DELAY MARGIN COMPUTATION OF A TIME DELAYED GENERATOR EXCITATION CONTROL SYSTEM USING REKASIUS SUBSTITUON

This paper investigates the delay-dependent stability analysis of a time delayed generator excitation control system including an automatic voltage regulator and a power system stabilizer (PSS) using Rekasius substitution. A modified Rekasius substitution method is proposed to compute delay margin for which the system is marginally stable. The proposed method first eliminates transcendental terms in characteristic equation of the excitation control system without making any approximation and then, computes stability delay margins corresponding to purely imaginary roots with the crossing frequency. In this study, a single-machine-infinite-bus system is chosen as a test system. For a wide range of PSS gains, delay margins of the control system are computed. The accuracy of complex roots and delay margins are verified by using an independent algorithm, the quasi-polynomial mapping-based root finder (QPmR) and time-domain simulations, respectively