,j∈{1,2,…,n},i≠j, if the line l i and line l j If it is not a vulnerable line or has no propagation relationship with other lines, then the corresponding and The values ​​of are all zero;

[0034] S25, using the correlation index of the vulnerable lines of cascading failures identified by screening Select key line pairs based on system requirements as the objects of N-2 constraints. The constraints are as follows:

[0035]

[0036]

[0037] in, Indicates the real-time power of the line where the power flow will exceed the limit after a line fault occurs. Indicates the line power before the line fault occurs. represents the outage distribution factor of the first fault-disconnected line, It represents the power of the first faulty line before the fault. represents the power of the second fault-disconnected line before the fault, Indicates the maximum transmission power of each line.

[0038] The specific implementation steps of step S3 are:

[0039] S31, the objective function of the simplified traditional power system economic dispatch optimization model is to minimize the generator power generation cost and load shedding cost:

[0040]

[0041] Among them, C G represents the cost of power generation by the generator, P G Indicates the generator output, represents the load shedding cost, Indicates load shedding amount;

[0042] S32, grid security constraints mainly include:

[0043]

[0044] Among them, P D Indicates the expected load size of the load node; Indicates the lower limit of generator output. Indicates the upper limit of generator output; P inj Represents the node injection power. For the generator node, the injection power is positive; for the load node, the injection power is negative; for other connection nodes, the injection power is zero; K P represents the generator power coefficient matrix, K D represents the load factor matrix; P L represents the power transmitted on each line, SF represents the power coefficient matrix, and P L represents the transmission power of each line, Indicates the maximum transmission power of each line;

[0045] S33, in the power system economic dispatch model, the generator output P G , node load shedding and line transmission power P L As the decision variable, the Gurobi solver is called to solve and obtain the solution that satisfies all constraints and minimizes the objective function.

[0046] The specific implementation steps of step S4 are:

[0047] S41, with economy as the goal, the objective function of the power system economic dispatch optimization model is to minimize the generator power generation cost and load shedding cost:

[0048]

[0049] Among them, C G represents the cost of power generation by the generator, P G Indicates the generator output, represents the load shedding cost, Indicates load shedding amount;

[0050] S42, the model constraints are as follows:

[0051]

[0052]

[0053]

[0054] P L =SF×P inj

[0055]

[0056]

[0057]

[0058]

[0059] Compared with the prior art, the present invention has the following significant effects: 1. The cascading failure simulation model proposed in the present invention can simulate the evolution process of cascading failures in reality, providing certain data support for analyzing the characteristics and hazards of cascading failures; 2. The present invention establishes a correlation index for judging the system lines in the process of cascading failure propagation based on the cascading failure model, and calculates the corresponding index value based on the fault data obtained from the model simulation; 3. After effectively adding safety constraints, the present invention can improve the resistance of the power system to cascading failures and the system stability under the condition of sacrificing a certain degree of economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 Schematic diagram of the method flow of the present invention;

[0061] Figure 2 This is a flow chart of the power system cascading failure simulation model of the present invention;

[0062] Figure 3 This is the load loss percentage probability distribution diagram of the IEEE30-node system after optimization without considering safety constraints in the present invention;

[0063] Figure 4 This is a load loss percentage probability distribution diagram of the IEEE 30-node system under the logarithmic coordinate axis after the present invention does not consider the safety constraint optimization;

[0064] Figure 5 This is the load loss percentage probability distribution diagram of the IEEE30-node system after optimization with consideration of safety constraints in the present invention;

[0065] Figure 6 This is the load loss percentage probability distribution diagram on the logarithmic coordinate axis of the IEEE 30-node system after the safety constraint optimization is considered in the present invention. DETAILED DESCRIPTION

[0066] The present invention will be described in further detail below with reference to the accompanying drawings and specific implementations.

