Improved Push-Pull Forward Three-Level Converter

Abstract

This paper proposes an improved push-pull forward (PPF) three-level (TL) converter. The proposed converter can operate in three-level and two-level modes. The flying capacitor can be removed by the proposed control. Four switches sustain only half of the input voltage, which can be clamped by the input divided capacitors. The others sustain one and a half of the input voltage in three-level mode and maintain the input voltage in two-level mode, so the voltage stresses of the switches can be reduced. As the freewheeling diodes connected with three-level legs are substituted for the MOSFETs to reduce the conducting loss, it is very fit for low and wide-range input voltage applications, such as fuel cell and solar cell. Operating principle is illustrated and verified by simulation.