含光伏电站的电网自适应接地距离保护研究

Research on Adaptive Grounding Distance Protection in Grid with Photovoltaic Power Plant

光伏电站并网使110 k V系统拓扑结构发生变化,同时光伏电站等效阻抗随运行方式的不同而改变,线路原有的距离保护受到影响。根据光伏电站的运行特性,推导了距离保护测量阻抗与光伏电站等效阻抗的关系,并对保护测量阻抗受到影响的机理进行了分析。根据不同运行方式下计算得到的光伏电站等效阻抗,提出了基于修正测量阻抗的自适应接地距离保护方案,使保护能够适应光伏电站运行方式的多样性,并且无需改变保护的整定值。在PSCAD/EMTDC中搭建了某地区光伏电站接入110 k V电网的实际拓扑结构并进行仿真分析,分析结果验证了所提方法的有效性和优越性。

With the development of smart grid, photovoltaic power is gaining wide applications. Integration of a photovoltaic power plant （PV plant） into the distribution network will change the topological structure of the 110 kV system. Meanwhile, the equivalent impedance of PV plant varies with the changes of operation modes, which may affect the original distance protection scheme. The relationship between the measured impedance of distance protection and the equivalent impedance of PV plant is derived based on the operation characteristics of PV plant. The impact mechanism of PV plant on the measured impedance of distance protection is reviewed. A method of adaptive grounding distance protection based on the measured impedance correction is put forward according to the real-time equivalent impedances of PV plant which is calculated in different operation modes. As a result, the proposed protection is supposed to be suitable for changes of operation condition of PV plant. Furthermore, the protection setting values are universally suitable in different operation modes. A typical distribution network with PV plant was simulated and analyzed in PSCAD/EMTDC, and the results have demonstrated the effectiveness and superiority of the proposed protection method.