Conception of a modular multilevel converter in a multi-terminal DC/AC transmission network

In the frame of a collaboration project within Swiss Competence Centre for Energy Research in the Future Swiss Electrical Infrastructure section, a Multi Terminal DC pilot has been implemented for studying the interaction between an HVDC and a high voltage AC grid. For the interaction with the medium voltage AC grid, a Modular Multilevel Converter is being designed for its features in low harmonic content, scalability, and flexibility. The energy buffering of the converter will allow the converter to sustain either AC or DC grids. The operation of the converter is described in details and simulated.