An Improved Phase Shift Control to Reduce Current Stress for Dual Active Bridge DC-DC Converter

For the study of dual active bridge (DAB) dc-dc converters, current stress optimization is a crucial issue. Triple phase shift (TPS) control provides three degrees of freedom to minimize current stress. Therefore, this paper proposes a control strategy for optimizing current stress under TPS control. First of all, an accurate model to describe the analytical expression of the DAB converter under TPS control is proposed. Based on the influence of different voltage conversion ratios, the relationship between current stress versus phase shift ratio, voltage conversion ratio is derived. Thereby, minimizing the current stress is transformed into an optimization problem under the constraint of inequality. The transmission strategy is segmented for different power transmission ranges, and the optimal phase shift ratios in each power range are obtained. The result of minimizing the current stress over the whole power range is then derived. The simulation is carried on under MATLAB/Simulink. The simulation results show that compared with the traditional control method, the proposed optimal control strategy can significantly reduce the current stress, especially in the case of voltage mismatch. The simulation results confirm the theoretical analysis and practical feasibility of the strategy.