Robust Delay-Dependent Stability Analysis of Pitch Angle Control Systems in Wind Turbines

The aim of this study is to conduct a robust stability analysis, using the Kharitonov's Theoreö, of the controller gains that guarantee system stability for the blade pitch angle control system of wind turbines in the presence of uncertainties in the system parameters. The Kharitonov method is a technique used to analyze the stability of polynomials with uncertain coefficients. For the pitch angle control system to be robustly stable, the four polynomials derived from the characteristic equation must be stable. In this study, the maximum time delay values, defined as the Stability Delay Margin (SDM), at which the closed-loop system will be marginally stable, will be analytically computed using the methods of exponential term elimination and Kharitonov's approach together. Finally, the verification of robust stability delay margins and the robustness of the system have been demonstrated through simulation studies conducted in the time domain.