Electric power system cascade fault relieving method and system based on accident disaster background

Abstract

The invention discloses a method and a system for relieving cascade faults of a power system based on an accident disaster background, which aim at actual engineering requirements and aiming at cascade faults of the power system, firstly, equipment risk indexes are established according to risk levels of disaster accidents, and the development mode of the cascade faults of the system under the disaster scene is refined by utilizing the indexes. From the perspective of operation control, a cooperative mitigation strategy of a system cascade fault under a disaster condition is formulated in combination with an optimal generator scheduling and load / generator shedding method; the strategy is combined with an active prevention measure, and aims to quickly cut off a potential cascade fault path at the first time after a disaster occurs, so that an affected interruption area is reduced to the greatest extent; the method can effectively reduce the influence of disasters and accidents on the operation of the power system.

Description

Technical Field

[0001] The present invention belongs to the technical field of power supply, and in particular relates to a method and system for alleviating cascading faults in a power system under accident and disaster background. Background Art

[0002] Against the backdrop of global climate change, extreme weather and climate events occur frequently. According to statistics from the China Electric Power Reliability Management Center, natural disasters and climate factors are the main causes of unplanned power outages on overhead transmission lines. Line failures caused by natural disasters are unpredictable, and the resulting impact increases the risk of secondary cascading failures in the power grid. Therefore, formulating cascading failure mitigation strategies at the operational level is of great significance for suppressing the propagation of cascading failures in the power system when disasters occur and minimizing the losses caused by disaster accidents.

[0003] Under severe weather conditions, a minor fault can propagate to large areas of the power system and may cause significant load drop due to cascading failures. A comprehensive and accurate analysis of cascading failures can be effectively used for risk assessment, identification of key components, and solving other related problems. In addition, in cascading failure analysis, any cascading path with any combination of independent faults is theoretically possible. However, the computational complexity of finding high-order nk contingencies makes traditional enumeration and random search methods infeasible. Existing studies have reduced the complexity of cascading failure analysis by selecting typical cascading fault propagation paths. However, these search criteria ignore the transmission lines that are most likely to cause the corresponding faults.

[0004] According to the different control timing, the strategies for mitigating large-scale power outages caused by cascading failures can be roughly divided into two categories: preventive control before the accident and emergency mitigation during the accident. Preventive control refers to taking corrective measures when the system is in an unsafe state to restore the system to a safe state, thereby ensuring the safe and stable operation of the system. In contrast, emergency mitigation measures implemented during an accident involve cutting off the cascading failure path to prevent the further development of the fault. Most of the existing studies on cascading failure control ignore the impact of natural disasters on the operation risk of transmission lines, resulting in a relatively rough assessment of the actual operation risk level of the power system. In addition, current research tends to treat preventive control and mitigation control in isolation, ignoring their complementary characteristics in terms of economic efficiency and safety. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method and system for mitigating cascading faults in power systems based on the background of accidents and disasters in response to the deficiencies in the above-mentioned prior art, so as to solve the technical problems that existing research is difficult to assess the operating risks of natural disasters on transmission lines, and the control strategies for mitigating disasters are difficult to balance economic efficiency and safety.

[0006] The present invention adopts the following technical solutions: A method for mitigating cascading failures in a power system based on accident and disaster backgrounds comprises the following steps: Establish a disaster risk index system for the power system according to the risk level of the disaster, and use the disaster risk index system to refine the development model of system cascading failures under disaster scenarios; According to the development mode of cascading failures caused by natural disasters, a cascading failure propagation model is established; according to the cascading failure propagation model, the islands in the power system are identified based on the breadth-first search algorithm, and the subsystem with the largest size and the highest weight coefficient is selected to form a new main system, and the cascading failure is continuously simulated; The cascading failure risk of the power system is evaluated based on the system data before and after the fault obtained by the cascading fault propagation model. According to the cascading failure risk of the power system, a cascading failure mitigation strategy including a mitigation control cost model and a coordinated control model is established, and the collaborative mitigation strategy of system cascading failures under disaster conditions is combined with active prevention measures to cut off potential cascading failure paths after the disaster occurs.

[0007] Preferably, the development mode of system cascading failure under disaster scenarios is detailed as follows: When the overhead line disaster operation risk value More than 1,000 is level 1, which poses a significant threat of causing significant damage; When the overhead line disaster operation risk value Level 2 is between 300 and 1000, indicating the possibility of severe losses; When the overhead line disaster operation risk value Level 3 is between 60 and 300, indicating considerable risk of severe loss; When the overhead line disaster operation risk value The value between 20 and 60 is level 4, which means causing greater losses; When the overhead line disaster operation risk value Values ​​between 5 and 20 are level 5, indicating a medium risk of general losses; When the overhead line disaster operation risk value Values ​​below 5, which fall into Class 6, are generally associated with minimal or no risk of suffering a loss.

[0008] Preferably, the overhead line disaster operation risk value for:

[0009] in, Indicates natural disasters The probability of causing line failure; For natural disasters Downlink line failure damage value; Indicates that natural disasters The transmission capacity loss value caused by line fault is: For natural disasters The social impact coefficient of the line risk caused by Represents the total number of natural disasters.

