Cascaded Modular Multilevel Converter and Cycloconverter Based Machine Drive System

Low-speed drive is one of the challenges for modular multilevel converters (MMCs) due to large capacitor voltage fluctuation. In this article, a cascaded MMC and cycloconverter (CCV) based machine system proposed ensure stable operation medium-voltage low-speed machine. The provides medium-frequency ac CCV, CCV converts input low-frequency output required by Detailed analysis about MMC's frequency, device current stress, submodule (SM) capacitance are given in article. Proposed can operate at zero/low frequency under rated load torque, while SM much smaller than that existing methods. Simulation experimental studies conducted, results verify effectiveness system.