| This thesis examines the use of a UPFC for mitigating interarea and torsional modes of power systems. A fundamental-frequency state-space model of a UPFC, under balanced operating conditions, is developed. A steady-state power flow model, a small-signal (linear) eigen-analysis model, and a large-signal transient stability model of the UPFC are deduced from the state-space model. A steady-state model of an conventional phase-shifter is also introduced.;The steady-state models are used (1) to identify operational characteristics of the UPFC, and (2) to compare the characteristics with those of a phase-shifter. The small-signal linear model is used to demonstrate the technical feasibility and effectiveness of a UPFC for damping interarea and torsional modes. The eigen analysis results are validated with those obtained from digital time-domain simulation studies based on the use of Electromagnetic Transients Program (EMTP).;The studies are initially carried out on a relatively small size power system to demonstrate principle concepts and technical merits/limitations of a UPFC. The final studies are conducted on a realistic size interconnected power system which exhibits simultaneous interarea and torsional dynamics. |
