Dynamic Modeling Based on Coupled Modes for Wireless Power Transfer Systems

A novel dynamic modeling method based on the concept of coupled modes is proposed for wireless power transfer (WPT) systems which use magnetic resonant coupling. The proposed method aims on the dynamics of the overall WPT system, including the nonlinear inverter and rectifier. It uses the slowly varying amplitudes and phases of coupled modes rather than resonant currents and voltages to describe the coupled resonances. Three analytical models-averaged model, small signal model, and conductance network model are developed sequentially by using the proposed method. The orders of the developed models are equal to or lower than that of the discrete state space model. In contrast, the existing dynamic modeling methods for WPT systems and resonant converters have to transform the discrete state space model into a higher order model or use complex currents and voltages in order to adopt the averaging method and obtain an analytical model. Simulation and experimental results give a firm support to the proposed method and models. The concept employed in this paper provides a deeper insight into the dynamic behaviors of coupled resonances.