Examination of Loads and Responses of a Wind Turbine Undergoing Variable-Speed Operation

The National Renewable Energy Laboratory has recently developed the ability to predict turbine loads and responses for machines undergoing variable-speed operation. The wind industry has debated the potential benefits of operating wind turbines at variable speeds for some time. Turbine system dynamic responses (structural response, resonances, and component interactions) are an importantconsideration for variable speed operation of wind turbines. We have implemented simple, variable-speed control algorithms for both the FAST and ADAMS dynamics codes. The control algorithm is a simple one, allowing the turbine to track the optimum power coefficient (Cp). The objective of this paper is to show turbine loads and responses for a particular two-bladed, teetering hub, downwindturbine undergoing variable-speed operation. We want to see the response of the machine to various turbulent wind inflow conditions. In addition, we compare the structural responses under fixed-speed and variable-speed operation. For this paper, we restrict our comparisons to those wind-speed ranges for which limiting power by some additional control strategy (blade pitch or aileron control, forexample) is not necessary. The objective here is to develop a basic understanding of the differences in loads and responses between the fixed-speed and variable-speed operation of this wind turbine configuration.