Research And Design Of Wireless Power Transmission Coils For Electric Vehicles Based On Finite Element Analysis

Wireless power transmission has become one of the hot technologies in recent years due to its advantages of convenience and security,and it has great socioecnomic benefits.With the promulgation and implementation of relevant national policies and regulations,electric vehicles have been vigorously developed and popularized.The problems of traditional wired charging,such as complicated operation,easy aging of connectors,and danger of bad weather,are gradually exposed.Therefore,research on wireless charging vehicles has become urgent and important.Compared with various wireless transmission methods of electric energy,magnetically coupled resonant wireless power transmission is widely used in the field of electric vehicle wireless charging due to its large transmission power,high efficiency,and moderate transmission distance.Therefore,this paper studies the coil that are suitable for magnetically coupled resonant wireless power transmission technology to achieve efficient transmisson of 6kW output power when the entire system works at 85 kHz.The main research work of the article includes:(1)The principle of magnetically coupled resonant wireless power transmission system is briefly analyzed.The high-frequency equivalent circuit model of the coil is established and the impedance frequency characteristics of the coil is analyzed.In order to obtain higher transfer efficiency,based on the analysis of the four basic compensation circuits and a doubleside LCC compensation circuit of magnetically coupled resonant wireless power transmission technology,a double-side LCC compensation circuit is used as the resonance compensation circuit of the coil,and the input,output power and transmission efficiency of the double-side LCC compensation circuit are analyzed.(2)Analyze the influence of coil mutual inductance,frequency and coupling coefficient on the output characteristics of magnetically coupled resonant wireless power transmission system.The reason of coil frequency splitting is analyzed by the reflection impedance theory,and the relationship between coil coupling coefficient and output power and transmission efficiency is given.According to the relevant parameters of the coil size,the influence of the coil diameter,shape,number of turns,pitch,and size on the self-inductance and coupling coefficient of the coil is studied.The design criteria of the response and the calculation method of the magnetic field around the coil are given.(3)Based on the research of the coil,the design of the transmit and receive coils that meet the requirements of the index is realized,including the calculation of the coil's self-inductance,mutual inductance,AC equivalent resistance,and distributed capacitance,and the correctness of the coil design is verified by the finite element simulation software.At the same time,the MnZn ferrite(hereinafter referred to as ferrite)required by the coil is designed by the finite element simulation software,and the anti-offset ability of the coil and the magnetic field distribution around the coil are simulated and analyzed.(4)The physical model and test platform of the wireless power transmission coil are set up.The experimental results show that the transmission efficiency of the two coils is greater than 93% when the coils are 140 mm apart and the output power is 6kW.At the same time,the output power and efficiency of the coil in the case of migration are tested,and give the offset range of the designed asymmetric structure coil.