Research On Wireless Power Transfer System Based On Magnetic MIMO

Wireless power transfer based on magnetic resonance is a new frontier in power supply technologies developed in recent years.The technology not only solves the problem of wired energy transmission portability,but also overcomes the inherent shortcomings of magnetic induction and microwave radiation power transfer.It has become a hot research subject in the academic and industrial fields.The principle of that is to transmit the power through the way of magnetic resonance between the source coil and the device coil.A single-coil magnetic resonance wireless power transfer system often requires that the source coil makes an exact alignment with the device coil,and the transmission power attenuates with the distance very quickly,thus limiting the practical application of the system.Based on the MIMO technology in wireless communication system,a wireless transmission system with dual source coils and single device coil is designed.The main research work of this article is as follows:First,the theoretical analysis of magnetic resonance wireless power transmission system was carried out,and the system characteristics such as frequency response and coupling coefficient were deduced and analyzed.Combined with the analysis method of the two port network,the system was intuitively analyzed,and the expression of the transmission performance parameters of the two port theory was derived.Analogous to the MIMO technology in the wireless communication system,this part introduced the magnetic MIMO system.Secondly,to achieve the efficient transmission of the power,an adjustment of changing the current phase of each transmission coil was proposed to control the maximum superposition of the magnetic field beam at the receiver.The feasibility of the scheme was verified by electromagnetic simulation by the COMSOL software.The principle of phase adaptive adjustment was introduced in detail,and a method for real-time measurement of impedance was presented.Furthermore,the principle of impedance matching was introduced in detail,and the impedance matching in magnetic resonant wireless power transmission system was analyzed.An impedance matching method of dual source coils was derived and proposed in circuit theory.According to this method,an automatic impedance matching network was designed,and the corresponding implementation method and control process were proposed.Finally,a prototype which runs at 6.78 MHz frequency was built,including the transmitter platform of the dual-source coils and the receiving modules with several different power loads.The principle and selection of each sub-module of the whole system were introduced in detail.The prototype tested two methods with different distances and positions respectively.The results of the test indicated that both of the two methods could effectively improve the receiving power,and the wireless power transmission prototype designed in this paper could operate steadily and efficiently.