A Smooth Mode Switching Strategy Between Grid-forming and Grid-following Controls

Conventional switching strategies between grid-following (GFL) and grid-forming (GFM) modes often face challenges such as transient current variations and power fluctuations. This paper proposes a smooth switching strategy based on a backup operation for a single converter. The GFM control loop maintains integrator assigned during GFL mode. Similarly, the GFL control loop preserves integrator assigned during GFM mode. And the mode switching is allowed at any time when the instruction arrive. The hardware-in-loop simulation results indicate that the maximum power fluctuation during mode switching is only 2% under Short-Circuit Ratio (SCR) of 10, and remains below 2% even under power step changes. Under weak grid conditions (SCR = 2), the power fluctuation remains below 2%, demonstrating the effectiveness of the proposed backup-based smooth switching strategy.