| The improvement of economic level and scientific technology takes the social modernization to a higher degree, the proportion of nonlinear load in power system is increasing day by day, resulted that the power quality problems become more and more serious and the adverse effects brought to the power users is increasing, power quality problem has already developed into a hot spot of concern, many experts and scholars put a great effort to the research of it. Transient power quality disturbances, such as voltage swell, voltage sag, voltage interruption, short pulse interruption and shock transient signal brought a lot of negative impact, causing huge economic losses. An efficient detection and analysis technology is the basis and prerequisite for improving the power quality, the accurate location of the disturbances’ time makes a big difference to the recovery of normal electric energy, it have great research significance. Mathematical morphology is a new mathematical theory, which has the advantages of small calculation amount, effective calculation process and it has been widely used in the field of nonlinear signal analysis. The focus of this paper is that according to the characteristics of transient power disturbance signal, using the mathematical morphology combined with other advanced signal analysis method to detect and analyze the disturbance. The purpose of the paper is achieving the correct positioning of the disturbance, the main contents include:Firstly, the definition of power quality was introduced, and the power quality disturbance signals were classified from different aspect. The mathematical models of the transient disturbance signal were established, and the experimental simulation was carried out on the Matlab software; this paper have introduced the current situation of the research on the filtering noise reduction and detection methods in the field of transient disturbance at home and abroad; the principle of mathematical morphology have also been introduced.Then, a new method for the detection of transient power quality disturbance was designed based on the mathematical morphology theory, Hilbert transform and differential algorithm. Based on the generalized morphological filter, the least mean square algorithm was used to construct a better performance of morphological filters by improving choice of filter parameters. The amplitude envelope signal can be obtained by making the filtered power quality disturbance signal to carry through Hilbert transform, the difference operation can make the disturbance characteristic be enlarged which was useful to locate the disturbance.Next, flexible morphology is a kind of analytical method based on mathematical morphology, which was developed on the basis of mathematical morphology. A flexible morphological filter was constructed to filter the power quality disturbance signal. The principle of morphological gradient transform and information entropy were used in this chapter. After morphological gradient transform, the disturbance signal can be amplified, and the information entropy of each signal can be obtained. According to the information entropy, the disturbance can be accurately located.Finally, the different performance of the basic morphology operation have been studied. A morphological difference filter is constructed by using the difference operation of the basic morphological operators. The simulation results showed that the filter was able to preserve the main features of the signal during filtering the noise. After the common transient power disturbance were filtered, the Local mean decomposition was used to calculate the signals’ instantaneous frequencies and the defects that the disturbance frequency was not obvious were improved. According to the difference of the instantaneous frequency in the signal mutation, the disturbance can be located. The effectiveness of the proposed algorithm was verified by the comparison of the different noise, the amplitude of the mutation and the complex disturbance. |
PDF Full Text Request