Study of Impact of Dual Setting Overcurrent Relay Characteristics on Protection Coordination in Synchronous DG based Microgrids

摘要

Communication-based protection plays a vital role in microgrid operation in smart power grids. Operation of microgrids with Distributed Generation (DG) has features like bidirectional flows and variable short circuit currents, which challenge the performance of conventional directional overcurrent relays (CDOCRs). In the microgrid scenario, dual setting overcurrent relays (DS-DOCRs) have shown better operation in line protection compared to CDOCRs. This paper investigates the performance of CDOCRs and DS-DOCRs and proposes a methodology for microgrid protection with the assistance of communication channels, which can be used to overcome the limitations of directional relay miscoordination. The relay coordination problem is formulated as nonlinear constrained optimization and solved by using the GA-NLP programming approach. The communication-based microgrid protection logic was tested for 9 bus microgrid test systems and IEEE 30 bus system, and the performance is found to be satisfactory.