Large scale integration of doubly-fed induction generators (DFIG) has important influence upon stability of transient power angle of traditional synchronous generators in the power grid.In this paper, DFIG is made approximately equivalent to a constant power source.Based on the equal-area criterion, it analyzes changes of transient power angle of the synchronous generator replaced by the doubly-fed induction generator with equal volume in different fault periods, and takes into account influence of different three-phase grounding fault transition resistances upon power characteristics of the synchronous generator.On that basis, it further analyzes the mechanism of the impact upon stability of the system's transient stability during grid-connected operation of the wind farm.Theoretical analysis shows that the system's transient power angle stability is enhanced through integration of the doubly-fed induction generator when transition resistance remains low, and may possibly be reduced while the resistance is high, thus producing negative influence upon grind connection of wind turbines.The correctness of the proposed view is verified through PSCAD / EMTDC simulation.%大规模双馈风电集中接入对电网中传统同步机组暂态功角稳定有重要影响.将双馈风电机组近似等效为恒功率源,基于等面积定则分析了不同故障时段双馈风机等容量替代同步机组时同步机组暂态功角的变化,考虑了不同三相接地故障过渡电阻对同步机组功率特性的影响,据此分析了风电场并网运行时对系统暂态稳定影响的机理.理论分析表明,当过渡电阻值较小时,双馈风机接入增强了系统暂态功角稳定性,当过渡电阻值较大时,可能降低了系统暂态功角稳定性,对风机并网产生不利影响.通过PSCAD/EMTDC仿真验证了所提观点的正确性.
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