Analysis and Performance Enhancement of Wireless Power Transfer Systems with Intended Metallic Objects

While detection of foreign or unintended metallic objects is an important topic for wireless power transfer (WPT), operation of WPT systems with intended metallic objects is largely an unchartered territory. This article presents a methodology for analyzing the effects of intended metallic object on a WPT system through the study of the magnetic field distribution and the use of a reduced-order equivalent model of the systems for comparing the WPT system with and without the metallic object. The methodology is applied to a metallic corona ring of low resistance used with a WPT system. The analysis quantifies how an intended metallic object could change the magnetic coupling between the transmitter and receiver coils, and alter the equivalent resonant tank parameters of the WPT system. Recompensation of the resonant tank can only enhance the power transfer capability but not the energy efficiency. The theory and practical verification of a new performance-enhancement method based on a combination of recompensating the resonant tanks and maximizing the equivalent mutual inductance of the Tx and Rx coils is presented. Such methodology provides a general approach to analyze WPT systems with or without relay resonators in the presence of intended metallic objects.