a Fayazi - Department of Electrical Engineering , Vali-e-Asr University of Rafsanjan , Rafsanjan , Iran.
h ghayoumi zadeh - Department of Electrical Engineering , Vali-e-Asr University of Rafsanjan , Rafsanjan , Iran.
a soltani sangi - Department of Electrical Engineering , Misagh Institute of Higher Education , Rafsanjan , Iran.

In this paper , an efficient optimized fractional-order fuzzy proportional-integral-derivative controller (FOFPID) based on biogeography-based optimization (BBO) method is designd for automatic generation control of a two-zone four unit hydro-thermal power system. Studies were conducted in two scenarios . In the first scenario , the simulation was carryout for power system with pure-thermal units and in the second scenario; the simulation was performed for hydro-thermal power system . In each scenario , Ten percent load changes have occurred in both areas . Moreover , the simulations were also performed by applying the conventional PI , PID , and the hybrid PSO-PS based Fuzzy-PI controllers for two aforementioned scenarios . The numerical simulation results illustrated that the proposed optimized control scheme outperforms the other controllers such as the conventional PI , PID , and the hybrid PSO-PS based Fuzzy-PI controllers under uncertainties in terms of minimizing frequency deviations . Such that we had a decrease for the Integral Square Time Square Error (ISTSE) and settling time , with a ۱۵% and ۴۳% reduction , respectively . Moreover , the simulation results were also demonstrate the effectiveness and the convergence of the BBO algorithm .

Automatic Generation Control, Load Frequency Control, Biogeography-Based Optimization Fractional-Order Controller