Cascade dual-buck full-bridge inverter with hybrid PWM technique

This paper presents a new type of cascade inverter, named cascade dual-buck full-bridge inverter. Compared to cascade H-bridge inverter, the proposed inverter has several advantages. First, it eliminates the possibility of shoot-through problems, which is the major failure of traditional voltage source inverters. Second, it does not need dead time, which fully utilizes the pulse width modulated voltage and transfers total desired energy to the load. In addition, it can use high-voltage power MOSFETs without the complexity of soft-switching assisting circuits to improve the system efficiency. In this paper, several PWM techniques are analyzed and compared, including bipolar PWM, unipolar PWM and phase-shifted PWM, when applied to the proposed inverter. It has been found out that a hybrid PWM technique with the combination of the two out of the three PWMs mentioned above leads to better performance of the cascade dual-buck full-bridge inverter in terms of less output current ripple and harmonics, no zero-crossing distortion, and higher efficiency. A prototype of the proposed inverter has been built and tested to verify the feasibility and effectiveness of the topology and the hybrid PWM technique.