The yaw system's braking torque is generally designed to withstand aerodynamic yaw loads and to hold the nacelle in a given position. Circumstances in which the yaw loads are higher than the yaw system's braking torque can occur a) because of reduced braking effectivity due to mechanical failures, brake wear or environmental influences [1; 2] and b) because of economic reasons the braking torque is designed not to withstand extreme aerodynamic loads as their appearance is considered rate and the consequences not serious [3]. In these cases, the nacelle will stip and turn around the tower axis. To analyze the loads and dynamics of the wind turbine during nacelle slippage a detailed yaw system model has been incorporated into a multibody system model based on a 3.3 MW wind turbine and load simulations have been conducted. The focus is to address uncertainties of the braking capabilities and compare different braking models during design load cases in which nacelle slippage can occur.
展开▼
