Methods For Detecting Sources Of Power Quality Disturbances

Power quality disturbance souce location, as the essential content of powerquality analysis, presents important references for finding the souce of powerquality,making the power quality management scheme and solving power qualityproblems. Voltage sag,voltage fluctuation and flicker are common and damagingpower quality disturbance problems. In this paper, power quality disturbance detectionmethod is researched. Main contents are as follows：Firstly, the paper systematically introducts the common voltage sag detectionmethods, including the methods based on energy and power,current and voltage,realcurrent component,sag classification, and some other improved algorithm.Theoreticalanalysis for all above methods are briefly executed.Secondly, in this paper, one sag source location algorithm base on least-squaresmethod is proposed. The parameters of fundamental voltage and current can beobtained by using Fourier algorithm with the samples of voltage and current at sagmonitoring point. Then, least-squares method is applied to estimate equivalentpotential and impedance of non-faulty side of power grid with the fundamentalvoltage and current parameters during the time before and after the sagdisturbance.Afterward,the sign of real part of the estimating equivalent impedance isused to locate the position of the sag source. The parameter estimation errors arereduced, and the sag source localization accuracy is improved by using least-squaresmethod and taking full use of currents and voltages signal during the sag. Thelocalization simulation results of fault,induction-motor starting and transformerenergizing have proven the viability and effectiveness of the proposed algorithm.Finally,the paper introduces the cause of voltage fluctuation and flicker.Thecharacteristic of different cuases of voltage fluctuation and flicker is analyzed. For theflicker that caused by the variation of fundamental voltage or current,it could belooked as small range and repeated voltage sag,least-squares method is expanded tolocate voltage flicker. But for the flicker that caused by harmonics and interharmonics,power direction method is used.Both of the methods are simulated and have beencertified their feasibility in the location of voltage flicker.