A Complete Small-Signal Modelling and Adaptive Stability Analysis of Nonlinear Droop-Controlled Microgrids

Nonlinear droop control has been introduced to establish an effective power-sharing between distributed generators without the need for communication links in microgrids (MGs). However, one of the missing studies in the literature is the effects of nonlinear droop relations on the stability of the MGs. In this article, the stability of an inverter-based MG operating with the nonlinear frequency droop-control has been analyzed. A complete small-signal state-space linearized model of the MG system, with optimized nonlinear droop relations, has been developed considering the dynamics of the overall system and is updated periodically. The stability of the system is then checked online at different operating points. Small-signal stability analysis of an islanded MG was performed using MATLAB/Simulink and the results were experimentally verified on an MG setup.