Inter-area oscillation damping in large scale power systems with unified power flow controllers

Power system oscillations occur in power networks as a result of contingencies such as faults or sudden changes in load or generation. They are detrimental to the operation of the system since they affect system stability and the optimal power flow through it. These oscillations do not usually damp out in tie-lines unless certain controls are applied to the system. Local and inter-area oscillations have traditionally been controlled by Power System Stabilizers (PSS). However, Flexible Alternating Current Transmission Controllers (FACTS) have significant potential as alternatives to PSS.;The main goal of this research is to damp inter-area oscillations by Unified Power Flow Controllers (UPFC). UPFC is a series-shunt FACTS device which is used for purposes such as the control of active and reactive power flow through the corridors of the system. However, using supplementary controls and proper coordination of UPFCs, they can be used for fast damping of inter-area oscillations in multi-area power systems.;The research consists of ten papers. There are several issues associated with dynamic control of FACTS devices which need to be taken into consideration. In the first two papers the role of pre-fault UPFC operating points on the stability and dynamic behavior of power systems is discussed. Linear approaches for the control of inter-area oscillations have been discussed in the third and fourth papers. Since the discussed algorithms for damping oscillations need global feedback data for control implementation, decentralized and wide-area methods for dynamic state estimation have been presented in the fifth and sixth papers. Seventh paper shows that using similar methodologies to UPFCs, multiple coordinated Static Synchronous Compensators (STATCOM) can also be used for controlling power system oscillations. A nonlinear method for controlling oscillations has been presented in the eighth paper. Finally, since FACTS placement plays an important role in the dynamic behavior of the system, the last two papers propose two different methods for optimal dynamic placement of UPFCs.