In this research paper an optimal 2-Degree freedom of proportional-integral-derivative controller (2-DOF PID) tuned by grey wolf optimization(GWO) is suggested for automatic generation control (AGC) of a multi-source power system comprising of two areas where each area contains a thermal unit, a hydro unit and a gas unit. The active response of the system is observed under two cases: with AC tie-line and with AC-DC tie-line. The optimal values of the 2-DOF PID controllers are achieved by taking integral time absolute error (ITAE) as objective function with the application of a disturbance of 0.01p.u. in area 1. To show the supremacy of the proposed controller the results obtained is compared with pre-published result such as DE tuned PID controller. Numerous time domain parameters such as settling time, peak overshoots and peak undershoots are computed and compared with the pre-published results so as to show the superiority of the suggested controller.