Axial symmetry DC magnetic bias simulation model for extra-high voltage transformer

Abstract

The invention discloses an axial symmetry DC magnetic bias simulation model for an extra-high voltage transformer, which belongs to the technical field of safe operation of electrical equipment in an extra-high voltage AC network. Through establishment of an equivalent axial symmetry simulation model of an actual three-dimensional model of the extra-high voltage transformer, a complicated magnetic field model is equivalent to a simple two-dimensional magnetic field model and dynamic inductance parameters are obtained; a load DC magnetic bias circuit model of the extra-high voltage transformer is established; current parameters are obtained through a four-order Runge-Kutta method; a time domain field-circuit coupling method is adopted to realize rapid calculation of the load DC magnetic bias of the extra-high voltage transformer; the simulation proves the high precision and high efficiency of analysis of DC magnetic bias through the extra-high voltage transformer to bring convenience to a large amount of researches on a DC magnetic bias problem of the transformer and help to safe and stable operation of the transformer.

Description

technical field [0001] The invention belongs to the technical field of safe operation of electrical equipment of an ultra-high voltage AC power grid, and particularly relates to a simulation model of axisymmetric DC bias of an ultra-high voltage transformer. Background technique [0002] UHV transmission has long transmission distance, large capacity, low loss and small footprint, effectively solving the problems of my country's power grid and energy development. As one of the key equipment of UHV power grid, UHV transformer has complex structure and high cost. Its safe and stable operation is directly related to the normal operation and reliability of UHV transmission system. [0003] The DC bias phenomenon occurs when the DC current is mixed from the neutral point of the transformer. Relevant studies have proved that the main reason for the DC bias problem of the transformer is that the geomagnetic storm and UHV DC transmission operate in a single-pole mode. The DC bias c...

AI Technical Summary

Problems solved by technology

The harmonic balance finite element method obtains the harmonic components of the unknown excitation current and magnetic vector potential by solving the magnetic field equation and the circuit equation, but it consumes more resources and the calculation efficiency is not high

The improved harmonic balance finite element method obtains higher calculation accuracy by simultaneously solving and superimposing each harmonic component of the magnetic vector potential, but this method is complicated to solve and takes a long time

J-A theory involves many parameters when analyzing the excitation characteristics of the transformer iron core under the condition of DC bias, and the calculation amount is very large after being combined with the transformer magnetic circuit model.

The time-domain field-circuit coupling method uses edge finite elements to establish a three-dimensional transformer magnetic field model. This method has high accuracy and stability, and can carry out detailed electromagnetic characteristics analysis under DC bias conditions, but it has certain computational efficiency. However, the solution of the three-dimensional magnetic field is complicated. For UHV transformers, large resistors in series need to be solved, and the calculation of the long-term transition process cannot be performed, and the efficiency is very low.

The adaptive optimization algorithm based on the field-circuit coupling calculation method improves the calculation efficiency by changing the step size, but this method is only verified for the bias calculation of small transformers. For UHV transformers that require multiple cycles Magnetic calculation analysis, calculation efficiency has not been greatly improved

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