A Novel Protection Scheme for Low Voltage DC Microgrid Based on Localized Measurement of Transient Reactor Voltage

Abstract

Fault detection in DC microgrid offers new challenges to detect and isolate the faulted segment within few milliseconds due to high rate of rise of fault current, absence of zero crossing, frequency and information of phasors. For reliable and secure operation of DC microgrid, a new protection scheme based on change in transient reactor voltage at one end of the cable is proposed for fault detection during grid connected and islanded mode of operation. Whenever the magnitude of change in transient reactor voltage observed at one end of the cable exceeds pre-defined threshold limit, an internal fault is detected. The proposed scheme is investigated for different transient and fault conditions such as internal faults at different locations with different fault resistances, external faults, AC side faults, load variation, DG outage and generation uncertainties due to change in environmental conditions to further demonstrate the feasibility and robustness of the proposed protection scheme. The simulation results confirms that the proposed protection scheme is fast, accurate, capable of identifying internal faults and types of faults in DC microgrid.