Design and Optimization of a Modular Wireless Charging Scheme for Electric Buses With High Misalignment Tolerance

Abstract

Modular design helps to improve the reliability and power density of power electronic systems, so cascading of power electronics modules is an effective method to improve the overall stability of the system. The application of the wireless power transfer (WPT) system to electric buses faces the challenge of higher power requirement; modularization provides a solution to the design of the wireless charging system for electric buses. A modular wireless charging system for electric buses is proposed in this study; the system consists of five identical 6.6 kW wireless charging modules distributed relatively disperse on the chassis. Through the design of coil layout, different modules on the receiver side can be decoupled from each other, which facilitate independent control. Each module utilizes the bipolar-solenoid coupling structure, which proves to have a high misalignment tolerance. In order to reduce the electromagnetic radiation for passengers on the electric bus, shielding is added on the receiver side. Five independent modules work collaboratively to compose a 30 kW wireless charging system for electric buses. The DC-DC efficiency is 87.44% in an aligned position at 200 mm transmission distance. With closed-loop control, the proposed system has high misalignment tolerance in the horizontal X-Y plane. Compared with the open loop control scheme, the average efficiency of the proposed system increases by 22.1% within 300 mm misalignment.