Identification of Vibration Modes in Floating Offshore Wind Turbines

• Published in: Journal of marine science and engineering 2023-10, Vol.11 (10), p.1893
• Main Authors: Serrano-Antoñanazas, Mikel, Sierra-Garcia, Jesús-Enrique, Santos, Matilde, Tomas-Rodríguez, María
• Format: Article
• Language: English
• Subjects: Active damping; active tower damping; Air-turbines; Barges; Comparative analysis; Control algorithms; Control systems; Control systems design; Damping; Decomposition; Degrees of freedom; Design; Energy consumption; Environmental impact; Filter banks; Floating; floating wind turbine; Fourier transforms; frequency; Methods; Offshore; Oscillations; pitch control; Turbine engines; Turbines; Useful life; Vibration; Vibration analysis; Vibration damping; Vibration mode; Wind; wind energy; Wind power; Wind turbines; Winds
• ISSN: 2077-1312; 2077-1312
• DOI: 10.3390/jmse11101893

Compared to onshore turbines, floating offshore wind turbines (FOWTs) take advantage of the increased availability of offshore wind while causing less environmental impact. However, the strong winds, waves, and currents to which they are subjected trigger oscillations that can cause significant damage to the entire structural system and reduce its useful life. To reduce these loads, active tower damping techniques such as filter banks can be used. These filters must be carefully tuned to block specific vibration frequencies. Therefore, it is essential to analyze the nature of the oscillations in the FOWT and to understand how the frequencies vary in time. This topic is usually approached from a point of view very focused on a specific turbine. What is proposed here is a general method, which can be applied to any type of wind turbine, to automatically study the relationship between vibration frequencies and the degrees of freedom (DOF) of the turbine, which facilitates the design of structural control. Each frequency is associated with the DOF of the FOWT that produces it. This methodology has been successfully validated in simulation experiments with the NREL 5 MW ITI Barge FOWT. Under the wind conditions of the experiments, the main frequency found is 0.605 Hz. This frequency coincides with the 3P theoretical frequency of the FOWT. This proposal may help to design structural control systems able to damp these vibration frequencies with accuracy and efficiency.