Fault-Ride-Through Performance of Grid-forming Battery Energy Storage Systems: Observations and Analysis of Synchronisation

The study shows that fault-ride-through (FRT) control strategies of the tested GFM-BESSs are effective in preventing LoS occurrence. This highlights a potential improved synchronisation of GFM-BESSs over synchronous generators (SGs) during faults, especially deep and prolonged faults. However, the possibility of LoS occurrence in GFM-BESS still exists. LoS occurrences of the tested GFM-BESSs were identified in shallow and medium fault cases. They could be attributed to the inactive state of the FRT strategies or suboptimal transitions of the

FRT strategies, causing synchronising issues. Overall, the results highlight the need for careful tuning of GFM-BESS control loops, particularly under shallow and medium fault scenarios.

In addition, network conditions can exacerbate LoS of the tested GFM-BESSs. Line disconnections in ring and lightly meshed networks to isolate faults may cause large angle changes during and after disturbances, creating synchronisation challenges for the GFMBESSs. Moreover, network protection schemes of tripping generation and loads in the local area following a fault may introduce additional angle transients, potentially imposing further challenges for control mode transitions within the GFM-BESSs. Considering such scenarios in tuning and performance validation processes is essential for developing robustly operating

GFM-BESSs.