Sigma-Z-source inverters

To increase the boost capability with minimum passive components, existing transformer-based Z-source inverter (ZSI) topologies require the turn ratio to be increased. This results in larger transformer windings to be used in high dc–ac voltage gain applications. This shortcoming is addressed in this study by introducing a sigma-ZSI (ΣZSI) that improves the dc–ac voltage gain by reducing the turn ratio leading to a lower winding transformer. The proposed topology is compared with the TZSI as they used the same number of transformers and capacitors configured in an X-shaped network. The comparison shows that the ΣZSI will have a higher dc–ac voltage gain at a turn ratio lower than 1.618 for a given shoot-through duty cycle allowing the use of smaller transformers. Simulation and experimental results have validated the effectiveness of the proposed ΣZSI.