ABSTRACT
Electric power systems are complex multi-component dynamic systems. Spread over vast geographical areas and no longer operating as isolated systems, but as interconnected systems, they are subjected to many kinds of disturbances and abnormalities. Their characteristics vary with the variation of loads and generation schedules. The present-day tendency of operating generators with relatively small stability margins has made these systems even more fragile. A good system should have the ability to retain its normal
operating condition after a disturbance. As stability is ultimately concerned with the quality of the electric power supply, it is considered as one of the main topics of power systems research.
