The stability analysis of a hybrid load frequency control (LFC) system with communication delays is presented comprehensively in this paper. Stability analysis, which contains delays, is done by using an exact and a direct analytical method. In the computation of delay margins gain and phase margins are also taken into account. Hybrid LFC schemes installed with proportional-integral (PI) controllers is carried out in case studies. In this method stability and relative stability regions are obtained. Also, the stability boundary curves are obtained as a function of the PI controller parameters. Gain and phase margins can be selected by considering time delay margin suitable with the controller gains for robustness purposes. The main purpose of this paper is to provide information for time delay of hybrid LFC system and determine the boundaries of constant phase margin and gain margin in a parameter space or a parameter plane. Then, the effects of adjustable parameters can be clearly defined. The time-domain simulation studies are carried out which indicate that results are convenient.

Keywords: Hybrid power systems, Microgrids, Power system stability, Renewable energy sources, Smart grids