Real-time Front-end Monitoring of Load, Mutual Inductance, and SOC in SS-Compensated Wireless Charging Systems

Abstract

This paper proposes a fast, accurate, and low-cost front-end real-time estimation method based on a two-coil series-series compensated wireless power transfer (WPT) system that allows the resonant frequencies of the transmitter and receiver resonators to be different. The proposed method offers simultaneous multiple functions of parameter estimation, primary-side control, and state of charge (SOC) monitoring. Its implementation is simple because only current detection on the primary side is needed. With the real-time estimation of the mutual inductance and load resistance, the output voltage and output current can be determined and regulated by the phase shift control with the primary side control. This implies that the constant-current (CC) and constant-voltage (CV) charging mode of the Li-ion battery can be selected with primary-side control, and the SOC can be calculated in real time. The simulation and experimental results show that the mutual inductance and the load can be estimated accurately in real time. With accurate estimation results, CC-CV mode charging can be realized, and the real-time SOC can be observed on the primary side accurately.