油–纸绝缘结构非线性交直流复合电场计算的定点频域有限元法

Analysis of Nonlinear Electric Field of Oil-paper Insulation Under AC-DC Hybrid Voltage by Fixed Point Method Combined With FEM in Frequency Domain

针对换流变压器交直流混合电压中含有高次谐波的特点,提出油–纸绝缘结构非线性交直流复合电场计算的定点频域有限元法,给出了定电导率的取值方法。采用定点法使得每次迭代的非线性有限元刚度阵与解向量不相关,从而提高了频域有限元法的求解速度。为验证该算法的有效性,针对一换流变压器阀侧绕组的典型模型,将频域法的计算结果与时域法的结果进行了对比,分析了不同算法的特点。计算结果表明,将定点法用于非线性交直流复合电场问题时计算量小,能够用来分析实际换流变压器的非线性交直流复合电场问题以及其他非线性非正弦稳态电场问题。

The fixed point method is adopted to analyze the nonlinear electric field under the AC-DC hybrid voltage, which contains many high order harmonics, and the formula of selecting fixed-point conductivity was proposed. For the stiffness matrix is independent of the current iteration＇s solution, the finite element method （FEM） in frequency domain can be used to obtain the steady periodic results effectively. To verify the proposed algorithm, a typical oil-paper insulation structure of converter transformer under the superimposed AC-DC voltage was calculated by different methods and the results show that the proposed method is suitable to analyze the nonlinear electric fields under AC-DC hybrid voltage of actual converter transformer and other periodic non-sinusoidal electric problems.