Dynamic Load Sharing Behavior for the Pitch Drive in MW Wind Turbines

For a wind energy system, main speed-increasing gearboxes, pitch drives and yaw drives are composed of a multistage planetary gear system. However, inevitable errors in the manufacturing and assembling of the gears lead to uneven load of distribution in the planetary gear system; thus, its service life and reliability decrease greatly, which would eventually affect the normal operation of the whole wind power system. In this study, a dynamic load sharing model of pitch drive is established with a lumped-parameter method. Given the manufacturing and assembly errors and central floating gear, the dynamic equations for each component, the stiffness matrix and damping matrix, the dynamic load sharing coefficient and the floating displacement of the sun gear are obtained according to the dynamic meshing force and damping load. Furthermore, the load sharing coefficient for external and internal meshing of the pitch drive for a 2 MW wind turbine with a three-stage planetary gear are achieved. Then, the floating displacement of the sun gear and the displacement of other gears are also obtained. Moreover, the influence of both external and internal meshing stiffness, the eccentric error and tooth frequency error for all components on the load sharing coefficient of all stages are investigated. Lastly, the theoretical components displacement of this model is compared with experiment results of the pitch drive under 50%, 100% and 150% rated torque in a test rig; the correctness of the model is verified by the experiment results.