Disturbance Source Identification of Voltage Sags Based On Hilbert-Huang Transform

This paper proposed a novel identification method for voltage sags (dips) based on Hilbert-Huang transform (HHT). Different voltage sag has distinct characters of fault time, three-phase amplitude and harmonics. And HHT is an excellent time-frequency representation and very suitable for feature extraction of voltage sags. The time-frequency absolute values of the instantaneous frequency differential curves can detect fault time correctly. The time-Instantaneous frequency curves are applied to detect the mutation point of the instantaneous frequency and reflect the phase angle shifts. Simulation results show that the proposed method can classify voltage dips caused by the line short circuit faults, the motor induction startup and transformer energizing concisely and correctly.