An Ultrafast Estimation Method for Coupling Coefficient and Receiver Resonant Frequency in Universal Wireless Power Transfer Systems

This paper proposes a fast and accurate front-end monitoring method to estimate the coupling coefficient and receiver resonant frequency of wireless power transfer (WPT) systems. The proposed method is developed for universal WPT systems with a series-compensated transmitter. The receiver parameters can be unknown and different from those on the transmitter side. This method is applicable to a range of receivers with first- or second-order compensation (i.e., series, parallel, and none-compensation). It can be extended to the systems with magnetic shielding, and has a strong immunity to the harmonics. Furthermore, a hardware-based identification approach is proposed for receiver compensation without any additional cost. The detection algorithms are analyzed in detail. The proposed scheme requires one additional phase detection sensor of the transmitter current. The zero-phase-angle frequencies of the WPT systems can be determined by fast frequency-sweeping processes with the receiver's active rectifier kept momentarily either short-circuited or open-circuited. Experimental results have been obtained to verify the proposed method, which can accurately estimate both coupling coefficients and receiver resonant frequencies within 2.5 ms to 8 ms.