Direct-current magnetic bias calculation method for extra-high voltage transformer parallel winding series resistance compensation

Abstract

The invention belongs to the technical field of safety guarantee of extra-high-voltage alternating-current power grid electrical equipment, and particularly to a direct-current magnetic bias real-timecalculation method for extra-high voltage transformer parallel winding series resistance compensation. The method comprises the following steps: constructing three-dimensional geometric models of three transformers and a direct-current magnetic bias calculation magnetic field model according to actual structural parameters of a main transformer, a voltage regulation transformer and a compensationtransformer of the extra-high voltage transformer; calculating a self-inductance value when different currents flow through each transformer winding and a mutual inductance value between the windings; in combination with an electrical connection relationship among the three transformers, establishing an overall direct-current magnetic bias equivalent circuit calculation model of the three transformers through series resistance compensation voltage; solving the direct-current magnetic bias circuit model by using a fourth-order Runge-Kutta method of inductance parameters; multiplying the instantaneous current value of the branch where the series resistor is located by the increased series resistor to perform voltage compensation; and calculating the voltage and current values of each transformer and carrying out FFT (Fast Fourier Transform) to obtain the voltage and current harmonic condition of each transformer under the direct current magnetic bias of the extra-high voltage transformer.

Description

technical field [0001] The invention belongs to the technical field of safety assurance of electrical equipment in an ultra-high voltage AC power grid, and in particular relates to a real-time calculation method for direct current bias magnetic field compensation of parallel winding series resistance of an ultra-high voltage transformer. Background technique [0002] With the rapid economic development in the southeast coastal areas, electricity consumption continues to increase, but my country's energy is mainly distributed in the northwest region, so large-capacity, long-distance power transmission technology is needed. Therefore, there are many UHV transmission lines in my country Putting into operation, UHV transformer is one of the key equipment of UHV AC transmission technology, its safe and stable operation is the key to ensure the normal operation of UHV transmission. UHV transformers have small resistance and large inductance, and are easily affected by DC bias. How...

AI Technical Summary

Problems solved by technology

In the case of UHV transformer DC bias, the magnetic flux leakage will increase due to the severe half-wave saturation of the iron core, and the circuit-magnetic circuit method does not fully consider the magnetic flux leakage, so there is a large error in the calculation of the DC bias; The wave balance finite element method solves and superimposes each harmonic of the magnetic vector position in the unit at the same time. For the DC bias calculation of a large model such as an UHV transformer, due to the large number of nodes and harmonic orders of the model, it will The calculation takes up a lot of resources and takes a long time; based on the time-domain field-circuit coupling method to calculate the DC bias problem of UHV transformers, the fourth-order Runge-Kutta method is used to improve the accuracy of calculations, but currently it is only for UHV transformers One of the transformers in the main transformer, voltage regulation transformer and compensation transformer (referred to as "three transformers") is analyzed. In actual operation, the main transformer, voltage regulation transformer and compensation transformer of UHV transformers are often operated together. Since the three transformers There will be a direct parallel connection of windings in the electrical connection between them, and the UHV transformer material has the characteristics of large inductance and small resistance. When calculating the DC bias, it will make the transition process very long, and the voltage on the large inductance is very large. The simulation calculation A small DC voltage error in the parallel circuit will also generate a huge DC current backflow because the resistance of the parallel circuit is too small, which will increase the DC component of the calculated current, affect the saturation of the iron core, and cause a large error in the calculation result

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