The Wavelet Analysis Of The Voltage Flicker Signal Of Power Network

With the rapid increase of portion of large capacity arc furnace load in power systems, voltage flicker has become a more serious problem. In order to find solutions to this problem, careful analysis and examination of voltage flicker are needed. The indices based on the statistical assessing can only offer the quantified seriousness. They are not be able to show the features of the flicker.Having summarized the original method of voltage fluctuation and flicker signal analysis, this paper put forward the method of using wavelet packet transform. Wavelet packet analysis is a kind of new analysis tool. It has good local nature both in time domain and frequency domain. It is more accurate and reliable than fourier analysis. The emulation result also shows that it is easy to get the information of the scope of frequency band with the use of multi-resolution analysis of the wavelet packet. And it can effectively separate different types of flicker signals.This thesis first introduces briefly the harm that the quality phenomenon of electrical energy and the various qualities of electrical energy bring. It also introduces the quality standards of electrical energy both in our country and in the world. And it focuses on the definition, the features and the occurring reasons of the voltage fluctuation and flicker. Then it moves on to explore and compare deeply the basic principles of the fourier transform and wavelet packet transform analysis method, and the present condition of the quality analysis of electrical energy. It also explains the characteristics, the requirements needed and the shortcomings of these methods. Finally, from the angle of the real-time inspection of the flicker signal and the voltage fluctuation, it puts forward the more effective voltage flicker analysis method which is based on the multi-resolution analysis of wavelet packet decomposing and the synchronous signal.With the use of the analysis method of multi-resolution analysis of wavelet packet transform, it is able to carry out the detection of voltage flicker signal, and todraw the frequency and amplitude of voltage. Therefore, the parameter to reflect the voltage flicker is obtained. Matlab emulation proves that wavelet packet transform is a kind of effective voltage flicker analysis method.voltage fluctuation; voltage flicker; wavelet packet transform;multi-resolution analysis...