Performance comparison of several classical controllers in AGC for multi-area interconnected thermal system

This paper presents automatic generation control (AGC) of interconnected two equal area, three and five unequal-areas thermal systems provided with single reheat turbine and generation rate constraints of 3% per minute in each area. A maiden attempt is made to apply integral plus double derivative (IDD) controller in AGC. Controller gains in the two-area system are optimized using classical approach whereas in the three and five area systems controller gains and governor speed regulation parameters (R_i) are simultaneously optimized by using a more recent and powerful evolutionary computational technique called bacterial foraging (BF) technique. Investigations reveal on comparison that Integral (I), Proportional-Integral (PI), Integral-Derivative (ID), or Proportional-Integral-Derivative (PID) controllers all provide more or less same response where as Integral-Double Derivative (IDD) controller provides much better response. Sensitivity analysis reveals the robustness of the optimized IDD controller gains and R_i of the five area system to wide changes in inertia constant (H), reheat time constant (T_r), reheat coefficient (K_r), system loading condition and size and position of step-load perturbation.