双馈异步发电机电刷滑环电阻变化理论与仿真研究

电刷与滑环间良好的电接触是双馈异步发电机稳定运行的前提．电刷滑环电阻是衡量电接触系统可靠性的重要指标。以1．5MW实际双馈风力发电机电刷滑环系统为研究对象．在计及周期性变化的滑环电阻的基础上，对运行过程中电刷滑环动态电阻进行定量分析和计算。利用PSCAD／EMTDC仿真软件．建立正常运行和故障运行下电刷滑环动态电阻数值模型和电路模型．并对电刷电流的间谐波进行理论分析和计算．通过对故障前后的电刷电流傅里叶变换值进行列比分析．得出结论：故障后电刷电流间谐波分量下降率远小于基波分量下降率．且故障下间谐波畸变率远大于正常时间谐波畸变率。该结论可作为双馈异步发电机电刷滑环运行稳定性的削据．对其状态监测和故障诊断具有实际指导意义。

Theoretical and Simulation Study on Resistance Variations of Brush and Slip Ring of a Double-Fed Induction Generator

Good electrical contact between the brush and slip ring is the precondition for stable operation of a double-fed iuduction generator （DFIG）. The brush and slip ring resistance is therefore an important indicator for evaluating the reliability of the electrical contact system. By taking a DFIG of 1.5 MW for case study, a quantitative analysis and calculation of the working resistance of the brush and slip ring is conducted with consideration of the cyclical ehange of the slip ring resistance. By using PSCAD/EMTDC simulation software, the numerical model and circuit model of the brush and slip ring dynamic resistance are established respectively under normal and fault working couditiuns, and a theoretical analysis of brush current interharmonic is carried out. Through comparing and analyzing the brush current beh~re and after the fault condition based on the FFF transformation, it is concluded that the decreasing rate of the brush current interharmonic component is far smaller than that of the fundamental eomponent before and after fault condition, and the THD of fault condition is much larger than that of the normal condition. This conclusion can provide a guidance for condition monitoring and fauh diagnosis of the brush and slip ring system and acts as an available criterion for the operation stability of the system.