Shielding Design for High-Frequency Wireless Power Transfer System for EV Charging With Self-Resonant Coils

Abstract

This paper provides a complete coil and shielding design solution for a 6.6 kW electric vehicle wireless power transfer system based on compact self-resonant (SR) coils. Due to the presence of a conductive vehicle body above the receiver coil, vertical fringing flux must be shielded in any electric vehicle wireless charger. Using high-frequency SR coils, parasitic capacitance introduced by standard shielding design approaches degrades the quality factor of the coils. In this work, the high-frequency parasitic capacitance introduced by the magnetic and conductive shielding materials is analyzed in detail, and a shielding geometry optimization method is proposed. Using ferrite and an additional dielectric spacer, prototype aluminum-backed SR coils are fabricated to validate the modeling. The total thicknesses of the transmitter and receiver coils are only 11.4 mm and 7.4 mm, respectively. The prototype coils achieve 92.3% DC-DC efficiency and 7.1 kW/dm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> volumetric power density. This paper demonstrates the first 6.6 kW WPT system for EV charging using compact megahertz-self-resonant coils including a complete magnetic and conductive shielding implementation.