Feasible Power Control Method with a Low Sampling Frequency for Bidirectional Wireless Power Transfer in Battery-Powered Railway Vehicle Systems

Abstract

Wireless power transfer requires a high operating frequency to ensure an electromotive force owing to the low coupling coefficient caused by a large air gap between coils. Traction inverters and inverters for auxiliary power units in battery-powered railway vehicles, have a switching frequency of 1-5 kHz owing to a high-power range. The sampling frequency of the microcontroller is selected based on its switching frequency. As the sampling frequency of a microcontroller is considered feasible if it is several tens of times the switching frequency, this paper proposes a feasible power control method with a low sampling frequency. The proposed control method is a feedback control of the average DC power per operating cycle, which eliminates the influence of single-phase power fluctuations. The controller gain is designed using a Bode diagram. 100-W-class experiments verified its inductance independence and high responsiveness, and full-scale 300-kW-class simulations demonstrated the effectiveness of the proposed power control.