Challenges with Multi-Terminal UHVDC Transmissions

The paper gives an overview of the operations aspects of parallel operation of HVDC converters, especially in multi-terminal schemes where the converters are located in different locations. For UHVDC schemes, plusmn800 kV or even higher the geographic distances between the stations can be very significant. Considering the high power rating of UHVDC transmissions, the reliability and availability aspects are considered during all stages of development and design. Thus, the consequences of any outage have to be minimized. It is important that faulty equipment is quickly and safely isolated from the remaining transmission system. In a multi-terminal transmission system the telecommunication is important for coordination of current order and maneuvers in the different stations even if there are back-up controls for not losing the power transmission in case of telecommunication failures. The control and protection systems for a multi-terminal UHVDC transmission are conceptually described.