Open-Circuit Fault Detection Method For Submodule In Modular Multilevel Converters

In this paper, the open-circuit fault of the submodule ( SM) in modular multilevel converter ( MMC) are analyzed. Aiming at the open-circuit fault characteristics of the submodule, a fault detection method based on the average value of the three-phase AC current is proposed. The average value of three-phase AC current is utilized to detect the occurrence of the submodule fault, the size of the AC average current is used to locate where the phase arm the fault submodule is on, the sign of the AC average current is employed to locate which arm of the faulty submodule is on. And then, the submodule fault switch can be determined by using the maximum size for the sum of three-phase AC average current.