PROJECT TITLE :

Optimal Phase Shift Control to Minimize Reactive Power for a Dual Active Bridge DC-DC Converter

ABSTRACT:

Under non-unity voltage gain conditions, modulating the phase shift ratios in a dual active bridge (DAB) dc-dc converter can reduce reactive power and boost efficiency. Because a DAB can run in four different scenarios (forward/backward, buck/boost) and each scenario has five operating modes, determining the best phase-shift ratios to yield the smallest reactive power is difficult. DAB operational scenarios (forward/backward, buck/boost) can be transformed into one another so that only one scenario (forward/buck) is needed to be optimised. Using a graphic method, this study demonstrates that each operational point of modes 1, 2, and 5 can be translated into Mode 3 with lower conduction losses, and only two modes need to be studied further. In order to optimise these two modes, the method is broken down into stages. Optimal phase-shift signals that reduce reactive power for four different DAB operating scenarios (forward/backward, buck/boost) have been described. Global reactive-power minimization control can be implemented using a simple table and control block diagram. The proposed control mechanism has been proven to be more efficient when compared to existing modulation schemes.