Matrix Persymmetry Analysis for Misalignment and Foreign Object Detection in Resonant Capacitive Power Transfer

Abstract

This paper introduces a persymmetry evaluation of capacitance matrices for resonant capacitive power transfer. Persymmetry analysis of the capacitance matrix indicates imbalances and allows for distinction between misalignments and foreign objects. Misalignment and foreign object detection are achieved with a parameter-based method. Voltages on the transmitter side of a resonant capacitive power transfer link are leveraged for detection. Simulations and supporting measurements were performed with a 13.56MHz resonant capacitive power transfer link incorporating a six-plate structure for electric vehicle charging applications. Metallic and living tissue objects can be detected with the foreign object detection method. Furthermore, lateral misalignment and its direction are detectable for realignment purposes. Simulations show that the foreign object detection range is sufficient to avoid exceeding the basic restrictions for electromagnetic field exposure for kW-range power transmission. The capacitance matrix persymmetry results indicate that both lateral misalignment and foreign object detection are achievable and distinguishable with the parameter-based method. This work introduces practical solutions to detecting imbalances in resonant capacitive power transfer systems, which may improve reliability and safety in applications such as electric vehicle charging and electrified roadways.

Keywords

• Capacitance matrix persymmetry
• electric vehicle charging
• foreign object detection
• misalignment detection
• resonant capacitive power transfer
• wireless power transfer