Novel Family of Single-Stage Three-Level AC Choppers

The capacitor-clamped base cell is presented. Based on the base cell, a novel family of single-stage three-level (TL) ac choppers is proposed. The converters can directly transfer unsteady high ac voltage with distortion into regulated sinusoidal voltage with low THD. The circuit configuration is constituted of a TL converter, and input and output filters. The topological family includes buck, boost, buck-boost, Cuk, Sepic, and Zeta modes. In order to achieve a reliable TL ac-ac conversion, a double transient voltage feedback control strategy of output voltage and the voltage across the clamp capacitor is introduced in this paper. A prototype of a 500 VA 220 V ± 10% 50 Hz ac/180-240 V 50 Hz ac converter is presented with the experimental results to prove that the converters have four improved advantages simultaneously, including the lower voltage stress of power switches, the bidirectional power flow, the low total harmonic distortion of output voltage, and the higher input power factor.