Research On Power Quality Detection And Application Based On Wavelet Algorithm

With the wide application of electric & electronic devices in power system, power quality problems have already become the focus to which both suppliers and users of electricity have paid close attention. To improve power quality, a monitoring and analyzing system must be established to detect, estimate and classify different disturbances. Traditional detecting and analyzing system have put emphasis on steady voltages and currents, Here a new analyzing method based on wavelet transform and wavelet packet transform have been presented. Then the analysis algorithm of electric power quality is posed by massive simulation, hardware experiments validated the method.Firstly, In the thesis the theoretical background of power quality phenomena is introduced. Disturbances classification, definition, characteristic and causation also are presented. Then, three transform-based methods, which are Fourier transform, wavelet transform and wavelet packet transform, and their applications are described and discussed in detail.Secondly, 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-resolution decomposition. By which, the accurate localization of fault signal can be realized, the duration and amplitude of which can also be obtained. In addition, wavelet and wavelet packet method is used to analyze static power quality. The voltage signal with harmonies and flicker are simulated with the methods of wavelet. As a result, the wavelet packet method has a good performance in high-frequency. It proved that all harmonies can be picked up by using the wavelet packet method. And it has a better performance on analyzing the harmonies signal.Finally, considering on-line monitoring and measurement system of power quality, based on wavelet transform for power quality analysis, the hardware system is designed base on DSP chip TMS320F240, and arithmetic program of harmonic current detecting is realized with assembly language. The experiments prove wavelet algorithm is a right method for harmonic detection, which form a solid foundation in practical application.