Segment Control Scheme of Inductive Power Transfer System for Rail Transit

Inductive power transfer is used to transfer energy across a relatively large air gap by electric resonance. The power supply region of primary coils along the track is segmented with gaps to minimize the capacity of the high-frequency inverters by reducing the loss of uncoupled region, and the several sets of secondary coils are installed aboard in the rail transit application. In this paper, the equivalent impedances of segmented primary coils, which will change when secondary coils run through the gaps between primary coils, are derived. The characteristics of resonant frequencies are obtained according to the derived equivalent impedances of primary coils. A resonant frequency tracking control method, in which the switching frequencies of inverters are modulated according to the measured curves of the resonant frequencies of the primary coil, is proposed to realize the primary resonance at all times while the secondary coil is running. Finally, the effectiveness of the proposed method is experimentally verified.