Optimum Design Of Resonant Coils For The Electric Vehicle Wireless Charging System

With continuous breakthrough of the wireless power transmission technology based on magnetic coupled resonances,the optimization design schemes of various parts of wireless charging System has been followed up.As a key component of the wireless charging System,the magnetic coupling structure is of great significance to improve transmission performance of system,especially in high-power magnetic resonant wireless power transfer systems such as electric vehicles,resonant coils usually have a large transmission distance because of their inherent characteristics,which results in a smaller coupling coefficient and a larger leakage inductance.A smaller coupling coefficient is bound to limit the transmission efficiency,resulting in a large magnetic field leakage,and a certain electromagnetic interference to the surrounding space and environment.Therefore,it is very important to optimize the design of magnetic coupling structure.First of all,as for characteristics of the relatively small coupling coefficient and the large leakage of magnetic field of resonant coils in high power wireless charging system,considering resonance coils and the core structure of magnetic coupling structure,a complete optimization scheme of resonant coils is proposed through derivation and analysis of formula after the circuit theory and electromagnetic field theory is used to model.In addition,the transmission direction of the system is also studied.Secondly,based on the proposed optimization scheme of resonant coils,parameters of coils are designed and transmission efficiency is optimized through the finite element analysis software,a set of optimal coil parameters is obtained,and this group of parameters can make the system get higher transmission efficiency.Then,based on the finite element software,a three-section non-uniform core optimization scheme is put forward under the constraint condition that the hysteresis loss is as small as possible,the transmission efficiency is high as possible and the core weight is as light as possible,and core structure after optimizing can not only reduce the core loss,but also increase tolerance of system to horizontal deviation on basis ofsatisfying constraint condition of the system to core weight.Finally,simulation and experimental research of resonant coils are carried out by establishing the whole circuit simulation model of 1kW and 20 kHz high-power magnetic resonant wireless power transfer systems.The simulation results show that the transmission efficiency of the system is higher than 97.4%,which meets the design requirements.