New measurement technique for modular multilevel converter with IGBT open-circuit failure detection and tolerance control for three-level submodule

Modular multilevel converter (MMC) served as a promising converter for High Voltage Direct Current (HVDC) transmission. However, reliability is one of the most important challenges. Redundant submodules (SMs) are often used to replace the faulty SMs to ensure continuous operation of the scheme and increase the system reliability. In this paper, a fault detection and clearance is proposed for three level SMs topology without additional voltage sensors or complex algorithms. The fault is detected using a measurement technique that has half the number of voltage sensors compared to conventional half-bridge. The main advantage of the proposed technique is the reduction of the number of voltage sensors with full estimation for the capacitors voltages. Moreover, it provides fault detection and tolerance control. A simulation model has been implemented to validate the proposed technique and to evaluate its performance.