Reactive power adjustment scheme of series transformer in unified power flow controller under DC magnetic bias

Abstract

The invention belongs to the technical field of transformers, and particularly relates to a reactive power adjustment scheme of a series transformer in a unified power flow controller under DC magnetic bias. The reactive power adjustment scheme comprises the steps of firstly building a magnetic circuit model according to a spatial geometry structure of the series transformer; calculating magnetic resistance of iron cores in different areas by adopting effective magnetic permeability and listing a magnet circuit equation; obtaining a coupled equation by combining a circuit equation of an external port of the transformer; carrying out discretization processing on a differential equation by adopting a theta integral method and calculating exciting current under asymmetric magnetic bias by adopting a Newton-Raphson method; carrying out harmonic decomposition on the exciting current; calculating reactive power of the series transformer under the asymmetric DC magnetic bias by combining subharmonic components of the exciting current and winding induction voltage; and feeding back a change of the reactive power of the series transformer in a magnetic bias state to a converter valve and improving the precision of voltage regulation through adjusting output of the reactive power. The reactive power adjustment scheme is high in calculation speed and wide in application range, and has very high practical application value.

Description

technical field [0001] The invention belongs to the technical field of transformers, and in particular relates to a reactive power adjustment scheme of series transformers under DC bias in a unified power flow controller. Background technique [0002] The series transformer is one of the key equipment of the Unified Power Flow Controller (UPFC) device. Its grid-side winding is connected in series with the transmission line, and its valve-side winding is connected to the converter valve. Its function is to inject a same-frequency voltage source with controllable amplitude and phase angle into the transmission line based on the voltage output by the converter valve, exchange reactive power and active power with the transmission line, and compensate the resistance of the transmission line pressure drop. [0003] Due to the inaccurate triggering angle of the power electronic switches of each phase in the converter valve, there will be a DC component generated and flowed into th...

AI Technical Summary

Problems solved by technology

This three-phase asymmetrical DC bias will cause irregular distortion of the excitation current of each phase winding, which will lead to different degrees of increase in reactive power loss of each phase winding of the transformer and increase the difficulty of voltage regulation.

And compared to the DC bias caused by the geomagnetic induction current (GIC) and the high-voltage direct current transmission (HVDC) flowing into the transformer through the grounded neutral point, the problems caused by the three-phase asymmetrical DC bias tape of the series transformer are more complicated. This makes it difficult for the series transformer to achieve precise regulation of the voltage

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