In this paper, the application of the Prony method for the estimation of dominant inter-area oscillations modes in large power systems is presented. The main goal of this paper is to compare the dominant oscillations modes extracted by the Prony method with those obtained by Eigen-value analysis. In order to achieve that, two testing systems have been designed. The first system is a multi-machine system consisting of 22 buses and 10 generators, and the second testing system is built on the same topology but with an integrated Fixed Speed Wind Farm (FSWF). In addition, the impact of the FSWF on inter-area oscillation modes will be discussed in this paper.