Linear Stability and Robustness Analysis of Droop-Controlled Islanded Microgrids

In this paper, the stability and robustness of a droop-controlled islanded microgrid including multiple distributed generator (DC) units is analyzed in the linear system framework. The nonlinear power system is linearized around an operating point, and theorems from linear algebra are used to analyze its stability. The stability of the droop-controlled microgrid system is analyzed for the case of dominantly resistive tie-line impedances for all values of resistive-inductive or resistive-capacitive loads. Moreover, Monte Carlo simulations are conducted to analyze the robustness of the droop-controllers in the presence of phase differences between neighboring DG's, and local voltage fluctuations.