A Three-Phase Bidirectional AC/DC Converter With Y–Δ Connected Transformers

This paper proposes a three-phase bidirectional ac/dc converter with Y-Δ connected transformers. The converter achieves both buck-boost ac/dc bidirectional conversion and electrical isolation with the single-stage structure. By introducing three dc-dc transformers, the total power is distributed and the current stress of the rectifier stage decreases. The Y-Δ connected transformers provide extra step-down conversion ratio and facilitate the converters' application in buck conversion. The circuit derivation, operation principles, and control strategy with the SVPWM algorithm are presented. A 3-kW prototype with 380-V dc and a 1.6-kW prototype with 48-V dc were built in the lab and experimental results verify the theoretical analysis well.