[0010] Preferably, natural disasters Social impact coefficient of line risk caused for:

[0011] in, For natural disasters The coefficient of the risk period of natural disasters; Indicates natural disasters risk weight.

[0012] Preferably, in the cascading fault propagation model, when the dispatching of the generator set cannot meet the power balance demand, two scenarios are included: After a period of ramp-up, if the output power of the generator is still greater than the system load value, the generator needs to be shelved according to the shedding priority of the generator to achieve power balance; If, after the specified generator ramp-up period, the system load continues to exceed the generator output power, it is necessary to reduce the load priority according to the load reduction assigned to each load. Coordinate load shedding measures; Power system island identification is performed based on a breadth-first search algorithm, and then the severity of the consequences is used To measure the scale of power system blackout caused by a cascading failure event with a complete fault path, use the average blackout consequence of a cascading failure in the power system Measuring the risk of cascading failure in a system.

[0013] Preferably, the generator node Priority of shedding and load shedding priority of load nodes Specifically:

[0014]

[0015] in, Represents a generator node The weight vector of Represents a generator node The power generation output, represents the weight vector of the load node, Indicates the load magnitude of the load node.

[0016] Preferably, the severity of the consequences and average power outage consequences They are:

[0017]

[0018] in, is the initial system load node set; represents the set of load nodes in the final system; and Represents the access nodes before and after the fault occurs. Load; Represents the set of all branches in the system; Representing a collection The number of elements in .

[0019] Preferably, the mitigation control cost model includes: System operation risk indicators For economic indicators and power outage risk indicators The sum of Economic Indicators of Coordinated Control To prevent and control costs and probability-weighted outage mitigation control costs The sum of the power outage risk index represents the total risk on all cascading failure paths; Prevention and control costs and probability-weighted outage mitigation control costs They are:

[0020]

[0021] in, Indicates the cascade path preventive control costs after control; , , , Respectively represent the generator before preventive control Active power of the generator after prevention control Cascading failures Active power and generator The adjustment factor.

[0022] Preferably, the coordinated control model includes: The goal of the coordinated control model is to obtain a control scheme with the lowest operating risk under given network topology and weather conditions, that is, to minimize the risk of power outage with the lowest control cost. The objective function is:

[0023] Preventive control power balance maintenance constraints:

[0024] Power balance maintenance constraints after emergency relief:

[0025] Preventive control of line flow constraints:

[0026] Line flow constraints after emergency relief:

[0027] Adjust load limit constraints after emergency relief:

[0028] Generator output limit constraints:

[0029]

[0030] in, For load nodes Load after preventive control; , , Respectively Power flow after line prevention control, cascading fault path After emergency relief Line power flow, The limit value of line power flow, , Indicates generator The upper and lower limits of active output, Indicates the cascading failure path Emergency relief load node The cutting load capacity, represents the number of generators, Indicates the load quantity, Indicates a cascading failure path.

[0031] In a second aspect, an embodiment of the present invention provides a system for mitigating cascading faults in a power system in the context of an accident or disaster, comprising: The indicator module establishes a disaster risk indicator system for the power system according to the risk level of the disaster, and uses the disaster risk indicator system for the power system to refine the development model of system cascading failures under disaster scenarios; The simulation module establishes a cascading fault propagation model based on the development mode of cascading faults caused by natural disasters. Based on the cascading fault propagation model, the islands in the power system are identified based on the breadth-first search algorithm, and the subsystem with the largest size and the highest weight coefficient is selected to form a new main system, and the cascading faults are continuously simulated. The output module evaluates the cascading failure risk of the power system based on the system data before and after the fault obtained by the cascading fault propagation model; establishes a cascading failure mitigation strategy including a mitigation control cost model and a coordinated control model based on the cascading failure risk of the power system, combines the collaborative mitigation strategy of system cascading failures under disaster conditions with active prevention measures, and cuts off potential cascading failure paths after a disaster occurs.

[0032] In a third aspect, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for mitigating cascading faults of a power system in the context of an accident or disaster when executing the computer program.

[0033] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, including a computer program, which, when executed by a processor, implements the steps of the method for mitigating cascading faults in a power system in the context of an accident or disaster.

[0034] In a fifth aspect, a chip comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for mitigating cascading faults of a power system in the context of accidents and disasters described above when executing the computer program.

[0035] In a sixth aspect, an embodiment of the present invention provides an electronic device, including a computer program, which, when executed by the electronic device, implements the steps of the method for mitigating cascading faults of a power system in the context of accidents and disasters.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects: A method for mitigating cascading failures in power systems based on accident and disaster backgrounds has established equipment risk indicators based on the disaster accident risk level. The indicators help to refine the development mode of cascading failures within the system under accident and disaster conditions; subsequently, at the operation control level, the optimal generator scheduling and load / generator shedding technology are used to develop a collaborative mitigation strategy for system cascading failures under disaster backgrounds; this strategy, coupled with active prevention and control measures, ensures that potential cascading failure paths are quickly cut off when a disaster occurs, thereby minimizing the area affected by power outages; in addition, the present invention has also developed a comprehensive disaster risk quantification theory that takes into account the possibility of risk occurrence, the degree of risk impact on transmission lines, and the severity of potential hazards; this framework can comprehensively quantify the operational risks associated with overhead lines during disasters. At the same time, an evaluation method for cascading failures under disaster scenarios has also been established to quantify the degree to which disasters increase the risk of cascading failures in the entire system.

