A Study on High Quality Single-Phase Seven-Level Grid-Connected Inverter Department of Electrical Engineering Graduate School, Chonnam National University - Le Tuan Vu

(Abstract)
Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. Multilevel inverters include an array of power semiconductors and capacitor voltage sources, the output of which generate voltages with stepped waveforms. The commutation of the switches permits the addition of the capacitor voltages, which reach high voltage at the output, while the power semiconductors must withstand only reduced voltages. There are three commonly topologies have been proposed for multilevel inverters: diode-clamped (neutralclamped); capacitor-clamped (flying capacitors); and cascaded multicell with separate dc sources. The most attractive features of multilevel inverters are that they can generate output voltages with extremely low distortion, they draw input current with very low distortion and they can operate with a lower switching frequency.
LINK
http://www.mediafire.com/file/4c4wv4gq7t47141/HIGH_QUALITY_SINGLE_PHASE_SEVEN_LEVEL.pdf