考虑交流非对称的HVDC换流器开关函数模型及其应用

发布时间：2018-11-19 14:29

【摘要】：高压直流输电技术的广泛应用,使得直流系统建模成为该领域的研究重点。换流器作为直流系统最重要的器件,其模型的准确性直接决定了直流系统建模的有效性。传统的换流器开关函数模型应用于交流系统非对称运行状态时,计算精度降低。为了提高换流器开关函数模型的计算精度,本文详细分析了三相非对称运行状态下换流器的换相过程,并着重考虑了直流侧二次谐波电流对换相持续时间的影响,建立了考虑阀导通偏移和换相角不等的换流器开关函数模型,相较传统的换流器开关函数模型,本文建立的模型能够显著提高分析精度。本文所建立的考虑交流非对称情况的HVDC换流器开关函数模型,在三个方面进行了应用：第一,将所建立的换流器开关函数模型应用于动态相量理论中。采用从PSCAD中采样、利用动态相量理论在MATLAB下编程实现计算,对换流器开关函数模型在动态相量理论中的应用进行了初探,验证了动态相量理论的分析精度的可靠性。第二,采用考虑交流非对称的换流器开关函数模型进行含直流馈入的交流系统故障分析研究。进一步建立了直流侧等值谐波阻抗模型及直流控制系统稳态响应模型,形成适用于交流系统故障计算的直流系统模型,并与传统的交流系统故障分析模型联立,形成了最终的含直流馈入的交流系统故障分析模型,通过仿真与计算验证了模型的有效性以及求解算法的收敛可靠性。第三,针对交流系统故障引发直流换相失败机理展开深入分析。基于HVDC换流器开关函数建模中对换流阀换相过程的分析,进一步分析了交流故障瞬间换流阀的实际触发导通过程,在此基础上,对交流系统故障引发直流换相失败的机理进行分析,提出了一种换相失败的预测方法,基于所做的对交流故障引发直流换相失败的机理分析,可以为解释换相失败下的一些特性提供理论参考。
[Abstract]:With the wide application of HVDC transmission technology, DC system modeling has become the research focus in this field. As the most important device of DC system, the accuracy of converter model directly determines the validity of DC system modeling. When the traditional switching function model of converter is applied to the asymmetrical running state of AC system, the calculation precision is reduced. In order to improve the accuracy of the switching function model of the converter, the commutation process of the converter under the condition of three-phase asymmetrical operation is analyzed in detail, and the effect of the second harmonic current on the duration of the commutator is emphatically considered. The switching function model of converter considering valve conduction offset and phase changing angle is established. Compared with the traditional switching function model, the model established in this paper can improve the analysis accuracy significantly. In this paper, the switching function model of HVDC converter considering AC asymmetry is applied in three aspects. Firstly, the switching function model is applied to the dynamic phasor theory. Sampling from PSCAD and programming under MATLAB using dynamic phasor theory, the application of switch function model of converter in dynamic phasor theory is discussed, and the reliability of dynamic phasor theory is verified. Secondly, a switching function model considering AC asymmetry is used to analyze the fault of AC system with DC feed. The equivalent harmonic impedance model of DC side and the steady-state response model of DC control system are further established to form a DC system model suitable for the fault calculation of AC system, and it is combined with the traditional fault analysis model of AC system. The final fault analysis model of AC system with DC feed is formed. The validity of the model and the convergence reliability of the algorithm are verified by simulation and calculation. Thirdly, the mechanism of DC commutation failure caused by AC system fault is analyzed. Based on the analysis of commutation process in HVDC converter switch function modeling, the actual trigger conduction process of AC fault instantaneous converter valve is further analyzed. The mechanism of DC commutation failure caused by AC system fault is analyzed, and a prediction method of commutative failure is proposed, which is based on the mechanism analysis of DC commutation failure caused by AC fault. It can provide a theoretical reference for explaining some characteristics of commutation failure.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM721.1;TM46

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