New multi-port hybrid DC circuit breaker for DC power grids

In the field of fault isolation and clearance in flexible DC power grids, hybrid DC circuit breakers (HDCCB) have been widely used because of their advantages. However, their development is limited by high construction costs and inapplicability in some fault cases. In addition, adaptive reclosing capability is required for overhead DC lines with high fault probability. Therefore, this paper proposes a new type of multi-port hybrid DC circuit breaker (MP-HDCCB) with current limiting, breaking, and self-charging capabilities. The capacitor polarity reversal circuit is designed to reduce the influence of capacitor pre-charging on the normal operation of the system and to solve the problem of two consecutive line faults occurring in a short period of time. In addition, the circuit breaker can limit the current and break in the face of a single line fault, multiple line faults at the same time, and bus faults. It also has the ability of adaptive reclosing and normal operation of the line after a bus fault. Based on the proposed topology, a 500 kV four-terminal DC system is designed, and a model is established in PSCAD/EMTDC to verify the capabilities of the circuit breaker. Results show that the circuit breaker has adaptive reclosing capability and can realize fault current limiting and breaking under different fault conditions.