Stability improvement by FACTS devices: a comparison between STATCOM and SSSC

The static synchronous compensator (STATCOM) and static synchronous series compensator (SSSC) have the capability of dynamically controlling the power flow through a line. This feature of STATCOM and SSSC is fully exploited in this paper to improve the stability limit of a simple power system first by raising the power-angle curve as much as possible to maximize the decelerating area and then fully utilizing it in counterbalancing the accelerating area. All the equations used in improving the stability limit by using STATCOM and SSSC are systematically derived. A theoretical comparison of some aspects of STATCOM and SSSC is also made. The above technique of improving the stability limit is then tested on a single machine infinite bus system equipped with a STATCOM and SSSC. The results obtained are also systematically described and compared.