The analysis and experiment of dc-link short-circuit of modular multilevel converter based high voltage direct current system

The dc-link pole to pole short circuit is one of the most serious fault of a modular multilevel converter. Because of this, it is also one of the most important research objects for institutes and companies. However, there are not so many papers about this experiment published yet. Actually, the short circuit current before blocking the sub modules is the combination of the ac injection current and the capacitor discharge current. This paper analyzes the model of the capacitor discharging circuit and demonstrates the results of the experiment done with a ±10 kV prototype MMC.