Analytical modeling of thyristor-controlled series capacitors for SSR studies

Thyristor-controlled series capacitors (TCSC) have dynamic characteristics that differ drastically from conventional series capacitors especially at frequencies outside the operating frequency range. Therefore suitable models are needed to properly study the applications of TCSC on a utility power system. An accurate analytical model of the TCSC which is valid in the frequency range from 0 Hz to twice the operating frequency is presented. The model incorporates the thyristor triggering logic, the synchronization system, and higher level control loops such as power oscillation damping loop. This model is suited for linearized analyses of a power system using frequency domain methods such as eigenvalues. It is particularly valuable in studying subsynchronous resonance (SSR) enables the utility industry to better evaluate interactions between TCSC and other devices.