直流偏磁及谐波条件下换流变压器温升的计算

发布时间：2018-04-27 23:28

本文选题：换流变压器 + 直流偏磁　；参考：《沈阳工业大学》2017年硕士论文

【摘要】：近些年来,我国高压直流输电工程的发展达到了前所未有的高度,为了满足直流输电的发展需要,作为高压直流输电系统重要设备的换流变压器也得到了越来越多的研究。直流电网和地磁暴等因素引起的直流偏磁现象逐渐增多,加上高压直流输电有较大高次谐波的特点,所以在运行中的换流变压器必然承受着直流偏磁和谐波对其的影响。发生直流偏磁的情况时,换流变压器将会出现励磁电流波形的严重畸变,而发生偏磁的电流越大则越容易出现半周期严重饱和的尖顶波电流波形。尖顶波的出现将使得换流变压器的漏磁增大,由漏磁引起的损耗必然增加,进而引起变压器的局部过热。高压直流输电中的负载电流中含有大量的高次谐波分量,谐波分量必然将产生与其对应的漏磁场和损耗。基波与高次谐波产生的损耗将共同作用于换流变压器的结构件上,损耗的分布一般不是均匀分布的而是集中在结构件的某个区域上,损耗过大将很可能引起变压器的某一区域的局部过热,进而将影响到换流变压器的正常运行状态。换流变压器的局部过热又将引起绝缘的老化影响其使用寿命,所以本文对换流变压器出现这两种特殊情况下的温升进行了仿真计算。本文的主要工作有以下两点:第一,采用实验的方式对换流变压器的铁心硅钢片在直流偏磁以及谐波的条件下进行了磁特性的测量。第二,基于有限元仿真原理对不同直流偏磁及5次、7次谐波条件下的一台实际的换流变压器温度进行了计算。对比分析了两种情形下的温度场分布情况:(1)分别使用正常磁特性曲线与直流偏磁磁特性曲线下的温度场仿真分布情况;(2)分别使用正常磁特性曲线与使用谐波磁特性曲线下的温度场仿真分布情况。仿真分析了4mm厚的铜屏蔽对于直流偏磁和谐波条件下漏磁场增大引起的温度升高的抑制作用。从仿真结果来看,换流变压器在发生较大直流偏磁以及承受高次谐波时将会出现局部过热现象,而这种现象必将会严重影响其使用寿命。本文对直流偏磁和谐波条件下的换流变压器温升进行的计算,为换流变压器温升问题的进一步研究奠定基础。
[Abstract]:In recent years, the development of HVDC power transmission project in China has reached an unprecedented height. In order to meet the needs of the development of HVDC transmission, the converter transformer, which is an important equipment for HVDC transmission system, has also been more and more studied. The phenomenon of DC bias caused by DC power grid and geomagnetic storms is increasing gradually, and higher The HVDC power transmission has the characteristics of higher harmonics, so the converter transformer in operation is bound to bear the influence of DC bias and harmonic wave on it. When the DC bias magnetic field occurs, the converter transformer will have serious distortion of the excitation current waveform, and the larger the magnetic current is, the more likely it will be half cycle and serious saturation. The emergence of the spike wave will increase the flux leakage of the converter transformer. The loss caused by magnetic flux leakage will inevitably increase and cause the local overheating of the transformer. The load current in HVDC transmission contains a large number of high order harmonic components, and the harmonic components will inevitably produce its corresponding leakage magnetic field and loss. The loss caused by high order harmonics will work together on the structure parts of the converter transformer. The loss distribution is generally not uniformly distributed but concentrated in some region of the structural parts. Excessive loss will probably cause local overheating in a certain area of the transformer, and will affect the normal running state of the converter transformer. The partial overheating of the device will cause the aging of the insulation to affect its service life, so this paper has simulated the temperature rise of the converter transformer under these two special circumstances. The main work of this paper is the following two points: first, the iron core silicon steel sheet of the converter transformer is under the condition of DC bias and harmonic. The measurement of magnetic properties is carried out. Second, based on the finite element simulation principle, the temperature of a practical converter transformer under different DC bias and 5 times and 7 harmonic conditions is calculated. The temperature field distribution in two cases is compared and analyzed. (1) the temperature under the normal magnetic characteristic curve and the DC bias magnetic characteristic curve are used respectively. The distribution of field simulation, (2) the simulation distribution of the temperature field under the normal magnetic characteristic curve and the harmonic magnetic characteristic curve is used respectively. The simulation and analysis of the inhibition effect of the 4mm thick copper shielding on the increase of the temperature caused by the leakage magnetic field increases under the condition of direct current bias and magnetic resonance. In this paper, the calculation of the temperature rise of the converter transformer under the condition of DC bias and harmonic wave will lay a foundation for the further research on the temperature rise of the converter transformer.

【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】：TM721.1;TM41

【参考文献】