**7. Conclusions**

This paper introduces a hybrid multimodule DC-DC converter for EV UFC to achieve both high efficiency and high power density. The hybrid concept is achieved through employing two di fferent groups of multimodule converters. The first is designed to be in charge of a high fraction of the total

required power, operating relatively at a low switching frequency. While the second is designed for a small fraction of the total power, operating relatively at a high switching frequency. To support the power converter controller design, a generalized small-signal model for the hybrid multimodule DC-DC converter is studied in detail. This in turn supports the analysis and control design. In addition, the e fficiency and power density for the conventional multimodule DC-DC converter based on the primary group, conventional multimodule DC-DC converter based on the secondary group as well as the presented hybrid DC-DC converter are evaluated. In which it has been shown that the presented converter can achieve both high e fficiency (99.6%) and high power density (10.3 kW/L), compromising between the two other conventional converters. Since the power switches are the key contributors to the losses and the volume of the overall converter. It is worth mentioning that the assessment provided in this paper takes into account the conduction losses and the volume of the semiconductor switches, assuming that the converters are operating under zero voltage switching (ZVS). Furthermore, cross feedback output current sharing (CFOCS) for the hybrid input-series output-parallel (ISOP) multimodule DC-DC converters to ensure uniform power-sharing among the employed modules and the desired fraction of power handled by each multimodule group is examined. The control scheme for a hybrid eight-module ISOP power converter of 200 kW is investigated. The controller is tested with a reference current that relies on reflex charging scheme. The power loss analysis of the hybrid multimodule converter is provided. Simulation results using the MatLab/Simulink platform are provided to elucidate the presented concept considering parameter mismatches. Simulation results show that the modular input voltage and the modular output current are equally shared among the four modules of each group with the required ratio between the two multimodule groups. Numerical calculation in terms of losses is carried out for the presented converter considering conduction losses of the power switches.

**Author Contributions:** M.E. and A.M. contributed to the whole research work and analysis tools; M.E. wrote the paper. This work was performed under the supervision with regular and continuous feedback of A.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by NPRP gran<sup>t</sup> NPRP (10-0130-170286) from the Qatar National Research Fund (a member of Qatar Foundation).

**Acknowledgments:** This work was supported by NPRP gran<sup>t</sup> NPRP (10-0130-170286) from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.

**Conflicts of Interest:** The authors declare no conflict of interest.
