基于脉宽调制的DFIG并网谐波/间谐波幅频特性分析

双馈感应发电机(DFIG)并网存在谐波/间谐波发射问题。文中采用DFIG理想阻抗模型与脉宽调制(PWM)开关函数，推导了背靠背双PWM变流器系统引起的输出端谐波/间谐波电压解析式。考虑滤波器结构及发电机异步特性的影响，推导了换流器直流电压为输入的DFIG并网谐波/间谐波电流的幅值和频率解析式，揭示了DFIG背靠背换流器调制谐波/间谐波的产生机理。针对实际运行工况，获得了背景谐波条件下DFIG谐波/间谐波的典型发射特性。最后，通过PSCAD仿真及某风电场风机实测数据验证了所推导解析表达式和机理特性分析的准确性。

Amplitude-Frequency Characteristic Analysis of Harmonic/Inter-harmonic of Grid-connected DFIG Based on Pulse Width Modulation

The grid-connected doubly-fed induction generator(DFIG)system is usually accompanied with the harmonic/inter-harmonic emission problem. By using the ideal impedance model of DFIG and the switching function of pulse width modulation(PWM), this paper deduces an analytical expression of harmonic/inter-harmonic voltage caused by back-to-back dual PWM convertor. Taking the filter structure and generator asynchronous characteristic into account, this paper also derives the amplitude and frequency formula for harmonic/inter-harmonic current with the DC voltage as input. Then the mechanism of modulation harmonic/inter-harmonic produced in the back-to-back convertor of DFIG is revealed. For the actual operation scenario of DFIG, the typical emission characteristics of harmonic/inter-harmonic with background harmonics are obtained. The PSCAD simulation and the analysis results based on the measured data of an actual wind farm show the accuracy of derived expressions and mechanism characteristic analysis.