This study addresses the calculation of current total harmonic distortion (THD) for three-phase (3P) pulse-width modulation (PWM) inverters. First, it demonstrates how an analytical approach to PWM current ripple normalised mean square (NMS) calculation introduced in the late 1980s for a two-level (2L) inverter can be used for current THD evaluation. Second, it is shown how to evaluate current THD for a three-level (3L) 3P inverter using the current ripple NMS concept. Though considered is a 3P cascaded inverter with one H-bridge per phase, the results are applicable to popular 3L neutral point clamped (T-type) and flying capacitor inverters.

中文翻译：

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三相电压源逆变器的分析电流THD评估

本研究解决了三相（3P）脉宽调制（PWM）逆变器的电流总谐波失真（THD）的计算。首先，它演示了如何在1980年代后期引入的用于两电平（2L）逆变器的PWM电流纹波归一化均方（NMS）计算分析方法可用于电流THD评估。其次，显示了如何使用电流纹波NMS概念评估三电平（3L）3P逆变器的电流THD。尽管考虑的是每相一个H桥的3P级联逆变器，但结果适用于流行的3L中性点钳位（T型）和飞跨电容器逆变器。