Synchronverters with Fault Ride-Through Capabilities for Reliable Microgrid Protection during Balanced and Unbalanced Faults

Synchronverters are inverters that provide damping and inertia, similar to synchronous generators. Like traditional inverters, synchronverters are adaptable to the microgrid's operation modes. However, synchronverters may generate oscillatory active and reactive powers during faults and produce phase currents with excessive magnitudes. Therefore, this paper develops two fault ride-through (FRT) strategies for synchronverters: average power control and enhanced power control. Both strategies aim to reduce power oscillations, limit current generation, and ensure compliance with grid codes during faults, regardless of the fault conditions and the grid's operation mode. Additionally, synchronverters with the proposed FRT strategies are incorporated into an optimal protection coordination (OPC) program for microgrid protection. The OPC program obtains the settings of time-current-voltage overcurrent relays (TIV-OCRs) and demonstrates the effect of the proposed FRT strategies on microgrid protection. The obtained settings are suitable for both the microgrid's grid-connected and islanded modes during balanced and unbalanced faults. Evaluation results demonstrate the capability of the proposed strategies to reduce power oscillations, limit current generation, and comply with grid codes. Furthermore, the OPC results reveal the most appropriate strategy to minimize TIV-OCRs' operating times in a coordinated manner, regardless of the fault type and microgrid operating mode.