Vulnerability And Improvement Strategy Analysis Of Cyber Physical Power Systems Considering Cascading Failures

With the development and promotion of smart grid strategy,the interaction between power system and information system is increasingly close.As a typical information Physical system,namely Cyber physical Power Systems(CPPS),smart Power grid has cyber-physical interaction in the process of generation,transmission and distribution of electric energy.In recent years,a number of blackouts caused by deliberate attacks on the power system have had a significant negative impact on the economy and society.Therefore,the safe and reliable operation of CPPS become particularly critical.In view of the risk problem caused by the integration of cyber system in power system,the previous research usually starts from a single system to analyze,resulting in deviation from the actual situation.Therefore,it is of great research value to evaluate the vulnerability of CPPS and analyze the vulnerability improvement strategies from a global perspective.The main research work of this paper is as follows:According to the structure of power system and cyber system in CPPS and the interdependent relationship between the systems,the "partial one-to-one" structure model of CPPS is established by introducing the theory of dependent network.The traditional CPPS modeling only considers the topological model,which has some limitations.In order to get close to the actual power flow distribution characteristics,the electrical dielectric number is used as the weight of the power line,and the power system side weight model is established.At the same time,considering the data transmission characteristics of the cyber system and the cyber of the node and its adjacent nodes,the edge weight model of the cyber system is established.Taking IEEE-39 node system as an example,a weighted IEEE-39 node CPPS model is established.In view of the important influence of the interaction between cyber system and power system on the vulnerability of CPPS,the interlocking fault model of CPPS was established based on the seepage theory by analyzing the interactive propagation mode of faults between networks and the failure rules of corresponding nodes.In order to quantitatively evaluate the vulnerability of CPPS,the load loss rate,network relative efficiency and node survival rate of power network are proposed as vulnerability assessment indexes.Considering that the shortest path calculation of traditional information network nodes is based on the hop number of nodes without taking into account the amount of information transmission,this paper uses Floyd algorithm to calculate the weighted shortest distance based on the weight of information edge,so as to select the optimal path for the efficient transmission of data.Combined with the power flow and topological characteristics of power network nodes,the important nodes of power network are identified.Under the background of attack,the important nodes in the power network are attacked,and a new deliberate attack strategy is established.Taking IEEE-39 node CPPS as an example,the vulnerability of CPPS under different attack types was analyzed by using two different attack strategies:random attack and deliberate attack.Then,Ie E-118 node CPPS is taken as an example to compare and analyze the vulnerability of different network scales under the same attack strategy.Based on the established CPPS model,a strategy of adding edge between networks considering the importance of balanced cyber nodes is proposed.At the same time,considering the edge weight of the cyber network,an edge enlargement strategy is proposed to reduce the average shortest path of the cyber network and increase the data transmission capacity of the network.By combining the above methods,a comprehensive vulnerability improvement strategy was proposed and compared with other vulnerability improvement strategies under the same attack mode to verify the effectiveness of the comprehensive vulnerability improvement strategy.Under the same attack strategy,the improvement effects of the comprehensive improvement strategy on the vulnerability of IEEE-39 node CPPS and IEEE-118 node CPPS were compared and analyzed.