Research On Two-stage Vehicle Charger Based On Soft Switch Technology

Facing the increasingly serious problems of global primary energy depletion and environmental pollution,electric vehicles have ushered in a new stage of rapid development due to their energy-saving and environmental protection characteristics.As an important power component of electric vehicle charging system,on-board charger also ushers in new development opportunities.In recent years,the performance of on-board charger is constantly improving and gradually becoming reliable The rapid development of high performance,high efficiency and small size has played an important role in the promotion and popularization of electric vehicles,so the research value of on-board charger is still great.According to the relevant standards of electric vehicle charger,this paper defines the vehicle charger as a two-stage structure and determines its power level as 3.3kw.Among them,the front stage AC / DC system of the on-board charger is selected as passive lossless soft switch boost PFC circuit is used to improve the power factor of the system and reduce the system loss.Full bridge LLC resonant converter is selected as the back stage DC / DC system of the vehicle charger.Due to the introduction of soft switching technology,the latter stage system can realize the wide range adjustment of output voltage and effectively reduce the switching loss of the system.The control strategy of the latter stage system is frequency conversion and fixed width control,and the voltage loop and current loop are designed to adapt to different charging modes.For the former AC / DC system,this paper analyzes the working principle of the passive lossless soft switching boost PFC circuit,analyzes the stability and anti disturbance ability of the single cycle control technology,designs the parameters of the main components of the main circuit,and designs the control part of the system.For the later stage DC / DC system,this paper analyzes the working principle of the full bridge LLC resonant converter,uses the fundamental wave analysis method to model the system,then analyzes the voltage gain characteristics of the system and divides the working area of the system.After that,the parameters of the main components of the converter are designed,and the design of the control part is completed by establishing the small signal model of the system.Finally,the simulation models of passive lossless soft switching boost PFC circuit and full bridge LLC resonant converter are built in Matlab / Simulink software to verify whether the designed vehicle charger system meets the relevant standards.The simulation results show that the power factor of the front PFC circuit is close to 1,and the harmonic distortion rate of input current is far less than 5%.The back stage DC / DC circuit can adjust the output voltage in a wide range,and the voltage ripple is small.The application of soft switching technology makes the system more efficient,which verifies the feasibility of the designed vehicle charger.Figure [82] table [7] reference [66]...