Research On Three-phase H-bridge Dynamic Voltage Restorer

With the development of science and technology,electric energy has become one of the most important energy sources in human life.Power quality problems affect the normal production and life of human beings,so people pay more and more attention to them.The renewal of power equipment is more frequent,and the harm caused by voltage sags is more and more extensive.Dynamic Voltage Restorer(DVR)is a power quality compensation device connected in series between power grid and sensitive load.It is one of the preferred solutions to solve the voltage sag problem in terms of practical application effect and cost.Firstly,this paper introduces the concept of voltage sag,and introduces its causes,characteristics,impact on user equipment,and some commonly used treatment schemes.Secondly,it analyses the different topological structures of DVR used in low-voltage distribution network,and makes a detailed analysis of the rectifier unit,inverter unit and coupling unit of DVR.The different compensation modes and control strategies of DVR are discussed.The three-phase H-bridge dynamic voltage restorer with full compensation mode is determined.Secondly,the common-mode interference of inverters in dynamic voltage restorer is analyzed and studied,and a solution to suppress common-mode current is proposed,which improves the anti-electromagnetic interference ability of inverters in DVR devices.Aiming at the overvoltage problem that IGBT may cause in the actual operation process,a buffer circuit is designed.The simulation and experimental results show that the overvoltage problem can be effectively suppressed and the safe operation of IGBT can be guaranteed.A voltage sag generator is designed to meet the requirements of different voltage sag depths,so as to verify the voltage sag compensation test of DVR prototype.On the basis of a DVR prototype with three single-phase H-bridge type,380/220 V voltage grade and 60 KA capacity,compensation experiments are carried out for different voltage sag depths and loads of different properties.The results show that the DVR prototype can compensate voltage sag quickly and effectively under different voltage sag depths and load characteristics,and can be satisfied.The relevant regulations of the foot industry provide a theoretical and practical basis for further improvement of the prototype.