定点时间周期有限元法及其在变压器直流偏磁特性分析中的应用

Fixed-Point Time-Periodic Finite Element Method and Its Application for DC Bias Characteristics of Transformer

根据稳态激励下电磁场场量周期性变化的特点,以矢量磁位和激磁电流为未知量,利用场路耦合的时间周期有限元法对变压器直流偏磁问题进行研究。采用能量法确定2D磁系统等效厚度,结合局部收敛的固定点法,选择合适的收敛因子及方程初值,有效地提高了基于场路耦合的时间周期有限元法方程的计算精度和计算效率。针对叠片铁心模型进行了不同条件下直流偏置的实验和计算,计算结果和测量结果基本吻合,验证了该方法在变压器直流偏磁计算中的适用性。通过人为增大电阻,设置补偿电压,为变压器在直流偏磁计算中因内阻小,电感变化剧烈而引起的不稳定问题提供了一个解决思路。

According to the periodic characteristics of the variables in electromagnetic field under steady-state excitation, the magnetic vector potential and the exciting current were taken as the unknown variables, the field,circuit coupled time-periodic finite element method was applied to study the DC-biased problems of power transformers. Achieving the equivalent, thickness of the 2D magnetic system by calculating the magnetic field energy, combining with the locally convergent fixed-point method, and choosing the suitable convergence factor and the initial values, the computational accuracy and efficiency of the proposed method are effectively improved. The experiment and calculation about transformer DC bias in different conditions were carried out on a laminated core model, and the results of the calculation agree with those of the measurement, which verify the proposed method can be used to study the DC-biased transformers. By artificially increasing the resistance and setting up the compensation voltage, this paper provides a solution to solve the stability problem caused by the small resistance and the drastic change of inductance in the DC-biased calculation of transformers.