Operation and Control of an HVDC Circuit Breaker With Current Flow Control Capability

Deployment of dc circuit breakers (DCCBs) will help to isolate dc faults in dc systems. Conversely, current flow controllers (CFCs) will be employed in dc grids to balance currents among transmission lines. However, the inclusion of these devices may incur significant capital investment. A way to reduce costs is by integrating current control capabilities into DCCBs. This article presents a new device, the CB/CFC, which combines a multiline DCCB with a half-bridge based CFC. The operating principles of the device are analyzed and its operating modes are classified. A level-shift modulation method ensuring that a single bridge of the CB/CFC is modulated for each operating mode is considered. This simplifies the control scheme for CFC operation. For completeness, the CB/CFC is compared with other alternatives available in the literature. It is shown that the presented device reduces the number of semiconductor components compared to other solutions. DC fault isolation and current flow control are verified through simulations conducted in Power Systems Computer Aided Design (PSCAD).