Single-Phase AC–DC Converter With Dual-Output Rectifier, Dual-Input DC Transformer, and Voltage-Split/Sigma Principle

A single-phase ac-dc converter with dual-output rectifier (DOR) and dual-input dc transformer (DI-DCX) is proposed in this paper. A voltage-split/sigma principle is adopted, that is, the grid voltage is split into two variable dc bus voltages first by the front-stage DOR, and then the two bus voltages are combined into an adjustable output voltage by the downstream DI-DCX. DC output voltage is directly regulated by the front-end rectifier. Therefore, no voltage regulation is required for the dc-dc stage, and a DI-DCX with optimized operation condition is employed to improve the overall efficiency of the ac-dc converter. Moreover, since the DOR has two different output voltages, three-level characteristic is achieved naturally to reduce switching losses of the converter. Zero voltage switching of all the active switches in the DI-DCX is realized as well. Detailed operation principles, control and modulation strategies, and characteristics of the proposed ac-dc converter are analyzed in detail. Experimental results of a 1.5-kW prototype are provided to verify the effectiveness of the proposed converter.