Advanced Current-Droop Control for Storage Converters for Fault Ride-Through Enhancement

A voltage source converter is necessary for microgrid to maintain the appropriate voltage and frequency. A low-voltage ride-through strategy based on improved current droop is proposed in this paper, and this strategy can enable the converter to ride-through voltage sag faults at the point of common coupling (PCC). Current droop is implemented by active current-frequency control and reactive current-voltage control without the need for power calculation and without an overcurrent beyond the active current. The reactive power support function is provided by regulating the reactive current. To resolve the problems of power-angle instability and slow response of current recovery after a fault, a power-angle-limiting controller is proposed. The lagging-loop controller is employed to constrain the power angle within a certain range around the prefault steady-state value so that the converter can ride through the transient state smoothly and recover to the prefault state rapidly. The proposed strategy is verified by simulations and experiments.