Journal of Modern Power Systems and Clean Energy

ISSN 2196-5625 CN 32-1884/TK

An Improved Modulation Strategy for Single-phase Three-level Neutral-point-clamped Converter in Critical Conduction Mode

1.School of Electrical Engineering, Xi’an University of Technology, Xi’an, China;2.Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy;3.Xi’an Jiaotong University, Xi’an, China;4.Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, U.K.;5.Department of Electronic, Electrical and Systems Engineering, University of Birmingham, Birmingham, U.K.

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This work was supported in part by National Natural Science Foundation of China (No. 52177193) and in part by China Scholarship Council (CSC) State Scholarship Fund International Clean Energy Talent Project (No. [2019]157).

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    Two-level totem-pole power factor correction (PFC) converters in critical conduction mode (CRM) suffer from the wide regulation range of switching frequency. Besides, in high-frequency applications, the number of switching times increases, resulting in significant switching losses. To solve these issues, this paper proposes an improved modulation strategy for the single-phase three-level neutral-point-clamped (NPC) converter in CRM with PFC. By optimizing the discharging strategy and switching state sequence, the switching frequency and its variation range have been efficiently reduced. The detailed performance analysis is also presented regarding the switching frequency, the average switching times, and the effect of voltage gain. A 2 kW prototype is built to verify the effectiveness of the proposed modulation strategy and analysis results. Compared with the totem-pole PFC converter, the switching frequency regulation range of the three-level PFC converter is reduced by 36%, and the average switching times is reduced by 45%. The experimental result also shows a 1.2% higher efficiency for the three-level PFC converter in the full load range.

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  • Received:April 03,2023
  • Revised:October 11,2023
  • Adopted:
  • Online: May 20,2024
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