Robustness Analysis And Optimization Of Electrical Cyber Physical System Based On Interdependent Networks

With the development of information technology,the traditional power grid has gradually evolved into a binary coupling system with equal emphasis on the physical power grid and the power communication network and it is called electrical cyber physical system(ECPS).The wide application of information technology improves the automation level of power grid,but it also seriously threaten the safe operation of the power grid,which is the main reason for the blackout accidents.In addition,due to the frequent interactions between the networks,failures in the power grid or power communication network can also spread to the other network,setting off a catastrophic chain reaction that can lead to the collapse of the entire ECPS.Therefore,it is of great theoretical value and practical significance to study the cascading failures of ECPS and the measures of robustness optimization.In this paper,the model of electrical cyber physical interdependent networks(ECPIN)model is established from the perspective of interdependent networks and the robustness change rule and first-order phase transformation process of ECPS are analyzed.Then the IEEE118 nodes system is taken as the research object and the corresponding robustness optimization measures are proposed.The main research work of this paper is as follows:(1)Firstly,a comprehensive summary is made on the application of interdependent networks theory in electrical cyber physical system.The structural vulnerability,the model of cascading failures and robustness optimization measures of ECPS are introduced comprehensively.(2)The model of electrical cyber physical interdependent networks is constructed based on the partially interdependent networks,which can better reflect the assortative feature,multiple support-dependence relations and the different size of subsystems to the electrical cyber physical system.Considering that the actual ECPS is faced with various attacks,combined with the percolation theory,the cascading failures of ECPIN is analyzed when the interdependent edges and the connecting edges are deliberately attacked.It is helpful to reduce the design cost by selecting proper coupling probability and the number of important nodes so that the robustness of ECPS and the first-order phase transformation at the critical threshold are studied.The results show that increasing the number of important nodes makes the ECPS more robust,but the robustness of ECPIN at the critical threshold is only related to the coupling probability.(3)Taking IEEE118 nodes system as the research object,a local load allocation strategy based on node residual capacity is proposed on the basis of the local load allocation strategy based on node capacity.This strategy takes into account the real-time change of node load in the actual ECPS,and reduces the probability of node overload.The simulation results show that the robustness of the ECPS is further improved.In view of the important position of key nodes in the complex network,different levels of protection are carried out for the key nodes because of limited cost.When some nodes are attacked,the failure probability of the protected node is _fP and the failure probability of the unprotected node is 1.The smaller P_f not only inhibits the intra-network diffusion and inter-network propagation of cascading failures,but also makes the cascading failures transition of ECPIN from first-order phase transition to second-order phase transition.