Initial Study of the Power System Stability Boundary Estimated from Nonlinear Modal Decoupling

The recently proposed Nonlinear Modal Decoupling (NMD) approach provides a new way to study stability of large non-linear multi-oscillator systems such as multi-machine power systems. The approach finds a coordinate transformation to decouple the mathematical model of the original system into as many decoupled nonlinear oscillators as the system's oscillation modes of interests so that individual decoupled one-degree-of-freedom oscillators can be easily analyzed to infer nonlinear modal dynamics and stability of the original system. By applying NMD to the IEEE 3-machine 9-bus power system, this paper studies the consistency between the stability boundaries obtained respectively from the original system and decoupled oscillators, which are the regions of attraction about a stable equilibrium. The paper proposes an approach to improve accuracy of the stability boundary estimated from the decoupled oscillators.