A Novel Operation Scheme for Modular Multilevel Converter With Enhanced Ride-Through Capability of Submodule Faults

Submodule (SM) fault is a common potential problem in the modular multilevel converter (MMC), which may lead to current distortion and even the collapse of the control system. This article proposes a novel operation scheme for SM fault in medium-voltage MMC applications. First, when the fault number is low, the capacitor voltages increase to a lower value according to the operation status. Second, when the fault number is higher, the capacitor voltages increase to the rated value and the zero-sequence voltage (ZSV) is injected to maintain the normal operation of MMC. In addition, a virtual voltage idea is applied to simplify the modulation under SM faults, where the reconfigurations of carriers are not necessary. Compared with the conventional fault-tolerant method, the proposed method can enhance the ride-through capability of MMC and simplify the modulation process under SM faults. Simulation and experimental results verify the effectiveness of the proposed operation scheme under severe SM faults.

Automated summary

The article proposes a novel operation scheme for SM faults in medium-voltage MMC applications, which enhances the ride-through capability of MMC under fault conditions. By controlling capacitor voltages and injecting zero-sequence voltage to maintain the normal operation of MMC, as well as applying the concept of virtual voltage to simplify the modulation process under SM faults.