Impedance Based Differential Protection for Zonal DC Microgrid

Abstract

DC microgrids are less complicated and more effective than AC microgrids, making them more attractive for power distribution. However, protecting the zonal DC microgrid using non unit protection scheme is difficult due to the bidirectional power flow. Existing unit protection schemes are sensitive during high resistance faults due to the low magnitude of the fault current. This article presents a novel unit protection algorithm to overcome the exit unit protection technique to identify the zonal DC microgrid high resistance fault. The proposed scheme identifies the fault using the impedance difference seen by the relays presented at the line ends. The impedance difference between external fault and steady-state condition is equal to line impedance. The impedance difference available at the relays is not equal to the line impedance during the external fault. In the case of internal fault, the difference is not equal to line impedance. Under the MATLAB/Simulink environment, the proposed algorithm is verified using a zonal DC microgrid for numerous fault scenarios, including internal fault, external fault, high resistance fault, and noise environment. The obtained simulation results reveal that the suggested method efficiently distinguishes internal and external faults.