Simulation Study Of A Hybrid Hvdc System Composed Of A Self-commutated Converter And A Line-commutated Converter

Development of large-capacity, gate turn-off thyristors (GTOs) has led to a self-commutated power converter (SCC) system applicable to electric power transmission systems. During introduction of the SCC systems, a hybrid HVDC system composed of a conventional line-commutated converter (LCC) and the SCC was studied. The LCC controls DC current as a rectifier and the SCC controls DC voltage as an inverter. In this paper, new control schemes, start-stop operations and behaviors of AC system faults of the hybrid HVDC system were studied by digital simulations. Comparisons were made to the HVDC systems, both terminals of which were composed of LCCs or SCCs, and to the hybrid HVDC systems.