Studies on the combination of RSFCLs and DCCBs in MMC-MTDC system protection

Abstract

The high rate of rise and large amplitude of a dc fault current in MMC-MTDC system make its interruption difficult for DC Circuit Breakers (DCCBs). In order to tackle this issue, this paper proposes a combined operation of a Resistive-type Superconducting Fault Current Limiter (RSFCL) and a DCCB. By analyzing the fault current in a symmetrical monopole MMC-MTDC system, the effectiveness and necessity of adding a resistive type fault current limiting device into the system after fault is established. With detailed modeling of the RSFCL and DCCB including the quench and recovery processes of the RSFCL, their combined operation is investigated. The influence of different parameters, such as the maximum quench resistance of the RSFCL, the insertion time of the energy absorption branch in the DCCB, and the quench and recovery process of RSFCL, on the fault clearing process are investigated in detail. The effectiveness of the combined operation is verified by extensive simulations in PSCAD/EMTDC. The results indicate that the combination of RSFCLs and DCCBs can obtain a suppression rate of at least 25% on the peak value of the fault current. Besides, the energy that DCCBs need to absorb in their arresters has been reduced by more than 60%, and the total fault clearing time is also reduced. Furthermore, all the converters remain unblocked, making the fast recovery of MMC-MTDC system possible through DCCBs reclosing. It is concluded that the combination of RSFCLs and DCCBs provides an effective solution to handle short circuit faults in MMC-MTDC systems.