Comparative Analysis and Optimization of Triple Active Bridge Transformer Configuration With Integrable Leakage Inductance

This article discusses an extensive analytical modeling as well as simulation and experimental result based investigative study on the realizable configurations of the three-winding transformer for a triple-active-bridge (TAB) converter with controllable leakage inductance feature. The requirements for a TAB transformer are also analyzed in detail by relating the leakage inductances with the maximum power transfer criteria and the achievable soft-switching range. Following this, three different winding structures, containing one symmetric and two asymmetric winding formations that are deemed appropriate for a TAB transformer design are thoroughly investigated and optimized for the design requirement. Also, precise analytical formulation of the transformer parameter such as leakage and magnetizing inductances, winding, and core losses is comprehensively carried out. The close agreement with a ~7% error margin between the mathematically obtained transformer parameters and the finite element method (FEM) simulation derived dataset upholds the accuracy of the proposed methodology. All the winding arrangements discussed in the article, are designed, fabricated, and tested in the laboratory with an experimental set-up of a 1.2 kW TAB converter supplying two loads at nominal voltages of 120 and 22 V, respectively. The experimental results reinforce the claims made by the analytical models, by reporting a converter efficiency benefit of 1% and 3.6% at full load and 50% loading condition, respectively, under the application of the proposed winding configuration over the conventional central limb wound transformer design.