Study On The Dynamic Characteristics Of TCSC And The Associated Over-Voltage Phenomena

Thyristor controlled series compensator is an important member of the Flexible AC Transmission family, and is a new development of conventional series compensating technology. The series compensation technology is one of the efficient measures for power transmission in huge amount and over long distance, as well as for rational division of load flows. In our country, power resource distribution is in disequilibrium, the transmission distance is long and the networks are weak. So, the application of series capacitors in EHV transmission systems is an economical choice for increasing power transfer capability and improving system stability, and it has brilliant prospects.The Thyristor Controlled Series Compensator (TCSC), composed of capacitor in parallel with thyristor-controlled reactor (TCR), is a topology variant circuit. In this paper, the analytical expressions are derived with the topological modeling method, which can describe the dynamic behaviors of TCSC in steady-state and transient respectively. The relation between the firing angle and TCSC dynamic characteristics is studied by means of Real-Time Digital Simulator (RTDS). The simulation results reveal that the transient process of ω₀ component is the reason for the excursion of the point when the capacitive voltage passes zero. So, employing the fundamental frequency component of capacitive voltage as the synchronous signal is suggested in this paper.Over-voltage is one of the main factors which affect the secure operation ofpower system. Using the real parameters of the Ping Guo thyristor controlled series compensation (TCSC) station, this paper studies the over-voltage phenomenon in the series compensated EHV transmission system by means of RTDS. The results show that the severity varies with different faults and operating modes, and overall, the over-voltage is under criterion and can be withstood.