Research On Distribution Network Vulnerability With Load Fluctuation

As the end power network unit of the whole power system network,distribution network is responsible for the distribution of electric energy according to the needs of users.When the vulnerable lines or nodes in the distribution network fail,the security and reliability of the whole distribution network will be affected.If not found and repaired in time,it is likely to expand the scope of the fault,and eventually lead to blackout.At present,the research on the vulnerability of power grid is mostly carried out in large power grid,and the research on distribution network is just starting,so it is necessary to analyze the vulnerability of distribution network.At the same time,in the real distribution network,the connected load is changing with time,which will lead to the redistribution of system power flow,thus affecting the safety of each branch.Therefore,through accurate load forecasting,the vulnerability of distribution network is predicted so that the operation and maintenance personnel can take protective measures for vulnerable lines in advance.(1)This thesis discusses the application of complex network theory of transmission network,analyzes the structure and operation characteristics of distribution network,and establishes a network model suitable for distribution network structure.The model can reflect the network topology of distribution network.The simulation results show that the distribution network model established by the theory is reasonable in theory.(2)In this thesis,four evaluation indexes of branch power flow active power degree,branch power flow active electrical intermediate number,branch static voltage stability index and power to flow impact vulnerability are proposed to two aspects of structure and state respectively.A kind of weight of vulnerability index is calculated by AHP based on expert experience knowledge,and the entropy weight method is used to analyze the trend contained in the index value Information to calculate another kind of index weight.Through the game theory,the comprehensive weight are calculated,and the comprehensive vulnerability of each line are calculated combined with the index data,which makes the evaluation results more accurate.The experimental data show that the method used in this paper can identify the vulnerable lines more comprehensively,and make up for the shortcomings of single index in the system vulnerability assessment.(3)The change of load will lead to the redistribution of power flow,which will lead to the change of power grid vulnerability.Therefore,to forecast the load in a certain period of time,analyze the system powers flow through the predicted value,and predict the vulnerable points of the power grid in advance,so that the maintenance personnel can deal with the power grid failure caused by the future load changes.This is of great significance of the safe and stable operation of power grid.In this paper,the improved grey Markov forecasting model based on particle swarm optimization is used to predict the load value in the future.The simulation results show that the predicted value of the method can change the load in real time,and make the prediction result more accurate.This makes the predicted value closer to the real value,which makes the vulnerability prediction of distribution network more accurate.