Hybrid Alternate-Common Arm Converter With High Power Capability: Potential and Limitations

This article studies a new hybrid converter that utilizes thyristors and full-bridge (FB) arms for achieving high-power capability with reduced semiconductor power rating compared to the FB modular multilevel converter. The study covers the theoretical analysis of the energy balancing, the dimensioning principles, the maximum power capability, and the limitations imposed by the discontinuous operation of the converter. Based on the analysis of these aspects, the theoretical analysis is concluded by identifying the operational constraints that need to be fulfilled for maximizing the power capability of the converter. It is concluded that the maximum power capability can be achieved for a certain range of modulation indices and is limited by both the commutation time of the thyristors and the power angle. Moreover, the
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capability of the hybrid converter is presented and discussed. Finally, simulation and experimental results that confirm the theoretical analysis and the feasibility of the studied converter are presented and discussed.