Research On Analytical Method Of Power Quality Disturbance Based On Wavelet Transform

In recent years, on the one hand, the widespread application of the power electronic elements and non-linear equipments has caused the voltage and the current in the electrical network distorted more and more seriously, and caused the power quality worsening. On the other hand, as a result of enhancement of the industrial automation level, more and more intelligent components such as microprocessor and PLC applies in the industrial process control, and these fine process control is easier to be perturbed by the disturbance of power system, which proposed to the power quality a higher demand and has brought the very tremendous pressure for the power quality analysis. Under the present situation of signals distorted seriously in the electrical network, the accurate detection and the localization of the power quality disturbance are the necessary prerequisite and the basis of monitoring and governing the power quality, and is also the foundation of measuring the electrical energy accurately and reasonably under the condition of distorted signals. At the same time, the classified criterion is complex and easy to make a mistake because the eigenvector which the power quality disturbance involves are too many. The research on classification of power quality disturbance after being transformed by wavelet directly is too less. The research on the voltage fluctuation and flicker is really few all over the world, but the degree that voltage fluctuation and flicker in the electrical power system had achieved cannot tolerate any more. This is needed to be solved urgently. In view of these problems, the problem of the analytical method of power quality disturbance based on wavelet transform has been studied systematically and deeply in the theory and been experimentalized fully in this dissertation.First, the problem has been studied, which exists in power quality analysis of domestic and overseas. The study status of power quality analysis in domestic and overseas has been overviewed. The Fourier transformation and the wavelet transformation elementary theory have been introduced and the advantages and disadvantages of the wavelet transformation and the Fourier transformation have been analyzed. Then, a mathematical model for signals of the power network has been established. Analysis method of power quality disturbance based on the wavelet transformation has been proposed, including detection and localization method of typical transient disturbance (voltage sag signals, voltage interrupt signals, impulse signal and so on), detection method of voltage fluctuation and flicker signals, and eigenvector extraction method of power quality disturbance signals. Finally, the simulative and experimental circuit of the power quality disturbance has been designed; the power quality disturbance which is simulated has been carried on the experimental test. The experimental result further confirmed that the analysis method which is proposed in this article is correct and effective. It has certain reference value and the practical significance to raise the level of the existing power quality disturbance analysis.