$\Delta V-\Delta I$ Plane-Based Line Faults Detection and Classification in DC Microgrid

Abstract

The high fault current rise due to instantaneous capacitor discharge necessitates quick line fault detection in DC microgrids. Hence, this paper proposes a communication-less <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta V-\Delta I$</tex-math></inline-formula> plane-based line faults detection and classification scheme in a Low-Voltage (LV) DC microgrid using local parameters. Simultaneous threshold violations of difference of successive line current and bus voltage samples, with sum of squared currents and disagreement of instantaneous line current to its average echo, aid the scheme to identify forward and backward faults and categorize Pole-to-Ground (PG) and Pole-to-Pole (PP) faults. The proposed scheme is time-efficient as it quickly detects and classifies the worst possible close-in and line-end PG and PP High Resistance Faults (HRFs) within 0.72 ms. The proposed method's feasibility is validated in Real-Time Digital Simulator (RTDS), Numerical Relay Development Environment (NRDE), and microcontroller-based hardware in loop setup. Comparison with previous techniques and tests on two LV DC microgrids indicate that the thresholds in the proposed scheme can aid in quick fault (even line-end HRFs) detection. Also, the proposed scheme is robust to grid-connected and islanded modes of operation, ring and radial configurations, noise, and non-fault events, like load switching, varying power output of sources, and AC side and internal converter faults.