Research On Two-stage Electric Vehicle On-board Charger

Nowadays,the development of the world economy is accompanied by the depletion of fossil energy and serious environmental pollution.These problems have made the traditional automobile industry face a new challenge of development.Because of their zero-pollution characteristics,electric vehicles conform to the concept of low-carbon travel advocated by modern society,which means that their development speed can also become faster and faster.Power batteries,used as power sources by electric vehicles,can be provided with energy by on-board chargers.Considered as the key technology,charging technology has played an important role in the development of electric vehicle industry.Therefore,the research and design of a high-performance on-board chargers can not only improve the performance and life of power batteries,but also have important and practical significance for the popularization of electric vehicles.After investigating the relevant technical indicators of the on-board chargers,this paper had determined to design a 6.6kW power class on-board chargers.Because the input end of the on-board chargers was directly connected to the power grid,the designed charger had adopted two-stage power conversion structure in order to meet the requirements of input current harmonics,power factor and output voltage range.The front stage had adopted three-phase staggered parallel Boost power factor correction circuit to improve the power factor of charger and reduce the pollution of power grid in the process of using.Based on average current control,the design of the control loop had adopted double closed-loop control strategy of voltage outer loop and current inner loop.The latter stage had adopted full bridge LLC resonant converter topology to meet the requirements of wide range output voltage and low output voltage ripple.And by parallel connection of two-phase LLC converter,the high conduction loss problem in high power applications had been solved,and the maximum carrying capacity and efficiency had also been enhanced.Based on PFM control strategy,LLC control loop had introduced Current loop and voltage loop to compete.And by comparing the switching frequencies of voltage loop and current loop,constant voltage or current output had been controlled to meet the current and voltage requirements of power batteries in different charging stages.In this paper,the working principle and characteristics of the front-stage staggered parallel Boost power factor correction circuit and the rear-stage full-bridge LLC resonant converter had been analyzed in detail.The design parameters of the main circuit had been given,and the front-stage and rear-stage controllers had been designed.What is more,in the environment of MATLAB/Simulink,the on-board chargers designed in this paper had been simulated under different working conditions.The simulation results had verified the correctness of the theoretical calculation of the main circuit parameters,completing the relevant design requirements.Figure [91] Table [6] Reference[63]...