Three-phase 48-pulse rectifier transformer

Abstract

The invention relates to the field of rectifier transformers, provides an arrangement, phase shift, connection and turn number selection method for one rectifier transformer with four valve side output windings, and realizes parallel 24-pulse rectification of non-uniform phase shift of one rectifier transformer and parallel 48-pulse rectification of two rectifier transformers. The rectifier transformer solves the technical problems of small magnetic leakage impedance between radial division valve side windings of the rectifier transformer, larger parallel circulating current generated by transformation ratio voltage difference of rounded turn numbers of a star-like winding and a triangular winding and larger harmonic current transmitted to a power grid; and on the network side, 5th, 7th, 11th, 13th, 17th, 19th, 23rd and 25th harmonic currents of a parallel 48-pulse rectification system consisting of two rectifier transformers are completely cancelled out in theory.

Description

technical field [0001] The invention relates to the technical field of converting alternating current into direct current, in particular to a rectifying transformer for converting alternating current. Background technique [0002] In order to convert AC power to DC power, a rectifier transformer and a rectifier are usually used to form a rectifier circuit, as shown in Figure 1. The rectifier transformer and rectifier are collectively called a rectifier unit. Figure 1 shows a six-pulse bridge rectifier circuit. In an AC cycle, or within a 360° electrical angle, the DC voltage Vdc contains six pulsating ripples, and each ripple has an electrical angle interval of 60°. [0003] During the rectification process, the rectifier will send a large amount of harmonic current to the grid. In order to reduce the harmonic current delivered to the grid, one of the effective methods is to connect multiple rectifier units in parallel, and the voltage on the valve side of each transformer ...

AI Technical Summary

Problems solved by technology

Since the rectifier transformer axially splits the leakage magnetic impedance between the windings on the valve side to be large, and the number of turns of the star-shaped and delta-shaped windings is selected appropriately, the balance reactor may not be used between the parallel rectifiers; however, the star-shaped and delta-shaped windings on the valve side become The circulating current (or current unequal) between the rectifiers caused by the voltage difference causes the 24-pulse rectifier system to still deliver the fifth and seventh harmonic currents that cannot be offset to the grid

[0009] At present, there is still no feasible technical solution to realize the parallel 24-pulse rectification of a rectifier transformer with four sets of valve side windings, and to effectively control (or eliminate) the circulating current and the harmonic current sent to the power grid; The main restrictive factors are: among the four sets of valve side windings, the radially split winding has a small leakage magnetic impedance, and the transformation ratio voltage difference generated by rounding the turns of the star-shaped and delta-shaped windings produces a large parallel circulating current between the rectifiers, which can lead to rectification The unit cannot work normally and outputs large harmonic current to the grid

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