Load frequency control problem in interconnected power systems using robust fractional PIλD controller

In this paper, a robust Fractional Order PIλD controller that contains an integral fraction action and a simple filtered derivative action, is investigated on Automatic Generation Control (AGC) of a three areas reheat-thermal system. For more realistic study some nonlinear constraints have been introduced such as Governor Dead Band (GDB), Generation Rate Constraints (GRC) and boiler dynamics. The optimal controller parameters are tuned through new evolutionary algorithm known as Differential Evolution (DE) algorithm by minimizing the Integral of Squared Error (ISE) index. Obtained results reveal clearly the superiority of the investigated controller compared to the other controllers such as PID, PIDμ and PIλDμ in terms of the performance index, peak overshoots, peak undershoots and settling time. Effectiveness and rapidity of the DE algorithm in the convergence have been shown and compared to Genetic Algorithm (GA). Finally, robustness analysis against higher degree of load disturbance and sever parametric variation demonstrates the effectiveness of the investigated controller.