A New LVRT Strategy with Reactive Power Support from Inverter-Based Resources During Unbalanced Faults on a Distribution System

With the increased integration of Distributed Energy Resources (DER), the sudden tripping of DER during a fault adversely affects the grid stability and operation. Hence, the DER is expected to exhibit Low Voltage Ride-Through (LVRT) capabilities with reactive power support during a fault, as per IEEE 1547. Determining the amount of reactive power during unsymmetrical faults in the distribution system is challenging as it requires unbalanced reactive power support depending on the type of fault. Proper reactive power support can also help minimize the voltage rise in the healthy phases. This paper proposes a novel Per-Phase Reactive Power Control (PRPC) strategy that enables DER to inject reactive power in faulted phases and absorb reactive power in healthy phases during an unbalanced fault. This strategy helps boost voltages on faulted phases while reducing the voltage rise on the healthy phases. Test results on a sample distribution system are given to illustrate the advantages of this proposed scheme.