Sverre Skalleberg Gjerde

PhD-topic: Integrated converter design with generator for weight reduction of offshore wind turbines

Project Description: Recent years have shown an increasing interest in offshore wind power. This is due to better,more stable wind conditions and less environmental impact than found onshore. As a result of the offshore conditions, few, large turbines have been pointed out as more beneficial than many small. However, larger turbines means higher current ratings, and therefore it is crucial to perform the transformation to higher voltage in the nacelle. But a distribution transformer would add significantly to the top weight, and hence increase the overall cost of the turbine. Therefore, the focus of this research project is to design a converter, which together with an
ironless axial flux permanent magnet (AFPM) - generator, will eliminate the need for a distribution transformer. The design of the converter includes an evaluation and identification of a suitable
converter topology and the synthesis of a control system which guarantees proper operation of the generator drive. The converter- and control system should also have a structure which provides the generator drive with redundancy, and ensure continuous operation even if some parts of the system fails.

Additionally, while medium voltage AC-grids have been applied to offshore wind farms so far, recent research has pointed out the possible advantages of a DC-collection grid. To follow up this
research trend, the converter will be designed for a DC-collection grid, and the control system should contribute to the stability of such a grid.