Modeling and stability analysis of autonomous microgrid composed of inverters based on improved droop control

This study is aimed at a microgrid composed of inverters. During autonomous operation of microgrid, every DG participates in the regulation of the voltage amplitude and frequency, while the change of the load power occurs. In this paper the virtual power droop control is adopted and virtual impedance is added to inverters. The small signal model of the microgrid system in autonomous operation is established. Because autonomous microgrid system is a complex nonlinear system, this paper adopts Lyapunov´s first method to analyze the system stability, and then based on it to estimate influence of control and line parameters of the interface inverter on the stability of the system. Finally, simulations are carried out using MATLAB to validate the selected control and line parameters. Experiments are carried out on the experimental platform controlled by TMS320F2812 DSP. The results show that the power can be shared well and the system operation is stable in case of unequal line impedance.