Improving system static security via optimal placement of thyristor controlled series capacitors (TCSC)

The thyristor controlled series capacitor (TCSC) is one of the most effective flexible AC transmission system (FACTS) devices. It offers smooth and flexible control of the line impedance with much faster response compared to the traditional control devices. While numerous studies concerning the utilization of these devices have been carried out so far, most of the research has focused on issues such as transient stability improvement, subsynchronous resonance (SSR) mitigation, damping of power swings, avoiding voltage collapse, etc. This paper on the other hand, is concerned with the enhancement of steady state system security against single contingencies via the use of TCSCs. Placing TCSCs at selected branches requires the analysis of the system behavior under all possible contingencies. This paper presents a systematic procedure to place and operate TCSCs in a power system. First the "single contingency sensitivity (SCS)" criterion for a given branch flow is defined. This criterion is then used to develop a branch's prioritizing index in order to rank branches for possible placement of TCSCs. Finally, optimal settings for TCSC parameters are determined for important contingencies. An example system is used to illustrate the implementation of the proposed method.