Small signal modelling and stability analysis of an islanded AC microgrid with inverter interfaced DGs

This paper presents a systematic way of developing a full dynamical linearized small signal state space model and stability analysis of an islanded AC microgrid with low inertial inverter interfaced DGs represented in the synchronous (DQ) reference frame. This AC microgrid accommodates four low inertial inverter interfaced DGs of unequal power ratings connected to each other through three lines and four loads such as resistive load, impedance load, constant power load and rectifier interfaced active load simultaneously, but connected at different nodes. To obtain the model systematically the whole AC microgrid system has been divided into the three sub-modules such as inverter sub-module, network sub-module and load sub-module. All the sub-modules are combined together on a common reference frame. The resulting state matrix of the islanded AC microgrid system has been utilized to obtain the eigenvalues (termed `modes´).