Small-signal modelling and stability analysis of island mode microgrid paralleled inverters

Abstract

The autonomous operation mode of paralleled inverters in microgrids can be intentional or unintentional in order to ensure the continuity of supply. In this mode the voltage and frequency magnitudes are held by local controllers using droop control, this latter is generally considered to be the most adopted technic for the primary layer in a multilayer control structure due to their main feature of sharing the power equally between inverters, without needing communication infrastructure, the design of droop parameters is very crucial because a bad design can lead to the instability of the system. This paper presents a small-signal analysis for an MG composed of parallel-connected inverters in island mode and controlled using the droop method, aiming to analyze the stability by performing eigenvalues and sensitivity analysis which allows obtaining the behavior of the system, analyze the interaction between the different elements and study the influence of the droop parameters on this later which helps in the design procedure, small-signal model and Simulink block model was developed and simulated. Simulation results show a high correspondence and agreement between the model developed using Matlab Simulink-SimPowerSystem library and the developed small-signal model which confirms the validity of this later.