Analysis Of Power Quality Disturbance Based On Coherent Atom Dictionary

The strength and weakness of power quality are an important standard of powersystem operation and management. It is essential to control and improve the powerquality which keeps the continuous development of the power system. In this regard,based on the idea of sparse decomposition, coherent atom dictionaries are designedin this paper. And disturbance detection, disturbance classification, parameterestimation and disturbance sources identification are researched in power qualitydisturbances. In connection with those, the main innovations are concluded in thispaper as follows:(1) In order to decrease the amount of calculation and improve the effect ofsignal decomposition, the atoms in atom dictionaries are designed based onanalyzing characteristics of power quality disturbance signals. For several commonpower quality disturbances, the coherent atom dictionaries which are fundamentalfrequency dictionary, similar fundamental frequency dictionary, oscillationdictionary, pulse dictionary and voltage flicker dictionary are proposed and designedin the paper. Simulation results show that the corresponding disturbances can beextracted accurately by using coherent atom dictionaries with matching pursuits (MP)algorithm, and the analytic representation of disturbances can be obtained.(2) The biggest problem to be concerning in matching pursuits algorithm is theamount of calculation. So the optimization methods for matching pursuits algorithmare established. The methods we used for contains that discretize the atomparameters, searching parameter, extract frequency of disturbance by FFT spectrumand obtain the better parameters of disturbance by PSO. The method of fundamentalamplitude correction based on recorded wave characteristics is established to solvethe inaccuracy problem that the amplitude of fundamental frequency component.And three kinds of iteration termination condition which are based on the feature ofextracted disturbance component, disturbance energy, the number of iterations areused. Then, the classification method of power quality disturbances is proposedbased on coherent atom dictionaries. The power quality disturbances can beextracted by coherent atom dictionaries one by one. The iteration terminationconditions decide the power quality disturbances to be extracted or not. Power quality disturbances classify according to the parameters of the disturbance.Simulation results show that the proposed method can not only classify correctly,but also obtain the parameters of the disturbance. The method can achieve thefunction of disturbance detection, disturbance classification and parameterestimation.(3) In order to identify disturbance sources of voltage sags, the identificationmethod based on oscillation dictionary is proposed. By analyzing characteristics ofvoltage sags which are caused by different types of disturbance sources, the featuresof voltage sags are constructed in terms of magnitude damping of voltage sags,magnitude of voltage sags, harmonic content, and voltage sags content. More overthe features of voltage sags are extracted by oscillation dictionary, and identificationmethod is established by the logical relationship of feature. Large number ofsimulation data show that the proposed method is simple, effective and with highidentification accuracy to single and composite voltage sags disturbance sources.