A design of fuzzy-based hierarchal approach is proposedto improve the frequency control in the power system. The simplified Great Britain (GB) frequency control model, was used as a single bus machine. A new simple tuning method is proposed with the aid of the conventional PID controller gains. The same gains are used to feed the fuzzy controller in the same loop without re-tuning the fuzzy gains. This method allows the fuzzy structure to supplement the conventional control rather than replacing it. Particle Swarm Optimization (PSO) is proposed to find the optimal value of the controller gains. Five modeling scenarios for the fuzzy control and two cases of uncertain parameters were considered to validate the model. Structures of fuzzy controller offered high stability and robustness in the simulation results. Therefore, the proposed hierarchal structuresare used in the real-time applications of the load frequency control in the power systems. (C) 2016 Elsevier B.V. All rights reserved.