Interaction of Forced Oscillation with Multiple System Modes

Forced oscillations in power systems can lead to disruptive large oscillations across the grid when resonating with inter-area system modes. This letter proposes a rigorous method for estimating the overall impact of a forced oscillation when the forced oscillation frequency is close to the frequencies of multiple system modes. Apart from providing analytical insight, the method is shown to be useful in offline analysis of forced oscillations in large-scale power system models and in measurement-based analysis.