Simplified LCL Filter State Space Modeling and Small Signal Stability Analysis of Inverter Based Microgrid

This work developed a simplified state-space model for both current-controlled and voltage-controlled inverter systems in the microgrid context. The photovoltaic sources are operated as current sources, and energy storage units are operated as voltage sources in a microgrid. The developed models in both cases accurately capture the dynamics of the system based on the first principle relations of the inverter's output LCL filter, voltage/power control loop, and current control loop. Furthermore, the presented simplified approach avoids the power electronics switching effect and its associated frequencies. The results show the eigenvalue stability analysis of the changing controller gains, and the step responses of the controller are presented to validate the effectiveness of the developed state-space model.