High Power Density Power Electronic Converters for Large Wind Turbines by Osman Selcuk Senturk

Dissertation submitted to Faculty of Engineering, Science, and Medicine at Aalborg University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering Aalborg University Department of Energy Technology Aalborg, Denmark November 2011 Abstract In large wind turbines (in MW and multi-MW ranges), which are extensively utilized in wind power plants, full-scale medium voltage (MV) multi-level (ML) voltage source converters (VSCs) are being more preferably employed nowadays for interfacing these wind turbines with electricity grids. For these VSCs, high power density is required due to limited turbine nacelle space. Also, high reliability is required since maintenance cost of these remotely located wind turbines is quite high and these turbines operate under harsh operating conditions. In order to select a high power density and reliability VSC solution for wind turbines, first, the VSC topology and the switch technology to be employed should be specified such that the highest possible power density and reliability are to be attained. Then, this qualitative approach should be complemented with the power density and reliability assessments of these specific VSCs so that their power densities and reliabilities are quantitatively determined, which requires extensive utilization of the electro-thermal models of the VSCs under investigation.
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