Evaluation of control methods for isolated three-phase AC-DC converter using modular multilevel converter topology

This paper discusses a novel isolated three-phase AC-DC converter using Modular Multi-level Converter (MMC) topology for a medium voltage application. The MMC at a primary stage of an isolated AC-DC converter can directly convert a three-phase AC into a high-frequency AC voltage of 1 kHz. In this paper, the features of the proposed circuit are discussed according to the voltage ratings of the switching devices. Moreover, the total harmonic distortion (THD) of the input current, the output voltage, the number of cells and the capacitance of the DC capacitor are evaluated on each switching devices in the proposed system. Finally, the proposed system performance with SiC MOSFET of 3.3 kV is demonstrated by the simulation. As a result, the proposed converter achieves the low THD of the input current waveform which is approximately 2.64%.