Research On Voltage Sag Detection Based On Double Dq Transform And Its Suppression Method

With the rapid development of economic,a variety of sensitive loads are used more and more widely in industry,and these loads demand for power quality higher and higher.Voltage sag have become an important reason that causes sensitive load not to work normally.Voltage sag can not only cause huge economic losses to enterprises,but also bring inconvenience to people’s lives.At present,the dynamic voltage restorer is an effective measure to suppress the voltage sag.This paper studies the detection method of voltage sag,suppression measures and the control method of dynamic voltage restorer.Firstly,this article gives an overview of the definition,causes and hazards of voltage sag.It also introduces the commonly used voltage sag detection methods,and analyzes some of them,and summarizes the advantages and disadvantages of various algorithms.For the shortcomings of the traditional detection methods,the detection algorithm based on double dq transform is used to obtain the characteristic of voltage sag.In addition,in the detection process,low-pass filters are needed to obtain DC components.Since the traditional low-pass filter has defect of long delay,this will affect the dynamic response and detection precision of detection algorithm.Therefore,the sequential low-pass filter is used instead of traditional low-pass filters in this paper.Matlab software is used for simulation.The simulation results show that the detection algorithm based on double dq transform combined with morphological filter can better meet the detection requirements of dynamic voltage restorer(DVR).Secondly,the suppression measures of voltage sag are elaborated from the three aspects of power supply side,equipment manufacturers and users.The structure and working principle of dynamic voltage restorer are introduced,and the commonly used control methods are classified.Aiming at the poor stability of the feedforward control strategy of dynamic voltage restorer,a compound control strategy is designed in this paper.This control strategy combines feedback control based on feedforward control and has the advantages of two control methods.Finally,Matlab software was used for simulation.By analyzing the feedforward control and the composite control of the Bode diagram and the unit step response,the linear and nonlinear loads were simulated and analyzed.The simulation results show that the composite control method has Good reliability and dynamic performance.