电力变压器直流偏磁问题的工程模拟.pdf

河北工业大学博士学位论文电力变压器直流偏磁问题的工程模拟姓名：赵志刚申请学位级别：博士专业：电气工程指导教师：刘福贵;景崇友20100501河北工业大学博士学位论文 i电力变压器直流偏磁问题的工程模拟电力变压器直流偏磁问题的工程模拟 摘摘 要要 电力变压器直流偏磁现象是变压器的一种非正常工作状况，是指在交流变压器激磁电 流中出现了直流分量，导致变压器铁心中产生直流磁通它使激磁电流峰值显著增大、波 形严重不对称和畸变，产生大量谐波,导致铁心振动加剧，而且可能引起系统保护继电器 的误动作，危害变压器和电力系统的安全运行；引起变压器铁心磁饱和，漏磁增加，损耗、 温升增大，并可能引发金属结构件局部过热 本文结合河北省自然科学基金重大资助项目《特高压电磁场的综合效应研究》 （No.E2006001036）的要求，对电力变压器直流偏磁问题进行了实验研究和仿真分析对 实验研究所得数据进行了处理和分析，获得了电力变压器直流偏磁条件下“叠积型”铁心 材料的电磁性能参数利用神经网络直流偏磁磁滞模型对该材料的磁滞回线进行了模拟并 对激磁电流进行计算建立了便于工程应用的三维有限元仿真模型，对直流偏磁条件下变 压器铁心的磁通分布和损耗分布进行了研究。

主要内容如下： 1. 提出可行的变压器直流偏磁实验方案，建立能真实地模拟运行的电力变压器发生 直流偏磁状况时的实验系统，并对相关模型进行实验研究 2. 根据变压器直流偏磁的基本特征，从工程应用的角度系统研究电力变压器遭受直流偏 磁时铁心的电磁特性问题基于完全按照电力变压器铁心的标准设计和叠装工艺制作的产 品级模型，对“叠积型”铁磁材料在直流偏磁条件下的平均 B-H 曲线、Φ-I 曲线，损耗曲 线等进行了详细考察，并与“标准条件”下获得的材料属性进行了对比分析，以解决直流 偏磁仿真研究中依赖的那些材料特性问题 3. 根据实验获得的“叠积型”铁磁材料在直流偏磁工作条件下的材料性能数据，提出并 建立神经网络直流偏磁磁滞模型，预测材料在不同的交流工作点以及不同的偏置磁场作用 时材料的磁滞回线，为计算绕组的激磁电流和考虑磁滞特性的电磁场数值计算奠定基础 4. 提出一种求解变压器在直流偏磁条件下绕组激磁电流以及铁心直流偏置磁通的工程方 法，进而确定了不同偏磁工况下激磁电流和铁心中工作磁通的波形对激磁电流计算结果 进行分析并与实验获得的数据进行对比，验证该计算方法的有效性 5. 针对目前广泛采用的两种引入直流量的实验方案（即直流量在同一个激磁绕组中串联 加载和直流量分别在两个激磁绕组中并联加载） ，用实验结合仿真的办法对其进行了研究， 考察了两者在直流偏磁实验中的区别和联系，从而确定了更接近直流偏磁真实情况且切实 可行的实验方案，并为三维有限元仿真模型的建立提供参考。

6. 确定电力变压器发生直流偏磁时的模型参数，利用三维电磁场分析软件 MagNet 对变 压器处于各种不同的偏磁工作状况下叠片铁心中的磁通分布和损耗分布进行仿真分析，并 与实验测量结果进行对比，验证本文仿真模型和计算方法的准确性 关键词关键词：电力变压器，直流偏磁，激磁电流，直流磁通，磁滞回线，神经网络磁滞模型， 有限元模型，铁心损耗，磁通分布 电力变压器直流偏磁问题的工程模拟 iiENGINEERING-ORIENTED MODELING OF POWER TRANSFORMERS UNDER DC-BIASED MAGNETIZATION ABSTRACT The dc-biased magnetization is an unusual exciting condition for the AC power transformers. The use of an iron core under dc-biased magnetization generates a dc component in the exciting current. The magnetic flux, the peak value of the exciting current increases significantly and the waveform of the current is seriously distorted with a lot of harmonics. The iron core is asymmetrical saturated and the leakage flux of the iron core is increased. The heavy noise, the serious vibration, and the local loss concentration can all occurre in dc-biased transformers. Moreover, the harmonics will cause the misoperation of the protective relay which is harmful for the safe operation of the transformers and the power system. The experimental research and simulation analysis of power transformers under different dc-biased magnetic field strength were completed according to the Natural Science Foundation of Hebei Province under Grant E2006001036. The measured induced voltage and exciting current was processed to obtain the electromagnetic properties of the iron core. A neural network hysteresis model was proposed to predict the hysteresis loops under dc-biased magnetization. The 3-D finite element model was presented to analyze the distribution of the magnetic flux and iron loss inside the iron core of dc-biased transformers. The main points of this paper are: 1. A practical experimental approach was proposed to invesgate the eletromagnetic characteristics of dc-biased transformers. The technical requirements for the dc bias experimental resreach were determined. And the measurements based on the laminated core model of product level were carried out. 2. The magnetic properties, such as the B-H curve, Ф-I curve and the loss curve, of the laminated ferromagnetic materials were measured and compared with those obtained under “standard” condition. This is essential in the 3-D finite element simulation of the transformers under dc-biased magnetization. 3. Based on the obtained material property database from experiments, a neural network hysteresis model was established to predict the hysteresis loops under different dc-biased magnetic field strength. The approach for calculation the exciting current of biased-transformer was presented, in which the predict hysteresis loop corresponding to the specific working condition is used. 4. An engineering-oriented method was presented and developed based on the MATLAB commercial software to compute the magnetizing current and the dc magnetic flux in the iron core. The comparison between the calculated results and the measured ones was carried out to validate the effectiveness of the proposed method. 5. Two experimental schemes for how the dc-biased magnetic field strength applied to the 河北工业大学博士学位论文 iiitransformer were proposed. The differences and relations between the two schemes were examined, that is useful for the establishment of the magnetic analysis model. 6. A practical method was proposed to simulate the distribution of magnetic flux and iron loss inside the laminated core under dc-biased excitation, which is based on the 3-D electromagnetic field analysis software, MagNet. The good agreement between the calculated results and the measured ones proves the effectiveness of the method. KEY WORDS：power transformer, dc-biased magnetization, exciting current, dc flux, hysteresis loop, neural network hysteresis model, finite element model, iron loss, flux distribution 河北工业大学博士学位论文 1第一章第一章 绪绪 论论 §1-1 特高压输。