The use of power system stabilizers (PSSs) to damp power system swing mode oscillations is of extreme practical importance. This manuscript presents an approach to the stabilization of a single machine infinite bus system (SMIB). The proposed control is based on the notch-filter approach to cancel the poles near to the imaginary axes. The approach is based on the root locus method. Application to Barka II power station connected to the main interconnected system of Oman is presented. The peak load at summer is considered as the system is near to instability. The Barka SMIB is modeled as a fourth order non-linear system. A linearized model is then obtained using MATLAB/Simulink. The simulation results validate the proposed design for the PSS.