Active Power Control of Grid-Forming Inverters for Transient Stability Improvement and Overcurrent Limitation

The grid-forming (GFM) inverter has attracted attention in recent years as a key solution to improve the stability of renewable-rich power systems. This study investigated the contributions of grid-following (GFL) and droop-controlled GFM inverters to the transient stability by focusing on their active power reference tracking capabilities. We propose an active power control method using variable gain for a GFM inverter. The proposed method adaptively varies the droop gain according to the measured active power to enhance the transient stability while preventing overcurrent at the GFM inverter. Numerical simulations showed that the proposed method can suppress the active power oscillations and the associated overcurrent that occurs after fault clearance in the conventional droop-controlled GFM inverter. It was also revealed that the transient stability is improved by replacing GFL with the GFM combined with the proposed method, owing to the lower reference tracking ability of GFM than that of GFL.