[0067] like Figure 1 As shown in Figure 1, the power system elastic and safe dispatch strategy based on the calculation of cascading failure accident chain indicators includes the following steps:

[0068] S1, based on the power system topology, relevant line parameters and constraints, a line overload cascading failure model of power system including hidden faults based on DC power flow calculation is proposed;

[0069] S2, based on the cascading failure accident chain data, calculates the line parameters in the power system that reflect the correlation of cascading failures and establishes corresponding power system operation constraints;

[0070] S3: Based on the grid line and load data, and with the premise of maintaining a certain power quality and ensuring power safety, establish a scheduling method model for regulating and dispatching power generation equipment and primary energy, so as to meet the consumption of all loads at the lowest power generation cost or fuel consumption;

[0071] S4 takes the minimum generator power generation cost and load shedding cost as the optimization goal, combines the conventional safety constraints of the power system, and adds the safety constraints considering the prevention of cascading failures of the power system to obtain the optimization strategy for the safe operation of the power system.

[0072] The technical solution of the present invention is described in detail below:

[0073] Step 1: Based on the parameters of the power system network model and the initial fault model under severe weather conditions, the cascading fault development link that characterizes invisible faults is added, and multiple cascading fault accident chains are simulated to obtain accident chain data, such as Figure 2 The main implementation steps are as follows:

[0074] S11, initializing power system network related parameters according to power system model data.

[0075] S12, sampling line faults caused by severe weather and setting them as system initial faults.

[0076] S13, check whether there is an island in the system. If no island is generated, continue sampling the fault line; if there is only one island, proceed to step S14; if the number of islands is greater than or equal to two, proceed to step S16.

[0077] S14, calculate the power flow based on the updated system topology and determine whether the power flow of each line is overloaded. For overloaded lines, calculate their fault probability according to the fault probability model of formula (1) and update the line status information.

[0078]

[0079] in, is the failure probability of line l, p l is the current load factor of line l, is the rated load factor of line l, is the maximum load rate of line 1. If a new line overload fault occurs, the number of islands is determined. If it is still one, step S14 is repeated. If the number of islands is greater than or equal to two, step S16 is performed. If no new line overload fault occurs, step S15 is performed.

[0080] S15: Line hidden fault sampling is performed to check for hidden faults in adjacent lines to the previously faulted line. If a new hidden fault has occurred, the process proceeds to step S14. If no hidden fault has occurred, the optimal load shedding model is used. The optimal load shedding model aims to minimize the total load shedding in the system while maintaining power balance and ensuring that the line flow does not overload. This cascading fault simulation concludes, the simulation count is incremented, and the process proceeds to step S17.

[0081] S16: For each island, determine its island type, calculate the number and type of nodes in each island, and record the total load loss. This cascading failure simulation ends, and the simulation count is incremented by one to proceed to step S17.

[0082] S17, if the number of simulations is less than the maximum number of simulations, then go to step S12; otherwise, the simulation is completed, and relevant data such as the fault line, the number of disconnected machines and the amount of load loss for each simulation are calculated and recorded.

[0083] The IEEE 30-bus system is simulated for cascading failures, with the maximum number of simulations NSmax set to 2000, simulating 2000 line failure scenarios. The initial load power factor of the system is set to =1.5, indicating that the system load is 1.5 times the default load. Set the system's line current upper limit coefficient to 1, indicating that the system's line current upper limit is the system default value. Take the line's rated load rate as =1, the maximum load rate of the line The system is simulated in 2000 scenarios. Figure 3 This is the probability distribution diagram of load loss percentage of IEEE30-bus system. Figure 4 It is the probability distribution diagram of load loss percentage under the logarithmic coordinate axis.

[0084] Step 2: Based on the acquired cascading failure accident chain data, a network parameter model is analyzed to obtain a method for identifying the key links of cascading failures in the power system and establish corresponding power system network constraints. The main implementation steps are as follows:

[0085] S21, for n lines in the power system The N fault chains {L1, L2, ..., L N The propagation relationship of} is represented by an undirected graph Indicates that:

[0086]

[0087] Among them, l h Indicates the transmission line; l a Indicates a fragile line; l h →l a Represents the propagation relationship, i.e. l h Line fault caused a Line failure; represents the propagation line set, whose elements are all lines with out-degree O>0 in the fault chain; represents the fragile fault set, whose elements are all the lines with in-degree I>0 in the fault chain; is an undirected graph The set of edges in , whose elements are all the propagation relations in the fault chain.

