Fault Ride-Through Behaviors Correction-Based Single-Unit Equivalent Method for Large Photovoltaic Power Plants

An improved single-unit equivalent method is proposed for large photovoltaic power plants (PVPPs) in this paper. The simulation of a 50 MW PVPP indicates that the equivalent errors are mainly caused by the inconsistence of fault ride-through (FRT) behaviors of active power between the detailed PVPP model and its traditional single-unit equivalent model. Taking a three-unit PVPP as an example, analytical expressions of FRT behaviors of the detailed PVPP model and its traditional single-unit equivalent model are derived, and the error sources are identified: the deviation of active power during fault, the difference of initial active power after fault clearance, and the mismatch of post-fault active power ramp rates. The derived expressions for FRT behaviors are then extended to large PVPPs, and are used to correct reference settings of the equivalent model's controller. Simulation results verify that the proposed method has good performance for different irradiance scenarios, voltage dips and grid strengthens.