The modular multilevel matrix converter (M3C) is an important part of the fractional frequency transmission system (FFTS). With many sub-modules, the single fault detection method is cumbersome and complicated. This paper analyzes the changes of the arm current and the capacitor voltage of the sub-module under different sub-module faults in the pre-charging process of the bridge arm, analyzes and summarizes the fault types and fault location criteria of the sub-module fault of the bridge arm, and verifies the pre-charging process of the fault bridge arm by simulation software. Finally, a batch non-invasive fault detection method for M3C converter is proposed by using the control system arm current and sub-module capacitor voltage sensors.

M3C, failure analysis, batch inspection, non-intrusive