Method for solving modal damping of shaft system of 1,000MW steam turbo generator set

The invention discloses a method for solving the modal damping of a shaft system of a 1,000MW large steam turbo generator set based on an excitation injection stimulated torsional oscillation test. The method comprises the following steps of: exciting a special modal torsional oscillation signal domega from the shaft system by applying a precise modal frequency pumping signal; performing frequency spectrum analysis on the domega and performing time domain analysis on amplitude to acquire precise modal frequency; analyzing variation trend data of the excited domega signal amplitude in a time domain; performing logarithm least square fitting on the variation trend data of the domega signal amplitude in the time domain to solve a total damping level D under the test condition; setting up a systemic nonlinear simulation model by taking PSCAD as a platform; setting mechanical damping as 0 and recognizing the damping of a corresponding work condition, namely electrical damping De; and calculating the mechanical damping of the corresponding work condition, namely Dm=D-De. The method can be used for recognizing the damping level condition of the 1,000MW steam turbo generator set under various work conditions, particularly the mechanical damping of the set.