This paper deals with the design of Fuzzy Proportional Integral and Derivative FPID controller self tuned by Relative Rate Observer RRO method. The developed approach is applied to the Load-Frequency Control LFC of the Egyptian power system EPS as a single area with multi unit power system. The studied power system comprises three power plants; non-reheat, reheat and hydro generation plants. The proposed FPID controller is designed on an average point of four loading conditions of the EPS during summer and winter of 2008. The effectiveness of the proposed FPID self tuned by RRO
(FPID-RRO) has been demonstrated by introducing the system nonlinearities using MATLAB-SIMULINK simulation program. Moreover, a comparison of the FPID with FPID-RRO controllers under different disturbances and parameter variations are presented to validate the FPID-RRO controller. The simulation results reflect and prove fast settling time and accurate tracking for the LFC of the Egyptian Power System.