Direct single-phase isolated improved gamma Z-source AC–AC converter suitable for DVR application

Abstract

A direct single-phase isolated improved gamma Z-source AC–AC converter is designed and manufactured in proposed paper. This converter contains an impedance source structure and its advantages. In general, these advantages are as follows. Firstly, the proposed structure has a wide range of output voltage as boost and buck as well as in-phase or out-of-phase states. Secondly, the proposed converter is electrically isolated thanks to a high frequency transformer (HFT), which significantly reduces the volume of the structure; therefore, in applications such as dynamic voltage restorer (DVR), there is no need to install a coupling transformer with the grid frequency which is very bulky and full of losses. Furthermore, the HFT of the proposed converter is a three winding transformer which also acts as the inductance needed for impedance source network. In addition, the safe commutation method has been utilized, which reduces the voltage spikes on the power switches. Finally, the analysis and design of this converter has been done, and then confirmed by a small-scale laboratory prototype.