Research On Islanding Operation Control Of Photovoltaic AC Microgrid

With the continuous increase of electricity load in the power system,the total installed capacity of coal-fired units is also increasing year by year.The air pollution caused by coal combustion has become one of the major factors affecting human health.In order to achieve the harmonious development of man and nature,it is necessary to reduce the proportion of coal consumption,and vigorously develop and use renewable energy.In this paper,for the micro-grid island operation mode,when the micro-power inverters are operated in parallel,circulation will occur in the system,affecting the problem of power sharing and system stability.A droop control method based on virtual impedance is proposed and simulated.The control method was verified.The specific research contents and conclusions are as follows:This article discusses the research background and significance of micro-grid and summarizes the research status of micro-grid at home and abroad.The composition of the photovoltaic AC micro-grid is analyzed,and the output characteristics and working principle of photovoltaic cells and batteries,as well as the topology and mathematical model of the grid-connected inverters are given.The causes of the circulation of the inverter parallel system,the droop control method of the micro-power grid-connected inverter and the influence of the line impedance on the system circulation are analyzed.Then a droop control method based on virtual impedance is proposed and a controller based on virtual impedance is designed.This paper studies the working mode of the micro-grid system,the control of the photovoltaic power generation unit,the analysis and control of the Boost chopper circuit,and the controller design of the photovoltaic grid-connected inverter.At the same time,the paper also analyzes the control of the battery energy storage unit,bidirectional DC/AC circuit analysis and control,and the controller design of the bidirectional power converter.The main circuit model of the photovoltaic AC micro-grid is established in the MATLAB/Simulink environment to verify the droop control method based on virtual impedance.Through the analysis of simulation results shows this control method can not only realize power split between the inverter,but also on the system circulation effectively suppressed,to improve the control precision and stability of the system...