Design Of Wireless Charging System For Electric Vehicles

Electric Vehicles(EVs)are becoming the focus of the entire automotive industry.As energy and environmental issues become more prominent,the replacement of traditional fuel vehicles by EVs has become a historical necessity.A series of problems in EV charging has been exposed,which has become an obstacle to the EV market.Therefore,Wireless Power Transfer(WPT)technology has been introduced into EV charging.Since auto parking and autopilot technologies are mature,the demand for wireless charging is growing.However,there are still many problems with the current wireless EV charging(WEVC)technology.For example,the relative position of the vehicle and the launching device and the state of charge(SOC)of the battery can make a significant impact on the charging process,and even destabilize the charging process.Therefore,before WEVC technology fully enters the market,there are still many problems to be studied.This paper aims to solve the problem that the mutual inductance and load change caused by the relative position and battery's SOC in WEVC system affect the output characteristics of the system(mainly the charging current),and the design method of WEVC system is studied..Firstly,the mutual inductance coupling model of wireless charging system is established.The series-series compensation is selected as the resonance compensation topology.The relevant circuit characteristics of the topology are derived.Based on this,the output characteristics of the system are studied with the mutual inductance and load.The shortcomings of the open loop system are pointed out.Secondly,the theoretical and simulation analysis of the working states of several DC-DC converters(Buck,Boost,Cuk,etc.)widely used in the field of power electronics are carried out,and the similarities and differences between the application of Buck and Boost converters in the system are compared.The Buck converter is selected as the charging controller from the perspective of system optimization.Thirdly,the adaptability of different structure magnetic couplers with different transmission positions and distances is studied.The guidelines for the magnetic coupler design are summarized.With the aim of the stability of the coupling coefficient,the coil and core configuration of the magnetic coupler are optimized,and a magnetic coupler with the flat core is designed.Finally,to validate the theory and simulation,a 500W prototype is built.The operating frequency is 85kHz.The transmitter dimension is 400mm*400mm,and the receiver dimension is 3 80mm*380mm.Through the experimental results,the system can achieve 4A constant current charging within 100mm offset and 10-25? load variation.