[0088] S22, find the vector and The number of propagation paths n1 and the number of vulnerable paths n2 can be calculated by calculating the proportion of each propagation relationship in the total fault chain, and the propagation probability matrix can be obtained, that is, the undirected graph Middle h Failure caused by a The probability of failure can be expressed as:

[0089]

[0090] in, is the propagation probability matrix, R is a set of real numbers, Indicates l h →l a The number of times this propagation relationship appears in all faults, and N is the total number of fault chains.

[0091] S23, perform row normalization and column normalization on the propagation probability matrix to obtain the corresponding row normalization matrix and column-normalized matrices That is, each element of the row normalization matrix is ​​the modulus of each element in the original matrix divided by the row vector of the row in which it is located. Similarly, each element of the column normalization matrix is ​​the modulus of each element in the original matrix divided by the column vector of the column in which it is located.

[0092] On this basis, the propagation value coefficient matrix is ​​obtained And the fragility coefficient matrix

[0093]

[0094] Where T is the matrix transpose.

[0095] S24, the obtained vulnerability coefficient matrix It can reflect the correlation of vulnerable lines during the propagation of cascading faults. The value of i and fragile lines j In terms of the probability that both are affected by the same propagation line and fail, The larger the value, the greater the probability of failure due to simultaneous influence.

[0096] Therefore, the correlation index of cascading failure vulnerable lines can be obtained

[0097]

[0098] Among them, i,j∈{1,2,…,n},i≠j, if the line l i and line l j If it is not a vulnerable line or has no propagation relationship with other lines, then the corresponding and The values ​​are all zero.

[0099] S25, add N-1 constraints to all lines in the power grid operation. Considering that if N-2 constraints are added to all lines, the feasibility is low from the perspective of power generation cost and computational complexity, the correlation index of the cascading failure vulnerable lines identified by the screening is used. The larger critical path pair is the object of N-2 constraint. The constraints are as follows:

[0100]

[0101]

[0102] in, Indicates the real-time power of the line where the power flow will exceed the limit after a line fault occurs. Indicates the line power before the line fault occurs. represents the outage distribution factor of the first fault-disconnected line, It represents the power of the first faulty line before the fault. represents the power of the second fault-disconnected line before the fault, Indicates the maximum transmission power of each line.

[0103] By processing the power system cascading fault accident chain data, the order of related line pairs in the IEEE30 system is obtained as shown in Table 1.

[0104] Table 1. Sorting of relevant line pairs in the IEEE30 system

[0105]

[0106] Step 3: Based on the grid line and load data, and with the premise of maintaining a certain power quality and ensuring power safety, establish a scheduling method model for regulating and dispatching power generation equipment and primary energy, so as to meet all load consumption at the lowest power generation cost or fuel consumption. The specific implementation steps are as follows:

[0107] S31, the objective function of the simplified traditional power system economic dispatch optimization model is to minimize the generator power generation cost and load shedding cost:

[0108]

[0109] Among them, C G represents the cost of power generation by the generator, P G Indicates the generator output, represents the load shedding cost, Indicates the load shedding amount.

[0110] S32, grid security constraints mainly include:

[0111]

[0112] Among them, P D Indicates the expected load size of the load node. The total power generation of all generators is equal to the sum of the load of all load nodes minus the load shedding amount; Indicates the lower limit of generator output. Indicates the upper limit of the generator output; the generator output cannot be lower than the lower limit and cannot be higher than the upper limit; P inj Represents the node injection power. For the generator node, the injection power is positive, for the load node, the injection power is negative, and for other connected nodes, the injection power is zero; K P represents the generator power coefficient matrix, K Drepresents the load factor matrix, and the injected power of each node can be calculated from the generator output power, load consumption power and load shedding amount; SF represents the power factor matrix, which is calculated from the power system network parameters; P L It represents the power transmitted on each line. The power injected by the node can be used to calculate the power flowing through each line. It indicates the maximum transmission power of each line. The absolute value of the line transmission power cannot exceed the maximum transmission power of the line. The load shedding amount of the load node cannot exceed the expected load of this node and cannot be lower than zero.

[0113] S33, in the power system economic dispatch model adopted by the present invention, the generator output P G , node load shedding and line transmission power P L Using the Gurobi solver as the decision variable, we can obtain a solution that satisfies all constraints and minimizes the objective function. In other words, the generator output power and load shedding obtained are the lowest-cost scheduling solutions among all scenarios that meet normal operating conditions, representing the most economical scheduling solution.

