The Research On The Power Quality Disturbances Based On The Wavelet Analysis

With the rapid development of the power system and the widely application of electronic devices to the power system, Power quality transient problems have already become the focus that numerous fields have paid close attention to. The power quality transient is detected and analyzed accurately, as to realize the fault localization, characteristic extraction, and identification, which is the essential presupposition and basis of monitoring and managing to power quality transient.Firstly, this paper puts forward various kinds of electromagnetic transient phenomena according to IEEE, Four common power quality transients, namely voltage sag, voltage swell, voltage interruption and surge are described carefully. And summarize the methods of analyzing the power quality transient problems. The following respect is the research on the detection and analysis of power quality transient.This paper adopts a novel digital signal processing method----the wavelet transform. According to the non-steady characteristic of power quality transient, the good time-frequency localization makes the singularity of signal can be signified as the wavelet transform modulus maxima. Using Mallat algorithm, the wavelet transform modulus maxima of singularity is extracted through Multi-solution analysis. By which, the accurate localization of fault signal can be realized, the duration and amplitude of which can also be obtained.To the question of denoising and compression in actual signal detection, the paper proposed a non-linear threshold method based on wavelet package transform. Due that the time-frequency resolution of wavelet package transform is superior to wavelet transform and the wavelet package coefficients of noise and signal are irrelevant. The noise and unnecessary information can be deleted combining the threshold method.Expressly speaking,this paper propose the application of wavelet package non-linear threshold on deleting transient pulse signal within normal power signal.This method can delete transient pulse signals completely, keep down usable signal,so this method can improve Power quality.Then a lot of simulations chosing different swings and frequencys and sum up some conclusions.The last, emulational tests have been done aimed at the above four power...