Study on the influence of TCSC structure and control on SSR damping using an improved s-domain model

This paper investigates the influence of basic TCSC main circuit structure and control on subsynchronous torsional damping of a nearby turbine-generator. An improved s-domain model based on dynamic phasor approach was used to obtain the results presented in the paper. The study is conducted on the System-1 of the IEEE Second Benchmark Model. Detailed eigenvalue analyses are carried out in order to evaluate the effect of the proportion of TCSC to FSC, Boost Factor and size of TCSC reactor on subsynchronous damping. The influence of constant current controller and synchronization system (PLL) parameters is also investigated. Finally, a simple Subsynchronous Damping Controller (SSDC) is added to the TCSC main control in order to demonstrate that the SSR damping capability of TCSC may be enhanced by proper modulation of firing angle. The results obtained in the time domain simulations are validated through PSCAD/EMTDC simulations.