Bidirectional Capacitive Multi‐Line Hybrid Circuit Breaker with Shared Isolation and Natural Zero‐Crossing for MT‐HVDC Grid Protection

ABSTRACT

Protection of multi‐terminal HVDC (MT‐HVDC) grids is complex, as multiple current paths branch out from the DC buses. This complexity significantly increases project capital costs. Although using several hybrid HVDC circuit breakers can address protection challenges, their adoption imposes substantial cost and more complexity on the grid. This work presents a bidirectional capacitive multi‐line hybrid circuit breaker (BCML‐HCB) built on thyristor technology. The core contribution lies in a Shared Isolation Circuit (SIC) that provides isolation for all lines linked to the same DC bus. The proposed architecture greatly minimises component usage and, in turn, reduces system capital expenditures. In addition, the BCML‐HCB eliminates the requirement for MOAs by ensuring stress‐free fault interruption. It accomplishes this by inducing a natural current zero‐crossing and interrupting precisely at that moment. The operational principles and performance of the designed BCML‐HCB are thoroughly confirmed through PSCAD/EMTDC simulations under different fault scenarios. Simulation results confirm the effectiveness of the BCML‐HCB, demonstrating fast fault isolation and its significant potential for cost savings in MT‐HVDC grid applications.