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Transformerless Three-Level DC-DC Buck Converter with a High Step-Down Conversion Ratio

  • Zhang, Yun (School of Electrical Engineering and Automation, Tianjin University) ;
  • Sun, Xing-Tao (School of Electrical Engineering and Automation, Tianjin Polytechnic University) ;
  • Wang, Yi-Feng (School of Electrical Engineering and Automation, Tianjin University) ;
  • Shao, Hong-Jun (School of Electrical Engineering and Automation, Tianjin University)
  • Received : 2011.12.11
  • Published : 2013.01.20

Abstract

For high power high step-down dc-dc conversion applications, conventional three-level dc-dc converters are subject to extreme duty cycles or increased volume and cost due to the use of transformers. In this paper, a transformerless three-level dc-dc buck converter with a high step-down conversion ratio is proposed. The converter comprises two asymmetrical half bridges, which are of the neutral point clamped structures. Therefore, the output pulse voltage of the converter can be obtained in terms of the voltage difference between the two half bridges. In order to realize harmonious switching of the converter, a modulation strategy with capacitor voltages self balance is presented. According to the deduced output dc voltage function, transformerless operation without extreme duty cycles can be implemented. Experimental results from a 1kW prototype verify the validity of the proposed converter. It is suitable for ship electric power distribution systems.

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