In recent years, the doubly fed induction generator (DFIG)-based wind power generation and high-voltage direct-current (HVDC) transmission are widely utilized in practice. The stability issues of sending AC grid, which is composed of line-commutated converter (LCC)-based HVDC and DFIG system, is worthy of attention. Commutation is an important factor in the impedance model of LCC-HVDC rectifier, due to the nonnegligible leakage inductance of transformer. However, it was overlooked in previous studies because there are many difficulties in modeling commutation overlap characteristic. In this paper, the spectral models of voltage and current mapping functions are proposed by 3-D Fourier series method, in which the commutation overlap angle is considered. Then, based on the concept of harmonic linearization, an analytical model that describes the commutation process is established and validated by simulations. The mechanism that the commutation overlap characteristic affects the impedance model of LCC-HVDC is investigated, and the simplified modeling method in different frequency bands is studied. The stability of sending AC grid is analyzed applying the Generalized Nyquist Criterion (GNC). The results of stability analysis show that the effect of commutation overlap cannot be ignored. The simulation results confirm the correctness of the obtained conclusion.

中文翻译：

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LCC-HVDC送交流电网换流重叠特性建模及稳定性分析


近年来，基于双馈感应发电机（DFIG）的风力发电和高压直流（HVDC）输电在实践中得到广泛应用。由基于线换流换流器（LCC）的高压直流输电和双馈风机系统组成的交流电网的稳定性问题值得关注。由于变压器的漏感不可忽略，换流是 LCC-HVDC 整流器阻抗模型中的一个重要因素。然而，由于换相重叠特性建模存在很多困难，因此在以前的研究中它被忽视了。本文采用三维傅里叶级数法提出了电压和电流映射函数的谱模型，其中考虑了换相重叠角。然后，基于谐波线性化的概念，建立了描述换相过程的分析模型并通过仿真进行验证。研究换相重叠特性影响LCC-HVDC阻抗模型的机理，研究不同频段下的简化建模方法。应用广义奈奎斯特准则（GNC）分析了发送交流电网的稳定性。稳定性分析结果表明换相重叠的影响不可忽视。仿真结果验证了所得结论的正确性。