Application of Hybrid Circuit Breakers for Future Multi-Terminal HVDC Grids: Limitations and Possible Solutions

This study explores the essential issue of protecting future multi-terminal high voltage direct current (MT-HVDC) grids against transmission line faults, which continues to be a key barrier to the wider implementation of HVDC technology in maximizing renewable energy utilization. In this regard, Hybrid HVDC circuit breakers (H-DCCBs) are viewed as a viable solution for protection against transmission line faults due to their technical superiority over other HVDC breaker types. However, it has become evident that when confronted with increased voltage levels and escalating requirements for fault-current interruption, H-DCCBs have certain limitations. In response, this paper analyses the operation of H-DCCB in depth, utilizing simulations on the PSCAD/EMTDC platform. The research provides greater insights into the performance and capacity limits of these breakers by closely evaluating their behavior under various operating situations. Furthermore, the study sheds information on the problems posed by the H-DCCB's major components, such as insulated gate bipolar transistor (IGBT) valves and metal oxide surge arrestors (MOSAs). This results in a better knowledge of how these restrictions affect fault current interruption capability. Lastly, a few design improvements in H-DCCB are proposed to overcome its inherent limitations.