计及发电单元故障特性差异的光伏电站短路电流计算模型

Steady short-circuit calculation model for a photovoltaic station considering different generation units'fault characteristics

光伏电站占比持续增加使电网故障特性发生根本性改变,电网保护整定计算中电源仍采用电压源串联电抗的传统短路计算模型已不再适用,如何建立可刻画实际光伏电站故障特征的短路计算模型具有重要意义。为此,通过揭示场站内光伏发电单元故障行为特性差异规律,探明了主导发电单元短路电流贡献迥异的主导因素,提出了基于暂态运行控制模式差异性的发电单元分群方法,进一步推导给出了适用于对称与不对称故障的光伏电站统一短路电流计算模型。最终,结合实际光伏电站运行数据,对比分析短路电流模型理论计算结果与详细电磁暂态仿真试验结果,验证了所推导模型的正确性。研究结果能为含光伏电站电网保护整定计算提供模型支撑。

With the increasing penetration of PV stations,the connected grid’s fault characteristics are fundamentally changed.As a result,the equivalent model(both voltage source and reactance that are connected in series)of traditional generators cannot be applied for calculating the protection settings of a power grid with large-scale PV stations.It is of great significance to build the fault current calculation model of PV stations based on their fault characteristics.In this paper,the difference algorithms of different generation units’fault characteristics are revealed in the PV stations.The main factors influencing the fault current contribution difference of the generation units are explored.A clustering method is proposed on the basis of the difference algorithms of the generation units’transient control modes.Further,a unified model for calculating the current contribution from a PV station is deduced under symmetrical and asymmetrical faults.Finally,using practical PV stations’operating data,both theoretical analysis calculation results and PSCAD/EMTDC electromagnetic transient simulation results are compared and analyzed.These results verify the correctness of the proposed fault current calculation model.The research will provide support for studying the protection setting calculation of power grid with PV station.