(IOP Publishing, 2022) Ros Ganuza, Javier; Olcoz Alonso, Álvaro; Plaza Puértolas, Aitor; Zientziak; Institute of Smart Cities - ISC; Ciencias; Gobierno de Navarra / Nafarroako Gobernua
Traditionally, stability assessment of wind turbines has been performed by
eigenanalysis of the azimuthally-averaged linearized system after applying the Multi-Blade
Coordinate (MBC) transformation. However, due to internal or external anisotropy, the MBC
transform does not produce an exact Linear Time-Invariant (LTI) system, and a Floquet analysis
is required to capture the influence of all periodic terms, leading to a more accurate stability
analysis. In this paper exponential integration methods that use system linearizations at
different blade azimuth positions are used to integrate the perturbed system state and compute
the Floquet monodromy matrix. The proposed procedure is assessed for a simple 6 DOF wind
turbine model and a more complex aeroelastic model of a 5MW onshore wind turbine. The
defined along-the-path or moving-point exponential integrator is found to be the suitable in
order to perform a Floquet stability analysis even using a coarse linearization grid.