A Method for the Analysis of the Aeroelastic Stability of Slender Wind Turbines and Its Validation

Aeroelastic stability has become an important constraint for current long and slender blade designs in the wind industry. In this work, we present a method for the stability analysis of wind turbines as three-dimensional multi-flexible-body systems. Aerodynamic forces are linearized via numerical perturbation and linear regression fit from multiple points around quasi-static equilibrium status. A novel coordinate transformation is proposed to convert the basis from the absolute frame of reference to the local frame of reference at the rotating center in a corotational formulation. The modal analysis is performed in the MBC generalized coordinates and damping ratios are extracted to assess the aeroelastic stability of wind turbines. Field validation is performed on two offshore prototype wind turbines, proving that the prediction of unstable wind speed ranges matches experimental data quite well.