A complete small signal modelling and adaptive stability analysis of nonlinear droop-controlled microgrids

A Nonlinear droop control has been introduced to establish an effective power sharing between the distributed generators without the need of communication links in microgrids (MGs). However, one of the missing studies in the literature is the effects of the nonlinear droop relations on the stability of the MGs. In this paper, the stability of an inverter based MG operating with the nonlinear frequency droop-control has been analyzed. Firstly, a particle swarm optimization technique (PSO) was used to optimize the nonlinear frequency droop relations for minimizing the operating cost of the MG. Secondly, a complete small-signal state-space model of the MG system with the optimized nonlinear droop relations has been developed and the model is updated periodically. The stability of the system is then checked automatically at different operating points. Small signal stability analysis of an islanded microgrid were performed using MATLAB/Simulink and the results were experimentally verified on an MG setup.