Study On Control Strategy Of Parallel System For Micro-Grid Inverters

The electrical age has promoted the industrial revolution and opened a new chapter in the development of human civilization.As the driving force of all development,energy is seeking alternatives to increasingly depleted fossil energy from petroleum,coal,wind and hydropower,which are now highly respected.Electrical technology has not only promoted the development of science and technology,but also driven by technology.In recent years,with the continuous development of new energy technology and the performance optimization of power electronic devices,distributed generation has become more stable.Of course,the research of grid connected technology has gradually matured after years of research.At present,the droop control technology of inverter is mostly used,which is efficient and efficient and simple to control.Considering that the output voltage and the impedance of the inverters and lines in the transmission process will affect the power sharing,further research and analysis are needed.Based on the parallel system of inverters,this paper establishes a mathematical model.Firstly,the circulating current between the systems is analyzed,and the instantaneous average current feedback is introduced to improve the equivalent output impedance of the inverters.The circulating current characteristics based on the control strategy are analyzed.Considering the limitation of this method when the phase difference of impedance is large,the virtual impedance is introduced to solve this problem and the phase difference of impedance is improved,then the two methods are combined to verify the applicability of this method in circulating current suppression.Then,the traditional droop control method is analyzed,and the influencing factors of power distribution in different line environments are deduced by formula,and the droop control coefficient is improved.Different from introducing large virtual resistance to reduce the difference of output impedance,this paper introduces virtual impedance based on instantaneous output power to balance the output impedance of the two inverters.Considering the influence of voltage drop caused by virtual impedance on power distribution,the control equation is improved.In order to ensure the quality of the voltage,voltage compensation is finally carried out.Finally,MATLAB/SIMULINK is used to verify the effectiveness and applicability of the improved method.