Exciter–Quadrature–Repeater Transmitter for Wireless Electric Vehicle Charging With High Lateral Misalignment Tolerance and Low EMF Emission

Abstract

In this article, an exciter–quadrature–repeater transmitter pad is proposed in order to achieve high lateral misalignment tolerance and low leakage flux emission in electric vehicle wireless charging applications. In the proposed WPT system, a single half-bridge inverter unit is needed to energize the exciter coil, which is magnetically coupled to two larger quadrature repeater coils. The currents in the two repeater coils naturally adjust based on the lateral misalignment of the receiver pad to reduce the leakage flux density around the charging zone. The system can maintain zero phase shift between excitation voltage and current and achieve constant current charging conditions with fixed compensation capacitors in the ±150-mm lateral misalignment range. In order to verify the attributes of the proposed wireless power transfer (WPT) system, a 3-kW experiment setup with a 200-mm vertical gap was built and compared to a three-coil WPT system, which consists of a small transmitter coil, a single large repeater coil, and a receiver coil. According to the experiment results, even under extreme 150-mm lateral misalignment, the proposed WPT system has 90.7% coil-to-coil transmission efficiency. Furthermore, it achieves a 30% reduction of leakage flux density compared to the three-coil system in the 150-mm lateral misalignment case.