Effect of Generic Synchronization Approaches on Subsynchronous Damping Characteristics of Thyristor Controlled Series Capacitor

Significance of applied synchronization approach on subsynchronous damping characteristics of Thyristor Controlled Series Capacitor (TCSC) has been widely recognized. However, the relation between inherent characteristics of torsional oscillations and the applied synchronization approach in connection of subsynchronous damping related studies of TCSC have often been left without clear explanation. In this paper effect of two generic synchronization approaches, zero-crossing and Phase Locked Loop (PLL) based synchronization, on subsynchronous damping characteristics of TCSC is studied in series compensated radial power system model. After short introduction of the studied synchronization approaches, their effects on both subsynchronous damping of the system and frequency dependent impedance of TCSC are illustrated. Thereafter, by taking into account the inherent characteristics of torsional oscillations and their modulation effect on synchronization signal, factors causing the discrepancies in subsynchronous damping results are illustrated and modeled.