Unidirectional hybrid circuit breaker topologies for multi-line nodes in HVDC grids

Interest in HVDC transmission increases, büt still fault handling is difficult because fault currents rise faster than in HVAC transmission. Therefore concepts for a fast turn off of DC lines, especially in case of a short circuit fault, are needed. Turning the complete DC-transmission system off is too slow and not suitable for large grids. To overcome this, several bidirectional HVDC circuit breaker topologies have been developed. However, fast bidirectional circuit breakers contain a huge number of semiconductors. As alternative unidirectional circuit breakers can be used, which have a lower number of semiconductors. This paper focuses on the applicability of unidirectional hybrid circuit breakers, which are derived from four bidirectional circuit breaker concepts. In addition, a detailed comparison of the unidirectional circuits breaker topologies is presented.