Study on the optimization factor of four-coil magnetic coupling resonant wireless power transmission system

Wireless power transmission (WPT) technology has been widely applied in various fields, such as electric vehicles and wireless sensor networks. Magnetic coupling resonance technology is one of the most important technologies in wireless power transmission. A large number of experimental studies have shown that wireless power transmission systems have good power transmission performances when they work at the natural frequencies. Nevertheless, many relevant parameters' differences in design, such as the choice of coupling coil structures and parameters, the coupling coefficient between transmitting coil and receiving coil and the quality factor of each coil, will lead to changes in terms of transmission performances. To reduce these adverse effects and make the wireless power transmission system maintain better transmission efficiency, a resonant magnetic coupling four-coil model with Series-Series-Series-Series (SSSS) structure is established based on the equivalent circuit theory. An optimization factor a is proposed to evaluate the transmission performances of the wireless power transmission system. Parameters characteristics of the optimization factor a between the excitation coil and the transmitter coil in the established symmetric structural system model are analyzed in detail. By means of the simulation analysis software MATLAB, the influences of the distance between the excitation coil and the transmitter coil and their respective radius on the optimization factor a are analyzed. And the variation tendency of a with regard to the parameters of the excitation coil and the transmission coil is clarified. Also, the influence of the optimization factor a on the transmission efficiency of the wireless power transmission system is analyzed and the variation trend is cleared up. By studying the optimization factor, the selection specification of system parameters is analyzed and provides a theoretical basis for system design. A resonant magnetic coupling four-coil wireless power transmission experimental system was built through optimization design. Theoretical models and experimental measures are in good agreement in terms of the influence of system transmission distance on transmission efficiency. After optimization, the transmission efficiency is increased by 3.1% compared with the system before optimization