考虑撬棒保护的DFIG等效序阻抗研究

Study on Equivalent Sequence Impedances of DFIG with Crowbar Protection

双馈感应风力发电机(DFIG)等效序阻抗特征对基于故障分量的继电保护原理影响重大。针对目前DFIG等效序阻抗理论分析及暂态变化过程研究的欠缺,首先给出了DFIG等效序阻抗的定义,考虑故障后投入撬棒保护这一情况,基于DFIG定子故障序电流推导了等效序阻抗的解析表达式。然后详细研究了DFIG等效正、负序阻抗的特征及其影响因素,指出等效正序阻抗有明显的暂态变化过程,其幅值较大且有波动,稳态相角在-90°^-180°之间;等效负序阻抗暂态过程不明显,其幅值较小,相角在0°~90°之间。最后通过仿真实验验证了理论分析的正确性。

The characteristics of doubly fed induction generator（ DFIG） equivalent sequence impedances（ ESIs）have a huge impact on fault component based relay protections. To provide theoretical basis for DFIG ESIs and related transient studies,the definition of DFIG ESIs is first given. Analytical equations of DFIG ESIs under activated crowbar protection are derived based on stator fault sequence currents. Characteristics and significant factors of DFIG ESIs are studied in detail. It is observed that equivalent positive sequence impedance has an evident transient change process while equivalent negative sequence impedance doesn’t. The amplitude of the former is larger and fluctuant while the latter is smaller,and the steady phase angle of the former is between-90° and-180° while the latter is between 0°and 90°. Finally,the theoretical analysis are verified by simulation experiments.