Wind Turbine Collective and Individual Pitch Control Using Quantitative Feedback Theory

Individual pitch control is an innovative technique in wind turbine control. It has the potential of reducing the asymmetric mechanical loads on the blades in large multi-megawatt turbines. As the mechanical fatigue is reduced, the lifetime of the turbine can be significantly extended. This work develops an individual pitch control for the National Renewable Energy Laboratory’s (NREL) 5 MW reference wind turbine. The individual pitch controller works along with a collective pitch controller, designed using Quantitative Feedback Theory (QFT) robust control. Simulations of the complete individual and collective pitch control system are conducted with the NREL’s computer-aided engineering tool for horizontal axis wind turbines (FAST). They show that the addition of the individual pitch controller significantly reduces the loads on the tilt and yaw directions in the nacelle and tower of the turbine at 1P and 3P frequencies, and on the blades at the 2P harmonic frequency.