大型换流变压器铁心饱和稳定性及漏磁场解析研究

发布时间：2018-03-19 17:22

本文选题：换流变压器　切入点：铁心饱和不稳定性　出处：《沈阳工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着现代电网电压等级越来越高及超高压直流输电技术应用,大型换流变压器内部会出现非常严重的直流偏磁现象。这种情况会造成换流变压器铁心饱和不稳定,引起换流变压器漏磁场和附加损耗增大,甚至发生局部温度过高现象,最后会危害换流变压器的正常工作运行。换流器的交流侧正序2次谐波分量和直流侧基频分量通过交直流系统间的相互作用,会引发换流变压器中铁心饱和不稳定现象的出现。通过对换流变压器漏磁场及附加损耗的研究,可以尽最大可能使变压器运行在正常条件下,从而提高变压器运行的经济性及安全性。变压器设计研发时,变压器附加损耗值是一个十分重要的指标,因此,深入研究变压器铁心饱和稳定性及漏磁场具有重要的工程意义。有限元法需要确定很复杂的边界条件,通常计算工作量很大而且计算周期较长,不易实现优化设计;而解析法物理概念分析清楚,方便编写优化程序,同时也在不断提高精确度,所以,设计工作人员希望提出一种能够将快速计算换流变压器的附加损耗的解析法的公式。换流变压器发生直流偏磁时,出现励磁电流畸变、附加损耗增大等问题。本文首先基于爱泼斯坦方圈对换流变压器铁心材料27ZH100电工钢片的磁特性在不同直流及温度条件下进行实验及测量研究,详细阐述并解释了BH曲线、BP曲线及磁导率曲线特性,为提高直流偏磁条件换流变压器漏磁场及油箱损耗仿真准确性提供参考依据。其次,研究换流变压器铁心饱和不稳定形成的机理,分析了换流器的交流侧正序2次谐波分量和直流侧基频分量相互之间作用,建立了换流变压器铁心饱和不稳定型等值电路。通过传递矩阵计算推导出换流变压器饱和不稳定判定因子,提出可以判定铁心饱和不稳定现象的方法。然后在MATLAB建立界面验证了该方法的正确性。最后,由于变压器复杂漏磁场分布,本文通过与理论相结合分析,在实际计算漏磁场时,通常设漏磁为理想分布,即变压器中漏磁力线都与铁心轴线平行,均作纵向漏磁处理,推导计算出换流变压器油箱损耗公式。根据换流变压器电磁设计理论,计算换流变压器漏磁场引起的油箱损耗,得出的解析法计算结果与有限元仿真结果基本吻合,验证了解析法计算方法的可行性。
[Abstract]:With the increasingly high voltage level of modern power network and the application of UHV direct current transmission technology, there will be a very serious DC bias phenomenon in large converter transformers, which will lead to the saturation instability of converter transformer cores. The leakage magnetic field and additional loss of converter transformer are increased, and even the local temperature is too high. Finally, it will harm the normal operation of converter transformer. The interaction between AC side positive sequence second harmonic component and DC side fundamental frequency component of converter through AC / DC system, Through the study of leakage magnetic field and additional loss of converter transformer, the transformer can operate under normal conditions as far as possible. In order to improve the economy and safety of transformer operation, the additional loss value of transformer is a very important index when the transformer is designed and developed. It is very important to study the saturation stability and magnetic flux leakage of transformer core in depth. The finite element method needs to determine very complicated boundary conditions, usually the calculation work is very large and the calculation period is long, so it is difficult to realize optimal design. And the analytical method of physics concept analysis is clear, convenient to write the optimization program, and at the same time is improving the accuracy, so, The design staff hope to put forward an analytical formula that can quickly calculate the additional losses of converter transformers. When DC bias occurs in converter transformers, excitation current distortion occurs. In this paper, based on the Epstein square ring, the magnetic properties of 27ZH100 electrical steel sheet of converter transformer core are studied by experiments and measurements under different DC and temperature conditions. The characteristics of BH curve and permeability curve are described and explained in detail, which provides a reference for improving the simulation accuracy of leakage magnetic field and oil tank loss of converter transformer under DC bias. The mechanism of saturation instability of converter transformer iron core is studied. The interaction between AC side positive sequence second harmonic component and DC side fundamental frequency component of converter is analyzed. The equivalent circuit of saturation instability of converter transformer core is established, and the determination factor of saturation instability of converter transformer is derived by transfer matrix calculation. A method to determine the saturation instability of iron core is proposed, and the correctness of the method is verified at the MATLAB interface. Finally, due to the complex magnetic leakage field distribution of transformer, this paper, by combining with the theory, calculates the leakage magnetic field in practice. The magnetic flux leakage is usually assumed to be an ideal distribution, that is, the leakage force line in the transformer is parallel to the core axis and is treated with longitudinal magnetic leakage. The formula for calculating the oil tank loss of the converter transformer is derived. According to the electromagnetic design theory of the converter transformer, The loss of tank caused by leakage magnetic field of converter transformer is calculated. The calculated results of the analytical method are in good agreement with the results of finite element simulation, and the feasibility of the analytical method is verified.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM41

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