[0037] Further, by refining the development pattern of system cascading failures under disaster scenarios, it is possible to summarize the line failures caused by various natural disasters, and thus derive the probability of line failures under various natural disaster conditions using statistical analysis methods. This enables us to estimate the load loss caused by the risk to the regional power grid, and the degree of capacity loss when the line fails is allocated according to the proportion of load loss.

[0038] Furthermore, in the event of a natural disaster causing a transmission line outage, timely implementation of power balancing strategies is essential to ensure the stability of the power system. In the event of a disaster, when the power system needs to take balancing measures, the optimal strategy is to prioritize generator ramping for dispatch operations. This approach requires an evaluation of the interaction between generator output and system load, resulting in two different situations in the generator dispatch process: if the generators have excess output capacity, then their output should be reduced accordingly, and if the total output of the generators is lower than the load, it is necessary to increase the output of the generators.

[0039] Furthermore, when the dispatch of generator sets cannot meet the power balance requirements, coordinated load shedding and generator tripping measures need to be implemented to ensure that the power system reaches a balanced state. There are generally two scenarios: after a period of ramp-up, if the output power of the generator is still greater than the system load value, the generator needs to be shelved according to the generator shedding priority to achieve power balance; if after the specified generator ramp-up period, the system load continues to exceed the output power of the generator, it is necessary to coordinate load shedding measures according to the load shedding priority assigned to each load.

[0040] Furthermore, the mitigation controls implemented after triggering are adjusted for individual fault paths, and conflicts only occur when the paths intersect and the mitigation measures are applied before the intersection. This reduces the conflicts between control measures. However, due to its post-fault nature, mitigation controls often involve a large amount of control work because the fault has already had a significant impact on the system. Therefore, it is necessary to establish a mitigation control cost model in order to reasonably select the timing of mitigation controls.

[0041] Furthermore, the goal of the coordinated control model is to obtain the control scheme with the minimum operation risk under given network topology and weather conditions, that is, to minimize the risk of power outage with the minimum control cost.

[0042] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0043] In summary, the present invention quickly cuts off potential cascading failure paths as soon as possible after a disaster occurs, thereby minimizing the affected interruption area and effectively reducing the impact of disaster accidents on the operation of the power system.

[0044] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 A schematic diagram of a breadth-first search algorithm used in the present invention; Figure 3 A schematic diagram of a computer device provided by an embodiment of the present invention; Figure 4 A block diagram of a chip provided according to an embodiment of the present invention; Figure 5 A diagram showing the evaluation results of the cascading failure of the power system according to the present invention; Figure 6 This is a diagram showing the results of the present invention's preventive control of cascading failures in a power system. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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.

[0047] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0048] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0049] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0050] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0051] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0052] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0053] The present invention provides a method for mitigating cascading failures of power systems in the context of accidents and disasters. Aiming at the actual needs of the project, the present invention first establishes equipment risk indicators based on the risk level of the disaster accident for the cascading failures of the power system, and uses these indicators to refine the development model of the system cascading failures under the disaster scenario. And from the perspective of operation control, combined with the optimal generator scheduling and load / generator shedding methods, a collaborative mitigation strategy for system cascading failures under disaster conditions is formulated. This strategy is combined with active preventive measures to quickly cut off potential cascading failure paths as soon as possible after a disaster occurs, thereby minimizing the affected interruption area.

[0054] See also Figure 1 The present invention provides a method for alleviating cascading faults in a power system under accident and disaster background, comprising the following steps: S1. Establish risk indicators based on the risk level of power system disaster accidents, and use risk indicators to refine the development mode of power system cascading failures under various natural disasters; According to the contemporary definition of safety risk, it includes a comprehensive assessment of the likelihood of adverse effects and the severity of the hazard. This definition has been expanded to include a risk table for overhead transmission lines in the event of natural disasters. A power system disaster accident risk indicator system is established based on the risk level of power system disaster accidents, and these indicators are used to refine the development model of power system cascading failures under various natural disasters.

[0055] The risk value of natural disasters on overhead transmission lines is defined as , the probability of overhead line failure due to natural disasters is The severity of the damage caused by the fault is , then (1) in, It is divided into two parts, which are calculated through statistical analysis: (2) in, The probability of natural disasters occurring; Represents the probability of failure due to a disaster.

[0056] The severity of the damage caused by the failure The calculation is as follows: (3) in, is the transmission capacity loss value of the line failure; Represents the social impact risk coefficient.

[0057] Formula (3) is extended to the situation of the combined impact of multiple natural disasters; considering that different types of natural disasters occur at different times, the corresponding risk characteristics and hazards are also different, the period coefficient of natural disaster risk and the risk weight of natural disasters are introduced, and the social impact coefficient of a natural disaster risk is obtained as follows: (4) in, For natural disasters The social impact coefficient of the line risk caused; For natural disasters The coefficient of the risk period of natural disasters; Indicates natural disasters risk weight.

