A Novel Simplified Single-Phase and Three phase Multi string Multilevel Inverter Topology for Distributed Energy Resources

The concept of multilevel inverters, introduced about 20 years ago entails performing power conversion in multiple voltage steps to obtain improved power quality, lower switching losses, better electromagnetic compatibility, and higher voltage capability. The benefits are especially clear for medium-voltage drives in industrial applications and are being considered for future naval ship propulsion systems. Several topologies for multilevel inverters have been proposed over the years; the most popular cascaded H-bridge apart from other multilevel inverters is the capability of utilizing different dc voltages on the individual H-bridge cells which results in splitting the power conversion amongst higher-voltage lowerfrequency and lower-voltage higher-frequency inverters. Considering the cascaded inverter to be one unit, it can be seen that a higher number of voltage levels are available for a given number of semiconductor devices. The simplified multilevel inverter requires only six active switches instead of the eight required in the conventional cascaded H-bridge multilevel inverter. In addition, two active switches are operated at the line frequency. The studied multistring inverter topology offers strong advantages such as improved output waveforms, smaller filter size, and lower electromagnetic interference and total harmonics distortion. Finally an asymmetrical configuration is proposed with this we are getting seven levels with six switches. Index items-Multistring inverter, DC/AC power conversion