Single-phase quasi Z-Source AC-AC Converter with a series connection of the output terminals

In this study, single-phase quasi Z-source AC-AC converter with a series connection of the output terminals is proposed. The proposed system has configuration that the input terminals of two single-phase quasi Z-source AC-AC converters are connected in parallel and their output terminals are connected in series. The proposed system can perform the in-phase and out-of-phase buck-boost voltage modes. In particular, the crossing control method to implement the in-phase buck voltage mode by controlling duty ratio (D) of upper and lower converters is proposed. To verify the validity of the proposed system, a DSP controlled hardware was made and PSIM simulation was executed. As a result, by controlling the duty ratio of the two converters, the desired buck-boost output voltages could be produced. For each voltage mode, as compared with the single converter operation, the proposed system could enhance the efficiency and input power factor according to different loads.