Nonlinear stability indexes of power swing oscillation using normal form analysis

We propose stability indexes of power swing oscillation taking nonlinearity into consideration using normal form analysis. For a relatively large oscillation to which eigenanalysis cannot be applied, we approximately describe the effect of nonlinearity up to the third order in the form of the change in oscillation characteristics (damping factor and period) with respect to the change in amplitude. Consequently, we can obtain approximated stability regions of oscillation modes in state space. It is also possible to apply the proposed indexes under auto-parametric resonance condition, when a ratio of eigenvalues is close to a simple whole number. We demonstrate the effectiveness of the proposed indexes by comparing with time-domain simulation results in longitudinal power system models.