The orthogonal Hilbert-Huang transform application in voltage flicker analysis

Abstract

In an electrical distribution system heavy loads can greatly change the load current. In a weak distribution system voltage flicker occurs as a result of randomly changing reactive power demand of the random process loads such as periodically turning on and off of heavy loads. As a major power quality problem voltage flicker can be extremely harmful to sensitive loads that require stable voltage. In this study voltage flicker is analyzed using the Orthogonal Hilbert Huang Transform (OHHT) instead of Hilbert Huang Transform (HHT) which is a new signal processing method can be used in the analysis of nonlinear and non-stationary signals. Two kind of analysis are performed. In the first one the Orthogonal Intrinsic Mode Functions (OIMFs) of voltage flicker are obtained and compared with the Intrinsic Mode Functions (IMFs) that are not orthogonal. In the second one, Hilbert transform (HT) is applied to the second OIMF component which is obtained from the first analysis in order to find the amplitude and the frequency of flicker signal. For the comparison purposes the second analysis is also performed for the second IMF component which is not orthogonal. Results of these two analyses showed us that using the OIMF components instead of the IMF components which are not orthogonal reduced the error rate remarkably.