An identification method of torsional modal parameters of generator shafts under ambient excitation

摘要

A method of identification of torsional modal parameters of generator shafts under ambient excitation, comprising: (1) a speed deviation signal dɷ being obtained by sampling and demodulating rotation speed pulse signal; (2) obtaining mode signals dɷ, of each order by filtering the speed deviation signal dɷ; (3) taking each mode signal dɷ; as input, a corresponding free vibration response RD, is obtained by shift and superposition of sub-samples selected with a predefined initial condition; (4) modal frequency and damping ratio are based on a character matrix and a shafts torsional vibration equation; (5) based on each mode signal dɷ,, a real-time damping character of torsional modes for generator shafts is given by moving a time window and repeating steps (3)-(4). The invention can be used to identify torsional modes not only for the cases of large/small perturbations but also for the cases of ambient excitation. It has an advantage of real-time monitoring dynamic oscillation in a power system.