Improved reliability of wind turbine towers with tuned liquid column dampers (TLCDs)

Modern wind turbines are supported by slender, flexible and lightly damped tall towers, which exhibit high susceptibility to wind-induced vibrations. This paper develops a framework that combines efficient dynamic response models and probabilistic assessment tools to show how to structural response and improve structural reliability when equipping modern turbines with tuned liquid column dampers (TLCDs). This study improves a dynamic model of a wind turbine to accommodate single or multiple TLCDs to control excessive vibrations. The model is subjected to stochastically generated wind loads of varying speeds to develop wind-induced probabilistic demand models for towers of modern turbines under structural uncertainty. Results indicate that a baseline TLCD with 1% of the total wind turbine mass achieves up to 47% reduction in peak displacements. Furthermore, the study constructs fragility curves, which illustrate reductions in the vulnerability of towers to wind forces owing to the inclusion of the damper. Annual failure probabilities computed based on the likelihood of wind speed realizations in West Texas and West California, U.S. demonstrate reliability gains of up to 8% using the baseline TLCD. This paper also observes that the use of two TLCDs with a total mass ratio of 1.5% yields marginal benefits over the baseline TLCD gains. Rather, increasing the mass of the baseline TLCD to 1.5% of the turbine mass reduces peak responses by 53% and the annual failure probability by as much as 11%. These results suggest a viable alternative to help achieving long-term reliability and risk targets for utility scale wind turbines.