2.4 kW prototype of on-road Wireless Power Transfer: Modelling concepts and practical implementation

This article focuses on Wireless Power Transfer, adapted to a dynamic charging infrastructure. The authors present a high-efficiency 2.4 kW prototype of electric road, designed according to an analysis based on phasor diagrams to size the key-elements of the SS resonant converter. It involves 50-cm square coils, with an air-gap of 15 cm between the ground and the on-board sides, for an automotive application. The system uses a ZPA method control on both ground and on-board parts of the air-transformer, implemented with a varying-frequency inverter. The experimental results show a very steady and stable on-board voltage despite the evolutive magnetic coupling with the displacement of the load, from -18 cm to 18 cm. The efficiency measures presented in this article reach 91% and never falls below 70%. These data being measured with an emitted voltage of 30 V (half the operating voltage), the operating efficiency reaches even higher values. The efficiency is also very stable with displacement. Furthermore, the system has a very good dynamic response: the switch between one coil to the next during the motion of the load does not exceed 4 ms, and the adaptive response to a 280 W output power step lasts only 1.1 ms before the permanent regime.