A fast fault diagnosis method for submodule failures in modular multilevel converters

To improve the reliability of modular multilevel converter (MMC), the fault submodules must be isolated rapidly. In this paper, a new fast fault diagnosis method is proposed containing two steps: fault detecting and fault locating. Fault detection step finds failures by improved predictive model which detects the fault by comparing the difference between the predictive value and the measured one of the arm current with the threshold value. Then the failures are located by the proposed location method which contains two process: feature mining and fault location. The proposed method could locate multiple submodule failures without additional sensors rapidly and can be easily implemented with a microprocessor. The proposed method has been validated by the simulation results.