Duffing oscillator order stopping oscillation system method for monitoring of low-frequency oscillation in power system

The measurement signals are represented as a typical nonlinear and non-stationary random process. The main characteristics of low-frequency oscillation (LFO) lie in that, both the appearance time of oscillation mode and the lasting time are uncertain, and the amplitude damping changes with time. Therefore, before parameter identification, whether the sustained and stable LFO is or not should be determined. The high approval methods for LFO analysis are not suitable for such situation. Then, a new method is proposed to monitor LFO based on order stopping oscillation system of duffing oscillator. The state of order stopping oscillation system of duffing oscillator is highly sensitive to periodic perturbation while it is quite insensitive to random small perturbation. The measured data used as the excitation (input signal), were put into order stopping oscillation system, and then the phase trajectories of system were obtained. Small perturbations' phase trajectory converged to the focal point, whose state is order stopping oscillation. The existence of LFO attractor was obtained by phase trajectory of weak damping mode and forced oscillation, javascript: void (0); while LFO caused by negative damp existed LFO repellor. Thus, according to the change of phase trajectory, whether there is a steady-state LFO can be judged, and the mode and damping characteristic can also be judged correctly. It is very significant in fast and accurate alarming, rationally selecting the oscillation suppression measures, and quickly suppressing the oscillation. Processing and characteristics of LFO were showed by using the method of graphic visualization, and then logarithm distance with equilibrium point provides a method of quantitative analysis.