Zero-voltage-switching PWM Full-bridge Three-level Converter

The most important advantage of the three-level (TL) converter is that the switches sustain only the half of the input voltage with the reduced output filter inductance, so it is very suitable for high voltage applications. Full-bridge (FB) converter is widely used in high power industrial applications. Thus,the FB TL converter will inherit the merits of both the TL converters and FB converters. However, due to the eight power switches in the FB TL converter, the efforts need to be concentrated on obtaining the optimal modulation strategy of the converter. This paper proposes a chopping plus phase-shift (CPS) control for the FB TL converter. The operation principle and characteristics of the FB TL converter are analyzed and verified experimentally. In order to avoid the unequal voltage stress of the switches due to the asymmetrical driving of the switches, the flying capacitor and the two clamping diodes are introduced and verified experimentally. In order to reduce the loss of MOSFETs' body diodes, a novel double phase-shift (DPS) control for the FB TL converter is proposed, which improves efficiency by reducing loss of switches' body diodes meanwhile maintains the converter's original advantages without adding additional components compared to the CPS control. The operation principle is verified experimentally. In addition, the concept of the DPS control is extended to hybrid FB converter and FB multilevel converter.