Sequence Domain Calculation of Active Unbalanced Distribution Systems Affected by Complex Short Circuits

In this paper, a calculation method for quantifying the impact of complex short circuits on active unbalanced distribution systems is proposed. Unlike previous distribution system short-circuit calculations, the proposed method is capable of solving complex short circuits with an arbitrary number of faulted busses and phases, without predefining the boundary (fault) conditions. Different short circuits are defined by simple inspection of these faults. Additionally, all distribution system elements are appropriately modeled and integrated in the proposed method, including electronically coupled distributed energy resources. The method can solve unbalanced systems, including mutually coupled sections, in unsymmetrical prefault states, and it is performed in the sequence domain. This makes the proposed method particularly fast and suitable for online distribution system analysis. The computation results show the advantages of the proposed method relative to previous short-circuit calculation methods, in regards to both the required calculation time and the accuracy.