A fast IVS controller for grid-forming converters: Reducing the current-limiting period to enhance transient stability

This paper proposes a fast internal voltage source (IVS) controller for grid-forming (GFM) voltage source converter (VSC) to enhance the transient stability. While conventional methods frequently suffer from degraded synchronization performance due to current-limiting mode, the proposed approach significantly reduces the post-fault transient period during which the current limiter remains active. The proposed control enhances the transient stability of the GFM-VSC and accelerates PCC voltage recovery across a wide range of grid strength conditions and various fault scenarios through a feedforward control scheme. These improvements are due to a substantial reduction in the current-limiting period. In particular, applying the proposed controller to the GFM-VSC can notably improve the PCC voltage recovery speed after a phase-jump fault in a weak grid. The stability enhancement and dynamic behavior of the proposed control are analyzed using an energy function-based large-signal model and graphical analysis. Finally, the effectiveness of the proposed control is demonstrated using down-scaled experiments. • A fast IVS controller is proposed to enhance the transient stability of GFM-VSCs. • The method minimizes the current-limiting duration, accelerating PCC voltage recovery. • Large-signal stability is analyzed using an energy function model. • Comparative analysis with existing methods highlights improved robustness. • Effectiveness is validated through down-scaled experiments under weak-grid conditions.