Modelling of MMC-HVDC Systems – An Overview

Modular Multilevel Converters (MMC) are presently the converter topology of choice for Voltage Source Converter High Voltage DC (VSC-HVDC) transmission schemes due to their very high efficiency. Accurate models of these complex MMC-HVDC systems are therefore required for research and development. There are numerous publications in this area; however these publications tend to focus on a particular component within the scheme, rather than the overall system. A key objective of this paper is to act as a guide for modelling MMC-HVDC systems by giving an overview of the process for developing a typical Multi-terminal (MT) MMC-HVDC (MTDC) model. The MTDC model developed in this paper is then employed to show the effect that selected MT control strategies can have on the MMC's arm currents.