Research On Cyber-Physical Power System (CPPS) Vulnerability Assessment Methods Considering Cascading Failures

With the developments of power system intelligentialize,there are more data requires to be generated,collected,transferred and processed.Conventional power systems are developing into cyber-physical power systems(CPPS)with the interdependence and fusion of cyber system and physical system.However,the cyber feature,bring new security challenges as well as improve the production efficiency,multiple practical cases show that the failure of cyber layers is a major factor leading to blackouts.Therefore,it is necessary to analyze and discuss the reliability and the vulnerability of CPPS.Against this background,this dissertation focuses on the quantified expression of cyber-physical impacts,the rapid identification of vulnerable points in cyber layer,and the vulnerability analysis of cyber-physical power systems considering cascading failures.The detailed contents of this dissertation are shown as follows:Function failure models for monitoring function and control function are proposed,and studied direct/indirect cyber-physical impact.Then,a method for calculating the availability of circuit breaker considering control function impact is presented.Based on analysis of power cascading failure caused by monitoring function failure,a reliability assessment method of Power CPS considering monitoring function and control function is given.A method to analyze the importance of cyber devices based on closeness centrality via effective distance is introduced.Firstly,the weighted digraph was ed from cyber system for quantitative analysis.Then,weights of each edge were calculated based on the reliability impact of cyber system to physical system.After that,concept of effective distance was introduced to evaluate the closeness centrality via effective distance for each node,which can quantificationally analysis cyber device importance from the view of load loss.Using complex network theory,a CPPS model,which consists of cyber layer,physical layer and cyber-physical interface is presented.Considering power flow properties,the impacts of cyber node failures on the cascading failure propagation process are studied.Moreover,two vulnerability indices are established from the perspective of both network structure and power flow properties.A vulnerability analysis method is proposed,and the C.PPS performance before and after cascading failures is analyzed by the proposed method to calculate vulnerability indices.In the case study,three typical scenarios are analyzed to illustrate the method,and vulnerabilities under different interface strategies and attack strategies are compared,and the effectiveness of proposed framework is exhibited.