Fault current limitation approaches for grid-following controlled DERs in microgrid environments

Abstract

The adoption of distributed energy resources in the electricity system is rapidly spreading worldwide, where power converters are the preferred method for better integration. However, the fault behaviour of these converter-integrated distributed energy resources is still uncertain and varies according to the considered model representation. Furthermore, the fault response of the converter-integrated resources is influenced by the thought control strategy, which adds complexity to the analysis. Aimed at a better understanding of the converter-integrated resources fault behaviour, this document presents an analysis of the fault response considering active-reactive power control as the main control strategy of the converter-integrated resources; different current limitation strategies are tested and linked to physical constraints of the power electronic converters, also aligning with the reactive power support during fault. The fault behaviour is studied in a microgrid operating in grid-islanded and grid-connected modes, where the obtained results validate the adequacy of the fault current limitation strategies by compelling the converter-integrated resource to have a more realistic behaviour. Additionally, this study investigates the impact of prioritising direct or quadrature current injection (id or iq) during fault. Lastly, this study demonstrates that the converter-integrated resource can adequately support the microgrid voltage while complying with the reactive power generation requirements, which are usual in national grid codes and not often considered in the revised fault current limiting strategies. Overall, this study provides several insights into the performance of converter-integrated resources under fault conditions while emphasising the importance of fault-current limitation strategies to assure a reliable and realistic microgrid operation. These findings affect modern power systems designs, analysis, and implementation of power control strategies.