| The carbon control targets of "carbon peak" and "carbon neutralization" have a profound impact on the development of China’s energy structure and energy system.Under the background of energy policy,smart grid,flexible grid,transparent grid and other new concept grid become the future development direction of power system.In this development trend of power system,the application depth and breadth of information technology,communication technology and electronic control technology have been greatly strengthened.With the increasing dependence of physical system on cyber system,power system has gradually become a typical cyber-physical system.The fault of cyber system will have a negative impact on the operation of physical system,including the process of fault handling.Therefore,it is necessary to consider the process of cyber-physical interaction in the reliability evaluation.Aiming at the reliability assessment of stock distribution network,this paper firstly proposes reliability models of system components based on the common structure of cyber-physical system of distribution network,especially the more detailed modeling of three-state or five-state for three types of IEDs which are cyber-physical coupling components.A reliability model that considers topology and time delay is established for the communication link of cyber system,and is integrated into the working characteristics of IEDs to realize decoupling between cyber system and physical system.Furthermore,a calculation method of the time that conforms to actual fault handling process is given.Based on the full binary tree,the fault handling and failure consequences of IEDs under different failure scenarios are analyzed.Then,the above results are summarized as the law of information failure’s influence on fault processing time and fault consequence,which is applicable to all open-loop distribution network topologies.This law considers the fault handling process involving human and machine participation,and transfer capacity constraints.In the end,an elaborate evaluation process of reliability of cyber-physical system in distribution network is given based on Monte Carlo method.And the following simulation analyzes the impact of cyber failure on power supply reliability in detail,which also verifies the effectiveness and practicability of the proposed method.As for the reliability evaluation problem in distribution network planning,the following section proposes an optimization model to explicitly evaluate the reliability of the distribution network considering cyber-physical interaction.At first,a general topology abstract model is given for cable network and overhead network of distribution network.After that,an explicit reliability evaluation optimization model is formed,and the big M method is used to linearize the nonlinear constraints.Among them,the optimization goal is to minimize power outage areas,the key optimization variables are switches’ states and virtual power flow,and the constraint conditions are set to consider the three stages of fault handling with distribution automation participation.More and more,this section considers three types of failure scenarios,including malfunction of the automation terminal,physical system failure and control/communication failure of automation terminal at the same time,physical system failure and misjudgment/miss-judgment failure of automation terminal at the same time.Through the analysis of these failure scenarios,the principle of fault equivalence is concluded and the modification constraints of the optimization model are given.Finally,the proposed model is solved by gurobi.The influence of reliability modeling and system switch configuration on reliability index is studied in 37 bus system.Besides,the versatility and calculation speed of the proposed model are verified in 6 distribution network systems of different scales. |
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