[0114] Step 4: Taking the minimum generator power generation cost and load shedding cost as the optimization goal, combined with the conventional safety constraints of the power system, the power system safe operation optimization strategy is obtained. The specific implementation steps are as follows:

[0115] S41, with economy as the goal, the objective function of the power system economic dispatch optimization model is to minimize the generator power generation cost and load shedding cost:

[0116]

[0117] Among them, C G represents the cost of power generation by the generator, P G Indicates the generator output, represents the load shedding cost, Indicates the load shedding amount.

[0118] S42, the model constraints are as follows:

[0119]

[0120]

[0121]

[0122] P L =SF×P inj

[0123]

[0124]

[0125]

[0126]

[0127] The economic dispatch model, incorporating safety constraints, calculates generator output and load shedding, meeting normal operating conditions. Furthermore, even after the identified critical line fails and is removed, the new system can still operate within the safety domain, thus satisfying the N-2 principle for critical lines. Due to the addition of these new constraints, the total cost of optimized dispatch under safety constraints is significantly higher than the total cost of the scenario calculated by the original model. This is within expectations, sacrificing some economic efficiency in exchange for greater safety and stability.

[0128] After identifying the critical lines and critical line pairs of the IEEE 30-bus system in step S2, corresponding N-2 safety constraints can be established for these critical links. The new generator output and heavy load shedding conditions are calculated. The generator output is 397.31 MW, and the load shedding is 75.69 MW. Based on this, 2000 simulations are performed using the same system parameters as in step S1. Figure 5 This is the probability distribution diagram of load loss percentage of IEEE30-bus system after considering safety constraint optimization. Figure 6 It is the probability distribution diagram of load loss percentage under the logarithmic coordinate axis.

Claims

1. A power system dispatching method based on cascading failure prevention, characterized in that: The steps include: S1, based on the power system topology, relevant line parameters and constraints, by calculating the DC power flow, a line overload type power system cascading failure model including hidden faults is established to obtain the cascading failure accident chain data; S2, based on the cascading failure accident chain data, calculates the line parameters in the power system that reflect the correlation of the cascading failure, obtains the key links of the cascading failure in the power system, and establishes the power system operation constraints corresponding to the key links of the cascading failure; S3, based on the grid line and load data, controls and dispatches power generation equipment and primary energy, with the premise of maintaining the set power quality and ensuring power safety, and establishes a dispatching method model that meets all load consumption requirements with the lowest power generation cost or fuel consumption. The specific implementation steps are as follows: S31, the objective function of the simplified traditional power system economic dispatch optimization model is to minimize the generator power generation cost and load shedding cost: Among them, C G represents the cost of power generation by the generator, P G Indicates the generator output, represents the load shedding cost, Indicates load shedding amount; S32, grid security constraints include: Among them, P D Indicates the expected load size of the load node; Indicates the lower limit of generator output. Indicates the upper limit of generator output; P inj Represents the node injection power. For the generator node, the injection power is positive; for the load node, the injection power is negative; for other connection nodes, the injection power is zero; K P represents the generator power coefficient matrix, K D represents the load factor matrix; P L represents the power transmitted on each line, SF represents the power coefficient matrix; P L represents the transmission power of each line, Indicates the maximum transmission power of each line; S33, in the power system economic dispatch model, the generator output P G , node load shedding and line transmission power P L As the decision variable, the Gurobi solver is called to solve the problem and obtain the solution that satisfies all constraints and minimizes the objective function. S4 takes the minimum generator power generation cost and load shedding cost as the optimization goal, combines the conventional safety constraints of the power system, and adds the safety constraints considering the prevention of cascading failures of the power system to obtain the optimization strategy for the safe operation of the power system.

