Research On Efficiency Of Wireless Charging System For Electric Vehicle

The large-scale popularization of electric vehicles will help alleviate the environmental pollution and energy shortage.The lack of charging pile has seriously limited the popularization of electric vehicles.Compared with the traditional wired charging pile,the electric vehicle wireless charging system has the advantages of small occupation area,high safety and high intelligence level,and can speed up the popularization process of electric vehicles.However,the wireless charging system is still faced with the problem of low charging power and low charging efficiency.It is of great practical significance to study the transmission characteristics of wireless charging system for electric vehicles.In this paper,we study the principle of resonant wireless charging system,and find the parameters that affect the transmission power and efficiency.Based on the analysis of the relationship curves between different parameters and transmission performance,the two most important factors that affect the performance of the system are the magnetic coupling structure and the system control strategy.By means of ANSYS electromagnetic simulation software,this paper Modeling the magnetic coupling mechanism which has different coil shape,different coil size and has magnetic core or not.Draw the change of coupling coefficient with the horizontal offset.The magnetic coupling structure with better performance is selected to provide guidance for the construction of the experimental platform.In this paper,the Simulink simulation model of the wireless charging system is established,which is based on the voltage regulation control strategy,the frequency modulation control strategy and the duty cycle control strategy,the transmission characteristics of the system under different control strategies are obtained.This paper focuses on the frequency splitting phenomenon of frequency modulation control strategy.In the process of building the experimental platform,this paper discusses the design process of DC chopper link,full bridge inverter,magnetic coupling mechanism,high frequency rectifier,power switch driver circuit,analyzes and explains the selection of the inductor core material,the type of the diode,the type of the power switching device and the selection of the coil conductor.The control circuit of the system is developed by using STM32f407 chip,and the control system of the device and the battery management system(BMS)are connected by wireless communication system.In the experimental part,the maximum transmission power of the system is about 6kW,and the maximum transmission efficiency is about 90%under the vertical interval of 20cm.Through the experimental verification of the simulation conclusion above the magnetic coupling structure and control strategy,puts forward the method of further improvement and perfection.