Application of Kharitonov's Theorem in Robust Stability of Voltage and Frequency of an Islanded Microgrid

In this paper, a simultaneous frequency and voltage droop control based on robust tuning is introduced instead of the conventional droop control for an islanded microgrid (MG). First, a small signal model for the MG including three inverter interfaced distributed generations (IIDGs) and three loads is presented. Then, by applying a step change in load as a disturbance, the system's behavior is analyzed and compared with two the mentioned droop control systems. Finally, using Kharitonov's theorem based a robust method, the coefficients of droop control are determined and robust stability of the system in presence of uncertainty in MG's physical parameters will be guaranteed. Results based on zero exclusion condition represent robust stability of the system.