Half-Cycle Resonance Tracking for Inductively Coupled Wireless Power Transmission System

Abstract

Resonance tracking technology is indispensable in inductively coupled wireless power transmission applications to counteract the detuning. In this paper, an ultrafast resonance tracking method is proposed that can accomplish resonance tracking within one-half oscillation cycle. The proposed method is implemented by synchronizing the operating frequency to the damped natural frequency, which occurs in close proximity to the resonance frequency. In addition, the tracking principle and tracking error theory are described in detail based on unloaded and loaded circuit models. A prototype is implemented and performance aspects including tracking accuracy, transient characteristics, induction voltage stability, and efficiency improvement are tested. The experimental results validate both the half-cycle tracking principle and the tracking error theory, where the tracking error is within 1.3% over the full range. Using the proposed method, the resonance tracking performance reaches the dynamic characteristic limit of the resonance loop, and is ten times that of a classical phase-locked loop-based tracking solution. This method could compensate for high-frequency detuning of up to several of kilohertz, caused by mechanical vibration and the chopper actions of the loads. The proposed method can be widely applied in the field, where both accurate and fast resonance tracking are required.