An Advanced Control Strategy for Enhancing Voltage Support With Minimum Active Power Curtailment During Asymmetrical Faults

During severe voltage events in power systems (sag, swell, and their co-occurrence), Distributed Generators (DGs) must remain connected for a specific duration due to stringent grid code requirements. Researchers have developed various control schemes for reactive power injection and consumption to support the voltage during this period. However, significant challenges remain, particularly during asymmetrical short-circuit faults. Over-voltage in the healthy phases of a three-phase system complicates reactive power injection. Additionally, active power curtailment is often necessary during reactive power adjustments, which needs to be minimized without compromising voltage support. This paper proposes an advanced voltage support control strategy to address the over-voltage issue during asymmetrical faults and enhance voltage support with minimum active power curtailment in compliance with voltage limits and safe current operating limits. The proposed voltage support scheme adapted phase-wise reactive power injection to address the over-voltage issue, which successfully regulates positive sequence voltage and reduces negative and zero sequence voltages. Based on the voltage event, the active power curtailment is minimized by adjusting active power delivery between healthy and faulty phases after reactive current reference generation. The proposed scheme is validated on a laboratory prototype of a grid-connected DG using a three-phase, four-leg converter under various voltage event severities and DG power generation scenarios.