Hybrid　dc　circuit　breakers　(HCBs)　are　vital　equipment　in　dc　grid　systems.　However,　HCBs　are　usually　costly　since　massive　full-controlled　power　semiconductors　are　required　to　withstand　high　surge　voltage　and　current　stresses　during　current　interrupting.　Thyristors　are　good　alternatives　in　realizing　HCBs　in　view　of　their　low　cost　and　high　current　carrying　capability;　however,　turning　off　the　thyristor　fast　and　reliably　is　a　challenging　task.　In　this　article,　a　novel　HCB　topology　is　proposed,　of　which　the　solid-state　part　is　realized　by　hybrid　connection　of　thyristors　and　insulated　gate　bipolar　transistor　(IGBT)　half-bridge　submodules.　The　use　of　IGBT　half-bridges　provides　a　negative　voltage　across　the　thyristors　to　turn　them　off;　accordingly,　thyristors　withstand　a　major　of　turn-off　surge　voltage　instead　of　IGBTs.　By　this　means,　a　low-cost　HCB　can　be　established　while　maintaining　a　high　breaking　speed.　Besides,　fast　reclose　and　rebreak　function　is　provided　by　the　proposed　topology.　Operation　principle　and　design　consideration　of　the　novel　HCB　topology　are　analyzed　in　detail,　and　the　effectiveness　of　the　proposed　HCB　is　verified　by　both　software　simulation　and　downscaled　experimental　results.　©　1986-2012　IEEE.