Fault Contribution of Grid-Following and Grid-Forming Inverters Considering Generic Inverter Controls and Ride-through Requirements

Gradual transformation of the synchronous generator (SG)-dominated power systems to inverter-based resource (IBR)-dominated power systems is bringing new challenges regarding power system protection. Traditional protection algorithms were originally developed for SG-dominated power systems and become less reliable in an IBR-dominated system. New protection schemes, compatible with IBR-dominated power systems, have been an ongoing topic of research. However, such research frequently omits fault-related controls or requirements that influence IBR's fault behavior significantly. This paper provides a study of the fault behavior of grid-following (GFL) and grid-forming (GFM) inverters considering fault-related controls and using electromagnetic transient (EMT) program. For both inverter models, EMT-based generic inverter models are used in this paper. Ride-through controls from IEEE-1547-2018 standards are included as necessary. In addition, the major functions of the generic models that effect fault behavior are explained. Then, the fault current contributions of the GFL and GFM inverters were simulated considering different controls and grid parameters using both a single-inverter-to-infinite-bus system and a modified IEEE 34-node system. The simulation results indicate that the fault current contribution of an inverter or an IBR-dominated system depends on the inverter's operating mode, whether the grid support function and momentary cessation is enabled or not, and fault location.