Multilevel Modular Converter Design and optimization
by Colin Oates, Alstom Grid, United Kingdom
Abstract - The Multilevel Modular Converter (MMC) originally proposed by Rainer Marquardt has made it practical to realise converters with ratings of up to 1000MW using standard industrial components. The use of many "submodules", in which all the power electronics is contained, to realise a converter where the AC and the DC voltages are under direct control and have very little noise content appears to be an ideal; however for these converters to operate against all the variations that might be expected in service requires careful consideration of the number of submodules that will be required. The presentation will give a general description of the converters being constructed for the "South West" HVDC link in Sweden and will then develop the mathematical description of the converters operation. From this it will be demonstrated how these variations are accounted for in the converter design.