This article describes the automatic generation control of a two area multi-unit interconnected power system with Proportional-Integral-Derivative controller with Filter (PIDF) tuned by teaching learning based optimization (TLBO) algorithm. Each area is equipped with three reheat thermal units with hydraulic amplifiers. The gains of the PIDF controllers are simultaneously optimized by applying a step load perturbation of 0.01 in area 1 considering integral time absolute error (ITAE) as the fitness function. The enhancement of the control behavior of the proposed optimized PIDF controller is proved in comparison with the conventional PID controller. The dynamic responses of the system is compared in terms of settling time, peak overshoots and undershoots. Further the sensitiveness and robustness of system is verified by applying disturbances in both the area simultaneously.