A Robust Compensation Method for Megahertz Wireless Power Transfer Based on Rectifier Input Impedance Analysis

Wireless power transfer (WPT) system working at megahertz (MHz) is a research trend due to its structure flexibility. However, the reactance variation caused by non-negligible influence of switches' parasitic capacitor and practical load change will decrease the system reliability and degrade the system performance, such as zero voltage switch (ZVS) condition, efficiency and constant source feature. In this paper, a reactance compression design method achieved by rectifier input impedance analysis is detailed introduced by principle. In addition, an optimization algorithm for determining the circuit parameters is developed based on the proposed principle. Finally, comparisons between proposed reactance compression design method and traditional design method are implemented through wide load variation tests ($5-50\ \Omega$) with maximum 20 W dc output power. The results show that the design method proposed in this paper can achieve a significant reactance compression effect and improve the system performance while the load variation.