Integrated Vibration Control and Energy Harvesting of Offshore Wind Turbines Subjected to Misaligned Wind and Wave Loading

Offshore wind turbines under combined wind and wave loading suffer from excessive vibration which damages the structural integrity and causes potential collapse of the wind turbines. In this paper, a three-dimensional pendulum tuned mass damper (3d-PTMD) is utilized to mitigate the bi-directional vibrations as well as harvest the kinetic energy. A linear electromagnetic energy harvester consisting of magnets and coil assemblies is connected with the pendulum to convert the kinetic energy of the pendulum into electricity. An analytical model of an offshore wind turbine coupled with the 3d-PTMD is established. To examine the performance of the 3d-PTMD in mitigating vibrations in the fore-aft and side-side directions, misaligned wind and wave loading is considered. For comparison, two linear tuned mass dampers are deployed in the side-side and fore-aft directions. A 5 MW baseline wind turbine model is utilized to examine the performance of the 3d-PTMD. Results show that the 3d-PTMD outperforms the traditional TMD in mitigating the bi-directional vibrations induced by misaligned wind and wave loading. In addition, considerable amount of energy can be harnessed using the energy harvester.