考虑双馈异步风机特性的自适应接地距离保护

研究风电场故障特性对继电保护的影响。针对双馈异步风机投入撬棒电阻后正序阻抗和负序阻抗不相等的特征,分析了传统接地距离保护I、II、III段在保护安装处所测量到的阻抗与实际阻抗的异同。若利用传统整定原则来整定接地距离保护II段,保护可能拒动。根据接地故障时的测量阻抗,提出了考虑双馈异步风机特性的自适应接地距离保护II段的整定方法。该方法在线计算自适应分支系数,使保护安装处的测量阻抗更为准确地反映保护安装处到故障点的距离。利用DIg SILENT仿真软件搭建含风机的线路模型进行仿真分析,验证了自适应接地距离保护的灵敏性,同时该保护的可靠性得到有效提高,且不失选择性。

Adaptive Ground Distance Protection Considering Doubly-Fed Induction Generator Characteristics

According to the characteristic of the doubly-fed induction generator (DFIG) that the positive sequence impedance is unequal to the negative sequence impedance after the crowbar resistance being activated, the impact of the wind farms′fault characteristic on the relay protection was analyzed in this paper.The difference between the measured impedance and the actual impedance of the line-to-ground protection for zones 1, 2 and 3 are discussed.The zone 2 of the ground distance protection with the traditional setting method would refuse to trip when a line-to-ground fault occurs.Based on the measured impedance when a line-to-ground fault occurs, an adaptive ground distance protection scheme considering the characteristics of the doubly-fed induction generator is proposed.The proposed scheme calculates the adaptive branch coefficient on line and makes the measured impedance reflect the distance from the relay location to the fault point more accurately.Finally, using DIgSILENT, a simulation based on the grid model with wind farms was carried out to verify the conclusion that the adaptive ground distance protection method is more reliable and sensitive while the selectivity is also guaranteed.