A 6.6-kW High-Frequency Wireless Power Transfer System for Electric Vehicle Charging Using Multilayer Nonuniform Self-Resonant Coil at MHz

A high-power, high-frequency wireless power transfer system for electric vehicles (EVs) is proposed in this article with lightweight and compact coil design. Leveraging a multilayer nonuniform self-resonant coil, no external capacitor is needed for compensation and the high-frequency conduction loss is mitigated by sharing current between multiple copper layers. The analytical model for the proposed coil is provided, and prototype coils with 200-mm radius are fabricated and tested, achieving a quality factor over 450 at 3 MHz. The optimized design for both coils and a GaN-based power stage are detailed and validated experimentally. Experimental tests show 95.2% dc–dc efficiency with 6.6-kW power transferred across a 100-mm coil-to-coil distance with 52.5 kW/m ² power density. The system demonstrates the first 6.6-kW wireless power transfer system for EV charging using compact self-resonant coils at MHz.