Asymmetrically Switched CHB Multilevel Inverters with Harmonic Mitigation Techniques Applied to Photovoltaic Power Generation

Abstract

For the last few years, Multilevel Inverter (MLI) researchers have been motivated to reduce the component count in a significant manner by keeping the output level generation the same or increasing enough to be noticed. In this work asymmetrically switched Cascaded H Bridge (CHB) multilevel inverters with fundamental frequency switching are proposed for photovoltaic (PV) applications. Essentially different types of asymmetrically switched improved CHB topologies are discovered in brief and compared with necessary figures of merits including scaled versions. It is an approach to design different levels of voltages with the same number of switches and reduced device count. This paper reports different types of harmonic mitigation techniques, where the best switching angle optimizations are proposed to generate different levels. Moreover, the performance of the topologies is evaluated through THD minimizations by reducing the lower order harmonics. A few combinations of DC voltage sources are used from PV panels/batteries as input to the inverters for generating different output levels and THD is compared for different mitigation techniques. Theoretical calculation of THD is also shown and compared to simulation results for the proposed inverters. The proposed and simulated inverters are verified and tested though hardware in loop (HIL) implementation. As MLI needs compact filter requirements and better quality of output THD, this kind of proposed CHB inverters is suitable for medium and high power PV applications especially grid-tied PV inverters.