Model-based aeroelastic analysis and blade load alleviation of offshore wind turbines

Offshore wind turbines take advantage of the vast energy resource in open waters but face structural integrity challenges specific to their operating environment that require cost-effective load alleviation solutions. This paper introduces a computational methodology for model-based two- and three-dimensional design of load alleviation systems on offshore wind turbines. The aero-hydro-servoelastic model is formulated in a convenient state-space representation, coupling a multi-body composite beam description of the main structural elements with unsteady vortex-lattice aerodynamics and Morison's description of the hydrodynamics. The aerodynamics does not require empirical corrections and focuses on a control-oriented approach to the modelling. Numerical results show that through trailing-edge flaps actuated by a robust controller, more than 60% reduction in dynamic loading due to atmospheric turbulence can be achieved for the sectional model and close to 13% reduction in blade loads is obtained for the complete three-dimensional floating turbine