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多导体传输线是导致PWM变换器产生电压反射和加剧电磁干扰的关键因素，构建数值计算过程简化并准确表征传输特性的传输线等效模型是实现电压反射衰减以及电磁干扰预测的要点。基于Kirchhoff Law的集总参数模型高频时不能准确描述其自身固有属性，须兼顾参数的频率变化及其趋肤效应等引起的分布特性差异，并通过部分元等效电路法对多导体传输线TEM模式下的频变分布参数等效模型建模。为快速确定等效模型宽频寄生参数，通过Neumann公式与镜像构型理论，并计及导致共模传导干扰加重的接地回路对模型参数的影响，推导出传输线的部分电容参数计算公式。考虑到趋肤效应和邻近效应对导体电流分布密度的影响，利用基于RL梯形等效电路的矢量拟合算法对多导体传输线频域响应有理函数施加迭代计算，消除了最小二乘拟合残差及其收敛性问题，进而完成了估算模型准确逼近与稳定收敛，对PWM变换器系统的电磁兼容研究具有理论指导意义。最终，仿真与测试数据均验证了所提出的多导体传输线分布参数宽频建模机理的有效性和准确性。“,”The multiconductor transmission line is the key factor to generate voltage reflection and to intensify electromagnetic interference for PWM converters. In order to study voltage reflection suppression rules and EMI estimation, to set up an equivalent MTL model with easy numerical computation is the main point to precisely describe transmission characteristics. The lumped parameter model based on Kirchhoff Law doesn’t accurately illustrate MTL’s high-frequency features with the impact of frequency parameter variation and skin effect, the frequency-dependent distributed parameter model by the partial element equivalent circuit method under the TEM propagation mode is employed. For obtaining precise distributed parameters in the high- frequency equivalent model, the calculation formula of parasitic partial capacitors by the Neumann Rule and the mirror image method was derived, in which grounding circuit’s impact on common mode interference was also considered. In view of the influence of skin and proximity effects on MTL’s current distribution density, aRL ladder equivalent model based modified vector fitting with iteration computation of rational function approximation via poles and residues was adopted to eliminate residual errors of least-squares and to realize stable convergence. Based on simulation and experimental results, the proposed equivalent MTL model reflects its distributive features, and provides theoretical guidance for EMC mechanism study of PWM converter systems with effectiveness and accuracy.