Analysis of Electromagnetic Transient Characteristics on the Winding of UHVDC Converter Transformers Based on an Improved Broadband Model

This work proposes an improved broadband equivalent circuit model of the winding system of an ultrahigh-voltage direct current (UHVDC) converter transformer and the validation experiment of the model conducted on a tapped transformer. The matrices of the inductance, capacitance, and resistance parameters in the improved model were all obtained by the finite element method according to the winding system structure of a UHVDC transformer. Then, the potential distributions along the windings under impulse voltages with different waveforms were studied in detail. Finally, the relationship between the potential gradient and waveforms was obtained. This work provides a convenient method to acquire the broadband electromagnetic transient characteristics of the winding systems within UHVDC converter transformers.