Modeling and optimization of an integrated transformer for electric vehicle on-board charger applications

This paper proposes a systematic approach to model and optimize an integrated transformer for on-board chargers in electric vehicles. The proposed approach includes a comprehensive transformer loss model with accurate electromagnetic description of leakage inductance and optimization process. The multiobjective optimization using genetic algorithm is presented to optimize the performance-space variables, i.e., volume, weight, and losses, by appropriate selections of design-space parameters, i.e., winding specifications and core candidacies. Four sets of integrated transformers are optimally designed and compared in terms of the theoretical analyses; finite-element analyses and experimental performance. As verification to the proof-of-concept, the integrated transformers are implemented and tested on a 3.3-kW on-board charger prototype. It has been shown that the measured losses agree with the theoretical computation. The peak efficiency of CLLC stage with the optimal selection of transformer reaches 98.2%, achieving efficiency enhancement and temperature improvement in comparison to other feasible candidates.