At the same time, even with the diesel generator connected, the coordination between the protection settings and the fault ride-through capabilities of PE units causes serious concerns. During a fault, all generating units experience Circuit Breaker Closed L WT B critical voltage sags due to the short lengths of lines in an island. A proper fault ride-through curve should be selected to prevent the immediate disconnection of PE units, while the protection settings should ensure that the fault is cleared Circuit Breaker Open PV Load Bus 5 ICB4 Photovoltaic CB4 Wind Turbine Utility Grid Batteries Energy Storage PEs Grounding Transformer Fault Bus 6 ICB7 CB5 CB7 CB9 CB10 CB6 CB8 CB11 ICB6 Fault Current L ICB2 CB1 L PV Bus 3 CB2 CB12 Bus 4 CB13 CB15 CB17 CB18 CB14 CB16 CB19 Utility Grid Bus 1 Grounding Transformer CB20 L L WT Distribution Grid Bus 2 CB3 Microgrid B (a) Current Through CB7, ICB7 (A) 480 460 440 420 X/R Ratio = 1 X/R Ratio > 1 X/R Ratio < 1 400 380 0 0.2 0.4 0.6 0.8 PV Short Circuit Current Power Factor (b) 1 figure 3. (a) A simplified microgrid model and (b) the impact of the wind turbine short circuit current angle to the fault current (ICB7). 24 ieee power & energy magazine may/june 2021