The Enhanced Modular Multilevel Converter With DC Fault Blocking Capability

The large energy-storage requirement and lack of dc fault-tolerant capability are the major drawbacks of modular multilevel converters (MMC). To address these issues, alternate hybrid topologies have been developed, but these are all non-modular, and hence, MMC remains the most preferred topology for high-power applications. In this article, a new submodule (SM) structure is proposed that consists of five switches and a capacitor. Based on this SM, a novel enhanced modular multilevel converter (EMMC) is developed, which is fully modular, scalable, and requires fewer switches and capacitors. It also possesses the features of reduced energy-storage requirement and dc fault-tolerant capability. The structures and operating principles of proposed SM and EMMC topology are presented. The proposed topology is compared with state-of-the-art topologies in terms of the switch counts, SM capacitors, and isolated power-supplies requirements to highlight the main features of EMMC. The proposed EMMC is an effective and more efficient converter solution compared with the major existing high-power hybrid converters. Moreover, it has a fully modular structure. A 21-level, grid-connected EMMC simulation model is developed to validate its working principles and dc fault-tolerant capability. The working principles and dc fault-tolerant capability are further validated using a scaled-down five-level EMMC experimental prototype.