AC Grid–DC Microgrid Coupling with High-Performance Three-Phase Single-Stage Bidirectional Converters

Abstract

This paper discusses bidirectional step-down topologies that enable the interface of the 400V unipolar DC microgrid with the European low-voltage three-phase AC grid. The study compares three single-stage non-isolated topologies, namely, the seven-switch buck converter, Swiss converter, and Y-converter, based on semiconductor stresses and losses, magnetic component sizes and losses, and heat sink sizes. The analysis is conducted for a 10kW converter designed for small commercial or residential use. The results indicate that the Y-converter has superior overall performance compared to the other topologies, making it a potentially better candidate for this application. A 10kW prototype of the Y-converter is constructed. It is demonstrated to have a peak efficiency of 99.26% and an efficiency of 97.47% at the rated output power.