Estimating Transient Stability Margin Regarding a Dominant Oscillation Mode

This paper proposes a method for estimating the transient stability margin of a multi-machine system regarding a single dominant oscillation mode under a disturbance. The nonlinear modal dynamics of the system regarding a dominant mode before it develops to an instability mode is characterized using an equivalent nonlinear oscillator that is modeled by a second order nonlinear differential equation and identifiable from measurements of the post-disturbance trajectory. With reasonable selection for the formulation of this oscillator, the unstable equilibrium points estimated directly by this equation can give conservative transient stability margin regarding that dominant mode. Case studies on the IEEE 9-bus and New England 39-bus power systems validate the proposed method.