Design of wireless power transfer system with input filter

For power electronic systems, adding filters to eliminate harmonic interference is a general and effective method, but the position and parameters of filters in wireless power transmission (WPT) system will greatly affect the system characteristics of WPT. The main reason for the harmonic interference in WPT is that the harmonics in the output square wave are loaded on the resonant coil of the transmitter, so in this study, a method of harmonic elimination by adding a second-order LCR filter to the resonant part (LCR-WPT) is studied. However, the WPT resonant part is precisely matched and designed; if a filter is added at the resonant part, it inevitably affects the resonance state, system output power and efficiency of the WPT. To ensure that the LCR-WPT has good system characteristics, this study analyses the mathematical model of the LCR-WPT and deduces a design method for the filter and an efficiency optimisation formula. This study also introduces LCR-WPT applications in two different control schemes. The experimental results show that the harmonic interference of the system is significantly attenuated after the filter is added; additionally, the efficiency of the system decreases by <10%, and the system still maintains sufficient output power.