Research And Improvement Of Efficiency In Wireless Power Transmission

In the 21 st century,with the development of science and technology,the concept of science and technology to improve life has gradually become the main guiding ideology of scientific research.In the modern society where electronic devices are used so frequently,various ways of charging have naturally become the main content of scientific research.As a new charging method,wireless power transmission has become the main research direction of modern electronic devices.Compared with the traditional plug-in wired charging method,wireless charging has the following advantages: No external physical connection is needed which makes the charging process convenient and fast;There is no exposed metal,so the charging process is safe and reliable;It doesn't requires any physical contact with metal,which reduces metal oxidation and corrosion;In addition,bad weather will affect the use of outdoor charging piles,but wireless charging will not have such a problem.Based on these advantages,more and more electronic equipments equip the function of wireless charging,and with the maturing of wireless charging technology,more and more wireless charging equipments enter into people's daily life.From the perspective of science and technology improving human life standard,the research on wireless charging is of great practical significance,which is worthy of more in-depth research by scholars.Firstly,the mutual inductance of coils with different shapes is analyzed.In the process of analyzing the mutual inductance of circular coils,we found that the calculation formula of the mutual inductance derived from the former scholars Kim(Hereinafter referred to as Kim formula)is wrong,when the transmitter coil and receive coil horizontal offset occurs,Kim formula calculation results are different from that of Neumann formula and F.W.Grover formula.Therefore,based on the magnetic vector method,we derives the formula of mutual inductance between circular coil again to find out the error source of the formula of Kim and correct Kim formula,and the correction of the formula calculation results are consistent with the results of Neumann formula and F.W.Grover formula.On this basis,in combination withthe current wire method,Neumann formula,F.W.Grover formula,Kim formula and modified Kim formula are applied to calculate the mutual inductance of the same model,and the results show that the modified Kim formula is correct and efficient.For other coils of various shapes and for different axial distances and horizontal offsets,the mutual inductance values of theoretical calculation and software simulation show good consistency,which makes the foundation for the improvement of efficiency in wireless power transmission.Secondly,after analyzing the influence of mutual inductance between coils on the power transmission efficiency and load power,we can conclude that the mutual inductance stability between coils is crucial to the power transmission efficiency and load power of the system.Therefore,in this paper,the winding method combining series and parallel is used to replace the traditional winding method,and the transmitting coil is optimized.The optimized coil can make the transmitting coil and the receiving coil still maintain the stability of mutual inductance under certain horizontal deviation,so as to maintain the stable transmission efficiency and load power of the system.Finally,in order to further improve the efficiency of wireless power transmission,this paper introduces electromagnetic metamaterials with magnetic negative structure into the wireless power transmission system.On the basis of elaborating the parameter inversion process of electromagnetic metamaterials in detail,a hybrid electromagnetic metamaterial is designed and applied to the wireless power transmission system according to the parameter inversion process.The simulation results show that the electromagnetic metamaterial can improve the power transmission efficiency in the wireless power transmission system with the transmitting coil and the receiving coil separated by 20 cm from 12.50% to 40.87%.