A Control Algorithm to Reduce The Tower Fore-Aft Oscillations Of A Variable Speed and Pitch Controlled Horizontal Axis Wind Turbine

In a horizontal axis wind turbine, while operating beyond rated wind speed (Vrat < Vw < Vcut−out ), the controller objective is to regulate the generated power at the rated value even when the wind speed changes. The pitch control algorithms, typically used for this purpose has influence on the tower oscillations. In this report, a new control technique is proposed, which, based on measured pitch angle, generator speed, power, and the wind speed estimate generates the commanded values for the two control inputs — pitch angle and generator torque. These control inputs are generated such that not only the power regulation is achieved but also the variation in the thrust force acted on the tower corresponding to the wind speed changes is less, which in turn reduces the tower fore-aft oscillations. Preliminary results are included in the report.