TMD stroke limiting influence on barge-type floating wind turbines

Abstract

In this paper, passive structural control techniques are applied to a barge-type Floating Offshore Wind Turbine (FOWT) to mitigate the impact of pendulum effect loads. The passive structural control device, a tuned mass damper (TMD) installed in the nacelle, is analyzed on a reduced dynamics FOWT model. Genetic algorithms are used for the optimization process, taking the tower fatigue as the fitness function, implemented as the standard deviation of the fore-aft tower top displacement. The optimization of the TMD shows that its resulting stroke is unfeasible in terms of space needed for installation. Therefore, the addition of stroke-limiting stops to the TMD should be considered. A new optimization, including stops, yields a clear improvement of the device performance while limiting the stroke to the nacelle dimensions. It is observed that the stops allow to mitigate the second collective platform pitch-tower bending mode in addition to the first one. Finally, a third case is presented, considering the whole stops configuration as additional variables in the optimization loop. This last case improved the TMD performance in terms of vibration suppression rate, proving the effectiveness of optimizing stops for mass and space constrained applications.