Reduction of magnetic field by low-order harmonics in magnetic resonant wireless power transfer system using high-frequency switching

Recently, dynamic wireless power transfer (DWPT) for battery electric vehicles has been actively studied because it can enhance their cruising range and reduce their charging time. An SS type WPT circuit is simpler and more efficient than a WPT circuit with a filter, such as an LCC type WPT circuit. By contrast, the leakage magnetic field generated by the harmonic current is a problem that needs to be addressed. The leakage magnetic field is limited by the Radio Act and the Ordinance for Regulating Radio Equipment in Japan. This study aims to reduce the leakage magnetic field generated by the harmonic current using a high-frequency switching technology. The inverter and rectifier are operated using pulse width modulation (PWM) with a high carrier frequency. The effectiveness of the proposed method was experimentally verified using a GaN inverter and rectifier. As a result, the proposed method can drastically reduce the leakage magnetic field, especially, the magnetic field generated by the current harmonics of order greater than five.