[0058] The disaster operation risk of overhead transmission lines is a comprehensive function of the risk failure probability, the transmission capacity loss value of the line failure, and the risk social impact coefficient, and its calculation formula is: (5) in, is the overhead line disaster operation risk value; Indicates natural disasters The probability of causing line failure; For natural disasters Downlink line failure damage value; Indicates natural disasters The transmission capacity loss due to line faults is shown below.

[0059] according to The size of the value can be used to divide the risk into different hazard levels, as follows: Values ​​over 1000 are classified as Level 1, with a significant threat of causing significant damage; Values ​​between 300 and 1000 (exclusive) constitute Level 2, indicating a high probability of loss; Values ​​between 60 and 300 (exclusive) are assigned to level 3, indicating considerable risk of severe loss; on the contrary, Values ​​ranging from 20 to 60 (exclusive) represent Level 4, which tends to trigger larger losses; Level 5, including Values ​​between 5 and 20 (exclusive) indicate a medium risk of average loss.

[0060] Finally, less than 5 Values ​​fall into Level 6, which is generally associated with minimal or no risk of suffering a loss.

[0061] We then used statistical analysis methods to derive the probability of line failure under various natural disaster conditions. We then used the Monte Carlo method to simulate the operating status of the line during the disaster and calculate the potential forced outage duration. This enabled us to estimate the load loss caused by the risk to the regional power grid.

[0062] In the above, step S1 summarizes the line faults caused by various natural disaster risks and comprehensively quantifies the severity of the risk disasters.

[0063] S2. Based on the development patterns of the cascading failures of the power system under various natural disasters obtained in step S1, a cascading failure propagation model under natural disasters is established; When a disaster occurs, when the power system needs to take balancing measures, the optimal strategy is to give priority to the ramping of the generators in the dispatching operation. The interaction between output and system load is evaluated, resulting in two different scenarios in the generator dispatch process; if generators have excess output capacity, then their output should be reduced accordingly.

[0064] (6) in, Represents generators adjusted in response to disaster events The active output power. Indicates that the generators before the disaster were reduced Active output power; After the disaster The rate at which the generator is adjusted downward per minute; and They represent the load node set and generator node set in the system respectively; Indicates the power adjustment period after a disaster event, usually set to 5 minutes to speed up power balance; is the active load of the load node.

[0065] If the total output of the generator is lower than the load, it is necessary to increase the output of the generator.

[0066] (7) in, Indicates generator rate of rise.

[0067] When the output of the generator satisfies equation (8) relative to the load, or when the output power reaches the maximum output power of the generator, the dispatching process of the generator is terminated.

[0068] (8) in, is the convergence coefficient, which can be set according to the accuracy conditions.

[0069] In step S2, when the generator group scheduling cannot meet the power balance demand, coordinated load reduction and generator tripping measures need to be implemented to ensure that the power system reaches a balanced state. There are generally two scenarios: After a period of ramp-up, if the output power of the generator is still greater than the system load value, the generator needs to be shelved according to the generator shedding priority to achieve power balance. The shedding priority is determined by its power output and the weight vector Decide that the priority The calculation formula is as follows: (9) If, after the specified generator ramp-up period, the system load continues to exceed the generator output power, it is necessary to reduce the load priority according to the load reduction assigned to each load. Coordinate load shedding measures. The load shedding priority of a load node is determined by its load magnitude. and the weight vector The formula for calculating this priority is: (10) The third part in step S2 is the identification of power system islands based on a breadth-first search algorithm. During the development of cascading failures, the power system disintegrates, resulting in the formation of several isolated subsystems, commonly referred to as "islands". These islands have lost all interconnections, and each island has a unique topology, power flow dynamics, and potential failure paths for continued cascading failures.

[0070] The present invention uses a breadth-first search (BFS) algorithm to identify the occurrence of these islands. BFS is a traversal algorithm for graph data structures that starts from a specified starting vertex and explores the graph layer by layer in a breadth-first manner until the target node is found or the entire graph is traversed. Essentially, BFS embodies an iterative approach in which the search starts from a source node and propagates outward, using a queue to maintain the discovered nodes, which are then used as the basis for further expansion to achieve traversal of the entire graph. The system is decomposed into multiple isolated subsystems, and the subsystem with the largest size and the highest weight coefficient is selected to form a new main system. This selection criterion ensures that cascading failures are continuously simulated in the newly formed main system.

[0071] The final step in step S2 is to assess the risk of cascading failures. It is used to measure the scale of power outage caused by cascading failure events with complete fault paths. The average power outage consequence of cascading failures in the power system is To measure the risk of cascading failure in the system. and The calculation formula is as follows: (11) (12) in, is the initial system load node set; represents the set of load nodes in the final system; and Represents the access nodes before and after the fault occurs. Load; Represents the set of all branches in the system; Representing a collection The number of elements in , i.e. the number of branches in the system; The higher the value, the more severe the consequences of a power outage caused by a potential cascading failure event in the system.

[0072] S3. Based on the severity of the consequences obtained in step S2, a cascading fault mitigation strategy is established, including a mitigation control cost model and a coordination control model, to determine the timing of mitigation intervention. According to the time sequence of control measures, the control of large-scale power outage accidents can be divided into preventive control before the accident and interruption control during the accident.

