AC Voltage Synthesis Using Arbitrary Two-Phase Voltages: Frequency, Phase, and Amplitude Modulation for Direct AC–AC Power Conversion

Usually, the dc-link is employed as the intermediate stage of ac–ac power conversion for high controllability, good output quality, and stability, while the large-volume dc capacitors will lead to high equipment failure rate and maintenance cost. This article proposes an arbitrary two-phase input voltages based ac voltage synthesis method for direct ac–ac power conversion, which can realize the three-phase output voltages with controllable frequency, amplitude, and phase. Besides, the current harmonics generated by the proposed voltage synthesis method can be eliminated naturally through the phases’ cross-coupling. This feature avoids the harmonic pollution to the input currents. The corresponding modulation strategy for ac voltage synthesis is derived and analyzed in detail. Finally, a 3-kW experimental prototype is constructed. The results are consistent with the theoretical analysis.