Stability analysis of pitch angle control of large wind turbines with fractional order PID controller

Abstract

This article proposes a robust delay dependent stability analysis of pitch control system of large wind turbines (LWTs) having communication time delay with fractional order PID controller. Fractional order proportional integral and derivative (FOPID) controller is used for pitch angle control. To analyze gain and phase margins effect, a gain and phase margins (GPMs) tester is added to the control path of the large wind turbine (LWT). An exact method in frequency domain is applied for the stability analysis of the LWT. Appropriate selection of FOPID controller parameters, large delay margins are obtained with respect to previous studies. A more robust control scheme is presented and analyzed with different operating conditions. As compared to literature studies, larger time delay margin is obtained. Moreover, in terms of control systems performance metrics better results are obtained with respect to previous studies in the literature. Validation of theoretical results are verified by simulations in Simulink/Matlab environment under various operating conditions. Also, delay margin accuracy is compared with the results obtained from Quasi-Polynomial Mapping Based Root finder (QPmR) method. The results show that better delay margin results are obtained with respect to previous studies.