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.

中文翻译：

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大型光伏电站基于故障穿越行为校正的单单元等效方法

提出了一种改进的大型光伏电站单机等效方法。50 MW PVPP的仿真表明，等效误差主要是由详细的PVPP模型与其传统的单机等效模型之间的有功功率故障穿越（FRT）行为不一致引起的。以三单元PVPP为例，推导了详细的PVPP模型及其传统的单单元等效模型的FRT行为的解析表达式，并确定了误差来源：故障时有功功率的偏差，初始值的差异。故障排除后的有功功率，以及故障后有功功率斜率不匹配。然后，将FRT行为的派生表达式扩展到大型PVPP，并用于更正等效模型控制器的参考设置。仿真结果验证了该方法在不同辐照度，电压骤降和电网加强情况下具有良好的性能。