Research And Design Of On-board Charger For Pure Electric Buses

In the context of traditional electric buses facing high charging costs and short driving range,the new online charging type of pure electric bus comes into public view.In order to realize the charger to efficiently and stably charge the pure electric bus online,this paper takes the on-board charger as the research object and designs a 60 KW pure electric bus onboard charger that adapts to wide range DC input and strong transient disturbance.First In the context of traditional electric buses facing high charging costs and short driving range,the new online charging type of pure electric bus comes into public view.In order to realize the charger to efficiently and stably charge the pure electric bus online,this paper takes the on-board charger as the research object and designs a 60 KW pure electric bus on-board charger that adapts to wide range DC input and strong transient disturbance.Firstly,by analyzing the national standard requirements of electric vehicle conductive on-board charger and the relevant design parameters of on-board charger produced by domestic and foreign manufacturers,the main technical indexes of on-board charger designed in this paper are determined,the overall structure block diagram of 60 k W on-board charger is designed,and the charging method of on-board charger designed in this paper is determined.Due to the use of the power supply of the road network(the variation range of DC bus voltage is 400-750v)as the energy input,the sliding contact network line will produce disorderly high voltage.At the same time,during the driving process of the pure electric bus,the DC voltage loaded into the on-board charger will cause frequent power failure or instant power on due to poor contact or disconnection of the sliding contact.To solve this problem,a voltage rise and fall circuit is adopted to realize a wide range of stable input and output of power supply voltage;The latter part adopts ZVS-PWM shift full bridge converter to realize soft switching,so as to effectively suppress the peak voltage of the power switch,make its work more stable and greatly improve the working efficiency of the whole machine.Secondly,the working principle and main circuit control strategy of buck boost voltage rise and fall circuit are deeply analyzed,and a PWM sliding mode controller based on piecewise power approach rate is designed.Based on the working principle of the basic circuit of ZVS-PWM phase-shifting full bridge converter,the main circuit parameters of ZVS phase-shifting full bridge converter are calculated,and the buck boost circuit and ZVSPWM phase-shifting full bridge converter are modeled and simulated by MATLAB simulation software,and the accuracy of the design is verified by simulation.Finally,the 60 KW vehicle charger prototype was tested and analyzed to show that the designed vehicle charger can achieve constant voltage and constant current charging,and the charging efficiency of the charger can always be maintained above 90% with the change of input voltage,which is in line with the design expectation.