Modeling Short Lines for Time-Domain Simulation of the DC Microgrid

This paper investigates the impacts of different short line modeling strategies on the accuracy of the electromagnetic transient studies performed on a DC microgrid. The results of detailed studies performed in the PSCAD/EMTD software environment indicate that inaccurate modeling of the impedances of even short lines, e.g., 20 m cables, which connect DERs to DC buses can cause significant error in simulation results. Based on the performed analytical and numerical investigations, it is shown that even the short cables in the DC microgrid should be represented by series RL branches or PI section models rather than ideal conductors. In addition, it was observed that there is no considerable difference between the results obtained using the RL model and the PI section model of short cables for typical transient, control, protection, and stability studies, i.e., studies that do not involve transients in the frequency range above tens of kHz.