A Low Order Model for Analyzing effects of Blade Fatigue Load Control

A new low order mathematical model is introduced to analyse blade dynamics and blade load reducing control strategies for wind turbines. The model consists of a typical wing section model combined with a rotor speed model, leading to four structural degrees of freedom (flapwise, edgewise, and torsional blade oscillations, and rotor speed). The aerodynamics is described by a model of unsteady aerodynamic. The equations of motion are derived in nonlinear and linear form. The linear equations of motion are used for stability analysis and control design. The nonlinear equations of motion are used for time simulations to evaluate control performance. The stability analysis shows that the model is capable of predicting classical flutter, and stall-induced vibrations. The results from the stability analysis are compared with known results, showing good agreement. The model is used to compare the performance of one Proportional-Integral-Derivative controller and two full-state feedback controllers.