Negative Damping Mechanism Analysis of Power System Stabilizer Based on Damping Torque

Abstract

Abstract Power system stabilizer plays an important role in suppressing the low frequency oscillations, but a PSS with poorly tuned parameters may produce negative damping and aggravate the system oscillation. The purpose of this paper is to study the mechanism of damping of a PSS in multi machine system and to analyze whether the PSS has produced negative damping. This paper adopts Park model for analysis. According to the concepts of complex frequency and generalized phasor, the correlation between the damping torque phasor and the real part of the complex eigenvalue is studied. With the auxiliary of Park equivalent circuits, the damping torque provided by the excitation system is separated from the electrical torque phasor. Then, the damping torque coefficient of the PSS is defined as an indicator of the damp effect of the stabilizer. Finally, the simulation results of single machine infinite bus system and 4-machine system demonstrate the validation of the proposed method for evaluating the damping effect of PSS on the system.