A single-phase isolated AC-DC converter using an interleaved MMC

Abstract

This work introduces a single-phase isolated ac-dc topology using an interleaved modular multilevel converter. There is a medium frequency transformer which provides the galvanic isolation and operates at 10 kHz, allowing the weight and volume reduction. Also, the transformer connects a modular multilevel converter with coupled interphase inductors at the high voltage side to a full-bridge converter at the low voltage side. The modular multilevel converter provides the current and voltage distribution in the submodules reducing the efforts on the switches while the full-bridge phase-shift converter controls the bidirectional power flow. The topology is well suitable for a wide range of medium voltage applications such as solid-state transformers, ac or dc distributed power systems and renewable energy systems. The principle of operation and the control scheme are presented. The topology validation is made through simulation concerning a single-phase converter with 13.8 kV / 60 Hz input line voltage, 4 submodules with 10 kHz switching frequency per arm, 11.27 kV/800 V − 10 kHz medium frequency transformer, 800 V dc output voltage and 100 kW power rating.