Analysis And Detection Of Power Quality Based On Wavelet And Hilbert Algorithm

With wide application of large number of sensitive power electronic devices in modern power system, both power department and their customers not only play attention to the stationary power quality, such as harmonics, voltage fluctuation and three phase unbalance of the voltage, but also to the transient power quality. Recently experts gradually focus on the transient power quality research, mainly including short-time voltage variation, sags, swells, pulse and surge. The transient power quality is detected and analyzed accurately, as to realize the fault time localization, characteristic extraction, and identification, which is the essential presupposition and basis of improving and managing to transient power quality.In this paper, the definition characteristics and the cause are described in detail. According to the electromagnetic transient phenomena of IEEE, IEC, etc., some types of power quality disturbances are studied in detail. The main contributions are giving as follows:(1) This paper provides a improved method of the power system harmonic detection. Individual FFT Harmonic detection method can not rule out the affect of the system noise. In this paper, the first step:removing the system noise of electric signal by wavelet denoising. And then, we can get more accurate results by carrying out FFT harmonic calculation. The method provides a more reliable basis of harmonic control for power system.(2) There are two methods of power quality disturbance signal detection are proposed. The first method is detection based on wavelet algorithm; the other method is based on Hilbert phase detection algorithm. This method is named as the Hilbert phase detection (HPD). These two methods were compared in this paper. On the non-noise signal processing, wavelet detection method and Hilbert phase detection method both get correct results. For detection of noised signals, the wavelet algorithm can not accurately locate the signal distortion, while the Hilbert phase detection algorithm locates the distortion accurately freeing from system noise.(3) In this paper, detecting the disturbance of the voltage fluctuations, frequency variations, voltage surging sag, voltage interruptions, transient pulse and transient oscillation of power quality based on Hilbert phase detection algorithm (HPD). The simulation experiment shows that the method is feasible. Combining with wavelet denoising algorithm, the detection results are more correctly.