Cable Fault Characteristics of Energy Storage in DC Microgrids

This paper analyzes the cable fault characteristics of energy storage system in DC microgrids and proposes a current limiting measure. Battery is treated as research object in this paper, which connected to DC bus by bidirectional DC-DC converter. Cable pole-to-pole and pole-to-ground fault responses are analyzed in stages under the charge-discharge mode of battery. For each stage, the circuit and current expressions of the fault transient process are given. Considering the vulnerability of power electronic devices, the current flowing through the diode are also analyzed. Theoretical analysis shows that the fault current rises rapidly and has a large amplitude. If the protection scheme fails to act in short time, it will create a threat to the DC equipment and power electronic devices. Therefore, a current limiting measure is proposed to suppress the fault overcurrent. Finally, the DC microgrid model is built in PSCAD/EMTDC software to verify the correctness of fault analysis and effectiveness of current limiting measure. According to the simulation waveform, the fault results were consistent with the theoretical analysis and current limiting measure effect is good.