Consistent Modal Calibration of a Pendulum-Type Vibration Absorber

2022 ◽  
Author(s):  
J. Høgsberg
Keyword(s):  
Wind Turbines ◽  
Offshore Wind ◽  
Vibration Absorber ◽  
Wave Loading ◽  
Offshore Wind Turbines ◽  
Stiffness And Damping

Abstract. Pendulum absorbers are installation in offshore wind turbines to mitigate excessive vibration amplitudes from wind and wave loading. The pendulum damper is placed inside the tower and attached to the structure at two distinct points: The tower top, where the pendulum arm is fixated, and at the position of the pendulum mass, which is connected to the tower wall by the damper. The present paper derives a modal calibration principle, which consistently accounts for different points of attachment for the absorber stiffness and damping.

Controller Design to Reduce Mechanical Fatigue in Offshore Wind Turbines Affected by Ice and Tide

2011 ◽  
Author(s):  
Katherine Faley ◽  
Mario Garcia-Sanz
Keyword(s):  
Wind Turbines ◽  
Controller Design ◽  
Weather Conditions ◽  
Offshore Wind ◽  
Control Technique ◽  
Offshore Wind Turbines ◽  
Mechanical Fatigue ◽  
New Strategy ◽  
Equivalent Mass ◽  
Stiffness And Damping

This paper presents a novel control structure to mitigate the mechanical fatigue in towers of onshore and offshore wind turbines. A general wind turbine dynamic model for both, (1) onshore and (2) offshore systems with the effects of ice and tide is included. These weather conditions further contribute to the uncertainties in the model, most importantly, in the values of tower equivalent mass, stiffness, and damping and increase the amplitude of the velocity of tip-tower vibrations at some particular frequencies, which creates greater mechanical fatigue. A novel control technique to attenuate such a mechanical fatigue is presented in the paper. It is based on the variation of the generator torque in the above rated wind speed region. The control strategy, designed by using Quantitative Feedback Theory (QFT), decreases the velocity of the nacelle movement due to the wind turbulences, thus reducing the associated mechanical fatigue. The new strategy is validated with a realistic nonlinear simulator under a set of different input scenarios and a Monte Carlo method for the uncertainty selection.

Efficient Multiline Anchor Systems for Floating Offshore Wind Turbines

2016 ◽  
Author(s):  
Casey M. Fontana ◽  
Sanjay R. Arwade ◽  
Don J. DeGroot ◽  
Andrew T. Myers ◽  
Melissa Landon ◽  
...  
Keyword(s):  
Dynamic Simulation ◽  
Wind Turbines ◽  
Wind Farm ◽  
Offshore Wind ◽  
Wave Loading ◽  
Peak Demand ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Anchor Systems ◽  
Floating Platforms

A mooring and anchoring concept for floating offshore wind turbines is introduced in which each anchor moors multiple floating platforms. Several possible geometries are identified and it is shown that the number of anchors for a wind farm can be reduced by factors of at least 3. Dynamic simulation of turbine dynamics for one of the candidate geometries and for two directions of wind and wave loading allows estimation of multiline anchor forces the preview the types of loads that a multiline anchor will need to resist. Preliminary findings indicate that the peak demand on the anchor may be reduced by as much as 30% but that anchors used in such a system will need to be able to resist multi-directional loading.

scholarly journals WAVE LOADS AND STABILITY OF NEW FOUNDATION STRUCTURE FOR OFFSHORE WIND TURBINES MADE OF OCEAN BRICK SYSTEM (OBS)

2011 ◽  
Vol 1 (32) ◽  
pp. 66
Author(s):  
Saskia Pfoertner ◽  
Hocine Oumeraci ◽  
Matthias Kudella ◽  
Andreas Kortenhaus
Keyword(s):  
Wind Turbines ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Modular System ◽  
Wave Loads ◽  
Wave Loading ◽  
Offshore Wind Turbines ◽  
Additional Stability ◽  
The Stability ◽  
Foundation Structure

The Ocean Brick System (OBS) is a modular system consisting of hollow concrete precast blocs (10m x 10m x 10m) piled up like cubes and interconnected to create a stiff, light and strong structure which can be used for artificial islands, artificial reefs, elevation of vulnerable low lands, deep water ports, breakwaters and foundation of offshore wind turbines. The paper focuses on the experimental results on the wave loading and the stability of the OBS used as a foundation of the support structure of offshore wind turbines. Diagrams for the prediction of total horizontal forces, vertical forces and overturning moments induced by irregular waves on the OB-structure are derived and verified through additional stability tests and stability analysis.

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