Modeling of Hybrid Farm in Grid Following and Grid Forming Modes for Short Circuit Studies

Hybrid renewable farms with a mix of solar and wind resources, along with a battery energy storage system (BESS) are growing. Such farms include numerous inverters, pad-mounted transformers, collector feeders, and dc-side components depending on the type of generation. Additionally, inverters in such farms typically employ different control strategies, such as 'grid following' (GFL) and 'grid forming' (GFM), based on the resource type or system requirements, where an inverter exhibits similar steady-state response but different fault behavior. This paper lays out a physics-based hypothesis to advocate the use of an aggregated model, while avoiding detailed modeling of all components of a hybrid farm. The hypothesis is substantiated by simulations of a hybrid farm using Electro-magnetic Transient (EMT) simulation, documenting how hybrid farms should be aggregated for short circuit studies with minimal errors.