الفهرس 
chapter 1Only 14 pages are availabe for public view
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Abstract
This thesis proposes a technique based on S-transform time- frequency analysis and Fuzzy expert system for classifying power quality (PQ) disturbances. The S-transform is a new time frequency analysis method. It has the features of both continuous wavelet transform (CWT) and short time Fourier transform (STFT). Through S transform time-frequency analysis, a set of feature components are extracted for identifying PQ disturbances such as; the amplitude of the S-transform matrix and the total harmonic distortion (THD). First, the original signals are transformed into a complex matrix by ST. The Matrix named S-matrix; the rows pertain to frequency and columns to time. Second, typical features are extracted from the matrix in order to classify power quality disturbances. At last, fuzzy expert system is used to classify and recognize the PQ disturbances. Two parameters, signal amplitude and total harmonic distortion, are the inputs to Fuzzy-expert system that uses some rules on these inputs to characterize the PQ events in the captured waveform (e.g. Sag, swell, interruption, surge, sag with harmonic and swell with harmonic). Several simulation using Matlab environment and practical data are used to validate the proposed technique. The objective of this thesis it to introduce a hybrid technique of S transform and fuzzy expert system for identifying and classifying the power quality disturbances.