Real Time simulation of MMCs using the State- Space Nodal Approach

The Modular Multilevel Converter (MMC) topology is becoming an attractive solution for HVDC and FACTS systems. MMC structures are composed from several hundreds to thousands of half-bridge converters. Such large numbers of power switches and electrical nodes introduce important computational difficulties in electromagnetic transient (EMT) type programs. This becomes particularly more complex for performing real-time simulations. The combined state-space and nodal method (SSN) offers an efficient solution for clustering each MMC arm in order to reduce the number of nodes and decrease computation time. Moreover, the proposed approach permits simultaneous parallel computations and maintains accurate results. This paper presents the modeling of MMCs using the SSN method. A practical MMC-HVDC system case is used for testing the model under transient events and the results are validated by comparing with a detailed representation of all MMC components.