A Dual PWM Modulation for Three-level Half Bridge Dual Active Bridge Converter

Aimed at the problem of large backflow power in three-level half bridge Dual Active Bridge DC-DC converter, a control modulation based on pulse-width modulation plus phase shift with three control degrees is presented in this paper. According to the position of port voltages of the converter, the whole operation is segmented into twelve modes in time domain. Then the transmission power, zero voltage switching conditions and backflow power at the forward transmission mode are analyzed in detail. Among the feasible modes, only four modes can achieve the minimum backflow power while meeting the requirements of zero voltage switching. Then the KKT conditions and graphic approaches are adopted to optimize the objective, that is, backflow power in these four selected modes. Finally, the presented scheme is validated by simulation.