Transformer-based multilevel inverters: analysis, design and implementation

In this study, a single-phase nine-level inverter using one transformer is proposed. The proposed inverter can generate nine levels with a reduced number of components by utilising one dc voltage source. Based on a four-arm power module, the voltage stresses on all the power switches are the same, making the proposed inverter be easy to construct. The proposed structure has ability to increase the output voltage with no need of any auxiliary boost system. Other features of the proposed structure are its extendibility to generate high number of levels. For this case, the optimum values of the turns ratio of the transformers for the developed structure are presented to generate maximum number of voltage levels for a given number of switches. Moreover, the proposed structure has low cost and volume in comparison with the relevant structures. In order to verify the performance of the proposed multilevel inverter, a prototype has been built and tested.