Protection algorithm based on differential voltage measurement for MTDC grids

Many point to point HVDC lines are already in operation in several countries. However, the development of multiterminal DC grids is slowed by the lack of efficient control and protection strategies that can be applied on such grids. This article deals with the protection aspect of those networks. Indeed, the resort to Voltage Source Converters (VSC) changes the constraints since the short circuit current can flow through the freewheel diodes in case of the event of a DC fault. This paper investigates a new protection algorithm suitable as main protection algorithm. It is based on the use of supplementary inductors placed at each end of the lines.