Prescribed-Time Tracking Control for Wind Turbines in Variable Speed Mode With Guaranteed Performance

This article aims to solve a challenging problem in tracking control of the wind turbines' rotor speed: achieving the tracking of the speed for the reference signal within a prescribed time so as to guarantee that turbines capture the maximum wind power. The difficulty is how to make the sign of the tracking error invariable on the whole time-horizon while keeping the difference between the high-speed shaft angle and the low one bounded. Based on barrier functions constructed with constrained boundaries and the reference signal, we develop a novel continuous feedback controller by introducing a time-varying function associated with the prescribed time. Superior to the existing tracking results of wind turbines, the presented strategy is capable of driving the speed to track the desired signal within a prescribed time and obtaining the guaranteed performance, which is characterized by nonovershooting tracking error and inviolate time-varying asymmetric output constraints. Finally, experiments by MATLAB and hardware-in-the-loop are conducted to exhibit the effectiveness/advantages of the developed technique.