Modeling Of Power CPS Cascading Failures And Analysis Of Protection Strategies

Power information physical system(CPS)has gradually become the future development direction of the power system by virtue of its intelligence and efficient services in power generation,transmission,and distribution.The coupling and interdependence of the power and information layers in the power information physical system optimizes the operation of the power system and also brings new fragile links,so that the failure of the single-layer network can be transmitted between the power network and the information network through the dependent side channel,Thereby increasing the probability of large-scale cascading failures.In addition,the diversity,complexity,wide area,and limitation of the power CPS system have brought challenges to the analysis of the occurrence and evolution mechanism of cascading failures and the study of methods to improve the robustness of the system.Therefore,according to the structural relationship of the power information physical system,constructing a practical cascading failure model,evaluating the vulnerable links of the system and giving corresponding protection strategies have certain theoretical and practical significance to prevent the occurrence of large-scale cascading power failure accidents.First,based on the composition and structure of the power CPS system,based on the basic principles of complex networks and dependent networks,the static topological characteristics of nodes such as "betweenness","degree",and "closeness centrality" are introduced into the unified model of power information physical system Establish the power network and information network models including abstract nodes and branches,and the "one-to-one correspondence" coupling model and adjacency matrix of the "betweenness-degree" and "closeness centrality" priority connection methods between the two network nodes.Taking IEEE9 node system as an example,the specific modeling method of electric power CPS system model is given.Secondly,as a typical dependent network,the power CPS system's cascading failures are bound to be affected by the actual operating characteristics of the two networks,power flow and information flow.Therefore,based on the interactive propagation model of faults between dependent networks and node failure rules,according to the Newton-Raphson method and Dijkstra method to calculate and analyze the shortest route strategy in the power network power distribution and information network data transmission,the establishment of the two networks dynamic operating characteristics The cascading failure model provides a simulation basis for studying the mechanism of fault interaction propagation in detail.Taking the IEEE39 node CPS as an example,the specific cascading failure development process is given.By comparing and analyzing the simulation results,it is concluded that the system with the "betweenness-degree" of the two coupling strategies under deliberate attack has a strong ability to withstand failure.Finally,considering that critical and vulnerable nodes are attacked is an important incentive for the system to change from a normal operating state to a fault state.Therefore,this paper puts forward three fragile indicators: power layer loadcutting rate,information layer network efficiency,and overall system topology node survival rate,and selects the vulnerable and key nodes in the system.Then,from the perspective of the faulted intra-network and inter-network propagation routes,the fragility of the system and the protection of key nodes,a comprehensive protection strategy of adding redundant edges between the networks,adding high-load nodes at the power layer and adding low-degree nodes at the information layer is proposed.At the end,the relevant algorithm is programmed in Python language,and the power system software Dig-SILENT Power Factory is used to simulate the power layer operation of the IEEE39 node CPS system.When the information node is intentionally attacked,the following conclusions are drawn:1)Compared with the "closeness centrality" coupling mode,system with "betweenness-degree" mode is more robust;2)The comprehensive protection strategy between the inter-network and the inner-network can significantly reduce the vulnerability of the system,and for system with "closeness centrality" mode,the strategy has better protection effect.