Sub-Synchronous Resonance Alleviation in Power Systems using Facts Devices
Flexible AC transmission systems (FACTS) have been extensively used in recent past for solving various power system steady state control problems. Additionally, series compensation of transmission lines is being done using capacitor banks so that overall power transfer capacity can be improved to ensure stable operation. However, this gives rise to sub-synchronous resonance (SSR) phenomenon under which there may be exchange of energy between mechanical and electrical system at frequencies below the synchronous value, damaging the axis system of generator. This paper investigates the effect of FACTS devices like Static Synchronous Compensator (STATCOM) and Unified Power Flow Controller (UPFC) for alleviation of SSR in a single machine infinite bus system. Simulation studies have been carried out (i) with no FACTS device and (ii) with FACTS device. These studies have shown that SSR in the system can be alleviated to a great extent by using STATCOM. With UPFC the system oscillations are damped out i.e. mitigation of SSR achieved and by equipping fuzzy logic controller better results have been obtained.
Keywords - FACTS, Fuzzy logic control, STATCOM, Sub synchronous Resonance (SSR), Torsional Interaction, Unified Power Flow Controller (UPFC)