Abstract
Abstract— At large scale power system with multi- machine and weak connection between areas which cause low frequency oscillation (inter area oscillation ) with lightly damped, that make system to be unstable and affecting the behaviour of generator units that may leads to system oscillations and /or blackouts. This paper will study and use low frequency analysis to discuss the effectiveness of PSS parameter variations on dynamic behaviour of the system ,applying eigenvalues methods . The study shows that variation of PSS parameter has an effect on the system dynamic behavior .and also on the system Eigen values , that assures the necessity of choosing the right parameter for a stabilizer design to reduce the inter area oscillation and reducing the settling time. Keywords—