Modeling and Stability Analysis of Parallel Droop-Controlled and Current-Controlled Inverters

As an integrated system consists of different sources and loads, stability issue is of great importance to microgrids. Existing works neglect the interaction stability issue between parallel droop controlled inverter and current-controlled inverter in islanded microgrids. This work is presented to fill this gap. Firstly, the small-signal terminal-characteristic model of inverters are conducted. Not only conventional output impedance and admittance but also the transfer functions representing the dynamic of fundamental angular frequency are considered in this model. Then the interaction stability of parallel inverters are studied based on generalized Nyquist criterion. Finally, the simulation results are presented to verify the analysis.