Several small-signal impedance models have been reported for type-III wind turbines for use in impedance-based system stability studies. Common to these models is the assumption that the dc bus between the rotor- and stator-side converters is an ideal voltage source. Under this assumption, there is no dynamic coupling between the two converters and the turbine can be represented by the impedance of the stator-side converter in parallel with the impedance of the induction generator with the rotor-side converter behind it. The assumption is well justified above the second harmonic frequency but introduces considerable error at lower frequencies, especially within 20–30 Hz of the fundamental frequency in which dc bus voltage control is active and dc bus capacitor impedance is high. This paper presents the development and application of full-order sequence impedance models for type-III turbines that include dc bus dynamics. The new models also consider the coupled current responses created by each of the converters as well as their coupling across the dc bus. Inclusion of these additional dynamics leads to more accurate prediction of turbine impedance responses and turbine-grid system stability. A comparison with existing models is presented to show the utility and limitation of each model. A practical resonance problem is also presented to demonstrate the application.

中文翻译：

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包括直流母线动力学在内的III型涡轮阻抗模型的开发和应用

对于基于阻抗的系统稳定性研究中使用的III型风力涡轮机，已经报道了几种小信号阻抗模型。这些模型的共同点是假设转子侧和定子侧转换器之间的直流总线是理想的电压源。在此假设下，两个变流器之间没有动态耦合，并且涡轮机可以由定子侧变流器的阻抗与感应式发电机的阻抗（其后面是转子侧变流器）并联来表示。该假设在二次谐波频率以上是合理的，但在较低频率下会引入相当大的误差，尤其是在基本频率的20–30 Hz以内，其中直流母线电压控制有效且直流母线电容器阻抗较高。本文介绍了具有直流母线动力学特性的III型涡轮机全序序列阻抗模型的开发和应用。新模型还考虑了每个转换器产生的耦合电流响应以及它们在直流总线上的耦合。包含这些额外的动态特性可以更准确地预测涡轮机的阻抗响应和涡轮机-电网系统的稳定性。与现有模型进行了比较，以显示每个模型的实用性和局限性。还提出了一个实际的共振问题来演示该应用。包含这些额外的动态特性可以更准确地预测涡轮机的阻抗响应和涡轮机-电网系统的稳定性。与现有模型进行了比较，以显示每个模型的实用性和局限性。还提出了一个实际的共振问题来演示该应用。包含这些额外的动态特性可以更准确地预测涡轮机的阻抗响应和涡轮机-电网系统的稳定性。与现有模型进行了比较，以显示每个模型的实用性和局限性。还提出了一个实际的共振问题来演示该应用。