Novel Sinusoidal Input Current Single-to-Three-Phase Z-Source Buck+Boost AC/AC Converter

This paper introduces a novel unidirectional unity power factor single-to-three-phase Z-source Buck+Boost AC/AC Converter (123ZBBC) topology to supply three-phase AC machines with widely varying rated voltage directly from the single-phase mains. Due to the integration of the boost circuit into the inverter stage, the proposed circuit benefits from a reduced realization effort and an increased robustness. Furthermore, the insertion of a front-end buck-stage allows to select an intermediate voltage which is lower than the peak mains voltage and on the other hand enables to achieve a sinusoidal input current within the entire mains period. The paper gives a detailed analysis of the proposed converter including the different conduction states, the modulation schemes in order to implement the power factor correction and the inverter functionality, as well as the corresponding closed-loop control enabling sinusoidal input current and output voltages. Furthermore, the converter operation is verified by circuit simulations and the stresses on the main components are analyzed and compared to a conventional single-to-three-phase Z-source based AC/AC converter system.