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UBC Theses and Dissertations

Wind and wave disturbance rejection control of floating offshore wind turbines Cortes Sanchez, Cristopher Jesus


The past few decades have seen an increasing interest toward wind energy since it has the potential to become the main global power source in the near future. Particularly, researchers are looking towards the development of offshore wind turbines since they have the potential to be way more efficient and have a higher rated power in response to stronger and steadier offshore winds. However, the harsh marine environment places challenges on the path to making offshore wind turbines an economically viable source of energy. Specifically, wind and wave disturbances act on the wind turbines inducing harmful loads on their major components, shortening their useful life and increasing maintenance cost. In this thesis, we propose a control method that rejects both wind and wave disturbances, thus reducing fatigue loads on the wind turbine structure while also maximizing power regulation. Based on a simplified control-oriented modeling technique, both wind and wave disturbance matrices are obtained from linearized state-space systems, and used to design a disturbance rejection H∞ controller. Furthermore, the proposed control method demonstrates the usefulness of including the wave disturbance matrix in the control design process, something that has been attempted in the past but not achieved yet in offshore wind turbine research. Finally, the performance of the designed H∞ controller is validated and compared against a baseline controller using Fatigue, Aerodynamics, Structures, and Turbulence (FAST), an open-source software package capable of modeling wind turbine systems and simulating their physical dynamics with high accuracy. This comparison demonstrates the effectiveness of the proposed method.

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