**5. Conclusions**

This paper presents a new series resonant DC–DC converter with voltage boost capability achieved by using the output-side boost voltage-doubler rectifier. Contrary to the baseline topology, the proposed converter contains the resonant capacitor between the transformer secondary winding and the bidirectional switch. As a result, the proposed converter can operate in the range of low voltages and high currents where the baseline topology cannot operate at all. However, the proposed converter experiences higher voltage stress of the bidirectional switch than that of the baseline counterpart due to the influence of the resonant capacitor voltage ripple, which results in e fficiency reduction. Nevertheless, the proposed converter expends the input voltage and power operating range and achieves a peak e fficiency of 96.5%. The proposed converter was justified for the module-level PV applications as it is capable of performing the maximum power point tracking and covers a wide voltage range of possible maximum power points that could be observed under shading operation. The main implementation challenge of the proposed converter is related to the design of the isolating transformer. In cost-sensitive applications, it is advisable to integrate the resonant inductor into the transformer, which, however, could result in high proximity losses in the transformer windings. Therefore, future research will be focused on the optimization of the passive components of the converter.

**Author Contributions:** Conceptualization, A.B. and A.C.; methodology, A.B.; software, A.B.; validation, A.C. and A.B.; formal analysis, A.C. and A.B.; investigation, A.B.; resources, D.V.; data curation, A.C.; writing—original draft preparation, A.C. and A.B.; writing—review and editing, A.C. and D.V.; visualization, A.C. and A.B.; supervision, A.C.; project administration, A.C.; funding acquisition, A.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported in part by the Estonian Research Council gran<sup>t</sup> PSG206, and in part by the Estonian Centre of Excellence in Zero Energy and Resource Efficient Smart Buildings and Districts, ZEBE, gran<sup>t</sup> 2014-2020.4.01.15-0016 funded by the European Regional Development Fund.

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