Modulation strategy for wide-range ZVS operation of a three-level three-phase dual active bridge dc-dc converter

The modulation strategy proposed in this paper enables wide-range zero voltage switching (ZVS) operation of a three-level three-phase dual active bridge (DAB) dc-dc converter. The circuit topology is analyzed and piece-wise linear equations are derived for most appropriate switching modes. Based on the results of a numerical optimizer a modulation scheme is derived, utilizing analytic equations. Compared to optimal control variables, the proposed modulation scheme generates a higher transformer rms current for low power transfers, however, for high power levels it operates with a close-to-optimal transformer rms current. Simulations of the converter, obtained using the proposed modulation strategy, verify zero voltage switching (ZVS) operation and demonstrate an accurate power transfer for the full voltage range. Finally, experimental results, obtained from a high-power prototype, support the theoretical model and confirm correct operation of the proposed modulation strategy.