Improved High-frequency Model of the Converter Transformer in UHVDC System

For an ultra-high voltage direct current (UHVDC) transmission system, this paper describes an improved high-frequency model of the converter transformer. Firstly, the transient model of the converter transformer with integrated leakage inductance and distributed capacitance is introduced. Secondly, based on the actual winding structure unit of a UHVDC converter transformer and the transient model mentioned before, the improved high-frequency model of the converter transformer is proposed. Then, based on the improved model mentioned previously, a ±800 kV UHVDC system is built in PSCAD/EMTDC. The results show that the transmission characteristics of converter transformer obtained by simulation is nearly consistent with the measured ones, and the accuracy of the improved model is proved. Finally, the improved model is applied to a ±1100 kV UHVDC system built in PSCAD, and the AC system-side noise of the converter transformer obtained by simulation can be adopted for the optimal design of the power line carrier (PLC) filter.