Centralized supplementary controller to stabilize an islanded AC microgrid

This paper presents a centralized supplementary controller to stabilize the dynamics caused by an active and passive loads, connected to an islanded AC microgrid with low inertial inverter interfaced DGs. The centralized supplementary controller has been designed on the basis of a linear quadratic regulator with prescribed degree of stability (LQRPDS). Eigenvalue based method has been utilized to analyze the stability of an islanded AC microgrid comprising of four low inertial inverter interfaced DGs having unequal power ratings and supplying active as well as passive loads. To explore this, a full dynamical linearized small signal state space model of the islanded AC microgrid represented in synchronous (DQ) reference frame has been considered. The effectiveness of the proposed controller has been verified by comparing the results with a centralized supplementary controller based on linear quadratic regulator (LQR).