A generalized method to analyze the small-signal stability for a multi-inverter islanded grid with droop controllers

In recent years, the concept of multi-inverter microgrid as the building block for the future distribution system has been commonly accepted and widely studied in literature. One of the recognized advantages of microgrids is the possibility of operate autonomously in absence of the main utility supply. In this case, droop control techniques are the most attractive solution for their capability of operate the microgrid without requiring any communication among the inverters. This paper proposes a simple mathematical model of droop controlled islanded microgrids, with the objective of providing a tool by means of which a microgrid of arbitrary complexity can be modeled, and the local droop controllers of the inverters can be designed to guarantee the small-signal stability and achieve a satisfactory dynamic behaviour. The proposed model has been validated through Matlab/Simulink simulation.