Modal Analysis of Multi-machine Power System for Load Perturbation

Load modeling has always been one of the important aspects of power system stability analysis. In this paper, efforts are made to study the modal behavior of multi-machine power systems for load perturbations. Provisions are made in the time-domain simulation environment to perturb different kind of load components by modeling them as ZIP loads. Resulting slip signals are subjected to Prony analysis to characterize the frequencies and damping of oscillations. Effects of continuous load variation on the power system stability is realized by performing random load perturbation in addition to sudden load changes. Further, an attempt is made to quantify the possible relation between the randomness of the continuous load change to the level of noise contamination in the slip signal of generators. Case studies are presented for 4-machine and 16-machine power systems.