Abstract
This paper sought to present harmonic-balanced method for finite element analysis of nonlinear eddy current field. The harmonic-balanced method can be used to compute the time-periodic electromagnetic field in harmonic domain, considering electric circuits coupled with the nonlinear magnetic field. 2-D and simplified 3-D model of laminated core is established and computed to prove the accuracy and validity of the proposed method. The calculated magnetizing current is compared with the measured results and the computed magnetic field is analyzed to investigate the effect of DC bias.
Highlights
The DC bias phenomenon is an abnormal operation state of the power transformer
The investigation of the DC biased problem originates from the effect of Geomagnetically Induced Current (GIC) [4]-[6] caused by solar magnetic disturbance on transformers and electric networks
With the development of high voltage direct current (HVDC) transmission, more attention has been paid to the DC biased problem in recent years
Summary
The DC bias phenomenon is an abnormal operation state of the power transformer. The direct current flows into the windings of transformers, which may lead to a series of problems in transformers and electric networks. The electric potential difference generates a direct current that flows into the windings of the power transformer (through the earthed neutrals in the AC network). It is difficult to obtain accurate results from the electric or magnetic circuit model, especially when magnetic field analysis is required to explore the mechanism of the DC biased problem. The time-stepping method is an alternative method to calculate the transient magnetic field, but accurate solutions of high order harmonic components in exciting current and magnetic induction require many more iterations in the time domain, which can reduce the effectiveness of this method. The nonlinear magnetic field under DC bias condition is analyzed thoroughly through harmonic analysis in order to investigate the mechanism of the DC bias phenomenon in the power transformer. 32 Xiaojun Zhao et al.: Computation and Analysis of the DC-Biasing Magnetic Field by the Harmonic-Balanced Finite-Element Method efficient method in analyzing the DC biased problem of power transformers
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