[0073] Since preventive controls are implemented before a cascading failure path is triggered, they act immediately when a failure occurs, effectively minimizing the risk of exposing the system to its impact. However, since it addresses all potential failure paths, while reducing the risk associated with a path, it may inadvertently increase the risk of other paths. The conflicting requirements imposed by different failure paths limit the effectiveness of relying solely on preventive controls to mitigate the risk of power outages. In contrast, mitigation controls implemented after triggering are adjusted for individual failure paths, and conflicts only arise when the paths intersect and mitigation measures are applied before the intersection. This reduces conflicts between control measures. However, due to their post-failure nature, mitigation controls often involve a large amount of control work because the failure has already had a significant impact on the system. By taking preventive controls before a failure occurs, the need for subsequent mitigation controls is reduced, reducing control costs. Conversely, implementing post-failure mitigation controls can alleviate the inherent contradictions of preventive controls and improve the overall ability to reduce system risks. Therefore, prevention and mitigation controls are highly complementary.

[0074] In order to better select the timing of mitigation intervention, the risk significance of the fault segment is defined to indicate the degree of influence of the fault segment in the same cascading fault path on the overall path. Its expression is as follows: (13) in, Risk is cascading failure path Before The risk of power outage; Indicates the cascading failure path Before The risk of power outage in the short term.

[0075] The higher the value of , the greater the contribution of this segment to the formation of the propagation failure path. Implementing mitigation controls in the segment with the highest risk value can effectively reduce the risk of the failure path and prevent the development of cascading failures.

[0076] In step S3, a mathematical model for alleviating control costs is established, specifically, the economic indicators for coordinated control It is the sum of the prevention control cost and the probability-weighted interruption mitigation control cost. Represents the total risk on all cascading failure paths. Since the impact of control measures on the power system is manifested as changes in the risk of power outages, and these control measures themselves generate control costs, in order to comprehensively evaluate the changes in power outage risks and control costs, the system operation risk index Defined as the sum of the economic index and the power outage risk index.

[0077] (16) (17) (18) (19) (20) Dear in, represents the cost of prevention; Indicates the cascade path preventive control costs after control; represents the sum of the emergency mitigation costs of each cascading failure path after preventive control; It represents the sum of probability-weighted emergency mitigation costs of each cascading failure path after preventive control. , , , Respectively represent the generator before preventive control Active power of the generator after prevention control The active power of the generator after preventive control Cascading failure paths Active power and generator The adjustment factor of represents the amplification factor; and Represent the cascading failure paths Emergency relief load node Cutting load and load loss cost coefficient; Cascading failure path Probability of achieving emergency mitigation.

[0078] Another part of step S3 is the coordinated control model, the goal of which is to obtain a control solution with the minimum operating risk under given network topology and weather conditions, that is, to minimize the risk of power outage at the minimum control cost.

[0079] The mathematical optimization model is as follows: (twenty two) (twenty three) (twenty four) (25) (26) (27) (28) (29) in, For load nodes Load after preventive control; , , Respectively Power flow after line prevention control, cascading fault path After emergency relief Line power flow, The limit value of line power flow, , Indicates generator The upper and lower limits of active output.

[0080] Equations (23) and (24) represent the power balance maintenance after preventive control and emergency relief, respectively. Equations (25) and (26) represent The power flow on the line does not exceed its limit after preventive control and emergency relief. Equation (27) ensures that the adjusted load does not exceed its limit after emergency relief, assuming that the maximum load reduction of the load node is 50% of its total load; finally, Equations (28) and (29) represent the constraints that the adjusted generator output does not exceed its limit after preventive control and emergency relief, respectively.

[0081] Furthermore, if we only consider the preventive control measures for all cascading failure paths before the failure occurs, that is, we only keep the set In , removing constraints (24), (26), (27), and (29), the model is transformed into a pure preventive control model. On the contrary, if only the emergency mitigation measures specific to each cascading failure path are considered, that is, in the set Only keep , and removing constraints (23), (25) and (28), the model is transformed into a pure emergency mitigation model.

[0082] In another embodiment of the present invention, a system for mitigating cascading faults in electric power systems under accident and disaster backgrounds is provided. The system can be used to implement the above-mentioned method for mitigating cascading faults in electric power systems under accident and disaster backgrounds. Specifically, the system for mitigating cascading faults in electric power systems under accident and disaster backgrounds includes an indicator module, a simulation module and an output module.

[0083] Among them, the indicator module establishes a power system disaster accident risk indicator system according to the risk level of disaster accidents, and uses the power system disaster accident risk indicator system to refine the development model of system cascading failures under disaster scenarios; The simulation module establishes a cascading fault propagation model based on the development mode of cascading faults caused by natural disasters. Based on the cascading fault propagation model, the islands in the power system are identified based on the breadth-first search algorithm, and the subsystem with the largest size and the highest weight coefficient is selected to form a new main system, and the cascading faults are continuously simulated. The output module evaluates the cascading failure risk of the power system based on the system data before and after the fault obtained by the cascading fault propagation model; establishes a cascading failure mitigation strategy including a mitigation control cost model and a coordinated control model based on the cascading failure risk of the power system, combines the collaborative mitigation strategy of system cascading failures under disaster conditions with active prevention measures, and cuts off potential cascading failure paths after a disaster occurs.

