Frequency splitting suppression method for four-coil wireless power transfer system

Magnetic resonant wireless power transfer (WPT) is an emerging technology that may create new applications for wireless power charging. However, frequency splitting occurs when the WPT system operates in the over-coupled regime. As a result, the transfer efficiency is very low at the original resonant frequency. In this study, the method of adjusting the load resistor is proposed to suppress the frequency splitting. The efficiency and input impedance can be obtained by solving the system equivalent equations. In addition, the resonant frequencies can be obtained by input impedance equation. The influences of the load resistor on the efficiency and the resonant frequencies are analysed for different transfer distances. Then, the method of adjusting the load resistor is illustrated. Frequency splitting is suppressed and transfer efficiency is improved at the original resonant frequency by the proposed method. The WPT system via magnetic resonance coupling is designed. Simulation and experimental results validating the proposed method are given.