Computation of stability regions for load frequency control systems including incommensurate time delays

Abstract

This article studies the impact of incommensurate communication time delays on stability regions defined inproportional-integral (PI) controller parameter space for a two-area load frequency control (LFC) system. Distributedpower generations and large power plants increase the complexity and control issues of interconnected power systems. Ininterconnected power systems, LFC systems need to have complex communication networks to exchange data betweencontrol center and geographically dispersed generations. The receiving/transmitting of remote measuring data throughcommunication infrastructures causes inevitable time delays, which adversely affect controller performance and stability ofthe LFC system. Time delays introducing feedback control loops of a multiarea LFC system could exhibit incommensuratecharacteristics. In this study, a simple graphical method based on extracting a stability boundary locus is implementedto get PI controller parameters responsible for stabilizing the LFC system having incommensurate delay values. Theboundaries of the stability regions in the PI controller parameter space are confirmed by time-domain simulations anda numerical algorithm known as the quasipolynomial mapping-based root finder algorithm. Results illustrate thatincommensurate delays have remarkable effects on the stability region.