Impact of Collector Network Aggregation of Solar and Type 4 Wind Farms for Short Circuit Studies

This paper studies how much detail is actually needed when modeling the collector networks of large solar PV and Type 4 wind farms for short-circuit studies. Using a detailed electromagnetic-transient model of a real 150 MW solar farm, the authors compare the complete collector system with simplified models that either replace the collector network with an equivalent representation or neglect its impedance altogether. For the tested three-phase, line-to-line, and single-line-to-ground faults, the collector network has little influence because the inverter-filter and pad-mounted-transformer impedances dominate; a lumped farm model reproduces the detailed model with errors below about 2% in the reported fault cases. A sensitivity study shows that error increases as collector feeders become much longer, but remains small for practical PV and Type 4 wind-farm layouts. The simplification also reduces computational burden dramatically, with a reported five-second EMT simulation dropping from roughly 12 hours for the detailed farm to about 9 minutes for the lumped model, supporting the use of aggregated IBR-farm models for efficient short-circuit analysis.