Short-Circuit Fault Ride-Through of Flying-Capacitor Multilevel Converters through Rapid Fault Detection and Idle-mode Operation

Throughout the lifetime of a dc-ac converter, abnormal ac-side short-circuit conditions may occur as a result of external component failure, grid faults, or accumulation of moisture and dust. In such conditions, converter protection is needed. Compared to a two-level converter, which may be powered down if a fault is detected, the flying-capacitor multilevel converter cannot maintain voltage balance of the flying capacitors using such an approach. This paper therefore proposes methods for fault detection, and subsequent idle-mode fault ride-through, that protects the converter from device failures while supporting flying capacitor voltage balance. This method is experimentally verified under different operating conditions and various levels on a hardware prototype.