Optimized Branch Current Control of Modular Multilevel Matrix Converters Under Branch Fault Conditions

The modular multilevel matrix converter (M3C) is a promising topology for high-voltage high-power applications. It features easy scalability, high-quality input and output waveforms, superior availability, etc. This letter aims to further increase the availability of the M3C when one or more of the nine branches are lost. A general nonlinear multivariable optimization model is set up to optimize the branch current configuration after the branch lost. The proposed method reduces system power capability loss after the branch failure. It achieves a smooth transition from a full M3C to a reduced topology without shutdown of the system. AM3C prototype with 27 cells is designed, and experiment results are presented to confirm the validity of this method.