Research On The Fixed-point Harmonic Balance Method For Nonlinear Eddy Current Problems

The eddy current effect in the solid conductor or the strand coil will influence the loss of the electric equipment. With the rapid improvement of the high voltage direct current(HVDC) transmission system, the electric equipment usually works in the DC bias, and the direct current may complicate the eddy current, and influence the eddy-current loss of the electric equipment. How to analyze the nonlinear eddy current problems accurately and efficiently has been an important part for electromagnetic field analysis. As a common method to analyze engineering electromagnetic field, the harmonic balance equation without time-varied elements can solve the nonlinear problems for the steady-state solution directly in the frequency domain.Sponsored by the National Natural Science Foundation of China under grant 51307057 and 51577066, this paper use the harmonic balance method to analyze the 1-D or 2-D nonlinear problems, an optimal fixed-point reluctivity and iteration are presented to ensure stable and fast convergence of harmonic solutions. As the solid conductor or strand coil is generally connected to the voltage source, the different coupling of magnetic field and electric circuit form should be investigated in harmonic domain. According to the harmonic solutions of the electromagnetic field, the nonlinear fields and eddy current influenced by the DC bias can be analyzed effectively.At the end of this thesis, according to the theory of nonlinear iteration, a new fixed-point method is presented without changing the constitutive relation. Combine the new fixed-point method and harmonic balance method, the 2D solid conductor model is computed respectively under sinusoidal excitation or dc-biased magnetization. Based on the fixed-point method, the computational memory and the speed of iteration are discussed comprehensively.