In this work, a modified power system stabilizer (MPSS) is proposed for the purpose of suppressing the subsynchronous resonance (SSR) oscillations. The suggested supplementary signal fed to the proposed controller is taken to be proportional to the angular speed difference between generator rotor proximity masses. The suggested MPSS controller is applied to a simple power system consisting of a single machine with a fast acting static exciter connected to an infinite busbar through a series compensated tie line. Genetic algorithms (GAs) are applied for the determination of a set of optimal parameters for all adopted controllers. A comparative study to the expected performance for the cases where the generator excitation is taken to be constant, or controlled by the conventional PSS, NDS against the suggested MPSS is presented when system is undergoing both small perturbations and large-scale disturbances, the results of which have confirmed the validity and efficacity of the MPSS controller.