Security Assessment Of Electric CPS Based On Hierarchical Structure Model

With the rapid development of smart grid,the information system plays a more and more important role in the operation of electric power system.The traditional electric power system has been transformed into a Cyber-physical System,which is closely related to the information system.The wide application of network technology in power CPS brings convenience to the production and management,also introduces many new threats.In recent years,the power grid faults caused by the failure of the information system and even the large-scale blackout occurred constantly.The security problems of power CPS are becoming more and more serious.The safety assessment of the electric CPS is a comprehensive assessment of threat and vulnerability,which is helpful to find out the weak link of the system and make the corresponding improvement plan.It has an important guiding significance for the reliable operation of the power grid and the architecture design of the energy system in the future.The existing model is limited to the security of a single space and does not evaluate the electric CPS as an organic body.Based on the above background,this paper studies the modeling method,risks and cascading failures propagating across spaces,and the safety assessment of electric CPS.Based on the hierarchical structure model,this paper makes a comprehensive analysis of the electric CPS safety risk from the static risk of electric CPS information equipment to the dynamic electric CPS cascading failure.The research content includes the following several aspects:(1)Research on the object oriented hierarchical model of electric CPS.First of all,the interactive mode of electric CPS is analyzed by means of energy flow and information flow.Then,an object oriented hierarchical modeling method and structure model are proposed according to the characteristics of the coupling between the discrete and continuous system.In this model,the electric CPS is divided into 5 levels:information device layer,communication subnet layer,network layer,information service layer and physical system layer.Object oriented method is used to define the relationship and structure of each level,which improves the feasibility of the analysis,evaluation and Simulation of electric CPS.(2)Analysis of faults and risk factors of electric CPS information system based on hierarchical structure.In this part,the risk sources of electric CPS are analyzed.Then,the faults and risk factors of electric CPS are analyzed separately from 5 levels on the basic of object oriented hierarchy.Finally,the faults of information system are classified.(3)Study on risk assessment method of electric CPS information equipment fault.Firstly,the coupling model of electric CPS information system in hierarchical structure is established.Then,an evaluation algorithm based on analytic hierarchy process(AHP)is used as the coupling model state transition function.The evaluation index is chosen as the input of the model,and the failure risk of information equipment is the output.The model takes the relationship between information system and power system into account,and fits static evaluation of electric CPS information system risk.Finally,the D2-1 substation is selected as an example to evaluate the equipment fault risk,and the result is consistent with the actual situation.(4)Study on risk propagation across space mechanism of information system,and safety risk assessment based on improved attack graph.First of all,this paper expounds the basic way of risk propagation across space in electric CPS basing on the analysis of the information system risk in electric CPS.Then,the safety risk propagation model of electric CPS is established according to the improved attack graph.The information equipment,the electric power service,and the power system faults are taken as nodes to establish risk propagation path.The sensitivity of node and attack path for fault propagation of information equipment is quantified by improved attack graph.Finally,combined with the results of fault risk assessment and sensitivity,the comprehensive security assessment of power CPS considered dynamic timing is carried out.