2. The power system dispatching method based on cascading failure prevention according to claim 1, characterized in that: In step S1, multiple cascading failure accident chains are simulated to obtain accident chain data based on the parameters of the power system network model, specifically: S11, initializing power system network related parameters according to power system model data; S12, sampling line faults caused by severe weather and setting them as system initial faults; S13, determining whether an islanding occurs in the detection system. If no islanding occurs, continue sampling the fault line. If there is only one isolated island, proceed to step S14; if the number of isolated islands is greater than or equal to two, proceed to step S16; S14: Calculate the power flow based on the new system topology and determine whether each line is overloaded. For overloaded lines, calculate their fault probability based on the following fault probability model and update the line status information: in, is the failure probability of line l, p l is the current load factor of line l, is the rated load factor of line l, is the maximum load rate of line 1; if a new line overload fault occurs, the number of islands is determined. If it is still one, step S14 is repeated. If the number of islands is greater than or equal to two, step S16 is entered; if no new line overload fault occurs, step S15 is entered; S15: Line hidden fault sampling is performed to check whether hidden faults have occurred in the lines adjacent to the previously faulted line. If a new hidden fault has occurred, the process proceeds to step S14. If no hidden fault has occurred, the process proceeds to the optimal load shedding model. The goal of the optimal load shedding model is to minimize the total load shedding of the system under the constraints of power balance and line power flow overload. The cascading fault simulation ends, the number of simulations is incremented, and the process proceeds to step S17. S16: For each island, determine its island type, perform load shedding based on the number and type of nodes in each island, and calculate and record the total load loss. This cascading failure simulation ends, and the simulation count is incremented by one, proceeding to step S17. S17: If the number of simulations is less than the maximum number of simulations, then go to step S12; otherwise, the simulation is completed, and the fault line, the number of disconnected machines and the amount of load loss in each simulation are calculated and recorded.

3. The power system dispatching method based on cascading failure prevention according to claim 1, characterized in that: In step S2, the method for identifying the key links of the power system is: S21, for n lines in the power system The N fault chains {L1, L2, ..., L N The propagation relationship of} is represented by an undirected graph express: Among them, l h represents the propagation line, l a Indicates a fragile line, l h →l a Represents the propagation relationship, i.e. l h Line fault caused a Line failure, Represents the propagation line set, whose elements are all lines with out-degree O>0 in the fault chain, represents the fragile fault set, whose elements are all lines with in-degree I>0 in the fault chain, is an undirected graph The set of edges in , whose elements are all the propagation relations in the fault chain; S22, find the vector and The dimension of can be used to find the number of propagation lines n1 and the number of vulnerable lines n2; calculate the proportion of each propagation relationship in the total fault chain and obtain the propagation probability matrix, then the undirected graph Middle h Failure caused by a The probability of failure is expressed as: in, is the propagation probability matrix, Indicates l h →l a The number of times this propagation relationship appears in all faults, N is the total number of fault chains; S23, perform row normalization and column normalization on the propagation probability matrix to obtain the corresponding row normalization matrix and column-normalized matrices On this basis, the propagation value coefficient matrix is ​​obtained And the fragility coefficient matrix S24, the obtained vulnerability coefficient matrix It can reflect the correlation of vulnerable lines during the propagation of cascading faults; The value of i and fragile lines j In terms of the probability that both are affected by the same propagation line and fail, The larger the value of , the greater the probability of failure due to simultaneous influence; Therefore, the correlation index of cascading failure vulnerable lines is obtained Among them, i,j∈{1,2,…,n},i≠j, if line li and line l j If it is not a vulnerable line or has no propagation relationship with other lines, then the corresponding and The values ​​of are all zero; In step S25, using the correlation index a of the vulnerable lines with cascading failures identified through screening, a pair of critical lines is selected according to system requirements as the objects of the N-2 constraint. The constraints are as follows: in, Indicates the real-time power of the line where the power flow will exceed the limit after a line fault occurs. Indicates the line power before the line fault occurs. represents the outage distribution factor of the first fault-disconnected line, It represents the power of the first faulty line before the fault. represents the power of the second fault-disconnected line before the fault, Indicates the maximum transmission power of each line.

4. The power system dispatching method based on cascading failure prevention according to claim 1, characterized in that: The specific implementation steps of step S4 are: S41, with economy as the goal, the objective function of the power system economic dispatch optimization model is to minimize the generator power generation cost and load shedding cost: Among them, C G represents the cost of power generation by the generator, P G Indicates the generator output, represents the load shedding cost, Indicates load shedding amount; S42, the model constraints are as follows: P L =SF×P inj

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