Research on Parameter Coordination of Fault Isolation Unit in DC Distribution System

Abstract

The high voltage DC circuit breaker (DCCB) is the key to the development of DC distribution network, but the interrupting capacity and reliability of DCCB need to be improved. A type of fault isolation unit for DC system is proposed in this paper, consisted of smoothing reactor, resistive superconducting fault current limiter (R-SFCL) and hybrid DC circuit breaker. This combination could reduce the level of the demand of operation time and interrupting capacity of DCCB, so as to improve the ability to isolate short-circuit faults effectively. The topology and interrupting process of DCCB are analyzed in this paper. On this basis, the influence on commutation process and the stresses of the whole machine, which is caused by the parameter selection of DCCB snubber branch, is studied. A simulation model composed of the devices mentioned above in PSCAD/EMTDC was built to analyse the millisecond-level interrupting process and the microsecond-level current commutation process. The rationality of the parameter selection method of the DCCB snubber branch and the necessity of installing the R-SFCL in the DC power distribution network are verified, which provides a theoretical basis for the coordinated application of hybrid DC circuit breaker and resistive superconducting DC current limiter.