Vulnerability And Resilience Analysis Of Distribution Network Under Earthquake Disasters

In recent years,earthquake disasters have occurred frequently all over the world,and China is one of the countries suffering the most from earthquakes.As a lifeline system,the power system is vulnerable to the earthquake,which will cause great direct or indirect economic losses.The distribution network is more vulnerable than the transmission grid.The earthquake disaster has a great impact on the distribution network,which will cause a large-scale blackout.The highly resilient distribution network can flexibly change its topological structure and operation mode,and can effectively deal with the low-probability-high-loss extreme disasters such as earthquakes,and quickly restore power supply after the disasters to reduce the impact of disasters on the distribution network.This thesis has done the following works on the vulnerability and resilience analysis of distribution network under earthquake disaster:(1)Taking the distribution network under the earthquake disaster as the research object,the earthquake disaster scene is modeled at fisrt.Considering the characteristics of the distribution network in earthquake-prone areas and the difficulties of uniform calculation of the line vulnerability,the distribution network area is divided into multi grids.Secondly,the magnitude of ground motion in each grid is calculated on the ground motion attenuation equation,and then based on the reliability model of the distribution network line following Weibull distribution and the vulnerability model of the distribution network line under earthquake disasters,the comprehensive failure rate model of the distribution network line is established.(2)Firstly,the risk assessment indexes of the distribution network are constructed from the perspective of graph theory.The network centrality of the complex network theory is used to describe the topological relationship and power flow of the distribution network.Risks of the distribution network under earthquake disasters are assessed to analyze the degree of the influence on network connectivity.The key lines set of distribution network is identified.Secondly,in view of the fact that earthquakes are extreme events with small probability and disaster data is difficult to be obtained,information entropy is used to reflect the uncertainties of the system.At the same time,the scenario with the highest entropy probability is taken as a typical fault scenario,and the corresponding set of vulnerable lines is selected.(3)The model for the resilience improvement measures which include line reinforcement and the optimal configuration of distributed power sources is set up and transformed into a two-stage integer linear programming problem.The total investment cost is minimized in the first stage.And the resilience evaluation index of the distribution network,calculated on the trends of the system function curve in a disaster,is maximized in the second stage.Finally,taking the IEEE33 bus test system as an example,the resilience analysis of the distribution network under earthquake disasters is carried out.The resilience indexes of the distribution network before and after the resilience improvement measures are compared to verify the feasibility of the proposed method.