A Research Of Grid-connected Control And Islanding Operation Strategy In Photo-Voltaic System

As the lifeblood of national economic development,Energy has attracted more and more attention.But with the rapid economic development,the two problems that is the energy crisis and environmental pollution have emerged.As the most common way of using solar energy,photovoltaic power generation has important theoretical and practical significance in solving the energy crisis,environmental pollution and realizing green sustainable development.The main researching aspects is as follows:This paper introduces several key technologies of photovoltaic power generation system,especially the grid-connected photovoltaic and photovoltaic network operation,and analyzes the present situation of PV power system.What's more,this paper introduces the basic principle of Auto-Disturbance-Rejection Control,and explains how it takes the advantages of PID,which is based on the idea of error elimination,introduce how LADRC works and finally the stability of the linear auto-disturbance rejection control has been proved,which lays the theoretical foundation for the following research.In this paper,the mathematical model of grid-connected photovoltaic system is established,and the coordinate transformation of the three-phase system is carried out,revealing the coupling relationship between the active power current and the reactive power current in the current control loop.Using LADRC,the controller is designed and decoupled,and the observer bandwidth is reduced by using the model system information of the system.The simulation results show that the output voltage has a fast response speed and good sine degree,which proves the correctness of the grid-connected PV system model and the excellent decoupling ability of the LADRC when handling coupling problem.The PV power which has the characteristics that output active power only commonly uses the P-Q control in the microgrid.The photovoltaic power in microgrids mostly runs at the maximum power point,but when the PV power is greater than the load power,this method is no longer reasonable.In this paper,the method of adjusting the output voltage of the photovoltaic cell to match the system load power is studied.Through simulation analysis,this method can effectively reduce the pressure of the energy storage system,which is helpful to improve the stability of the whole microgrid.