Amplitude and Energy Contribution Analysis of Multi-Type Fault Current Limiting Devices in DC Grids

This study develops a method to decompose and quantify the fault current limiting ability of fault current limiting devices (FCLDs) and calculate the amplitude and the energy limiting contribution of FCLDs in dc grids. The coupling of multi-type FCLDs and the mechanism of fault current limiting of modular multilevel converter (MMC) are studied by analyzing the
$\lambda $
–
$i$
flux circuit in a single-terminal system. Based on this analysis, the fault current limiting contributions of FCLDs are obtained by decomposing the fault current limiting ability. Furthermore, a method that can transform dc grids into the superposition of several single-terminal systems is proposed. The decoupling between FCLDs and the decoupling between MMCs are realized in the dc grid, and the fault current limiting contribution of FCLDs on any MMCs’ fault current in the dc grid can be calculated. The proposed method is validated on a scaled-down single-terminal system in the laboratory and on a simulation model based on
Zhangbei
dc grid in PSCAD/EMTDC. An application that optimizes FCLD parameters economically through contribution analysis is proposed to illustrate the significance of this study.