Comparison of full and reduced scale solar PV plant models in multi-machine power systems

Accurate modeling of solar photovoltaic (PV) plant is of utmost importance to study system behavior during transient events. However, model accuracy and computational efficiency is inversely related, thus a simplified equivalent model for solar PV systems using collector system equivalencing approach is recommended for system modeling and grid interconnection studies by Western Electricity Coordinating Council (WECC). This paper compares steady state and dynamic behavior of a large 117-inverter based, 147-MW solar PV plant connected to IEEE 39-bus system, both at inverter terminals and at Point of Interconnection (POI) modeled with and without collector system equivalencing. These comparisons are performed under different scenarios including: single-generator model, two-generator model, five-generator model and a full scale model of PV plant. Our findings show that both the steady state and dynamic response of all models under all scenarios shows a good match.