Research On Active Distribution Network Fault Restoration Method Considering Resilience Improvement

With the increasing frequency of global extreme natural disasters,distribution network is vulnerable to the impact of catastrophic events,which leads to large-scale,long-term blackouts.How to use the characteristics of flexible resource decentralized supply,from the perspective of resilience restoration,to explore the decision-making methods and implementation strategies of fault restoration after extreme disasters,is the urgent task of current research on distribution network fault restoration.The main work of this paper is as follows:Firstly,the path planning method based on graph theory and the related algorithm for solving the shortest path are introduced,which are used to optimize the restoration path and dispatch the emergency power supply vehicle(EPS);A mixed integer linear program(MILP)method for solving the distribution network fault restoration model is introduced.In order to solve the problem that is difficult to deal with in the optimization solution,the nonlinear constraint linearization method is proposed,which lays a foundation for the follow-up research of distribution network fault restoration.Secondly,in view of the problem that the superior power grid cannot usually restore the power supply to the interrupted load in time after the extreme disaster,flexible resources such as microgrid and EPS are introduced to support the restoration of the distribution network.The access of distributed generator(DG),microgrid and EPS improves the ability of continuous power supply for critical load,but also makes the fault restoration of distribution network more complex.Aiming at the variability and scarcity of generation resources,the optimization model of priority to restore critical loads by using microgrid is established.The reserve capacity state is incorporated as constraints of the restoration problem to ensure that restored critical loads can have a continuous power supply.In addition,due to the limitation of the service capacity of the microgrid,an EPS scheduling method that considers optimal driving path and restoration cost is established,thereby reducing the loss of load outage.The original mathematical model is treated nonlinearly by using big-M and other technologies,and the MILP method is used to solve the distribution network restoration model.Finally,in order to maximize the resilience of the distribution network after the disaster,a hierarchical service restoration method considering the resilience enhancement is proposed.For the evaluation of system resilience in restoration stage,the resilience index considering the economic benefits of distribution network is defined.Based on the restoration of all critical loads,a third-level restoration model with the maximum resilience metric as the objective function is established to guide the restoration of noncritical loads in each period.Considering the fluctuation of DG output,the resilience metric is regarded as a random variable,and non-parametric kernel density estimation method is used to comprehensively evaluate the contribution of restoration strategy to the improvement of system resilience.The PG&E 69-node feeder system is used to verify the effectiveness of the hierarchical service restoration method.