Transformer DC magnetic bias suppression system and suppression method

Abstract

The invention discloses a transformer DC magnetic bias suppression system and suppression method. In the DC magnetic bias suppression system, a primary side three-phase winding of the transformer is athree-phase star connection; the DC magnetic bias suppression system further comprises a three-phase DC magnetic bias suppression winding, a rectifier circuit, an AC power supply, a detection moduleand a control system, the phase windings of the three-phase DC magnetic bias suppression winding respectively correspond to a common core of the phase windings of the primary side three-phase winding,the winding directions are opposite, the phase windings of the three-phase DC magnetic bias suppression winding have equal numbers of turns of winding, the head and the tail of the three-phase DC magnetic bias suppression winding are connected to form an open triangle connected to a DC end of the rectifier circuit; an AC end of the rectifier circuit is electrically connected with the AC power supply; and the control system controls that the DC magnetomotive force generated by the three-phase DC magnetic bias suppression winding to be equal to the DC magnetomotive force of the primary side three-phase winding, and that the directions are opposite. The transformer DC magnetic bias suppression system disclosed by the invention has the advantages of simple structure, easy control, no influence on the neutral point grounding and the protection device of the transformer, high cost performance and high practicability.

Description

technical field [0001] The invention belongs to the field of transformer DC bias suppression, in particular to a transformer DC bias suppression system and suppression method. Background technique [0002] In recent years, the problem of transformer DC bias has attracted more and more attention. The reasons for transformer DC bias problems under different operating environments are as follows: 1) The main reasons for the DC bias of converter transformers are: the firing angle of the converter is unbalanced during normal operation; the power frequency current flows through the DC line; the converter station Positive-sequence second harmonic voltage appears on the AC busbar; the ground potential of the converter station rises due to current injection into the ground electrode during single-pole return operation. 2) The change of the geomagnetic field caused by the solar magnetic storm phenomenon produces a low-frequency (0.001Hz~1Hz) geomagnetic induction current close to DC,...

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Problems solved by technology

3) The urban subway adopts DC power supply, and there is a DC current leaked from the rail to the ground. The leaked DC current is injected into the three-phase winding through the neutral point grounding pole of the transformer, so that a DC component appears in the winding, resulting in DC bias

At present, the device still has some shortcomings: 1) It does not eliminate the DC current, but only leads the DC current to other transformers without DC blocking devices; 2) The capacitors in series have large capacity, occupy a large area, and are expensive; 3) The capacitors are two There may be a danger of explosion due to a large current at the terminal due to lightning strikes and other reasons; 4) DC blocking capacitors are used in normal conditions, and the bypass switch needs to be quickly used to ground the neutral point of the transformer when a fault occurs. The control is complicated and the reliability of fault protection is reduced. 5) Changing the zero-sequence impedance will have an impact on relay protection, insulation coordination, etc., and the protection setting needs to be reset

[0006] The above methods all install additional devices on the neutral point of the transformer to weaken or block the DC current at the neutral point of the transformer. The structure and control are complicated, and it will affect the neutral point grounding and protection devices of the transformer, and the practicability is low.

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