Research On On-board Charging System Of Electric Vehicle Based On Composite Energy Storage

Pure electric vehicles,as the main development object of new energy vehicles,have developed rapidly in recent years.However,the difficulty of charging and the slow charging of electric vehicles have always hindered the further promotion of electric vehicles.At the same time,the frequent start-up,acceleration and braking of electric vehicles with single battery energy storage will have adverse effects on the service life of batteries under complex conditions.Therefore,this paper designs a high-power factor and high-power vehicle charger based on the composite energy storage of supercapacitor and storage battery.Part of its topology structure is shared with the drive system of electric vehicle.The on-board charging system adopts a two-stage fast charging method,in which the positive and negative pulse charging method is used to charge the batteries rapidly,and the supercapacitor is used to absorb the high-energy and negative pulses emitted by the batteries in the positive and negative pulse charging method,so as to restrain the impact of the high-energy and negative pulses on the sys.At the same time,on the basis of sharing part of the topology structure,the fuzzy algorithm is introduced into the composite energy storage management to smooth the power output of the battery.This article mainly carries on the research and the design from the following aspects:Firstly,lithium-ion batteries are selected as the main energy storage components in this paper.After analyzing the research status of vehicle chargers at home and abroad and referring to the technical specifications of vehicle chargers issued in China,the three-stage switch structure is adopted in the vehicle charging system in this paper.The front stage is a three-phase voltage-type SVPWM rectifier with APFC function,the middle stage is a phaseshifted full-bridge ZVS converter with electrical isolation and soft-switching function,and the latter stage is a compound energy storage bidirectional DC/DC converter designed in this paper.Firstly,the three-stage switch structure of the vehicle charging system is analyzed and designed.The working principles of three-phase voltage-type SVPWM rectifier and phaseshifted full-bridge ZVS converter are analyzed respectively,control modes of which are feed-forward decoupling SVPWM control based on two-phase rotating coordinate system and average current double closed-loop control.Then,the parameters are calculated separately.The latter stage converter is a common topology between charging system and driving system.Aiming at the latter stage converter as charging system,the working principle and control mode of charging stage are analyzed,and the parameters are designed.The working principle and corresponding control mode of the post-stage converter at driving state are analyzed separately.At the same time,two fuzzy controllers are designed to smooth the output power of batteries and reduce the adverse effects of excessive output current on batteries under two special working conditions of electric vehicles.The on-board charging system is simulated and validated by the simulation software of MATLAB/Simulink.The results show that all levels of switches in the charging system achieve their specified design goals.The input voltage and current of the network side remain in phase with a power factor of 0.995.In the charging stage,the high-energy negative pulse emitted by the battery can be absorbed by the supercapacitor,which can effectively prevent the system voltage production.In the driving stage,two fuzzy controllers can operate normally and smooth the output current of the battery under two special working conditions.