A 5kW Bi-directional Wireless Charger for Electric Vehicles with Electromagnetic Coil based Self-Alignment

Abstract

Wireless Power Transfer (WPT) systems have been gaining traction in Electric Vehicle (EV) applications, primarily as an enabling technology for autonomous vehicles. Regardless of the coil type, misalignment between the transmitter and the receiver, which degrades the efficiency, has become a major impediment to the adoption of WPT systems. This paper proposes a compact WPT system for the rear of an EV, capable of correcting misalignment using two integrated electromagnetic coils. Electromagnetic simulations were performed to verify the 5kW WPT system under varying operating conditions with a maximum efficiency of 96.5%. An experimental prototype of the dual coil system was built with a charging pad volume of 1570 cm3. The symmetric nature of the system architecture allows for bi-directional power transfer; enabling Vehicle-to-Grid (V2G) operation in the proposed WPT system. The system currently achieves WPT at 5 kW with an efficiency of 89.8%. The system successfully aligns the transmitter and receiver pads within 1.75 seconds and corrects horizontal misalignment as large as 240 mm; 20% greater than the charging pad width.