A hybrid multi-converter system combining single-phase converters with three-phase converter

A new hybrid multilevel multi-converter system combining three single-phase GTO converters with a three-phase NPC IGBT converter is proposed. The GTO converters can adjust the output voltage, though they operate in square-wave switching to minimize the switching-related device losses. The IGBT converter not only cancels the harmonic voltages generated by the GTO converters but also controls the resultant output voltage. The system can accomplish a wider adjustable output voltage range compared with other hybrid systems. A control strategy in relation to a required reference voltage is proposed to obtain minimum harmonic distortion in the resultant output voltage. A 1.5 kW prototype is built and experimental results verify the validity of the proposed system and control strategy. Comparative studies on hybrid converter system performance with a different number of GTO converters are also included