To maintain stability of the power system, large grid-connected wind farms are required to have capability of low voltage ride through (LVRT). These years, the research on LVRT of doubly-fed induction generators (DFIG) has become a hot issue The paper introduces the device of braking resistor and its effect contributed to the transient characteristics of DFIG. Contributions of the braking resistor to capability of LVRT of DFIG with a voltage dip on the grid side are analyzed in detail. The enhancement of capability of LVRT based on DFIG is analyzed with the braking resistor placed respectively at the low side of the transformer of wind farm and at the terminal of DFIG. The result shows that the braking resistor of the proper size can substantially improve the capability of LVRT in the grid -connected wind farm, and the enhancement is better with the braking resistor placed at the low side of the transformer of the wind farm rather than the terminal of doubly-fed induction generators.%为保持系统稳定,必须要求大规模并网风电场具有低电压穿越能力.双馈感应发电机(DFIG)低电压穿越功能已成为研究热点.介绍了串联制动电阻装置对双馈感应发电机暂稳特性贡献的机理.详细分析了在电网故障情况下,制动电阻装置对双馈风电场低电压穿越能力的贡献,分别就制动电阻接在风电场升压变处与接在双馈感应发电机机端对低电压穿越的改善效果进行分析.试验结果表明:故障期间投入适当大小制动电阻,能较好地提高双馈风电场低电压穿越功能;将制动电阻放置在风电场升压变处贡献效果优于将制动电阻装置放置在双馈感应发电机机端处.
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