Influences of Wind Shear and Tower Shadow on the Power Output of Wind Turbine

Abstract

The influences of the wind shear and tower shadow on the power output of wind turbines in terms of power fluctuation and power loss are investigated. Firstly, the wind shear model and the tower shadow model are described in detail. The tower shadow model is modified in view of the cone-shaped towers of modern large-scaled wind turbines. Subsequently, power fluctuation and power loss due to wind shear and tower shadow are analyzed for NREL 5 MW baseline wind turbine with blade element momentum(BEM) theory. Results indicate that the power fluctuation is mainly caused by the tower shadow, whereas the power loss is primarily induced by the wind shear. The power loss can be divided into wind farm loss and rotor loss. The wind farm loss is a constant while the rotor loss is strongly influenced by the wind turbine control strategies. When the variable-speed controller works, the rotor loss stabilizes around zero, but when blade pitch controller works, the rotor loss increases as the wind speed intensifies.