Offshore Wind Turbine Load Reduction Employing Optimal Passive Tuned Mass Damping Systems

Offshore wind turbines can capture the high-quality offshore wind resource but suffer from increased loading from waves and ice. Reducing these loads through structural control techniques has the potential to be an economically viable solution. Both fixed-bottom and floating substructures are considered in this paper, which will investigate a fixed-bottom monopile as well as a barge, spar buoy, and tension-leg platform for the floating platforms. A set of optimum passive tuned mass dampers are developed by creating a limited degree-of-freedom model for each of the four offshore wind platforms. These models are then integrated into an optimization function using a genetic algorithm to find a globally optimum design for the tuned mass damper. The tuned mass damper parameters determined by the optimization are applied to a series of wind turbine design code simulations using FAST. A sensitivity analysis of the tuned mass damper parameters and a study on the effect of misaligned wind and waves on load reductions are also conducted. Results from these simulations are presented, and tower fatigue damage reductions of up to 20% are achieved for the various tuned mass damper configurations.