Research On Characterization Detection Method And Compensation Strategy Of Voltage Sag

With the rapid development of science and technology,and the expanding scope of various high-tech applications,the high demand for power quality is increasing.Because of the result caused by voltage sag problems is too harmful,so the attention it received is extensive.For the reasons of voltage sags,this paper analysis different types of short circuit fault that is the single phase short circuit,phase-phase short circuit,the three phase short circuit and the busbar short circuit,then we get the voltage sag characteristics generated by different type of faults,thus it can provide a basis for the classification of the faults.For the accurate detection of duration,amplitude and phase jump of voltage sag,this paper studies from two aspects that three phase and single phase fault.In view of the three-phase voltage sag detection,this paper studies respectively from symmetrical and asymmetrical voltage sag.For the symmetrical voltage sag,it can be quickly and efficiently detected by the dq transform.As for the unbalanced voltage sags,it should firstly change the unbalanced voltage symmetrical components into three groups symmetrical components,and then use dq transform for each set of symmetrical components,finally obtain characteristics through the linear combination.For single-phase voltage sags expect for the common detection algorithm,a voltage sag detection based on complex wavelet transform and RMS algorithm is present in this paper.The principle of wavelet singularity detection and its application in the starting and ending times for voltage sag detection are studied in detail.Using the fourth derivative of a complex Gaussian wavelet and RMS algorithm to detect the begin-end time,phase jump and amplitude of voltage sag.The performance of the algorithm is validated and confirmed through simulation studies about voltage sag problem with distortion or not using the Matlab/Simulink analysis program.For the effective compensation for voltage sags,this article mainly studies the dynamic voltage restorer(DVR)from the three compensation strategies that the full voltage compensation,the same phase voltage compensation and the minimum energy compensation strategy,and systematicly introduces the structure and control method of DVR.For the three different compensation strategies,this paper analysis and compares their advantages and disadvantages through the modeling,then it can make the appliance energy consumtion minimization and get the optimal compensation effect by choosing the appropriate compensation strategy for different type of voltage sags.