Investigation And Enhancement Of Power System Stability Problem Using Appropriate Facts Devices Case Study: Gilgel-Gibe I To Jimma Transmission Line.

Abstract

Electric Power demand has increased substantially while the expansion of power generation and transmission systems has been severely limited due to scarce resources and environmental restrictions. As a result, some transmission lines are heavily loaded and the system stability is disturbed. Transient stability analysis has recently become a major issue in the operation of power systems; due to an increasing stress on power system networks. This problem requires evaluation of power system?�?s ability to withstand disturbances while maintaining the reliability and quality of power service. An equal area criterion is one of the techniques which used to examine the stability of single machine connected to infinite bus without solving swing equation. However, Thyristor Controlled Series Capacitor (TCSC) is a variable capacitive and inductive reactance device that can be used to provide series compensation in power transmission line. In this thesis the power system from Gilgel-Gibe I to Jimma town substation is modeled with the inclusion and absence of TCSC for transient stability analysis. The simulation is carried out using MATLAB-Simulink software based on the actual parameters of the case study for result analysis and its discussions. Accordingly, the output of the simulation result shows that after the application of three phase fault for system without TCSC the active and reactive power oscillation is very high and power transfer capability is less. The voltage at the grid side reduced to zero and current is highly increased this results zero power transfer capability of the transmission line until the breaker clear the fault. After the fault is cleared the power transfer capability is less than before the fault happened on the system. However by changing the firing angle of the thyristor controlled reactor in decreasing mode comes with the reduction of the system impedance. This is further indicated with an increment of active and reactive power with slight oscillation, and power transfer capability of transmission line is improved. Particularly, the performance of TCSC is analyzed and the best firing angle for the reduction of the system impedance is obtained around 75o.