Research on the breaking branch for a hybrid DC circuit breaker in±500 kV voltage‐sourced converter high‐voltage direct current grid

Abstract

In order to construct the voltage-sourced converter high-voltage direct current grids, the high capacity direct current circuit breakers (DCCBs) are in demand. The hybrid DCCB has been the mainstream proposal, where the high-voltage solid-state switch (HVSS) is the key component for breaking the final fault current. Investigating the current commutation between the breaking branch and energy-absorbing branch, a hybrid DCCB with repositioned current commutation module (CCM) and redesigned HVSS is proposed in this study. By analysing the equivalent circuit of the CCM and HVSS, the detailed transient stages during current interruption procedure have been revealed, and the comparisons of different topologies for HVSS are made in-depth. The repositioned CCM can greatly decrease the transient voltage stress for HVSS and CCM whilst the improved HVSS including metal oxide varistor can maintain better interruption performances. Then the actual prototypes are developed to verify the effectiveness of the improved hybrid DCCB topology. In the end, a 500 kV DCCB is realised based on the proposed HVSS, which can ensure the reliability and convenience of the hybrid DCCB.