Dimensioning and design of a Modular Multilevel Converter for drive applications

The Modular Multilevel Converter is an upcoming topology for medium voltage drive applications in the megawatt power range. This paper presents the procedure of the converter's dimensioning, which is used for the design of a prototype MMC-System. The voltage rating and the required size of the capacitors in the cells are calculated. The inductance of the arm choke, depending on the modulation strategy is determined. The prototype is realised by using self-powered cells, which are pre-charged without any additional power supply during the start-up phase. The design of the complete prototype including the signal processing is shown. This system provides the opportunity to analyse different control schemes, modulation strategies, impacts on the machine etc.