Damping improvement by SSSC and STATCOM in a part of Iran electrical network

If a disturbance occurs in a power system and then it is cleared, the machines in that system will initially oscillate, and then, when the transient energy becomes zero, they will settle at stable operation point. In this paper, the rate of reduction in transient energy is considered as an index of system damping. This concept is then used to find the additional damping provided by Static Synchronous Compensators (STATCOM) and Static Synchronous Series Compensators (SSSC). Analytical expressions for the index of system damping, provided by these devices, are derived and compared for the classical model of single machine connected to infinite bus (SMIB). The proposed technique, which is based on the rate of dissipation of transient energy, is then tested on the SMIB and the 6-machine SISTAN system. SISTAN system is a part of Iran national grid. The results derived from this new index verify the capability of these devices in damping power system oscillations.