Modular Multilevel Converters for HVDC Applications: Review on Converter Cells and Functionalities

TLDR

The paper focuses on high‑power, high‑voltage DC applications. The study derives multilevel voltage and current source converter topologies using modularity and introduces various high‑power converter types. Converter cells are treated as building blocks; combining them yields a range of voltage and current source modular multilevel converter topologies that are thoroughly discussed. The study analyzes modularity, highlighting challenges and opportunities for high‑power applications.

Abstract

In this paper, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies. The paper is primarily focused on high-power applications and specifically on high-voltage dc systems. The derived converter cells are treated as building blocks and are contributing to the modularity of the system. By combining the different building blocks, i.e., the converter cells, a variety of voltage and current source modular multilevel converter topologies are derived and thoroughly discussed. Furthermore, by applying the modularity principle at the system level, various types of high-power converters are introduced. The modularity of the multilevel converters is studied in depth, and the challenges as well as the opportunities for high-power applications are illustrated.