The nonlinear behavior of prestressed tuned mass damper for vibration control of wind turbine towers

Large capacity wind turbine towers with low natural frequency and low damping are subjected to resonance from wind action in its environment; thus, tuned mass dampers (TMD) are usually utilized to mitigate excessive vibrations. A novel prestressed tuned mass damper (PS-TMD) has been proposed by authors in previous work, and its vibration suppression performance has been verified under linear condition by simulations and tests. Since the pendulum and bottom cable of the PS-TMD are flexible, the additional deformation induced by these flexible cables will trigger nonlinear stiffness effect. To achieve the more accurate parameters design and optimal vibration control, the nonlinearities in the PS-TMD from the flexible cable deformation are explored in this paper. The mathematical model of the WTT with the nonlinear PS-TMD system is derived. The dynamic coefficient is obtained with the harmonic balance method, and different influential parameters affecting the performances of the WTT are discussed. Numerical simulation on vibration suppression of the WTT under both harmonic and wind excitations shows that the nonlinear PS-TMD is capable of providing smooth and excellent vibration suppression over a wide frequency range than the WTT with linear PS-TMD.