Fatigue Damage of Wind Turbine Gearbox Under Extreme Wind Conditions

This paper presents a study of quantifying wind turbine gearbox damage under extreme wind attaches and various pitch system response speed. The evaluation is performed by constructing a 1.5MW variable-speed wind turbine model which integrates multi-body dynamic model of a three stage gearbox in the assist of GH bladed software. The internal excitation is considered by introducing a time varying stiffness and gear damping in the gearbox. The result shows that extra damage caused by extreme wind gust is higher than that under normal condition. The increase of the extreme wind attach frequency will significantly increase the gear damage. Each extreme wind attach will cause 15% and 5% extra damage when it occurs below and above rated wind speed range respectively. The trend of extra fatigue damage is positively related to the power generated by a wind turbine. Faster pitch speed response can help to reduce fatigue damage under extreme wind condition. The result shows the importance of counting extreme wind attaches within wind turbine operating period and the optimization of pitch system response is the key to reduce the damage and control the risk. This is meaningful for gearbox health management and control strategy optimization of a wind turbine design.