This paper presents a fuzzy logic-based automatic generation control (AGC) algorithm aimed at alleviating the frequency instability caused by the integration of renewable energy sources into the power grid. Unlike traditional AGC methods, the proposed method effectively handles system nonlinearity and uncertainty without requiring an accurate mathematical model. The algorithm was implemented and tested in a MATLAB/Simulink environment. Simulation results show an improvement: frequency deviation overshoot was reduced from 5.6% to 2.3%, and settling time from 15 s to 8 s under step disturbances. Even under high renewable penetration (up to 50%), the overshoot remained below 3.5%, and settling time under 10 s. These findings indicate that the proposed fuzzy logic AGC enhances frequency stability and maintains robust performance under varying operating conditions.