Comparison of Modular Multilevel Converter and Neutral Point Clamped Converter Topologies for MVDC applications

The utility grid is experiencing a shift from a top-down architecture to a decentralized system with a hybrid AC and DC network. This includes MVDC networks. The AC-DC power converter is a key technology for this transition. This article presents a comparison between the 3-Level NPC and MMC topologies in terms of size, power losses and DC fault response for MVDC networks. It was found that the 3L-NPC has lower costs related to semiconductor devices. In terms of efficiency, the MMC converter has a better performance, namely thanks to its reduced switching losses. Regarding passive elements, both topologies seem to be comparable. Finally, the MMC offers more flexibility in DC fault handling, namely thanks to the use of bypass thyristor.