Extended State Observer based Fault Detection and Location Method for Modular Multilevel Converters

Modular multilevel converter (MMC) is a promising converter in medium and high voltage applications due to its modularity and easiness to meet any voltage level by cascading the sub-modules. However, large amount of modules not only increase the failure probability of the devices, but also increase the difficulty of the fault diagnosis, which have brought a challenging for popularization and application of the MMC. Therefore, an extended state observer based fault diagnosis strategy for MMC is proposed in this paper. The extended state observer is designed based on the circulating current equation. The output of the extended state observer is compared with the theoretical value calculated by the modified switching models to locate the fault. The simulation is modeled and carried out in Matlab/Simulink. The effectiveness of the proposed strategy is verified by the simulation results.