Three-phase isolated DCM SEPIC converter for high voltage applications

The analysis of an isolated single-stage three-phase ac-dc converter with high power factor, based on the modularity of dc-dc SEPIC converters operating in discontinuous conduction mode is presented in this paper. The ac input is star-connected while the output of the modules are series connected. Doing so, the converter can provide a high step-up ratio and, consequently, besides high output voltage, a natural unity power factor is achieved. A review of the PFC three-phase SEPIC converters is performed, and discussion regarding to the advantages and drawbacks of the proposed connection when compared to previous solutions is made. Additionally, experimental results for a 4 kW, 380 V line-to-line input voltage and 1200 V output voltage laboratory prototype are presented in order to validate the analysis.