Robustness Optimization Of Electrical Cyber-Physical System Based On Dependent Network Theory

With the wide application of communication technology,computer technology and control technology,the traditional power system has developed into a electrical cyber-physical system combined with information network.Electrical cyber-physical system is a binary coupling system formed by the deep integration of power grid and information system.The extensive application of advanced information and communication technology improves the controllability and observability of power system.However,the informationization of physical power grid not only improves the level of power automation,social production efficiency and user experience,but also brings many hidden dangers to the security of smart grid.The faults of power system or information system may spread to each other’s network,resulting in the transmission of interlocking faults,thus seriously affecting the safe operation of electrical cyber-physical system.The losses caused in the process should not be underestimated.Therefore,it is of great theoretical value and practical significance to study the modeling method of electrical cyber-physical system and the method of improving system robustness.Based on the research results of interdependent network theory and aiming at improving the robustness of electrical cyber-physical system,this paper makes a deep research on the modeling method and robustness optimization strategy of electrical cyber-physical system.The main research work of this paper is as follows:(1)Firstly,a comprehensive summary is made on the application of dependency network theory in electrical cyber-physical system at home and abroad.This paper introduces the development and research status of the theory of dependent networks,and makes detailed explanations,summaries and inductions on the modeling methods of electrical cyber-physical systems and the research of robustness optimization.(2)From the perspective of complex network,based on the corresponding electrical cyber-physical system of 220 kV power grid in a province of central China,the cascade failure model of the system is a nonlinear load-capacity model.Then,considering the practical problems of power network expansion,this paper studies how to add stations under cost constraints to optimize load distribution and improve system robustness.Based on the research results of robustness of existing electrical cyber-physical system,four possible additional power stations are proposed for the first time from the perspective of increasing nodes.The validity of four node allocation strategies in optimizing load distribution and improving system robustness for electrical cyber-physical system corresponding to a provincial power network and IEEE 118-bus system in central China is verified.The results show that in the four strategies,when the physical nodes are allocated to connect large and small power load nodes,only a few nodes need to be allocated to achieve the established degree of optimization,and the implementation of this strategy has certain practical basis and advantages in the actual power grid construction.This conclusion has certain guiding significance for the optimal allocation of limited resources in power system planning.(3)According to the deployment rule of the components in the actual electrical cyber-physical system,the modeling method of the electrical cyber-physical system is improved.Considering the "island operation" phenomenon of the actual power system,the cascade fault model of the electrical cyber-physical system is constructed based on the interaction and interaction of the components in the actual power system.Comparing the improved electrical cyber-physical system with the existing system based on the maximum connected subset concept as the fault model,the results show that the system vulnerability under the maximum connected subset fault model is much higher than that based on the actual improved cascade fault model in the whole process from the beginning of the attack to the end of the attack,and the node survives in the early stage of the attack.The attenuation speed of the rate varies greatly.The cascade fault model in this paper is more suitable for the operation mode of actual power system in layered and partitioned operation.Even if the system has incomplete topology,the normal operation of the connected subset can be maintained as long as the active power balance of the connected subset is guaranteed,and the system has a certain degree of robustness against attacks.(4)Under the improved electrical cyber-physical system modeling and cascade failure model,a DB(Degree and Betweenness)attack strategy based on node degree,median and neighbor information is proposed by analyzing the characteristics of key components in the actual electrical cyber-physical system.The research shows that DB attack strategy has the highest degree of damage to electrical cyber-physical than the other three attack strategies.Obviously,DB attack strategy is more effective than other strategies in identifying important nodes in electrical cyber-physical system.In practice,if we pay attention to and strengthen the protection measures for high DB value nodes,it will help to avoid large-scale failure of the system and enhance the robustness of the system.The failure of information network is more destructive than that of power network in electrical cyber-physical system.In the actual power system operation,we should strengthen the protection measures for the important nodes in the information system to avoid large-scale cascade faults caused by the faults of the important nodes,so as to enhance the robustness of the system as a whole.