Identification method for shaft-system torsional-vibration modal parameters of generator unit under environmental excitation

An identification method for shaft-system torsional-vibration modal parameters of a generator unit under environmental excitation mainly includes: (1), collecting and demodulating a rotating-speed pulse signal of the generator unit to acquire a shaft-system rotating speed difference signal domega; (2), subjecting the acquired shaft-system rotating speed difference signal domega to filtering to acquire a torsional-vibration modal signal domegai of each stage of the generator unit; (3), taking the modal signal domegai of each stage of the generator unit as input data, intercepting sub samples satisfying certain initial value conditions and subjecting the sub samples to linear superposition to acquire a free response RDi corresponding to each stage modality; (4), creating an eigenmatrix mathematic model on the basis of the free responses, and calculating modal frequency and damping by eigenvalue decomposition; (5), moving a data window based on the modal signals domegai, and repeating the step (3) and the step (4) to acquire real-time torsional-vibration modal damping curves of the generator unit. The identification method can be used for identifying torsional-vibration modalities of unit sides or power grid sides during disturbance, can be also used for identifying modalities during noise disturbance under operating environments and the like, and has the advantage of capability of monitoring dynamic vibration of power grids in real time.