HVDC grids are expected to be a solution to upgrade the existing AC system. However, their development presents several technical challenges like power flow control, grid protection and interconnection of grids with different technology or voltage levels. One required technology for the development of such grids is the DC-DC converter capable of operating at hundreds of kilovolts and hundreds of megawatts. While different DC-DC converter topologies have been proposed in literature, most studies focus on the topology itself and there is a lack of studies that deal with their grid integration. This paper studies the role of DC-DC converters in the protection of HVDC grids acting as firewalls to stop the propagation of faults. The effects of blocking the converter or actively controlling its operation during faults are presented. The results demonstrate the capabilities of DC-DC converters beyond DC voltage transformation.

J. Paez, J. Maneiro, D. Frey, S. Bacha, A. Bertinato and P. Dworakowski