System Dynamic Modelling of Three Different Wind Turbine Gearbox Designs under Transient Loading Conditions

Wind turbine (WT) drivetrain design configurations affect dynamic loads experienced by the drivetrain components under different operational conditions. This paper presents system modelling of dynamic loads experienced by key mechanical components within WT gearbox under different operational conditions by using MATLAB/Simulink. Two operational conditions of WTs are considered; normal operation and shutdown, using torque spectrums measured from a field operating wind turbine. The torsional dynamic loads under these conditions differ significantly; during normal operation, the maximum torque ratio is below the recommend value however it exceeds the recommended level during shutdown. It has been found that the shutdown event has a considerable effect on gear loading; it causes occurrences of loading reversal of gear meshing forces. Moreover, the variation range of meshing forces between planetary and sun gears is five to six times higher than that during normal operation. During shutdown, the most dominated vibration frequency of the WT drivetrains is the lowest one which is very close to the estimated natural frequency of the low speed shaft and that may cause the resonance of the drivetrain system.