Analysis of the Energy Dissipation Characteristic in an MMC-Based MVDC System With the Liquid Metal Current Limiter

Abstract

Utilizing DCCBs to realize selective protection is a promising solution for dc fault isolation. While the large fault current and high fault energy make the dc fault interruption a crucial problem in the medium-voltage dc (MVDC) distribution system. A novel fault isolation strategy based on the liquid metal current limiter (LMCL) is proposed in this article to reduce the breaking current and dissipated energy of the dc circuit breakers (DCCBs). Based on a three-terminal MVDC distribution system, the fault current and energy dissipation characteristics for the reactor fault current limiter (L-FCL) and the LMCL are analyzed theoretically. The simulation results show that under the same breaking current, the dissipation energy and the dissipation time in the LMCL case are reduced by 48% and 41%, respectively. Besides, the influence of system parameters on breaking current and energy dissipation characteristics under the LMCL case is further analyzed. Finally, an experiment circuit is designed to verify the proposed scheme.