Power system modelling for stability studies are useful in understanding the system behavior in the event of a disturbance. Due to approximated lower order models and cost, the actual behavior of the system is different than expected from the model. Therefore, system identification by estimating modal parameter is highly useful for developing low order model and tuning linear control system which includes the effect of unknown disturbances. In this paper, three types of time domain techniques namely Prony analysis, eigenvalue realization, matrix pencil method is used for estimating the modal parameters in the oscillatory data. A WECC 9 bus system is considered as a case study. The transient oscillatory data is simulated using PowerWorld and the modal parameters are estimated using the three time domain techniques. The application of the time domain techniques is also discussed in view of power system operation and stability and the results are compared with convectional modal analysis.
