An Integrated Multiport Circuit Breaker With Current Flow Controlling Capability for Meshed Multiterminal HVDC Grids

The operation of HVdc grids faces two critical challenges: 1) fast interruption of dc-side fault currents and 2) power flow management to prevent dc lines from overloading in some scenarios. To overcome such challenges, dc circuit breakers (DCCB) will be required to protect the system, and current flow controllers (CFCs) will be required to control lines' currents. A DCCB and CFC can be combined into a single integrated device with multiple functionalities. To this aim, this article presents an integrated device with current flow control and fault current interruption capability. Furthermore, by implementing a minor modification to the proposed topology, the provided CFC-DCCB showcases not only the capacity to interrupt current flowing from the converter to the dc bus during a dc bus fault but also the capability to interrupt a faulty line, even in the event of an ultrafast disconnector failure. The operational principle of the integrated device is described, and its performance is examined in PSCAD/EMTDC using a modified meshed version of the CIGRE B4 grid. Moreover, a scaled-down three-terminal VSC grid was built to verify the proposed integrated device's CFC experimentally.