Reduced Order Model for Control Applications in Offshore Wind Turbines*

:A reduced order model for application in model-based observers and controllers for offshore bottom-fixed wind turbines is developed. The model includes a description of aerodynamic and hydrodynamic loads, drive-train dynamics, a mode-shape based model for the tower and sub-structure, and a description of wind behaviour based on an equivalent wind formulation. An explanation of the main control objectives with corresponding control laws are also included. Models are verified by comparison with results obtained from the software tools USFOS by MARINTEK/NTNU and HAWC2 by DTU wind energy, and they show good agreement.