Average loss calculation and efficiency of the new HVDC auto transformer

For the upcoming need to transfer bulk power over long onshore distances, HVDC power transmission is the preferred choice. However, components like HVDC-DC converters and a protection concept for DC line faults present challenges, that still have to be solved. As up today, the sections of a segmented DC transmission corridor would still be linked via an AC connection, leading to high transformation losses, and high investment costs. In this paper the conversion efficiency of the new HVDC auto transformer is compared to the conventional two stage topology with a full AC link.