Study Of Eliminating Harmonic Currents For Pure Electric Bus Charging Station With New Harmonic Suppression Transformer

With the increasing depletion of petroleum and exacerbation of environmental pollution,it needs a significant reduction of petroleum consumption in the near future.As for the transportation,electric vehicle is believed to be the best solution.The popularity of electric vehicles can be expected.The development of the electric vehicles is inseparable from the popularity of electric vehicles charging stations.The electric vehicle charger,which is the core equipment of charging stations,is a typical nonlinear device and will result in harmonics pollution.With large-scale operation of electric vehicle charging stations in the future,it will make a serious harmonic pollution to the utility grid system.They present a potential problem to the utility grid system in the forms of harmonic currents.So it is very necessary to do the research on harmonic characteristics of electric vehicle charging stations and give the available program of harmonic suppression.This paper,by taking Matlab/Simulink software as simulation tools and pure electric bus charging station as the study object,is committed to using the New Harmonic Suppression Transformer(NHST)which is based on Inductive Filtering Theory to eliminating harmonic pollution in pure electric bus charging stations.The main contents are as follows:(1)The basics of the electric vehicle charging stations basics is introduced,including the wiring of distribution system wiring and charging mode of pure electric bus charging station.The modeling solution of three-phase high frequency charger is finished by replace the high-frequency power conversion section with the equivalent variable resistance.The harmonic generation mechanism and characteristics of the three-phase high frequency charger and the 12-pulse rectifier circuit are analyzed.(2)The basic harmonic suppression mechanism and realization conditions of the NHST are analyzed base on the single-phase harmonic equivalent circuit.The wiring schemes and reactive power compensation principle of NHST which are applicable for 6-pulse charger and 12-pulse charger are proposed respectively.(3)A new pure electric bus charging station topology which is built by 12-pulse DC power supply system based on NHST is proposed and its and its advantages are analyzed.Unlike conventional charging stations,the new topology is the DC bus structure,which can reduce the harmonic currents and the charger energy conversion,and can more easily access distributed new energy.(4)Matlab/Simulink simulation models of the pure electric bus charging stations traditional topology based on the traditional transformer and the traditional topology based on the NHST are designed and the simulation is conducted.Simulation results show that the NHST is very effective in eliminating harmonic current at the pure electric bus charging stations.The novel pure electric bus charging station topology based on the 12-pulse DC power supply system consisting of NHST is simulated.The simulation results show that effect of the novel charging station topology on harmonic suppression is better than the traditional charging station topology.