Research On LCC-S Compensation Topology In Wireless Power Transfer System For Electric Vehicle

In order to alleviate environmental pollution and resource shortages,various countries are actively promoting the development of electric vehicles(EV).Electric vehicles have the advantages of zero emissions,low noise,and energy saving.However,the range anxiety and the difficulty of charging are still the major barriers to the popularity of the EVs.The wireless power transfer(WPT)technology is preferable for EVs due to its advantages of convenience,reliability,and security.At present,wireless charging technology has not developed in high-power battery charging for electric vehicles.Thus,a LCC-S compensation topology in wireless power transfer system for electric vehicle was studied.Firstly,the principle of the inductive wireless power transmission system is analyzed.Wireless EV charging system is based on the principle of electromagnetic induction to achieve power transmission.Then,the characteristics of the wireless power transmission system are discussed,including reactive power compensation,output characteristics,the effect of mutual inductance on power and efficiency,as well as frequency bifurcation.Secondly,based on fundamental harmonic approximation(FHA),the analysis of the LCC-S compensation topology is presented,and the basic characteristics are described.The operation modes based on steady-state analysis are discussed.With the proposed method,the current on the transmitter coil is constant,irrelevant to coupling coefficient and load condition.When the WPT system works on the resonant frequency,it can realize power transfer on different operating conditions by controlling the input voltage.A numerical method of tuning the circuit to realize zero-voltage switching(ZVS)is introduced.According to the influence of dead time on soft switching of power converter,the main circuit parameters of the converter are optimized.Thirdly,in order to verify the correctness of theoretical analysis,a Buck converter is established to adjust the output voltage on load accurately.A reasonable digital controller is designed,thus realizing the closed-loop control of the system.Circular couplers are the most common topology in the literature;however,they have fundamentally limited coupling.A double D(DD)pads can provide larger charge zone than that circular pads for a similar material cost and are smaller.This paper proposes a new design and control method which makes it possible to implement the CC/CV mode charge during all over the charging process.The wireless charging system with the proposed integration method is able to transfer 1.5 kW(overall dc to dc)at an air gap of 150 mm,the maximum efficiency is 91.4%.