Reliability Modeling And Evaluation Method Of Distribution And Consumption Cyber Physical Systems

Development of microgrid(MG)and active distribution system(ADS)is an important solution for the renewable energy sources(RES)connecting to the main grid and improving the operation efficiency of power system.MG and ADS achieve the coordinated control of various distributed generation(DG)and demand response resources via introducing the intelligent measurement,information communication and control technology,which can increase the consumption of RES,improve the utilization of assets and enhance the reliability and power quality.MG and ADS have also evolved into typical cyber physical systems(CPS).Information and communication technologies guarantee the active operation and control of MG and ADS.However,failure of information system will bring potential negative effects to power system,such as failure of voltage frequency control,failure of protection system,cascading failures and so on.Therefore,according to the concept of CPS,from the perspective of the integration of cyber and physical system,exploring the modeling methods of MG and ADS cyber systems,analyzing the mechanism of cyber physical interaction,quantifying the influence of information system faults on power grid reliability,identifying and improving system weaknesses are significant for MG and ADS to accelerate the development process and guarantee safe and stable operation of power grid.In the active operation process of the distribution and consumption systems,the RES access to the grid,the complex control functions of the system,and the deep coupling of cyber physical systems are gradually presented.These features make the reliability assessment face severe challenges.Therefore,this dissertation focuses on the coupling mechanism of MG and ADS cyber physical systems and its impact on the system reliability and other issues.The main contributions are introduced specifically as follows:(1)Based on the physical system model,information system model and reliability evaluation method of cyber physics hybrid,DG output and load timing models and physical element outage models are established.The fault types of communication link connectivity and transmission validity under different communication modes and communication network structures are analyzed.Based on the adjacency matrix and depth-first search,the communication link connectivity evaluation method is proposed,and the information delay and error are established.The influences of cyber physical fault interaction on reliability assessment is studied.On basis of traditional reliability assessment framework,the reliability assessment architecture for distribution and consumption cyber physical systems is proposed.(2)For the problem that the cyber element of the island MG directly causes the physical element to fail,and the cyber element fault indirectly affects the system reliability through the frequency control process,the direct and indirect effects of the cyber element failure on the system reliability are analyzed,and the cyber and physical faults coupling relationship are established.A quantitative evaluation method for the consequences of system failure under the two types of cyber elements is proposed.Generalized reliability index system is established to represent control failure.Sequential Monte Carlo simulation algorithm based on frequency control simulation is proposed.The simulation results are used to analyze the influence of two kinds of cyber element faults on the reliability of island MG,and a feasible method to improve the control performance of island MG is proposed.(3)The influence of MG protection device failure on system reliability is analyzed and the relationship between protection misstrip failure and misoperation failure on MG is studied.The reliability models for the misstrip failure and misoperation failure of the protection devices are established.A quantitative evaluation method for the consequences of protecting failures is proposed.Considering the economical demand of MG operation and the timing characteristics of controllable micro-source output,a system state generation method based on optimal operation strategy is proposed and a nonlinear optimization model is established.The sequential Monte Carlo simulation method based on the protection system failure consequence model and the optimized operation strategy is used to evaluate the impact of protection device failure on the reliability of the MG.(4)In view of the problem that cyber failure deteriorates system reliability during distribution automation fault self-healing process,the influence of cyber element failure and information transmission delay on distribution automation fault processing is analyzed.An information link reliability model based on hybrid communication network,considering route transfer and access network service load rate is established.The role of information failure in fault location,fault isolation and fault recovery is analyzed,and a quantitative evaluation model for information failure leading to load shedding is established.The reliability assessment method combining physical element failure and information link failure is studied.The influence of information failure on ADS reliability is analyzed by simulation examples.