Fault Ride-Through Strategies for Synchronverter-Interfaced Energy Resources Under Asymmetrical Grid Faults

Abstract

Synchronverters are inverters controlled to behave like synchronous generators. However, unbalanced faults or voltage dips may stimulate synchronverters to generate excessive currents and cause instantaneous active and reactive power oscillations at twice the grid's fundamental frequency. Therefore, this paper proposes three fault ride-through (FRT) strategies to remedy these power oscillations and the unlimited current generation during unbalanced faults. The first strategy is based on an instantaneous active and reactive control that significantly reduces power oscillations. The second strategy relies on an average active and reactive control that ensures the delivery of average active and reactive power and maintains sinusoidal phase currents. Finally, the third FRT strategy employs a comprehensive instantaneous active and reactive control to eliminate power oscillations and maintain sinusoidal currents simultaneously. The proposed FRT strategies are equipped with a power management controller that delivers the required active and reactive power during normal operation and limits the inverter's phase currents during faults. Further, the proposed FRT strategies maintain the intrinsic features of synchronverters and ensure seamless activation of the proposed FRT strategies. Comparative results confirm the efficacy of the proposed strategies to reduce power oscillations, limit current generation, maintain synchronverters' intrinsic features, and comply with grid codes.