Investigations on the family of center-point-clamped AC-AC direct power converters

Abstract

Buck and buck-boost ac-ac converter topologies with a center-point-clamped circuit configuration have been recently reported in literature. These converter circuits reduce the voltage stress on the bidirectional switches employed in corresponding direct ac-ac converters. This new topological structure enables access to the mid-point of voltage terminals. This paper introduces a family of such ac-ac direct converters which are solid state functional equivalents of ac transformers with a continuously variable transformation ratio. The family of proposed variants include buck, boost, and buck-boost converters. This paper is aimed at presenting the operating principles, design guidelines, dynamic analysis and the results of a comparative study of these converters. Detailed design equations are provided along with typical examples of design of various converters for power conditioning applications. Experimental waveforms obtained with scaled laboratory prototypes presented in the paper verify that proposed converters offer reduced voltage stress on the bi-directional switches when compared to conventional ac-ac direct power converters. They also confirm the applicability of this novel family of direct ac-ac converters called Center-Point-Clamped Switched Mode Power Converters.