Research On Detection And Treatment Of Three-phase Unbalanced Voltage Sag

With the rapid development of today’s society and economy,people’s requirements of power quality are increasing gradually,as well as voltage sags,an important factor of power quality,are being valued.In order to reduce the number of problems caused by voltage sags in the grid connection of new energy,and weaken the impact of voltage sag on sensitive devices such as precision processors and controllers,what is more,reduce the economic loss of enterprises,caused by the voltage sag.As a result of that,the detection of voltage sag is of great significance,and also,the study of the dynamic voltage restorer(DVR)structure and its compensation method and control strategy or algorithm are of great significance.In this paper,the study of voltage sag includes two parts,the first is the detection algorithm of voltage sag,the second is the compensation of voltage sag.For the detection algorithm of voltage sags.Firstly,this academic paper briefly introduces the existing detection methods which used commonly,and then,it is improved on the basis of the existing detection method.In the absence of noise,the improved detection algorithm can quickly extract the required DC component.In addition,in order to meet the needs of industrial environments,this paper combines the moving average filtering(MAF)algorithm with the advanced detection algorithm,which suppresses the amplification of noise contained in the signal effectively and accelerates the detection speed.What is more,this paper proposes a new fast detection algorithm for three-phase unbalanced voltage as well.The advantage of this new algorithm is that it avoids the problem of double frequency components generated in coordinate transformation effectively and reduces the delay caused by filtering out double frequency components.So,the new detection algorithm speed of voltage sag is further improved without amplifying the noise signal.For the compensation of voltage sags.After a brief introduction of existing governance methods,this article research on the dynamic voltage restorer.First of all,this article analyzes the basic structure of the DVR and the functions of each component unit,then,selects a series-parallel hybrid DVR device based on three single-phase full-bridge inverter structures.Secondly,the compensation strategy and control algorithm are studied,and a fuzzy PID control method based on neural network is proposed,the control method has the advantages of linear control and non-linear control.So that,it can adjust the control parameters according to the actual situation during work,when used in DVR.In this study,a complete simulation model of voltage sag detection and treatment was built in Matlab,by setting different faults such as single-phase voltage sag,voltage phase jump,and three-phase unbalanced voltage sag.The new fast detection algorithm for three-phase voltage and adaptive neuro-fuzzy PID control method are simulated to verify the rapidity and effectiveness of the detection method and control strategy.