An advanced protection scheme for medium-voltage distribution networks containing low-voltage microgrids with high penetration of photovoltaic systems

Abstract

This article aimed at the development of an advanced adaptive protection scheme that can provide protection for both medium-voltage distribution networks and their included low-voltage microgrids with high penetration of photovoltaic systems in a thorough manner. On the one hand, the scheme can address those issues related to the protection coordination between medium-voltage and low-voltage protection systems while still be able to prevent the low-voltage microgrids from unwanted tripping for disturbances on adjacent medium-voltage feeders. Moreover, the safe operation of low-voltage microgrids in different operation modes as well as their reliable transition between these modes can be guaranteed. On the other hand, this scheme can enable the connected photovoltaic systems at both medium-voltage and low-voltage networks not only to meet the fault ride through but also fault dynamic voltage support requirement imposed by new grid codes. The developed scheme was validated on a real medium-voltage network consisting of various low-voltage microgrids by simulating in the software environment DIgSILENT/PowerFactory. The transient models of photovoltaic and battery energy storage system were considered in detail with regards to the new grid code requirements in order to achieve a higher degree of realism of the simulated networks.