Fundamental frequency model of thyristor-controlled series capacitor for transient stability studies

This paper presents a fundamental frequency stability model for a thyristor-controlled series capacitor (TCSC). The paper first analyses the factors that influence the transients of TCSC when the operation condition changes, and time domain simulations are performed. Assuming that the dynamics of TCSC can be predicted, a simplified fundamental frequency model is derived on the basis of simulation results. The model inherently incorporates the thyristor triggering logic and the synchronization system. In transient stability programs, the TCSC is thought of as a variable impedance. Therefore the computation burden does not increase too much and the results are accurate. However, the presented model is only suitable for TCSC in capacitive zones. For the transition from a capacitive vernier mode to bypass mode, the TCSC is modeled with its detailed dynamics.