A Protection Strategy for Micro-Grids Based on Positive-Sequence Impedance

Abstract

ABSTRACTIn recent years, the concept of micro-grid has appeared as an appropriate way for the integration of Distributed Energy Resources (DERs) in the distribution networks. However, micro-grids have encountered a number of challenges from control and protection aspects. One of the main issues relevant to the protection of micro-grids is to develop a suitable protection technique which is effective in both grid-connected and stand-alone operation modes. This article presents a new micro-grid protection strategy based on positive-sequence impedance using Pha-sor Measurement Units (PMUs) and a designed Microprocessor-Based Relay (MBR) along with a narrowband communication system (only to exchange digital information, not electrical power). The main attribution of the proposed scheme is that it has the ability to protect micro-grids containing either radial or looped feeders; additionally, the capabilities of automatic updating of pick-up threshold value and single-phase tripping have been considered in the...