[0084] In another embodiment of the present invention, a terminal device is provided, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the power system cascading fault mitigation method in the context of accidents and disasters, including: A disaster accident risk index system for power systems is established based on the risk level of disaster accidents, and the disaster accident risk index system for power systems is used to refine the development model of system cascading failures under disaster scenarios; a cascading failure propagation model is established based on the development model of cascading failures caused by natural disasters; based on the cascading failure propagation model, islands in the power system are identified based on the breadth-first search algorithm, and the subsystem with the largest size and the highest weight coefficient is selected to form a new main system, and cascading failures are continuously simulated; the cascading failure risk of the power system is evaluated based on the system data before and after the failure obtained by the cascading fault propagation model; a cascading failure mitigation strategy including a mitigation control cost model and a coordinated control model is established based on the cascading failure risk of the power system, and the collaborative mitigation strategy of system cascading failures under disaster conditions is combined with active prevention measures to cut off potential cascading failure paths after the disaster occurs.

[0085] See also Figure 3 , the terminal device is a computer device, and the computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the computer program 63 is executed by the processor 61, the method for calculating the fluid composition in the reservoir transformation wellbore in the embodiment is implemented. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the power system cascading fault mitigation system in the accident and disaster background of the embodiment are implemented. To avoid repetition, it is not described one by one here.

[0086] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Figure 3 This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0087] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0088] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the computer device 60.

[0089] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is to be output.

[0090] See also Figure 4 , the terminal device is a chip, and the chip 600 of this embodiment includes a processor 622, which may be one or more, and a memory 632 for storing a computer program executable by the processor 622. The computer program stored in the memory 632 may include one or more modules, each corresponding to a set of instructions. In addition, the processor 622 may be configured to execute the computer program to execute the above-mentioned power system cascading fault mitigation method in the accident disaster background.

[0091] In addition, the chip 600 may further include a power supply component 626 and a communication component 650, wherein the power supply component 626 may be configured to perform power management of the chip 600, and the communication component 650 may be configured to implement communication, for example, wired or wireless communication, of the chip 600. In addition, the chip 600 may further include an input / output interface 658. The chip 600 may operate based on an operating system stored in the memory 632.

[0092] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and the extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs. It should be noted that the computer-readable storage medium here can be a high-speed RAM memory, or a non-volatile memory (Non-VolatileMemory), such as at least one disk memory.

[0093] One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the corresponding steps of the method for mitigating cascading faults in a power system in the context of an accident or disaster in the above-mentioned embodiment; one or more instructions in the computer-readable storage medium are loaded and executed by a processor as follows: A disaster accident risk index system for power systems is established based on the risk level of disaster accidents, and the disaster accident risk index system for power systems is used to refine the development model of system cascading failures under disaster scenarios; a cascading failure propagation model is established based on the development model of cascading failures caused by natural disasters; based on the cascading failure propagation model, islands in the power system are identified based on the breadth-first search algorithm, and the subsystem with the largest size and the highest weight coefficient is selected to form a new main system, and cascading failures are continuously simulated; the cascading failure risk of the power system is evaluated based on the system data before and after the failure obtained by the cascading fault propagation model; a cascading failure mitigation strategy including a mitigation control cost model and a coordinated control model is established based on the cascading failure risk of the power system, and the collaborative mitigation strategy of system cascading failures under disaster conditions is combined with active prevention measures to cut off potential cascading failure paths after the disaster occurs.

[0094] 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, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. 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 claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0095] It is planned to use the statistical data of natural disasters and line failures in a certain area in the past to evaluate the risk failure probability of actual overhead transmission lines; the transmission lines are assumed to operate under different weather conditions. Cascading failure simulation and cascading failure mitigation strategy simulation are carried out; the mitigation strategy model is solved by the commonly used particle swarm optimization algorithm; the solution is based on a two-layer decomposition optimization scheme, the initial value of the prevention and control scheme is selected, and the optimal solution of the blocking scheme is obtained under a given prevention and control scheme.

[0096] The main natural disasters in the region include heavy rain and floods, ice and snow, thunderstorms, strong winds, fires and earthquakes. Table 1 lists the occurrence of overhead line tripping caused by natural disasters over a six-year period: Table 1 Transmission line tripping in the past six years

[0097] Calculate the probability of overhead transmission line failure caused by different natural disasters, denoted as %, as well as the corresponding scores and the operational risk R of the transmission line under natural disasters, are calculated using a simplified formula; the results are in Table 2.

[0098] Table 2 Risk values ​​of transmission lines under natural disasters

[0099] The natural disasters corresponding to the highest operational risk values, namely floods and rainstorms, have been selected as the target for evaluating the cascading failures of power systems under disaster conditions; the evaluation results are as follows Figure 5 As shown; Figure 5 The vertical axis represents the number of transmission lines that cause cascading failures under natural disasters, while the horizontal axis represents the simulation results of the Indl index of cascading failures caused by the corresponding transmission lines. A higher value indicates that the probability of cascading failures on the line is greater. The purple bar graph on the left shows the simulation results of system cascading failures without natural disasters, while the yellow bar graph on the right represents the simulation results of system cascading failures under heavy rain and flood disasters. Figure 5 It can be seen that under normal conditions without natural disasters, there are only 16 potential cascading failure triggering points, while under heavy rain and flood disasters, the number of potential cascading failure triggering points surges to 35, an increase of 219%. This shows that natural disasters can significantly increase the possibility of cascading failures.

