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

Authors: ŞAHİN SÖNMEZ

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

Keywords: Incommensurate time delays, stability region, PI controller design, load frequency control systems

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