It's necessary to establish the three-phase model of the three-winding transformer, along with the wide use of the three-winding transformer and the increasing number of asymmetric load. By analyzing the three-winding transformer's electrical relationship among the three windings, a systematic analysis method for multi-winding transformer is presented based on the magnetomotive force balance equations, output-port equations and voltage transfer equations, and the three-phase model of three-winding transformer is deduced. The singular problem of the three-phase admittance matrix of the three-winding transformer is solved by adding additional conditions. The model can be easily applied to the flow calculation, Based on the three-winding transformer model, the penetration of negative sequence and harmonic produced by electrified railway in the power system is analyzed based on the measured data. The results show that the three-winding transformer model combined with other models of power system components can be easily used in electrified railway negative sequence and harmonic penetration calculation, providing basis for the negative sequence and harmonic suppression.%三绕组变压器的广泛应用和不对称负荷的大量增多,需要建立三绕组变压器的三相模型.通过分析三绕组变压器的电气量关系,给出了以磁势平衡方程、端口输出方程和电压传递方程为基础的多绕组变压器系统化分析方法,推导出三绕组变压器的三相模型.通过附加条件,解决了三绕组变压器三相导纳矩阵奇异的问题,可以方便地应用于潮流计算.以三绕组变压器模型为基础,基于实测数据分析了电气化铁路产生的负序、谐波在电网中的渗透情况.分析结果表明,三绕组变压器模型与其他电力系统元件模型结合能方便地应用于电铁负序、谐波渗透计算,为电力系统负序及谐波抑制提供依据.
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