[0100] At the same time, under natural disaster conditions, the severity of the consequences of cascading failures (Indl) also increased significantly. Taking branch 9 and branch 42 as examples, under normal conditions without disasters, the Indl of cascading failures that may be caused by these two trigger points are 0.093 and 0.036 respectively. After the heavy rain and flood disasters, the Indl of cascading failures that may be caused by these two trigger points increased to 0.345 and 0.523 respectively, and the risk index increased by 371% and 1453% respectively. According to the data provided in the figure, the average power outage consequences (IndR) of the system before and after the natural disaster are calculated, which are 0.052 and 0.253 respectively, indicating that the risk of cascading failures of the entire system has increased significantly.

[0101] In order to compare and analyze the effectiveness of the control strategy, new indicators are defined, namely the reduction of IndR (ΔIndR) and the reduction of E (ΔE). The unit cost of load shedding during the control process is set to 200 yuan / MW, and h is 500,000. For the system with the highest cascading failure risk mentioned above, flood and rainstorm, a coordinated control model is formulated and solved. The details are shown in Table 3.

[0102] Table 3 Performance of different control strategies under flood and rainstorm conditions

[0103] Control strategy 1 is a purely preventive control method that excludes emergency mitigation intervention. Its control idea is to adjust the unit output to optimize the power flow distribution before the fault occurs, thereby reducing the probability of cascading failure. It only reduces the control pressure once the cascading failure path is triggered by increasing the operating cost in normal system operation, thereby reducing the occurrence of line overload after the fault. However, the preventive effect is limited, resulting in a small reduction in power outage risk (ΔIndR), poor control performance, less reduction in operating risk (ΔE), and a relatively low cost-effectiveness ratio.

[0104] Control strategy 2 is a pure emergency mitigation strategy that does not include any active preventive measures. Its control idea is to control the spread of the fault by urgently cutting off the load and quickly restoring the normal operation of the overloaded line after the fault occurs. Compared with control strategy 1, it shows stronger control effect and better economy. However, since this strategy only implements control after the cascading fault path is activated, the line overload phenomenon is more common after the fault, resulting in higher emergency mitigation costs and significant post-fault control pressure.

[0105] Control strategy 3 represents a coordinated control method that combines preventive control and emergency mitigation. On the one hand, preventive control before the fault reduces the probability of fault occurrence and alleviates the line overload caused by the cascading fault path, thereby alleviating the control pressure after the fault and reducing the emergency mitigation cost after the fault. On the other hand, emergency mitigation after the fault can alleviate the conflict between the cascading fault paths, increase the reduction in power outage risk (ΔIndR), and enhance the overall control effect. Therefore, this strategy provides the best control performance and the highest cost-effectiveness ratio.

[0106] In the prevention stage, the output of the generator sets is adjusted to optimize the power flow distribution, thereby reducing the operating pressure of the system and pre-mitigating the severity of the power flow overload that may be caused by the fault. The results of preventive control are as follows: Figure 6 shown.

[0107] like Figure 6 As shown, the control strategy proposed in the present invention can optimize and adjust the output of the generator according to the actual grid operation conditions and the risk level of the line under disaster scenarios, thereby reducing the risk of system cascading failures at a lower cost and pre-sharing some of the prevention and control pressure after failures.

[0108] In summary, the present invention provides a method and system for mitigating cascading failures in an electric power system based on accident and disaster backgrounds, which effectively blocks cascading failures after a natural disaster occurs, thereby minimizing the area affected by the power outage and comprehensively improving the ability of the electric power system to resist risks.

[0109] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0110] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0111] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0112] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0113] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0114] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0115] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0116] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0117] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0118] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0119] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for mitigating cascading failures in a power system based on accident and disaster background, characterized in that: The following steps are involved: Establish a disaster risk index system for the power system according to the risk level of the disaster, and use the disaster risk index system to refine the development model of system cascading failures under disaster scenarios; According to the development mode of cascading failures caused by natural disasters, a cascading failure propagation model is established; according to the cascading failure propagation model, the islands in the power system are identified based on the breadth-first search algorithm, and the subsystem with the largest size and the highest weight coefficient is selected to form a new main system, and the cascading failure is continuously simulated; Evaluate the risk of cascading failure of the power system based on the system data before and after the fault obtained by the cascading fault propagation model; According to the cascading failure risk of the power system, a cascading failure mitigation strategy including a mitigation control cost model and a coordinated control model is established. The collaborative mitigation strategy of system cascading failures under disaster conditions is combined with active prevention measures to cut off potential cascading failure paths after a disaster occurs.

