Design and real-time simulations of robust controllers for uncertain multi-input wind turbine

The problem of uncertainty in wind turbines is caused by factors like the random and stochastic nature of the wind, variations in the moment of inertia of its rotating parts, damping, stiffness factors, and discrepancies between its actual and mathematical model. The presence of uncertainty would deteriorate the wind turbine's performance, which can significantly affect rotor speed. Therefore, robust control strategies for speed control are necessary in the presence of uncertainties and wind disturbances, with the help of the control input taken as the blade pitch angle. Hence, a robustly stabilizing proportional-integral (PI) controller is designed under the purview of Kharitonov's polynomials to control the rotor speed for a ± 25% uncertain multi-input wind turbine. The robustly stabilizing ( K p , K i ) region of the designed PI controller is obtained by Kharitonov's theorem based on the 16-plant model after the formation of Kharitonov's rectangles. A ( K p , K i )-subregion is also extracted for all plants individually to achieve the desired time response specifications. The purpose of this analysis is to make sure that a simple PI controller can be made robust when there is a provision to choose its parameters from the stabilizing regions achieved. Real-time simulations are also made on the OPAL RT OP5700 Simulator to validate the performance of robust controllers designed in MATLAB. The real-time results clearly validate the performance of robustly designed controllers.