A Protection-Interoperable Fault Ride-Through Control for Grid-Forming Inverters

Differing from synchronous generators (SGs), grid-forming inverter-based resources (GFM-IBRs) exhibit rapid variations in their output impedances during transmission line faults due to the overcurrent limitation. As a result, the source dynamics during the fault period deviate significantly from those under pre-fault conditions. This fundamental difference alters the fault responses of incremental quantities, thereby jeopardizing the reliability of the supervising elements in protective relays that are based on these quantities. To address this challenge, a protection-interoperable fault ride-through (FRT) method for GFM-IBRs is proposed. This method dynamically adjusts power control of GFM-IBRs in response to the changes in output impedance, effectively mitigating variations in source dynamics and thereby preserving the reliability of incremental quantity-based supervising elements. This method also ensures effective overcurrent limitation and transient stability of GFM-IBRs. Controller hardware-in-the-loop (CHIL) and experimental tests validate the effectiveness of the proposed method.