Submodule Fault-Tolerant Control of Modular Multilevel Matrix Converters With Adaptive Optimum Common-Mode Voltage Injection

The modular multilevel matrix converter (M3C) is an attractive topology for high-voltage and high-power direct ac-to-ac power conversion applications. SM fault-tolerant control is of great importance for the M3C. This letter proposes an optimum common-mode voltage injection (CMV) method which can maximize the input and output voltage ranges of the M3C after nonredundant submodules (SMs) are failed. The injected optimum CMV is calculated in real-time according to the relationship between the fundamental reference voltage and maximum available voltage of each branch, which can be adaptive to different load and fault conditions. The operating area of the M3C after the fault when employingthis method is also discussed. Experimental results implemented on an M3C prototype with three SMs in each branch are presented to validate the proposed method and analysis.