Accurate Discrete-Time Modeling and Boundary Analysis for High-Order Wireless Power Transfer Systems

The traditional stroboscopic mapping (SM) only focuses on the behaviors in periodic time instants, which will lose the details of multiple state changes during an operating period and cannot be used to analyze the characteristics of the studied system accurately. In this paper, an improved full-power stroboscopic mapping (IFSM) model is proposed for high-order WPT systems and DC-DC converters, which has generality and high accuracy. The dual-side LCC compensated wireless power transfer (WPT) system for electric vehicles (EVs) is taken as an example to present the derivation of the discrete-time model. Based on the proposed model, the possible zero current switching (ZCS) points of the system are calculated and compared for the optimal power transfer ability. The process of the boundary calculation of the output current operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is proposed, which aims to provide guidelines for adopting different control strategies when the battery packs are charged in different modes. It is found that the CCM/DCM boundaries are highly related to the operating frequency and equivalent resistance of the battery packs, while the coupling coefficient of coils has little influence on it. A dual-side LCC WPT prototype is built, and both the simulation and experimental results match well with the theoretical analysis.