Bidirectional Isolated Single-Stage Single-Phase AC-AC Converter

The objective of this article is to propose a bidirectional isolated single-stage single-phase ac-ac converter (BISS-converter) with quasi-resonant (QR) topology. The proposed converter is composed of multiple bidirectional flyback-type dc-dc converters (BFDCs) and two bidirectional dc-ac unfolders. Because the unfolder only switches at the zero crossing of the ac line voltage, there is only one set of high-frequency pulse width modulation (PWM) signal, which is used to control the BFDCs to generate the desired rectified sinusoidal currents. Advantages of the proposed BISS-converter include high conversion efficiency, single-stage high-frequency power conversion, simple control circuit, flexible capacity, and bidirectional power flow capability. Moreover, the controller can maintain the zero voltage switching to reduce the switching loss without the need for valley detection. Also, with the interleaved operation between BFDCs, the current ripple of the output can be reduced greatly. The hardware experimental results are shown to verify the performance of the proposed BISS-converter.