A single-stage three-phase AC-AC converter for inductive power transfer systems

A three-phase ac-ac matrix converter for inductive power transfer (IPT) systems with soft-switching operation and bidirectional power flow is introduced. The proposed converter can generate high-frequency current directly from a three-phase ac power source without a dc link. Unlike conventional ac-dc-ac converters, the proposed converter can provide a high frequency current without any current sag around ac source zero-crossings for IPT systems. The proposed topology is expected to have high reliability and extended lifetime due to the soft-switching operation and elimination of short life electrolytic capacitors. Soft-switching operation will also reduce switching stress, switching losses, and electromagnetic interference (EMI) of the converter. A simple control strategy based on energy injection and free oscillation technique is used as the control method. The proposed converter is comprised only seven switches, which in turn increase the reliability, efficiency and reduce cost. The converter operates in eight modes, which are described in detail. Theoretical analysis and simulation results on a 2kW IPT system, show that the current control method can fully regulate the output current with low ripple which is suitable waveforms for IPT applications.