Design And Optimization Of Medium Range Wireless Power Transfer System Based On Electromagnetic Metamaterials

Wireless power transfer(WPT)and electromagnetic metamaterials are two cutting-edge technologies emerging in this century.The former is widely used in medical,electric vehicles,consumer electronics and other fields,while the latter is still in the preliminary stage of development.This thesis combines the two organically,and focuses on the problems of low efficiency and electromagnetic leakage in the meterlevel transfer distance of the magnetic coupling resonant radio energy transfer system.The electromagnetic regulation performance of the electromagnetic metamaterials used in the system is studied.The main research work and achievements include the following aspects:1)The transmission characteristics of two coil structures and four coil structures commonly used in magnetic coupling resonant wireless power transfer system are analyzed theoretically.The conversion from four coil structure to two coil structure is described,and the optimal load matching problem required by the four-coil structure system for maximum efficiency transfer is explored.Two kinds of matching methods to achieve the optimal load of WPT system based on the change of relative position are compared and analyzed.The calculation method of self-inductance and mutual inductance of corresponding coil structure is given,and the simulation and numerical calculation are mutually verified,which solves the difficulty of mutual inductance measurement between mid-distance resonant coils.This can accurately predict the final experiment results.2)The internal mechanism of electromagnetic metamaterials as focusing and shielding electromagnetic waves is introduced,and the optimal design scheme of electromagnetic metamaterials is given.Through the simulation,the structural parameters of the electromagnetic material which the relative permeability are-1 and near-zero at 3 MHz are obtained.A simple WPT system simulation model was established to verify the electromagnetic characteristics of the two kinds of electromagnetic metamaterials.3)The performance of common power amplifiers is compared and analyzed,and the relationship between the components of Class E power amplifiers is analyzed in the optimal working state.The performance indexes are verified by circuit simulation.A set of 3 MHz power amplifier has been developed with the energy conversion efficiency of 95% and the power output of 100 W.4)An experimental prototype of the medium range WPT system is built.The experimental results show that the transfer efficiency of the system is improved by 27 %when the transfer distance is 120 cm after loading the focused electromagnetic metamaterial.After loading the shielded electromagnetic metamaterials,the magnetic field strength decreased significantly,with a decrease rate of more than 40 %.When the WPT system is offset,the electromagnetic material can effectively enhance the antioffset ability of the system,and the effect is better when the lateral offset occurs.The above research results show that loading different types of electromagnetic metamaterials can effectively improve the transfer efficiency of WPT system,and also take into account the electromagnetic leakage problem.The research results are helpful for the engineering application of medium distance WPT system.