Design And Analysis Of Dynamic Voltage Restorer Control System In Weak Grid

With the widespread Application of the electrical and electronic equipment, therequirements of power consumers for Power-Quality (PQ) more and more strict. At thesame time, with the application of the power electronic equipment, the electromagneticinterference (EMI) of the distribution system is more and more. The power-qualityproblem is increasingly serious. Voltage sag and voltage swell are two of the mostimportant power-quality (PQ) problems that encompass almost80%of the distributionsystem PQ problems [1]. The method of compensating voltage sag and voltage swell wasresearched. The Dynamic Voltage Restorer (DVR) is one of the modern devices used indistribution systems to protect consumers against sudden changes in voltage amplitude.DVR are primarily used in distribution systems what is always the weak grid. Theimpedance of weak grid often fluctuates and cannot be neglected. The impedance of weakgrid may influence the control system of the DVR. In this paper, the control system of theDVR in weak distribution systems is discussed. Firstly, the paper designed the outputvoltage closed loop control system of DVR, and analysis the existing problems of thecontrol system in weak distribution systems. Secondly, the paper proposed an improvedcontrol system which is applied well to weak distribution systems. The improved controlsystem can eliminate the influence of impedance of transforms and weak distributionsystems to DVR control system by using the load voltage closed loop control system.Thirdly, the paper proposed an improved method of design of the parameters of control indigital control system. The parameters of control by the improved method can applied wellto digital control system. In the end of the paper, the two kinds of DVR control system areverified by an experimental DVR system with a full digital controller. Comparisonsbetween the output voltage closed loop control system and load the voltage closed loopcontrol have been analysis. Practical tests on a10kW test system and simulation test inMATLAB demonstrate a close correlation with the analysis.The improved control system and method of pole assignment applied well to thedistribution systems. The control system of DVR has faster response and higher controlprecision, and the disturbance of PCC voltage and load current has better inhibition.