基于材料性能工程模拟与定点谐波平衡法的电力变压器直流偏磁数值仿真及有效性验证

Accurate simulation of ferromagnetic material property is an important foudation for the study of dc-biased problems. The eddy-current and hysteretic problems in power transformers under dc-biased magnetization can be analyzed in frequency domain by the fixed-point harmonic-balanced method, which contributes to numerical analysis of eletromagnetic field and electrical engineering. Based on the successful application of harmonic-balanced FEM on the dc-biased problem, this project plans to set up an experimental system consist of two square laminated cores, aiming to study the influence of dc bias on the equivalent magnetic circuit length and obtain the dc-biasing magnetic characteristics under different dc-biased magnetizations. The harmonic-blanced method is employed in the coupled electric-magnetic circuit model of three-phase power transformers to compute the magnetic flux and magnetizing current in harmonic domain, and then the operating characteristics of power transformers can be analyzed. The fixed-point technique is combined with the harmonic-balanced FEM to study the variation and distribution of the eddy current in the shielding screen of power transformers. The measured dc-biasing hysteresis loops are modeled by the neural network, thus the dc-biasing hysteresis and relative loss characteristics are analyzed in the numerical computation of power transformers by the fixed-point harmonic-balanced FEM, taking account of the hysteresis effects under dc-biased magnetization.

铁磁材料特性的精确模拟是研究直流偏磁问题的重要基础。基于定点谐波 平衡法在频域内研究直流偏磁条件下变压器的涡流及磁滞问题具有重要的理论意义和工 程价值。本项目在前期已将谐波平衡有限元法成功应用于直流偏磁问题研究的基础上，拟建 立双方型叠片铁心的实验与测量系统，研究直流偏磁对变压器铁心等效磁路长度的影响规 律，获得不同偏置水平下变压器铁心的直流偏磁磁化特性和损耗特性。将谐波平衡法引入到变压器的电路-磁路耦合模型当中，在频域内对铁心柱磁通和励磁电流的各谐波分量进行同步计算，分析直流偏磁对电力变压器运行特性的影响。基于定点谐波平衡有限元法，研究直流偏磁条件下变压器屏蔽板内涡流的变化与分布。由测量得到的直流偏磁磁滞特性,建立基于神经网络的直流偏磁磁滞模型，在有限元计算中考虑磁滞效应，分析直流偏磁对电力变压器磁滞特性及相关损耗特性的影响。

随着我国高压直流输电的规划及发展，变压器直流偏磁问题不仅对设备运行产生一系列影响，如局部过热，振动噪声等，而且会进一步威胁电力系统的安全稳定运行。铁磁材料磁性能的精确模拟为数值计算与仿真分析的准确性提供数据基础，频域高效数值计算方法是求解多谐波激励下非线性电磁场的重要手段，本项目将二者相结合深入研究变压器直流偏磁相关问题。（1）搭建平台并设计实验，对电工钢片和产品级叠片铁心进行磁性能测量，基于不同类型的磁滞模型对磁滞回线进行拟合，研究频率、磁密等对磁化特性及损耗特性的影响；（2）将谐波平衡法应用于电路-磁路耦合模型，用于分析变压器直流偏磁特性，研究了不同偏置量对励磁电流和铁心磁通的影响规律，同时结合定点法，在计算中考虑铁心磁滞特性，合理确定定点磁阻值保证方程收敛。（3）提出适用于谐波激励下非线性涡流问题求解的谐波平衡分解算法，研究了块状导体和细线导体不同形式的场路耦合关系，比较了分解算法和定点算法的收敛性。（4）基于TEAM P21基准问题，设计并进行了谐波激励条件下的导磁构件与非导磁构件杂散损耗的实验及仿真研究；将实验测量和仿真结果相结合，提出了有效的构件杂散损耗确定方法，研究了不同谐波次数、相位等对杂散损耗的影响。本项目研究工作在电工材料磁性能工程模拟、频域高效数值计算、变压器结构件杂散损耗确定等方面具有重要的科学意义和工程价值。