The effect of a speed exclusion zone and active tower dampers on an upwind fixed-hub two-bladed 20 MW wind turbine

Abstract

Large two-bladed offshore wind turbines possess cost-saving potentials in their complete life-cycle, together with general structural blade advantages, compared to similar three-bladed machines. However, the general dynamics and tower-eigenfrequency interactions are challenging. Therefore, a speed exclusion zone for the partial load region and two straightforward pitch- and generator-driven tower dampers for the whole power production region are introduced. They enable the incorporation of a reasonable controller for a two- and a three-bladed baseline reference to facilitate a fair and objective turbine comparison. The outlined control features significantly reduced tower fatigue loads by 18 % and 70 % in the case of a three-bladed 20 MW and a two-bladed 20 MW turbine, respectively.