Method for screening, separating and monitoring subsynchronous modal signals

The invention relates to a method for screening, separating and monitoring subsynchronous modal signals. The method comprises the following steps of: screening and separating the subsynchronous modal signals of current and rotating speed signals of a power generator; acquiring electrical quantity signals and mechanical quantity signals of the power generator by using fixed sampling frequency by using a protective device or a monitoring device, wherein the electrical quantity signals are three-phase current IA, IB, IC and the mechanical quantity signals are the rotating speed omega to omega 0 and the omega 0 is the average rotating speed in a time slot; calculating the per-unit value of three-phase current, wherein the basic value is the rated current, and the rotating speed signal omega is the per-unit value and the basic value is the rated rotating speed; filtering by using a low pass filter and a high-order band-pass filter group; calculating the corresponding frequency of the signal and the amplitude value sequence of the signal; and screening and modifying the amplitude value so as to separate out the required multi-modal separation result. According to the method, each piece of subsynchronous modal quantity of the electrical quantity (three-phase current) signals and the mechanical quantity (rotating speed) signals of the power generator can be separated and screened automatically; the filter parameters are not required to be adjusted when the inherent modal frequency of different units are different; and the method has a simple principle and is easy to implement.