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The blade aerodynamic asymmetry fault must be detected early due to its important effect on wind turbines. This paper develops a fault diagnosis approach based on the current and power characteristics of a Doubly fed induction generator (DFIG). First, the blade aerodynamic characteristics and the influence on the nacelle and tower vibration under an aerodynamic asymmetry fault are analysed and an improved Blade element moment (BEM) method considering the blade, nacelle and tower vibration is proposed to calculate the aerodynamic torque. Then, the electrical characteristics of the DFIG are analysed. The output power is shown to decrease with oscillation when aerodynamic asymmetry occurs. In addition, the same modulation harmonic frequency as the blade rotating frequency exists in the stator and the rotor current. Finally, simulations under constant and stochastic wind conditions via MATLAB/Simulink show the effectiveness of the proposed method in this paper. [ABSTRACT FROM AUTHOR]

The effects of wind shear and the tower shadow contribute to periodic fluctuations in the wind speed and aerodynamic torque, which cause several problems. This study develops an equivalent wind speed model for large-scale, n-bladed wind turbines that includes the wind shear and the tower shadow effects. The comprehensive model is used to derive the disturbance components of wind speed caused by wind shear, the tower shadow, their synthesis, and the equivalent wind speed and to delineate their spatial distributions in the rotor disk area. Simulation results reveal that the effects of wind shear, the tower shadow, and the equivalent wind speed on the disturbance components fluctuate periodically and are closely related to the wind turbine correlation parameters, such as the rotor radius, hub center height, tower radius, distance from the tower midline to the blade, wind shear exponent, and blade number. [ABSTRACT FROM AUTHOR]