Developing A Smart Power-Voltage Relay (SPV-Relay) with no Communication System for DC Microgrids

Abstract

Microgrids are considered a prospective way towards improving electric service resiliency, reducing costs, and upgrading service reliability. DC microgrids offer many advantages rather than AC microgrids. In spite of the numerous features and advantages of DC microgrids, their protection faces significant challenges such as self-limited current of photovoltaic (PV) systems, long time constant of wind energy systems, dependability on communication systems, etc. The paper introduces a new protection scheme for DC microgrids using the rate of power (dP) and rate of voltage (dV) and mapping them as dP-dV profile. The new scheme is titled as smart power/voltage relay (SPV-Relay). The proposed scheme is applicable for all types of renewable energy sources (RESs) and energy storage systems independent of the power rating and configuration of the DC microgrid. The proposed concept of SPV-Relay is described and the method used for fault discrimination is explained. The relay characteristics are developed considering all the DC microgrid components. Three operating zones are identified on dP-dV profile to discriminate between various fault types and locations. The sensitivity and stability of the proposed relay are evaluated under different fault conditions as well as different control schemes and operational scenarios for DC microgrid.