Optimal Simultaneous PWM Control for Three- Phase Dual-Active-Bridge Converters to Minimize Current Stress in the Whole Load Range

In order to reduce the current stress and improve the efficiency of three-phase dual-active-bridge (3p-DAB) converters in the whole load range, in this article, a simplified derivation based on a segmented analytical method is proposed to obtain an optimal simultaneous pulsewidth-modulation (PWM) control scheme. First, the average transferred power and the current stress of the 3p-DAB at different modes can be calculated based on the segmented analytical method. Second, in the light of the expressions of current stress and average transferred power of the 3p-DAB, the current stress minimization problem can be transferred into inequality constraints’ issues for different modes. The optimization process is derived step by step and the closed-form analytic expression of the optimal control strategy is presented. Then, a simple table of the global optimal control scheme that minimizes the current stress under buck or boost operating scenarios can be obtained. Furthermore, a closed-loop control structure is designed to implement the optimal simultaneous PWM control in practice. Finally, experimental comparison with existing modulation schemes has been implemented on a laboratory prototype to verify the theoretical analysis and the outstanding performance of the proposed strategy.