Modeling of Islanded Microgrids Using Static and Dynamic Equivalent Thevenin Circuits

In this paper, a new modeling method based on the equivalent Thevenin circuit is proposed for inverter-interfaced microgrids. The proposed method approximates the entire network connected to each inverter with an equivalent Thevenin circuit. The equivalent circuit is studied in two forms: static impedance and dynamic second-order RL branch. The static impedance equivalent circuit provides a good steady state but not a good transient response. To cope with this issue, the static impedance is replaced with a dynamic second-order RL branch, which results in appropriate transients. Both static and dynamic models are validated using a microgrid test system simulated in MATLAB/SimPowerSystems.