Analysis of Collective and Enhanced Individual Pitch Control Strategies for Wind Turbines

In the nominal operating region of wind turbines, collective pitch control (CPC) regulates power by maintaining rated rotor speed, while individual pitch control (IPC) mitigates cyclic blade loads caused by wind variations like wind shear or turbulence. However, tuning CPC presents a significant trade-off, as improving power regulation often leads to an increase in fatigue blade loads. Additionally, IPC implementation via Multi-Blade Coordinate (MBC) transformation suffers from coupling between IPC loops, reducing controller effectiveness. Prior studies suggest that azimuth offset and static inverted decoupling enhance classical IPC implementations by mitigating this coupling. However, a comparative performance analysis between both implementations remains unexplored. This study addresses this analysis through a multi-objective optimization approach to tune CPC and IPC strategies for a 15 MW reference wind turbine. Four configurations (baseline CPC with conventional IPC, CPC+IPC, CPC+IPC with azimuth offset, and CPC+IPC with static inverted decoupling) are optimized. Results show that a well-tuned CPC improves IPC effectiveness, while the incorporation of azimuth offset or static inverted decoupling in IPC significantly improves both objectives, achieving reductions of approximately 19% in damage equivalent load on the blades and 60% in the integral squared error of power output compared to the baseline CPC with conventional IPC, and around 9% and 30% relative to the CPC with conventional IPC.