A Hybrid Multi Converter System Having Full Adjustable Output Voltage Range

This paper proposes a new arrangement and new control strategy for a hybrid multi-converter system. It consists of two GTO converters and a neutral-point-clamped IGBT converter connected in series. A bulky and expensive transformer with phase-shifted secondary windings, which the original arrangement required, is not necessary. Phase-difference control between the two GTO converters is proposed and it expands the adjustable output voltage range up to 100%. Phase-difference control however increases harmonic distortion of the output voltage. Third-harmonic injection to a sinusoidal reference is also proposed to reduce the harmonic distortion. Finally, the effectiveness is verified by simulation and experimental results.