Today a power system interruption is far more serious, work is interrupted, and modern domestic heating plants cease operating, the processing material is damaged, transportation is impaired and normal life of whole communities is disrupted. This greater dependence on a continuous supply of electrical energy has developed with the ability to build a high degree of reliability into the system. System disturbances caused by the load fluctuations result in changes to the desired frequency value. Automatic Generation Control (AGC), is very important issue in power system operation and control for supplying sufficient and both good quality and reliable electric power. This work deals with the AGC of Electrical (single and multi-area) power systems by using fuzzy logic controller (FLC). Three intelligent AGC controllers have been developed to regulate the power output and system frequency by controlling the speed of the generator with the help of fuel rack position control. The first one is fuzzy based gain scheduler (FGS), the second one is Fuzzy based proportional integral controller (FPIC), and last one is Fuzzy frequency controller (FFC).