Optimal phase-shift control of three-level dual-active bridge DC–DC converter with minimum reflux power for wide voltage conversion ratio range application

摘要

Three-level dual-active bridge (3L-DAB) DC-DC converter under conventional phase-shift (CPS) control would produce large reflux power and current stress, especially when the voltage conversion ratio is varied in a wider range, which will lead to high power loss and low system efficiency. An optimised phase-shift (OPS) control strategy is proposed to control the 3L-DAB operating at the point with minimum reflux power. The power characteristics of 3L-DAB under CPS control are analysed. Then the mathematical model of the reflux power is established, and the relationship equations among the reflux power, phase-shift (PS) ratios, and voltage conversion ratio are deduced. The minimum reflux power and optimal PS ratio are calculated by using the segmentation optimisation algorithm in different ranges of transmission power and voltage conversion ratio. Performance comparative analysis between CPS and OPS controls is carried out later. Adopting the proposed OPS control strategy, the reflux power of 3L-DAB is minimised, as well as reducing the current stress and increasing the efficiency in a wide voltage conversion ratio range. An experimental prototype was developed to verify the effectiveness of the OPS control strategy and the correctness of the theoretical analysis.