Thyristor switched capacitors (TSCs) have found an ever increasing role in the operation of flexible AC transmission systems or FACTS. The ability of these static var compensators to regulate the voltage by consuming or supplying reactive power quickly is not only viable for transmission but is an effective measure for increasing power quality at a distribution level. The proposed design uses a variable number of logically switched capacitors to supply reactive generation per reactive demand. The design ensures that the capacitors are safely switched into service, reactive demand is accurately calculated, and the TSC will respond quickly to changes in demand. While providing fast and safe operation, the conceptual design is also flexible enough to allow for optimization of the TSC to meet the demands of specific loads.

This research work deals with the analysis, design and implementation of thyristor switched plain capacitor banks and thyristor switched shunt filter banks. Performances of various thyristor switched capacitor (TSC) topologies are also investigated by simulations. The theoretical findings have been verified by carrying out experimental work on two prototypes implemented within the scope of this research work, one is a wye-connected laboratory prototype and the other is a delta-connected application prototype integrated to some of the SVCs existing in Turkish Coal Enterprise s Plants. The advantages of back-to-back connected thyristor switches over conventional electromechanical contactors are also made clear by conducting an intensive experimental work in the laboratory. A good correlation have been obtained between theoretical and experimental results.