Analysis And Research Of Magnetic Coupling Resonance Wireless Energy Transmission Characteristics

The magnetic coupling resonant technology in wireless power transmission is usually applied to electric field, portable mobile device, medical device and underwater submarine due to its advantages of low radiated power, long transmission distance and high efficiency. However, the biggest issue currently is that two coils with the same resonant frequency have a critical coupling factor when the energy is transmitted through near-field coupling. The voltage gain rises with the increase of the coupling coefficient between the two coils when the coupling is weak,and the receiving coil will obtain the maximum power at the critical coupling coefficient. If the coupling coefficient increases larger than the critical coupling coefficient, the phenomena of frequency splitting will occur. In order to solve the problem above, a novel high efficiency WPT with auxiliary coil is proposed. Unlike the relay coil, the self-resonant frequency of the auxiliary coil is different from that of transmitting and receiving coils.Firstly, this paper will introduce the background and some basic information about the wireless power transfer system.Secondly, the wireless transmission system is analyzed by using the coupling mode theory, the equivalent circuit method and the scattering parameter analysis method. Besides, the expressions of the load power and transmission efficiency of the system are also deduced under each model. The establishment of these methodologies is of huge significance for the future work in this area.Thirdly, the voltage gain impaction caused by the loading auxiliary coil technology is the main study in this paper. The voltage gain expression for the novel system is derived and the optimum mutual inductance between the auxiliary coil and the transmitting coil and the receiving coil are also given based on the equivalent circuit of this novel WPT system. The simulation results show that the auxiliary coil can effectively suppress the frequency splitting phenomenon and stabilize the voltage gain in the "overcurrent region" by the voltage gain maximum value tracking method.Lastly, the transfer efficiency effect is also analyzed. The research method is similar to the voltage gain. The simulation results show that the efficiency of the whole system can reach more than 80% after adding the auxiliary coil. Compared with the traditional two-coil magnetic coupling resonant system, the transmission efficiency is improved by 30% when the distances between the transmit and receive coils are 10cm and 15cm, respectively.