Cascading Failure Modeling And Reliability Analysis Of Power Cyber-Physical System

With the promotion of Smart Grid and the development of i nformation technology,the data acquisition,transfer and control are more and more frequent.The power physical system is more connected to the cyber layer,and the power grid is evolving towards power cyber physical system.At present,the cyber-physical coupling has not been fully explored yet,the security and stability of power grid brought by cyber-physical function has been highlighted.More and more studies show that many blackouts are related to the information systems.The security and stability of power cyber physical system should be evaluated from the whole point of view.Based on this,the power cyber physical system is discussed from two aspects in ou r paper: the modeling of cascading failure between networks and the reliability analysis.The main work is as follow:First,the concrete integration framework of power cyber physical system is summarized and the research object is concretized.In the modeling of cascading failure,a one-to-one coupling topological model of nodes between networks is established,the evolution process of cascading failure is analyzed based on the theories of interdependency and percolation,the difference of fault evolution between one-to-one coupling and multidependency coupling is compared and multi-coupling interaction model is proposed.In the reliability analysis,the model of component failure is screened and the basis of component level reliability analysis is established,the basic methods of reliability analysis is compared and the applicability of Monte Carlo method is illustrated.Second,considering that the existing models can not reflect the redundant links between networks,a cascading failure model based on control threshold is proposed,and the solution process of percolation critical value is deduced theoretically.Two robustness factors,the number of dependency links and control threshold,can describe the control function from cyber nodes to power nodes.Based on this model,the remainding nodes and the proportion of gaint connected graph via the ratio of initial attacking nodes in the coupling topology Small World network-Small World network,Small World network-Double Star network,are simulated.The results show that the proposed model can beter describe the coupling mechani sm between networks in the cascading failure process.The results also reveal the influence on the percolation of the network topology,it is beneficial for improving the robustness of power cyber physical system.Finally,the Substation Automation System based on the IEC 61850 standard is selected for a typic power cyber physical system,the reliability analysis method of power cyber physical system is discussed.The impacts caused by cyber components to main physical equipment are classified.The cyber-physical interface matrix is proposed to measure the probability of that impacts.Then,the reliability analysis method of the substation considering the impacts of cyber layer is put forward based on the interface matrix.And the calculation of actual substation shows that,the failure in cyber layer obviously increases the power loss of whole system,while it has relatively small impact on the risk of cascading failure.Finally,the sensitivity analysis of information transmission delay is implemented.The changing magnitude of expected demand not supplied increases significantly with the increase of transmission delay rate of process bus.