Robust Stability Region for Time-Delayed Single-Area LFC-EV System

The share of renewable energy sources (RES) in power systems is rising due to environmental concerns. This increment leads to the lack of inertia and insufficient damping which pose a significant threat for frequency stability and dynamic performance of load frequency control (LFC) systems. Various methods have been employed to overcome this drawback. One of these is the utilization of electric vehicles (EVs) for frequency regulation. Furthermore, in practice, systems do not always operate under identical conditions. Therefore, parametric uncertainties should be considered in controller design. This paper applies Kharitonov's theorem and stability boundary locus method to determine a set proportional-integral (PI) controller gains defined as a robust stability region that ensures the stability of the time-delayed LFC system with EV aggregator having uncertainties in system parameters. The impacts of the level of uncertainties and time delay on the robust stability region are investigated. Results indicate that robust stability regions shrink as the level of uncertainties and time delay increase.