Co-ordination of thyristor-controlled VAr compensator and auxiliary controller of excitation system for small signal stability enhancement

Technical advantages of co-ordinating thyristor-controlled static VAr compensators (SVC) and power system stabilizers (PSS) for stability enhancement during small signal dynamics are presented. The technical feasibility of the co-ordinated scheme for simultaneous damping of inertial and torsional oscillatory modes in a series-capacitor-compensated system is demonstrated. The investigations show that the co-ordinated scheme not only increases the overall system damping, but also prevents undesirable interactions between oscillatory modes. New control schemes for SVC and PSS, based on multi-input control concepts, are given. The studies are performed on system-1 of the second IEEE benchmark model, using an eigenvalue analysis method. The analytical results are verified by digital computer simulation studies, using the Bonneville Power Administration´s Electromagnetic Transients Program (EMTP).