Voltage Control Grid-Forming For Enhanced Large Disturbance Stability Under Unbalanced Conditions

As converter-based generation becomes increasingly dominant, Grid-Forming (GFM) control plays a key role in regulating voltage and frequency. While various strategies have been proposed to improve GFM performance under large disturbances, most of them focus on balanced conditions. This work presents a direct Voltage Control GFM (VCGFM) that enhances the large disturbance stability under unbalanced scenarios. Building on a virtual power-based method previously validated in balanced cases, the VCGFM is extended to integrate a negative sequence control. A current limitation scheme is introduced to limit both positive and negative sequence currents. The proposed control is validated through numerical simulations and experimental tests under diverse balanced and unbalanced grid disturbances. The method aims to preserve the voltage-source behavior of the VCGFM while maintaining synchronization and limiting currents during severe asymmetrical faults.