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UBC Theses and Dissertations

Position control of a floating offshore wind turbine system using aerodynamic force Han, Chenlu


As a renewable and environmental-friendly energy source, wind energy has experienced a significant increase in its popularity. To take advantage of the stronger and steadier offshore wind resource, utility-scale floating wind turbine systems need to be deployed in offshore wind farms. To maximize the overall power production, the distribution layout of wind turbines in the wind farm should be optimized and updated in response of real-time wind direction changes. To achieve this goal, it requires both a wind farm level layout optimization algorithm for computing the optimal layout and a wind turbine level position controller for ensuring successfully position transfers. In this thesis, we first propose a mechanism to move the floating wind turbine by passively utilizing the aerodynamic thrust force from the wind. Advantages of this actuation mechanism include its general applicability and easy implementation to modern floating wind turbine systems, without the need for energy consumption and hardware modifications. Secondly, we introduce the concept of the movable range of a floating wind turbine which describes the feasible range of its equilibrium position under the constraints of the power requirement and safety limits. This movable range information is critical in the wind farm layout optimization algorithm as it determines the set of feasible layouts from which the optimal solution should be sought. A numerical algorithm is proposed to obtain the movable range of a wind turbine system, and the computed result is validated in widely-adopted wind turbine simulation software. In addition, the influences of wind speed and direction, required power, and catenary line length on the movable range are analyzed. Finally, three position controllers for the floating wind turbine, that is, a model-free controller, a model-based open-loop controller and a model-based state feedback controller, are designed. Their simulated control performances are compared in terms of position transfer, power regulation and vibration suppression. We demonstrate that it is possible to achieve the desired position transfer while maintaining a smooth and uninterrupted wind turbine operation.

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