Designing of Power System Stabilizer based on the Root Locus Method with Lead-Lag Controller and Comparing it with PI Controller in Multi-Machine Power System

Shadi Jalali, Ghazanfar Shahgholian


This paper presents a method for designing a multi-machine power system stabilizer. The conventional design technique using
a single machine infinite bus approximation involves a frequency response estimation called GEP(s). Frequency response
is estimated between the input AVR and electrical output torque. The power system stabilizer is designed by frequency
response and based on the root locus method to improve the damping of oscillatory modes. By using this method, we can
adjust the structure of the PSS compensator and its parameters in the multi-machine system and it does not need to know
the equivalent reactance of output and voltage of the infinite bus or the other estimations in every machine. In the proposed
method, information available at the high voltage bus of the step-up transformer is used to set up a modified Heffron-Phillips
model. Finally, this method is examined on three test systems. Simulation results indicate the performance and effectiveness
of the proposed method.


Roots locus method; Frequency response; Small signal stability; Power system stabilizer

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