Large-signal stability analysis of islanded DC microgrids with multiple types of loads

Due to the lack of support for the power system, the small inertia of the system, and the access to negative impedance elements, the stable operation of the islanded DC microgrid can be challenging. To ensure the stability of the system in a large operating range, a system-level large-signal stability analysis is carried out for a droop-controlled dc microgrid in this article. Firstly, the system-level equivalent model of the DC microgrid is established, the steady-state of the DC microgrid is analyzed and the instabilities principle, as well as their physical interpretation, is revealed. Second, necessary and sufficient conditions of the DC microgrid are deduced by the Lyapunov direct method, and the load limit of the DC microgrid is obtained under the restriction of stability and voltage deviation. Third, the correctness of the theoretical analysis is verified by the simulation results of a droop-controlled DC microgrid system.