Analysis Of DC Bias Problem Based On Harmonic Balance Decomposition Method

With the rapid development of high-capacity and HVDC power transmission systems,electrical equipment such as transformers are more easily operate at high electromagnetic energy densities.Power transformers are easily affected by DC bias and appear abnormally working.By accurately and efficiently calculating the electromagnetic conditions inside these electrical equipment,it can provide an important basis for the design and optimization of the power transformer structure.In this paper,Based on the circuit-magnetic coupling equation of harmonic balance decomposition method,the DC bias problem of laminated iron core and three-phase three-column transformer is calculated and analyzed and Field-Coupled Equations for Harmonic Balanced Finite Element Decomposition Algorithm The electromagnetic properties of three-phase shell-type transformer in the case of no-load asymmetric DC bias are calculated and analyzed.In this paper,the periodic state variables are expanded in the Fourier form of complex numbers.Compared with the triangular function,iterative process avoids the repeated formation of coefficient matrix,reduces the memory requirement and improves the computational efficiency.Finally,by comparing the experimental results and calculation results of DC bias under different conditions,the validity of the algorithm in DC bias analysis of transformers is verified.Based on the calculated harmonic vectors,the variation law of transformer field current and iron core flux density under DC bias conditions was analyzed.