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。

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.