大型光伏电站汇集系统的故障特性及其线路保护

集中式与分布式光伏系统在拓扑和控制上的显著区别,造成两者故障特性的不同,导致现有含分布式光伏的配电网故障分析方法和保护原理在集中式光伏电站汇集系统中无法适用。为此,针对广泛应用于集中式光伏逆变器中的正负序双同步旋转坐标系电流控制器,计及直流侧光伏电池板电源特性影响,推导出不同控制目标下故障电流统一表达式。在此基础上,结合现场短路试验数据,考察850 MW大型光伏电站内35 k V汇集线路的电流保护性能,证明架空线下游电流保护存在不能正确动作现象,同时提出距离保护新配置方案。在PSCAD/EMTDC中搭建光伏电磁暂态详细模型并利用现场实测数据验证了模型的正确性,大量仿真实例证明了新保护配置的有效性。研究结果为大型光伏电站汇集系统保护配置提供参考。

Fault Characteristics and Line Protection within the Collection System of a Large-Scale Photovoltaic Power Plant

Centralized photovoltaic(PV)systems have different fault behaviors from distributed PV systems due to the differences in the structure and controls.This makes fault analysis and protection methods in distribution networks with distributed PV not suitable for centralized PV plants.Therefore,the widely-used current controllers under the double synchronous rotating frame (DSRF) are considered,as well as the characteristics of PV arrays,and then a consolidated expression for the fault current is calculated under different controls.Based on the analyzed fault current characteristics and the on-site short test data,the performance of current protection relays on 35 kV collection lines is evaluated within an 850 MW large-scale PV plant.The evaluation revealed that the overcurrent relays at the downstream side on overhead lines might malfunction and thus a new relay scheme is proposed using distance elements.In the PSCAD/EMTDC,an electromagnetic PV transient model in detail is built and verified using the on-site test data.Finally,considerable simulation results verified the proposed relay scheme.The research in this paper can help inprove the protection performance within PV plants.