A method for calculating DC magnetic bias of three-phase transformer in frequency domain

Abstract

The invention relates to a three-phase transformer DC magnetic bias frequency domain calculation method, which comprises the following steps of: a loop equation describing the characteristics of an external port of a circuit is written; the corresponding magnetic circuit model is established and the corresponding magnetic circuit equation is written; the periodic variable of the electromagnetic field generated in each region is expressed by complex series; the Harmonic balance circuit equation and harmonic balance magnetic circuit equation are obtained by harmonic balance method; each physicalquantity of the harmonic balance circuit equation and the harmonic balance magnetic circuit equation is decomposed and written into matrix form, and the matrix is transformed into rows and columns bythe parallel solution method; the decomposed matrix is solved by Jacobian iterative method, and then the magnetic flux in the magnetic circuit and the current in the circuit are obtained. The invention adopts the complex number form of the Euler formula introduced by the Fourier series in the column writing equation. Compared with the triangular series form, the magnetoresistive rate matrix presents regularity, reduces the repetition formation of the magnetoresistive rate matrix in the program, thereby reducing the storage memory and increasing the calculation speed.

Description

technical field [0001] The invention relates to the technical field of calculating a magnetic circuit coupling model of a DC bias circuit of a transformer, in particular to a frequency-domain calculation method for a DC bias of a three-phase transformer. Background technique [0002] DC transmission technology has developed rapidly due to its advantages in improving the economy, stability and flexibility of power system operation, and has been widely used in my country. With the increase of the voltage level and the increase of the electric load, the DC bias phenomenon of the transformer becomes more and more prominent. The DC bias phenomenon is an electromagnetic effect that causes the DC magnetic potential and the corresponding DC flux to appear in the electromagnetic field of the transformer. Under the influence of the DC bias, the iron core of the transformer works in a half-saturated state, resulting in a sharp increase in the excitation current of the transformer. Pro...

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Problems solved by technology

Among them, the time-domain finite element method iteratively solves the discretization of time. When solving the eddy current problem, it needs to go through half a cycle to reach a stable state; the coefficient matrix of the time-period finite element method is asymmetrical, which requires a large amount of time in the calculation process. Internal memory; the research on the DC bias problem requires a lot of harmonic analysis, which needs to be carried out after Fourier transform in the time domain, which brings inconvenience to the post-processing of the time domain calculation results

In the transformer DC bias problem, various harmonics exist at the same time, and the transformer core is mostly in a deep saturation state. The traditional frequency-domain finite element algorithm can only calculate a single frequency, and cannot calculate the magnetic field when the core material works in the deep saturation region.

At present, most of the transformers at home and abroad are analyzed for DC bias of single-phase transformers, and there are few calculations and analyzes of asymmetric DC bias for three-phase DC bias.

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