Robust two-degree-of-freedom controller for automatic generation control of multi-area system

This paper proposes a novel, integer-order based, two-degree-of-freedom Proportional plus Integral plus Double Derivative (2-DOF-PIDD) controller for automatic generation control of a three unequal area thermal system considering reheat turbines and appropriate generation rate constraints. The performance of proposed 2-DOF-PIDD controller is studied and compared with conventional integral (I) controller and recently reported single degree of freedom based Proportional plus Integral plus Double Derivative (PIDD) controller. Nature-inspired firefly algorithm (FA) based optimization is employed to search for optimal controller parameters and governor speed regulation parameters simultaneously. Critical examination clearly reveals that proposed 2-DOF-PIDD controller gives better dynamic responses than I and PIDD controller in terms of settling time and reduced oscillations. Analysis also explored the superiority of FA over bacterial foraging optimization and artificial bee colony techniques. Furthermore, proposed controller is tested against several uncertain circumstances such as different loading condition, wide variation in inertia constant (H), different position of step load perturbation (SLP) to check the robustness. Proposed controller is also found to have performed well when the system is subjected to a higher degree of SLP and simultaneous occurrence of SLPs.