Characteristic Modes Analyses for Misalignment in Wireless Power Transfer System

Abstract

This paper presents a novel method for assessing misalignment scenarios in Magnetically Coupled Resonant Wireless Power Transfer (MCR-WPT) system through measurements using Characteristic Modes Analysis (CMA). Based on the metric parameters of Characteristic Modes (CMs), including resonant frequencies, magnetic field plots, and current distributions, the dominant CM is identified. Its impact on the system’s total power is evaluated and compared with the system’s behavior in proximity to resonance. To establish a comprehensive and concise reference delineating the applicability of CMA in the field of Wireless Power Transmission, this contribution conducts a detailed investigation about the various types of unexpected misalignments between the Transmitting (Tx) and the Receiving (Rx) coils due to typical movement of the device or the user from both analytical and experimental perspectives. Besides, the various misalignment scenarios were systematically and progressively explored, accounting for both minor and significant degrees of variation. The proposed MCR-WPT system consists of two identical loops characterized by a singular turn, a radius R of $0.0625\lambda $ and a width w of $0.025R$ . Notably, results based on CMA guided by The Coupled Mode Theory (CMT) demonstrate a great affinity with the measurements of the fabricated prototypes. Consequently, this marks the inaugural confirmation of CMA’s applicability in the field of Wireless Power Transmission, which opens avenues for improving PTE using previous research findings deploying principles of selective excitation through CMA concepts.

Keywords

• Characteristic modes
• coupled mode theory
• coupling
• misalignment
• power efficiency
• Qi standard