In this study, Prony and Eigensystem Realization Algorithm (ERA) are compared for identifying electromechanical and forced oscillation modes. The varying number of excited modes in practical power systems makes the process of determining model order challenging. Prony requires an iterative procedure, while ERA utilizes Singular Value Decomposition (SVD) for direct model order determination. Comparitive studies shows that ERA accurately estimates the signal, and generates fewer insignificant modes compared to Prony. Identified modes are used to design a filter, which estimates desired signal frequency. The filtered signal’s periodogram is then compared with detection threshold to detect Forced oscillation (FO) at specific frequencies.