A Study On The Harmonic Based On Large-scale Electric Vehicle Charger

Electric Vehicles have the advantages of less pollution, lower energy consumptionand lower noise than the traditional cars, it is of great significance to the environment,energy and power system. So the promotion of Electric Vehicles is imperative. However,The power quality is impacted by harmonics generated by the charging machine, becausethe charging machine contains a lot of power electronic devices, which presents nonlinearcharacteristics. It will produce harmonic pollution in the distribution network, and makethe power factor decreasing. Therefore, the study on the harmonic of Electric Vehiclechargers is of practical significance.In this paper, Matlab/Simulink is applied to building the simulation model of theElectric Vehicles charging machine(station), analyzing the harmonic characteristics; Then，the work is to compare simulation results between different situations, make reasonableassumptions and quantize the harmonic current and power factor. On this basis, dependingon constraints and the corresponding objective function, build the optimization model ofElectric Vehicle charging combination; Thus obtain charging combination meeting theobjective function and constraints, and finally verify the charging combination.Firstly, introducing the charging mode and the type of charger, analyzing theharmonic characteristics of electric vehicle charging machine in theory and the effects ofharmonics on power system.Based on the principle of charging machines, using the power system simulationsoftware Matlab/Simulink, to build6-pulse uncontrolled rectification charger models. Onthis basis, study the variation of each harmonic current, each harmonic ratio and the totalharmonic distortion. The main simulation is to analyze the harmonic current variation withcharger number and Electric Vehicles mixing charging of different starting battery.According to simulation data of the electric vehicle charging station, analyze theharmonics and power factor varing with different charging periods and quantize theharmonic current and power factor； Depending on the constraints and the correspondingobjective function, build the optimization model of Electric Vehicle charging combination and obtain the optimal charging combination of Electric Vehicles. The paper verifies thevalidity of the charging combination with two methods. The first one is to comparevariation of harmonic currents and power factor by appling Matlab/Simulink simulationmodels to make simulation analysis; The second one is to analyze and compare by usingthe established mathematical model, which will stand up for the control strategy ofElectric Vehicles charging in large scale.