Estimation of Leakage Inductance in High-frequency Three-Winding Transformers for Electric Vehicle On-board Chargers

This paper reviews several methods to estimate the equivalent circuit model parameters of high-frequency three-winding transformers, considering measurement accuracy and tolerance to measurement errors. First, several equivalent circuit models of the three-winding transformer are reviewed and different methods to estimate the model parameters are investigated. A sensitivity analysis is performed to evaluate the accuracy of each method and its tolerance to measurement errors. In addition, transformer designs with E-cores and U-cores are simulated in ANSYS and their leakage inductance parameters are estimated for various winding arrangements. A three-winding transformer for EV charger application is simulated and the impact of the transformer model on the converter operation is discussed. Finally, a three-winding transformer prototype is built and tested to compare the accuracy of each estimation method with respect to the 3-D FE simulations. The comparison shows that methods based on one-port impedance measurements yield the most accurate estimation results.