Analysis of Reactive Power of Transformer Core with Subsynchronous Components

With the increase of subsynchronous oscillation phenomena and risks caused by long-distance wind power transmission systems, power transformers often operate with subsynchronous components, which causes asymmetrical bias magnetization of the core and leads to harmonic distortion and increase in reactive power. Aiming at this mixed time-frequency domain problem of power transformer reactive power with subsynchronous components, firstly, this paper established a 3D field-circuit coupling finite element model based on the fixed-point method to solve the magnetizing current. Secondly, the analysis method of transformer fundamental reactive power characteristics based on the maximum fundamental reactive power and average fundamental reactive power, and a transformer multi-frequency reactive characteristics analysis method based on the multivector power theory are proposed. Thirdly, the no-load experiment of a physical transformer model shows that the time-domain field-circuit coupling model proposed in this paper can accurately simulate the spectral characteristics of the significant components in the magnetizing current. Finally, through the simulation of this transformer, the fundamental reactive power characteristics and multi-frequency reactive power characteristics of the transformer are calculated and analyzed. © 2022 Chinese Machine Press. All rights reserved.