Method and system for voltage sag check based on digital morphological transform

The invention discloses a method and a system for voltage sag check based on digital morphological transform. The demodulation process includes the following steps: setting the sampling frequency, and acquiring voltage signals of a distribution network according to the sampling frequency; selecting voltage signals at the time moments of n-i,..., n-2, n-1, n, n+1, n+2,..., n+i from the acquired voltage signals and combining the voltage signals into a first calculation sequence, and performing symmetric differential operation on the voltage signals in the first calculation sequence and combining the voltage signals into a second calculation sequence, wherein i