Damping of Low-Frequency Oscillations in Inter Connected Power Systems

Abstract

Stability study is the most important studies in power system; which keep the system secure and continuous operation. Stability of power system means the ability of the synchronous generators to be in synchronism when small or large disturbances occur in load or network of power system. If one of the generators losses the synchronism the other generators will be overload and make the network separate which cause blackout of the system; so that the instability problem must be solved quickly. This thesis concerned to study and analyzes the small signal, transient stability problem, and damping of low frequency oscillations by using power system stabilizer for multi machines system. The nonlinear equations which represent the system have been linearized and then placed in state space form in order to study and analysis the dynamic performance of the system. IEEE system (10 machines-39 bus bars) has been taken as case study. The AVR system causes negative damping of oscillation; so that the PSS was designed and added in optimal location by using participation factor technique to increase the damping ratio. The eigenvalue and time domain simulation methods were used to analyze the system stability; finally, the responses and results have been represented for several cases by using time domain simulation. Result obtained showed that the system without PSS is oscillatory and after add PSS to the optimal M/Cs the system return back to stability conditions after few cycles.