ABSTRACT
High-voltage direct current (HVDC) energy transmission was developed in the late 1920s, and the first commercial HVDC submarine cable started operation in 1954. This system used mercury-arc valves, which required constant maintenance and rebuilding. The thyristor-based HVDC system uses current-commutated converters, because the thyristors cannot be switched off. The current source inverter–based system is designed to transfer large amount of power for long distance or bridged long water ways, sea crossing where the alternating current (AC) cable cannot be used because of the large capacitive current. The voltage source–based HVDC system is designed for less power than the classical thyristor-based HVDC system. Most classical HVDCs in operation are point-to-point transmission systems where a large amount of energy is transported between two regions. In case of a ground fault in the AC system, the converter control will reduce the direct current voltage to limit the current flow to the prefault value.
