Dynamic Model of the DC Fault Clearing Process of a Hybrid Modular Multilevel Converter Considering Commutations of the Fault Current

Hybrid modular multilevel converter that consists of a combination of half-bridge submodules and full-bridge submodules (FBSMs) can block dc fault current. However, in the case of distant bulk power transmission, the large excess energy that stored in the long-distance line will greatly affect the fault clearing time and FBSM capacitor overvoltage. During the fault clearing process, several commutations of the fault current from one arm to another may occur during the fault clearing process. A dynamic model, in which the commutations of the fault current are considered, is proposed to describe the fault clearing process after converter blocking in precise detail. The fault clearing time and FBSM overvoltage can be exactly estimated. The analytical analysis model is verified by the simulation and experimental results.