Stability margin analysis for PI pitch controllers on large wind turbines

This work addresses blade pitch controllers for variable speed wind turbines for the purpose of maintaining power at rated value during above rated wind speeds. The work proposes a collective proportional integral (PI) pitch controller design that accounts for the effects of low frequency aero-elastic modes to enhance the performance of the basic PI controller used in industry. Validation was performed by testing the proposed controller on a non-linear model for the DTU10MW turbine under turbulent wind conditions. Statistical analysis of fatigue loads at the main shaft bearing were further investigated to verify that the proposed controller does not add excessive loading compared with the basic controller.