Transformer-based inverter with reduced number of switches for renewable energy applications

Multilevel inverters generate high-level voltage with high quality and low-harmonic distortion, and these unique properties have increased their applications in renewable energy sources. However, these inverters require several passive components and a complex pulse width modulation (PWM) control method. Besides, they suffer from voltage balancing problems. In this work, a new inverter has proposed that generates seven-level voltage from one DC source by reduced number of switches which does not exhibit any voltage balancing problem. The proposed inverter without any extra boost circuit is able to increase the input voltage. The voltage stress on all the switches in the proposed inverter is the same. In this study, variable amplitude phase disposition PWM control method that is compatible with the proposed inverter is developed. Moreover, extended structure of the proposed inverter and its new algorithm in generating all odd and even voltage levels are proposed. To validate the performance of the inverter, a prototype has been built and tested and also its performance has been modelled using PSCAD/EMTDC software package. Very good agreement has been achieved between experimental results and simulations.