Grid-side main circuit of industrial transmission system, transformer and control method

Abstract

The invention discloses a transformer, which is applied to a grid-side main circuit of an industrial transmission system and connected with an AC bus. The transformer comprises at least two primary windings and at least two secondary windings corresponding to the primary windings, wherein the primary windings are in series connection, the secondary windings are mutually independent, and predetermined phase difference is reserved between two adjacent secondary windings. Because the primary windings are in series connection, the secondary windings are mutually independent, and the predetermined phase difference is reserved between two adjacent secondary windings. Secondary current harmonic of the transformer can be reduced when the transformer is connected with a grid-side converter containing a large number of high-power semiconductor devices. Furthermore, compared with a transformer with split windings, short-circuit impedance of the transformer provided by the invention is less than short-circuit impedance of the transformer with the split windings under a condition of the same primary short-circuit impedance, so that the size and the cost of the transformer can be reduced under the same capacity. In addition, the invention further discloses a grid-side main circuit comprising the transformer of the industrial transmission system and a control method.

Description

technical field [0001] The invention relates to the field of circuit technology, in particular to a network-side main circuit of an industrial transmission system, a transformer and a control method thereof. Background technique [0002] High-power industrial transmission systems, such as metallurgical rolling mills, mine hoists, etc., require active rectification units on the grid side due to the requirement that energy can be fed back to the grid during braking. Under medium-voltage application conditions, the main circuit of the active rectifier unit mainly includes a transformer, a grid-side converter and a control circuit. For the grid-side converter, a three-level neutral point clamped converter is often used. [0003] In the field of industrial and rail transit applications, due to the demand for super large capacity, the common DC bus technology is usually used, and multiple grid-side converters share the DC bus. This structure is helpful for improving the system eff...

AI Technical Summary

Problems solved by technology

[0004] One is that the three-level neutral point clamp converter contains a large number of high-power semiconductor devices, such as IGBT, IGCT, IEGT, etc., and the switching frequency is generally low due to the turn-on and turn-off losses. In this case, the secondary side current harmonics of the transformer are relatively large; the other is that for high-power AC drive systems, the grid-side converter does not have a separate reactor, which is usually equivalent to the short-circuit impedance of the transformer. For the split winding As far as the transformer is concerned, in order to suppress the pulsation value of the secondary side current of the transformer, a large short-circuit impedance is usually required to realize it, so the short-circuit impedance of the transformer is required to be large, which will be a big challenge for the volume and cost of the transformer

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