An Enhanced Voltage Support Control Strategy with Improved Active Power Deliverability of a DG During Unbalanced Microgrid Faults

Numerous control methods have been developed to support voltage during unbalanced microgrid faults. However, most of these methods focus on reactive power injection, which often results in active power curtailment, whether the microgrid is grid-connected or in islanding mode. This curtailment can cause an imbalance between power supply and load, leading to significant stability issues during islanding operations. To address this, we have developed a voltage support control strategy aimed at enhancing both voltage support and active power deliverability. The proposed control has greater flexibility of controlling three-phase-wise and single-phase-wise active and reactive power control with three current regulators only. Furthermore, it possesses current limiting capability during faults in compliance with voltage limits. The performance of the proposed control strategy was validated using a three-phase four-leg converter connected to a Thévenin equivalent microgrid with a Short Circuit ratio(SCR) of 3. Compared to conventional voltage support control, the results demonstrate the proposed method's superiority.