Cross-Coupling Analysis and Decoupled Coil Design for Modular WPT System

Abstract

Employing multiple modules can enhance the power capacity of wireless power transfer (WPT) systems, potentially paving the way to high-power applications such as heavy-duty electric vehicles. However, the modular design of WPT systems faces the challenge posed by complex cross-couplings, and current research lacks generic decoupling solutions tailored for modular WPT (MWPT) systems. To address these challenges, this article comprehensively investigates the impact of three categories of cross-coupling on the parameters of MWPT systems and identifies that the same-side cross-couplings are detrimental to system performance. Upon analysis, a decoupled coil suitable for MWPT systems is proposed, which can eliminate the detrimental same-side cross-couplings between adjacent coils by over 98%. Moreover, compared to the conventional square coils, the proposed decoupled coil structure has the same mutual inductance between the primary and secondary sides, without increasing size or including extra magnetic cores. Based on the proposed decoupled coil structure, this article further introduces a current-balancing control scheme, enabling independent control of each module’s output in the MWPT system and simplified determination of control parameters. Finally, 7.6-kW two-module WPT prototypes with conventional coils and proposed decoupled coils are designed. Compared with the system employing conventional coils, the system employing the proposed decoupled coils reduced the maximum primary-side current by 6.7%–19.5% at the aligned and misaligned positions, respectively. Moreover, the efficiency at the aligned position reached 95.1%, representing a 0.7% improvement over the system with square coils.