The Establishment Of Single-bus DC Microgrid Model And Its Stability Analysis

In modern power systems,microgrids are drawing attention due to the effective integration of distributed generation units and local loads.This paper focuses on some key issues of DC microgrids;modeling and equivalent model analysis of the system,and analyzing the small-signal and large-signal stability of the DC microgrid,and finally the coordinated control strategy among the various systems.Techniques such as improved methods of DC droop control have been studied in depth.Considering the impedance of the cable,the microgrid branch is simplified as the Thevenin equivalent circuit with virtual impedance,and the output impedance model of the branch is established.Starting from the output impedance model of the system node and the branch,the node of the DC microgrid is established.Impedance model,through the node impedance method to determine the stability of the system.By building a small signal model of photovoltaic-energy storage DC microgrid,the influence of static operating point change on the resonance peak of the converter,the influence of the output impedance of the power supply side on the shunt impedance of the power supply load,and the shunt impedance and line of the load load are analyzed in detail.The relationship between the parameters,and using the parallel impedance method to analyze the impact of the filter parameters on the system’s small signal stability.When the DC microgrid adopts the bus voltage control strategy,the system is a nonlinear system.Therefore,when analyzing the stability of the system,a nonlinear analysis method is used.In this paper,the switching theory is used in the stability analysis of the bus voltage control DC microgrid.By establishing a unified mathematical model of the system under the voltage control strategy,the Lyapunov direct method is used to study the parameter boundary conditions of the large signal stability of the DC microgrid.According to the stability criterion of the switching system,the influence of mode switching on the stability of DC microgrid is analyzed.The research on the control methods of the various components in the DC microgrid was carried out.Through the DC droop control,the power sharing problem of the parallel unit in the system operating in the constant voltage mode is solved.With the goal of maximizing the use of renewable energy and improving the system stable operation interval,a DC microgrid off-grid and grid-connectedoperation is proposed.Unified coordination of control strategies.Based on this,a seamless switching method of PV cell operating mode based on drooping translation is proposed,which enables the photovoltaic cell to switch smoothly between constant voltage sagging mode and maximum power tracking mode.