Individual Pitch Control with a Reduced Actuator Duty Cycle*

Individual pitch control (IPC) is used to mitigate loads on wind turbines, the most commonly applied method being based on a simple proportional integral (PI) formulation. Recently, a nonlinear PI (NPI) formulation has been proposed. Under simplified inflow conditions, NPI has been shown to provide load reductions that are similar to the standard PI formulation, but with a reduced pitch activity. This is interesting, because pitch activity can increase operation and maintenance costs, reduce component lifetime, in addition to implying an expenditure of energy to drive the actuators. This study focuses on the tuning and testing of NPI-IPC under more realistic inflow conditions.The analysis is conducted using two different wind turbines: the IEA Task 37 reference turbine, and the G2 scaled wind turbine for wind tunnel testing. Turbulent inflow conditions are generated based on standard turbulence models and with large eddy simulations (LES). The baseline PI and advanced NPI controllers are tuned by numerical optimizations driven by a fatigue-oriented cost function, based on aeroservoelastic simulations. Results confirm that, while the two controllers achieve a similar fatigue load mitigation, the NPI formulation is associated with a reduced actuator duty cycle.