Research On Fault Location,Recovery And Reconstruction Of Distribution Network Based On Improved Whale Algorithm

With the aggravation of global environmental problems and the shortage of traditional fossil energy supply,Distributed Generation(DG),which is mainly based on photovoltaic power generation and wind power generation,has been widely concerned by all countries as an energy shortage solution.In 2020,China clearly put forward the goal of "double carbon",and DG,which is mainly based on new energy,will be vigorously developed in China.Generally,a single distributed power supply has a small capacity,and it enters the main network by accessing the distribution network or is directly supplied to users.With the increasing number of DG access and wider distribution,the distribution of power flow in distribution network is complicated,and the direction of current is no longer single direction when a fault occurs.Therefore,it is of great significance to quickly locate and isolate the fault section of distribution network for power supply recovery of power system.The traditional fault location method for distribution network with DG is not ideal,and the network loss is large in the process of fault recovery and reconstruction.Therefore,this paper aims at the distribution network with DG to locate the fault section quickly and accurately and optimize the network index of recovery and reconstruction.The research contents are as follows:(1)Firstly,the research background of fault section location and fault recovery and reconstruction is introduced,and the main factors causing distribution network faults are analyzed,and the shortcomings of existing research schemes are pointed out,which is helpful to formulate effective fault location methods and fault recovery and reconstruction schemes in the following.(2)Then analyze the main types and development status of distributed power supply.According to the grid-connected criteria and network constraints of distributed power supply in various countries,when the distribution network containing DG fails,the grid-connected DG will be removed as soon as possible.Therefore,regardless of the isolated island operation of the distribution network,the distribution network is still radial.Analyze the influence of DG on the relay protection performance of the power system and the location of the fault section of the distribution network,which will pave the way for the following study on the influence of DG on the distribution network in different locations and capacities,and(3)The basic principle of the traditional Whale algorithm is analyzed.Aiming at the problems that the traditional algorithm is easy to fall into local optimum and has insufficient convergence,Sobol sequence is used to generate initial population,adaptively adjust weight and differential mutation perturbation factor to improve the optimization performance of the Whale algorithm.Considering the network structure of China’s distribution network and the characteristics of FTU collecting current information,the switching function and fitness function suitable for DG grid connection are constructed,and the corresponding network model is built.The current information uploaded by FTU is converted by binary coding.The improved whale algorithm is used to solve the fault section of the distribution network model with DG.The simulation results of an example show that the fault location method proposed in this paper can accurately locate the fault section in the case of single fault,multiple faults or distorted current information,which improves the rapidity and accuracy of the whale algorithm.(4)The common power flow calculation methods in power system are analyzed,and different types of DG grid-connected nodes are classified and studied,and the forward pushback method is improved by node stratification to improve the applicability of this method in power flow calculation when the distribution network is connected to DG.The IEEE33-node example model is used to verify the effectiveness of the improved forward push-back method when DG is connected to the grid at different locations and capacities.(5)The improved Whale algorithm is used for fault recovery and reconfiguration of distribution network,and the objective function and constraint conditions of distribution network containing DG are constructed.The node model is simplified by hierarchical partition method,which greatly reduces the complexity of the network during reconfiguration and improves the reconfiguration rate.In the simplified model,the distribution network without DG and DG connected to the grid are studied respectively.The results show that the fault reconstruction method used in this paper can improve the power supply quality and voltage level under single fault and multiple faults,and the optimization effect of reducing network loss is also obvious.