A systematic hub loads model of a horizontal wind turbine

The wind turbine industry has focused offshore on increasing the capacity of a single unit through up-scaling their machines. There is however a lack of systematic studies on how loads vary due to properties of a wind turbine and scaling of wind turbines. The purpose of this paper is to study how applied blade modifications, with similarities such as mass, stiffness and dimensions, influence blade root moments and lifetime damage equivalent loads (DELs) of the rotor blades. In order to produce fatigue load blade root moment trends based on the applied modifications. It was found that a linear trend of lifetime DELs based on the applied modifications of blades, which have effect on the natural frequency of blade of the original or reference model. As the control system was tuned for the specific frequency of the reference model. The linear trend of lifetime DELs was generated as long as the natural frequency of the reference model was preserved. For larger modifications of the wind turbine the controller would need retuning.