Control Strategy Research And System Design Of Wireless Charging In Electric Vehicles

Wireless Power Transfer(WPT)technology refers to the wireless connection between power supply and vehicle power battery.There is no direct electrical connection,so the problems such as the interface limitation and the safety problem in traditional wired charging system can be effectively solved.In wireless charging system of electric vehicles,the factors such as coil coupling coefficient,frequency and equivalent load have an impact on transmission characteristics to result in difficult control in the system.In this paper,aiming at Magnetically Coupled Resonant(MCR)wireless charging method which has been widely applied,according to SAE J2954 standard,the control strategy and the system design of the 3.3kw wireless charging system are studied on.(1)The characteristics of typical resonant topological compensation structures of wireless charging system are analyzed.According to the standard SAE J2954,LCCL-S-LCL resonant topology suitable for wireless charging of electric vehicles is selected.The formulas of system transmission characteristics with LCCL-S-LCL topological structures are deduced.In addition,the effects of the factors such as frequency,coupling coefficient and load on the system transmission characteristics are analyzed by use of simulation method.(2)The charging and discharging characteristics of power batteries are studied on,and unilateral control and bilateral control of wireless charging system are compared.An intelligent wireless charging control method based on fuzzy adaptive PID control with bilateral control is proposed.After the fuzzy membership function of normal distribution is determined,the fuzzy control rules are formulated,and the fuzzy reason and the anti-fuzzy calculation are carried out,the intelligent control strategy of wireless charging system is developed.Then the simulation design and the performance analysis of the fuzzy adaptive PID controller are finished.The simulation results show that the system can automatically adjust the PID controller parameters according to the deviation between the reference value and the actual output value.(3)According to the designed control strategy,the Boost type power factor correction circuit,high frequency inverter circuit,resonant compensation circuit,passive lossless soft switch Buck circuit,control and protection circuit including sampling and driving circuit are designed.The control flow of the system is determined.The simulation analysis on the power factor correction circuit and passive lossless soft switch Buck circuit is finished.(4)According to the designed wireless charging system with LCCL-S-LCL type,the system simulation design is finished based on MATLAB/Simulink software.The simulation analysis of the output control effect is completed.In addition,the experimental platform is built.The power factor correction function,frequency tracking function and output control effect are tested.The experimental results show that the proposed wireless charging control strategy and the system design for electric vehicles is possible.