Delay-Dependent Stability of Load Frequency Control in Networked Power Systems Integrated with Electric Vehicles

Abstract

In this paper, impact of the integration of plug-in-electric vehicle units in enhancingthe delay-dependent stability margin of a class of networked load frequency control systems isinvestigated using the classical Lyapunov-Krasovskii functional approach. In networked controlsystems, owing to the use of communication links, time-delays get introduced in the feedbackpath. These communication network-induced delays invariably exert a negative influence onsystem performance and stability. Furthermore, if the delay magnitude exceeds a critical margin,called stable delay margin, the system loses stability. In recent times, electric vehicle aggregatorsare integrated as a distributed generation source in the load frequency control systems forenhancing the grid frequency compensation. In such systems, in addition to improved frequencycompensation, integration of electric vehicles also paves way in the enhancement of stable delaymargin. To study this impact of integration of electric vehicle aggregators on stable delaymargin, in this paper, two types of centralized load frequency control systems are considered.Furthermore, time-delays in the centralized control loop and electric vehicle aggregator loop areconsidered to be non-identical, and appropriate participation factors for effective load sharingare incorporated in the system framework.