Methods for the Tower Fatigue Loads to Cumulative Based on Wind Direction Probabilistic

The wind turbine tower bears alternating fatigue load with a life of 20 years. The fatigue load mainly comes from turbulence. The turbulence intensity changes with the wind direction as the influence of surface roughness and wake. The general tower fatigue loads to accumulate does not consider the influence of the wind direction. It is assumed that the wind direction is always in one direction for load calculation and simulation. However, the wind turbine will yaw according to the main wind direction to always make the wind turbine in the optimal wind direction at a specific wind turbine site. Three methods are discussed in this paper for the tower fatigue loads to cumulative based on wind direction probabilistic. The calculation efficiency of equivalent fatigue accumulation for the tower of the wind turbine based on wind direction probability distribution is greatly reduced as the innovative use of the ranking method to simplify the engineering application.