Performance of Grid-Following and Grid-Forming Inverters Under Unintentional Islanding Events: A Comparative Study

The increasing integration of inverter-based resources in smart grid systems has deepened the necessity to understand the difference between grid-following and grid-forming inverters’ operational performance, particularly under abnormal conditions such as unintentional islanding events. This work provides a comparative assessment, showing that while grid-following inverters perform well under strong grids, their stability degrades under weak grids due to their dependence on the grid reference voltage. On the other hand, grid-forming inverters improve the system stability under weak grids, as they operate as an independent voltage source. However, the widespread misconception in academia and industry that grid-forming inverters are always good and grid-following inverters are generally bad is challenged by this work’s results. Despite the stability advantages of grid-forming inverters, they significantly increase the size of non-detected zones and extend the detection time of unintentional islanding events, with various cases failing to meet standards, while grid-following inverters offer quicker and more expectable responses. A Random Forest-based islanding detection scheme is proposed to address the protection difficulties allied with both inverter types. The findings prove that this model can reduce the size of the non-detected zone and the detection time, emphasizing the necessity of intelligent protection schemes in future microgrid applications and the significance of performance-based inverter selection.