Efficiency Optimization of Dual Active Bridge DC– DC Converter with Triple Phase-Shift Control

The primary purpose of this paper is to obtain accurate analytical expressions of the dual active bridge (DAB) converter under the three-degree of freedom control technique. This technique, known as triple phase-shift (TPS) modulation, is utilized for the efficiency optimization of different operating zones and modes of the DAB. Three operating zones and modes have been retained to analyze the converter. Depending on the operating regions and due to the high nonlinearity of the obtained expressions, two optimization techniques have been used. The offline particle swarm optimization (PSO) method is utilized in local optimization (LO) and results in a numerical value. The Lagrange Multiplier (LM) is utilized in global optimization (GO) and results in a closed form expression. In the case of LO, the optimal duty cycles that minimize the power loss are not the optimal values for the minimum root-mean-square (RMS) current or peak current stress. Conversely, in the case of GO, the optimal duty cycles minimize the RMS, peak current and power loss at the same time for the entire power range. Detailed analyses and simulation results from MATLAB/Simulink are given to prove the effectiveness of the proposed method.