2. The method for mitigating cascading failures in a power system based on accident and disaster background according to claim 1 is characterized in that: The development model of system cascading failures under disaster scenarios is detailed as follows: When the overhead line disaster operation risk value More than 1,000 is level 1, which poses a significant threat of causing significant damage; When the overhead line disaster operation risk value Level 2 is between 300 and 1000, indicating the possibility of severe losses; When the overhead line disaster operation risk value Level 3 is between 60 and 300, indicating considerable risk of severe loss; When the overhead line disaster operation risk value The value between 20 and 60 is level 4, which means causing greater losses; When the overhead line disaster operation risk value Values ​​between 5 and 20 are level 5, indicating a medium risk of general losses; When the overhead line disaster operation risk value Values ​​below 5, which fall into Class 6, are generally associated with minimal or no risk of suffering a loss.

3. The method for mitigating cascading failures in a power system based on accident and disaster background according to claim 2 is characterized in that: Overhead line disaster operation risk value for: in, Indicates natural disasters The probability of causing line failure; For natural disasters Downlink line failure damage value; Indicates natural disasters The transmission capacity loss value caused by line fault is: For natural disasters The social impact coefficient of the line risk caused by Represents the total number of natural disasters.

4. The method for mitigating cascading failures in a power system based on accident and disaster background according to claim 2, characterized in that: Natural disasters Social impact coefficient of line risk caused for: in, For natural disasters The coefficient of the risk period of natural disasters; Indicates natural disasters risk weight.

5. The method for mitigating cascading failures in a power system based on accident and disaster background according to claim 1, characterized in that: In the cascading fault propagation model, when the dispatch of generator sets cannot meet the power balance requirements, there are two scenarios: After a period of ramp-up, if the output power of the generator is still greater than the system load value, the generator needs to be shelved according to the shedding priority of the generator to achieve power balance; If, after the specified generator ramp-up period, the system load continues to exceed the generator output power, it is necessary to reduce the load priority according to the load reduction assigned to each load. Coordinate load shedding measures; Power system island identification is performed based on a breadth-first search algorithm, and then the severity of the consequences is used To measure the scale of power system blackout caused by a cascading failure event with a complete fault path, use the average blackout consequence of a cascading failure in the power system Measuring the risk of cascading failure in a system.

6. The method for mitigating cascading failures in a power system based on accident and disaster background according to claim 5, characterized in that: Generator Node Priority of shedding and load shedding priority of load nodes Specifically: in, Represents a generator node The weight vector of Represents a generator node The power generation output, represents the weight vector of the load node, Indicates the load magnitude of the load node.

7. The method for mitigating cascading failures in a power system based on accident and disaster background according to claim 5, characterized in that: Severity of consequences and average power outage consequences They are: in, is the initial system load node set; represents the set of load nodes in the final system; and Represents the access nodes before and after the fault occurs. Load; Represents the set of all branches in the system; Representing a collection The number of elements in .

8. The method for mitigating cascading failures in a power system based on accident and disaster background according to claim 1, characterized in that: The mitigation control cost model includes: System operation risk indicators For economic indicators and power outage risk indicators The sum of Economic Indicators of Coordinated Control To prevent and control costs and probability-weighted outage mitigation control costs The sum of the power outage risk index represents the total risk on all cascading failure paths; Prevention and control costs and probability-weighted outage mitigation control costs They are: in, Indicates the cascade path preventive control costs after control; , , , Respectively represent the generator before preventive control Active power of the generator after prevention control Cascading failures Active power and generator The adjustment factor.

9. The method for mitigating cascading failures in a power system based on accident and disaster background according to claim 1, characterized in that: The coordinated control model includes: The goal of the coordinated control model is to obtain a control scheme with the lowest operating risk under given network topology and weather conditions, that is, to minimize the risk of power outage with the lowest control cost. The objective function is: Preventive control power balance maintenance constraints: Power balance maintenance constraints after emergency relief: Preventive control of line flow constraints: Line flow constraints after emergency relief: Adjust load limit constraints after emergency relief: Generator output limit constraints: in, For load nodes Load after preventive control; , , Respectively Power flow after line prevention control, cascading fault path After emergency relief Line power flow, The limit value of line power flow, , Indicates generator The upper and lower limits of active output, Indicates the cascading failure path Emergency relief load node The cutting load capacity, represents the number of generators, Indicates the load quantity, Indicates a cascading failure path.

10. A power system cascading fault mitigation system based on accident and disaster background, characterized in that: include: The indicator module establishes a disaster risk indicator system for the power system according to the risk level of the disaster, and uses the disaster risk indicator system for the power system to refine the development model of system cascading failures under disaster scenarios; The simulation module establishes a cascading fault propagation model based on the development mode of cascading faults caused by natural disasters. Based on the cascading fault propagation model, the islands in the power system are identified based on the breadth-first search algorithm, and the subsystem with the largest size and the highest weight coefficient is selected to form a new main system, and the cascading faults are continuously simulated. An output module, which evaluates the cascading failure risk of the power system based on the system data before and after the fault obtained by the cascading fault propagation model; According to the cascading failure risk of the power system, a cascading failure mitigation strategy including a mitigation control cost model and a coordinated control model is established. The collaborative mitigation strategy of system cascading failures under disaster conditions is combined with active prevention measures to cut off potential cascading failure paths after a disaster occurs.

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