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It has been widely accepted to apply dc circuit breakers (DCCBs) to protect dc grids. Nevertheless, existing DCCBs have one or more following limitations: insulation recovery scheme of mechanical switch, additional precharge power supply, high conduction loss, unreliable current-breaking process, and unidirectional design. In this letter, a new DCCB with low conduction loss, simple precharging scheme, and reliable breaking ability is proposed. The proposed DCCB could break both fault and operating current actively with the same simple operation sequences. Moreover, bidirectional topology possessing all advantages mentioned previously is also presented. Topology introduction, parameters designing, and scaled-down experiment of the proposed DCCB are all presented in the letter. [ABSTRACT FROM AUTHOR]

The reliability of meshed DC grids mainly relies on their ability in DC fault protection and line power flow managing. Multiple DC circuit breakers (DCCB) and current flow controller (CFC) need to be installed, which significantly increases the system cost. A novel current flow controller integrated with hybrid dc circuit breaker (CFC-IHCB) is proposed to significantly reduce the loss and cost of the whole system. Only one unidirectional IGBT string based main breaker branch is needed for n lines, and the CFC function is integrated into the load communication switches (LCSs). The basic working principle of proposed topology is presented and analyzed. The functionality is verified and a comparison of the proposed solution and other DCCB/CFC solutions is given based on a multi-terminal HVDC system case study. [ABSTRACT FROM AUTHOR]

Two key challenges in meshed multi-terminal dc (MTdc) grids are line power flow management and fault current interruption, which can be solved by current flow controllers (CFCs) and hybrid dc circuit breakers (HCBs), respectively. However, the power losses and the implementation costs of CFCs and HCBs are relatively high. In order to overcome these drawbacks, a combined HCB (CHCB) is proposed in this article by fully utilizing the core ideas of the interline dual H-bridge CFC and the HCB. The proposed device can substitute multiple HCBs at a dc bus with greatly reduced cost. In addition to the fault current interruption capability, the current flows in the adjacent lines can be controlled by the embedded multi-line CFC in the CHCB expanded from the existing interline dual H-bridge CFC. The system-level behavior of the proposed CHCB is similar to the separate solution of the typical HCB and the multi-line CFC. Extensive simulations and experiments verify the effectiveness of the proposed device. Besides, a comparison of the proposed CHCB and the separate solution is presented. [ABSTRACT FROM AUTHOR]