A Comparative Study of Modulation Strategies for Diode-Clamped Full-Bridge Three-Level Isolated DC/DC Converter

The diode-clamped full-bridge (FB) three-level isolated DC/DC converter (TL-IDC) is one of the most competitive candidates for the medium-voltage applications. Many modulation strategies have been proposed for the diode-clamped FB TL-IDC. However, there is no comparative study on theses modulation strategies. Consequently, this paper conducts a comprehensive comparison and analysis among main modulation strategies for the diode-clamped FB TL-IDC in terms of the duty cycle loss, ZVS range, transformer's voltage stress, power device currents, thermal performances, and converter's efficiency with the consideration of the types of the used power switch (i.e., MOSFET or IGBT) for the primary-side power switches. To verify the comparison and analysis results, an experimental prototype is built for implementing and testing these main modulation strategies. The outcomes of this paper can be considered as a reference for selecting the modulation strategy for diode-clamped FB TL-IDC applied in terms of different applications.