Dual-Active-Bridge Isolated DC-DC Converter with Variable Inductor for Wide Load Range Operation

This article explores the use of a variable inductor as a reactive element for energy transfer in a dual-active-bridge (DAB) converter. By using a controlled variable inductor, the optimal switching region in the operation of the phase-shift DAB can be extended, and thus, high efficiencies can be achieved over wider load ranges compared to the traditional solution. Moreover, the combined use of the variable inductance together with the phase shift, as two control parameters, allows for the linearization of the DAB converter transfer function, which improves the stability and the performance of the controller. And finally, due to the controlled saturation of the device, it is feasible to reduce the magnetic core size, yielding a size optimization of the full converter. This article develops a circuit-based model to simulate the converter system, aiming to study the proposed improvements. Furthermore, a 2-kW SiC-based DAB converter prototype is constructed, including a controlled variable inductor. The experimental results presented in this article validate the studies carried out for the different operation conditions.