Modelling and Control of the Modular Multilevel Converter (MMC)

The Modular Multilevel Converter (MMC) represents an emerging topology with a scalable technology making high voltage and power capability possible. The MMC is built up by identical, but individually controllable submodules. Therefore the converter can act as a controllable voltage source, with a large number of available discrete voltage steps. This characteristic complicates the modelling both mathematically and computational. A mathematical model of the MMC is presented with the aim to develop a converter control system and the model is converted into the dq reference frame. Block diagrams for control of active power and AC voltage magnitude are shown.