On the Potential of Pitch Control for Increased Power Capture and Load Alleviation

Wind turbine control is a research area that is gaining increasing interest, and numerous simple and advanced control schemes have been suggested, especially for load alleviation. The performance of such controllers is often compared to the performance of simpler controllers, thus relative to a moving reference. This study is focused on estimating the upper limits of the power increase and load variation alleviation that are achievable through pitch actuation. Knowing these upper limits, the potential of improving existing controllers can be assessed. The achievable power output increase and load variation reduction are estimated through numerical optimization of the pitch and generator torque actuation. Results show that the potential of increased power output at below rated wind speeds through optimized pitch actuation is greatest for inflows that varies with the azimuthal position of the blades. It is shown that at above rated wind speeds, the potential of decreasing the wind shear induced load
variations beyond what is possible with a simple cyclic pitch scheme is limited. The results presented in this study are all obtained from simulations with deterministic inflow because the absolute upper limits are sought, and turbulent inflow is assumed to decrease these limits.