Calculation method for parasitic capacitance of high-frequency transformers

High-power multi-port converters can have high-frequency oscillations that seriously threaten system reliability, with the parasitic capacitance of the high-frequency transformers (HFTs) being one of the important factors. This paper summarizes the existing methods for calculating the parasitic capacitance of solid wires and litz wires and presents a piecewise solution method based on the electric field lines between solid wires to calculate the HFT parasitic capacitance. This study also corrects the shortcomings of the existing analysis method for litz wires. The analytical method for calculating the parasitic capacitance for typical C-type and Z-type winding arrangements and arbitrary multi-turn, multi-layer winding arrangements is re-derived taking into account the influence of the isolation layer in high-voltage, high-capacity transformer windings. Comparisons with finite element predictions and experimental data verify the accuracy of this method as a foundation for calculating the parasitic capacitance of HFTs for system design and analyses. © 2021, Tsinghua University Press. All right reserved.