Research On The Control Strategy Of Dynamic Voltage Restorer

One of the common problems in electricity quality is the voltage sag,which may lead to a shutdown of equipment that are sensitive to the change of voltage and cause a major loss economically.Nowadays,dynamic voltage restorer(DVR),which is considered as the most efficient resolution for this problem,could reduce the voltage sag effect on those sensitive equipment significantly.Therefore,optimizing both controlling strategy and detecting method on DVR has important practical meaning in the sense of refining dynamic response and compensation.Single-phase voltage sag or three-phase voltage sag is commonly seen on a low-voltage grid.In this paper,taking considerations from both economical and reliability perspectives,a main circuit topology structure of DVR has been proposed to tackle this problem.By applying three single-phase full-bridge inverter structures,control and compensation on each phase can be realized.In addition,by using coupling structure of high voltage capacity and grid,the cost of DVR can be deducted dramatically.Based on the structure of main circuit topology,analyses have been conducted on threephase/single-phase dq detection based on Instantaneous reactive power theory,single-phase ?? detection,and augmented single-phase dq detection.Through the experiment,it can be concluded that augmented single-phase dq detection can shorten detection time significantly,moreover,improve the detection accuracy.In this paper,double closed loop compound control has been chosen as the controlling strategy.Furthermore,proportional resonance control is introduced to reduce the influence of the harmonics wave on voltage compensation.Simulation experiments validate that double closed loop compound control improves both efficiency and stability.Simulation models on both single-phase and three-phase DVR have been established.Through the simulation of voltage sag,especially in the presence of fundamental wave and harmonic wave,conclusion can be drawn that new main circuit topology structure combining with proposed detecting and controlling methods,can efficiently compensate single-phase or three-phase voltage sag,hence,maintain the load voltage at a stable level.