Analysis Of Harmonic Characteristics In Electric Vehicle Charging Station And Suppression Strategy

As one of the applications of clean energy,electric vehicles(EVs)have the advantages of energy savings and environmental protection and are an important means to solve the problems of air pollution and energy security.With the development of the electric vehicle industry,EVs and their basic charging facilities are becoming increasingly popular.Because the EV charger contains a large number of nonlinear components,a large amount of harmonic current will be injected when it is connected to the grid with high permeability.This may reduce the power quality of the power system and pose a serious harmonic threat to other devices in power grids.Therefore,it is of great practical significance to analyze the harmonic characteristics in the charging process of EV charging stations and take effective harmonic suppression measures.First,the principle of the EV charger is described.Based on the comprehensive analysis of many kinds of chargers in the current market,it is determined that the charger in the charging station is an active power filter(APF)compensation charger and PWM rectifier charger.Then,the Fourier transform method is applied to theoretically analyze the harmonic characteristics of the selected charger,and the harmonic variation law of the charging station in the whole charging cycle is studied.In addition,the simulation model of the charging station is built in MATLAB/Simulink,the harmonic characteristics of the charger are verified by simulation,and the changes in the total harmonic distortion rate(THD)in different charging stages are analyzed.Second,aiming at the harmonic characteristics of the EV charging station,especially the continuous increase in the THD of the charging station in the constant voltage stage,the advantages and limitations of various harmonic suppression methods are analyzed.Harmonic cancellation based on harmonic complementary characteristics is selected as the harmonic suppression method.It can not only solve the problem of harmonic increase in the constant voltage stage but also save investment.The harmonic cancellation caused by the type,service time,initial charge state and power of chargers are analyzed.Then,the influence of the above factors on harmonic cancellation and the effectiveness of the proposed suppression method are verified by simulation.Finally,the influence of harmonic suppression on the configuration proportion of chargers in charging stations is considered.In the case of charging with the most severe harmonic pollution in the charging station,the harmonic cancellation of the charging station is analyzed in detail in the aspects of different quantity ratios and power ratios of the APF compensation charger and PWM rectifier charger.Then,the variation law of the THD is studied,and the proportion of each charger in a charging station is determined.The correctness of the analysis results and the feasibility of charger planning are verified by simulation.This work contributes to the design and construction of practical charging stations.