Efficient modeling of hybrid MMCs for HVDC systems

Modular multilevel converters (MMCs) have become the most promising converter technologies for medium/high-power applications, specifically for high-voltage direct current (HVDC) transmission systems. For the analysis of the large-scale MMCs-embedded power systems, i.e., multiterminal dc (MTDC) systems and dc grids, modeling and simulation plays an important role in transient and fault analysis. However, it is time consuming and infeasible to model and simulate large-scale MMCs-embedded power systems with detailed switching model (DSM). To accelerate time-domain simulation and improve computational efficiency, an equivalent circuit model (ECM) is proposed for hybrid MMC configuration based on various SM circuits. The proposed ECM can significantly improve simulation efficiency and be applied to the analysis of normal and fault operations of the MMC systems. The effectiveness of the proposed ECM is verified in the PSCAD/EMTDC software environment.