Research On Cyber-Physical Fusion Based Analysis And Risk Assessment For Active Distribution Network

Power cyber physical system features in combining the information communication network,data processing,computational analysis and physical system dynamics,which greatly improves and contributes to analyatic precision,optimal decision making and control,self-adaptivity to complex scenarios of power grid.Traditional classic theory and method architecture of power system have not been established in a view of cyber and physical fusion system,in which the complex interaction mechanism between cyber and physical space has not been considered,and the association between heterogeneous systems is dissevered and isolated.Research on the theory and methodology architecture of power cyber physical systems is necessarily needed in order to improve safety,reliability and economical efficiency of the power grid in complex time-varying stochastic scenarios.This paper mainly studies the dynamic power flow,operation scenarios analysis and risk assessment of active distribution network in the context of cyber physical fusion.For active distribution network,a novel dynamic power flow method is proposed including the mixed logical dynamics model of energy stortage.The solving method and iterative mechanism are also presented.By implementing the analysis of system’s power flow distribution under multiple time-varying scenarios in continuous time period,credible capacity evaluation of intermittent distributed energy resources’ active power output is derived.And it also helps contribute to an accurate operation analysis under steady-state and inherent characteristics exploring of active distribution network under multiple stochastic time-varying scenarios with multivariable and strong uncertainty.For active distribution grid,probabilistic operation scenarios with limited number are determined according to the statistics of intermittent distributed energy resources fluctuation rate,and contingency states coupling of cyber systems and physical network.The probability of these scenarios are calculated in terms of the probability sequence format.Combining with practical physical meaning,random sequence theory is used to calculate the distribution network’s stochastic time-varying operation scenario set of intermittent power sources contributed fluctuation scenario and security risk scenario in power cyber physical network.By utilizing the scenario tree approach,it quantitatively analyzes the evolution of uncertain scenario while the computation complexity has been reduced.Besides,the corresponded local area power consumption capacity and security operation states during scenario evolution have also been analyzed.Probability model of risk considering its categories in cyber space is proposed.Based on attack graph,mechanism and process of risk conduction are studied,calculation model of risk conduction path randomness and node vulnerability is proposed.A risk index architecture of active distribution network is established combining risk factors from cyber and physical system,including overload,voltage violation,distribution generation and trans space cascading failure risk.Detailed risk evaluation model is proposed.According to the combinations of security boundary condition based on risk indexes,operation state of distribution network considering risk of cyber physical fusion system is determined.Analysis of risk state transition and risk warning mechanism are established and described based on event-driven hybrid system model.