Advanced Single-Phase Nine-Level Converter for the Integration of Multiterminal DC Supplies

This paper presents a new symmetrical single-phase nine-level dc-ac converter for the applications of distributed generation systems. The proposed multilevel inverter (MLI) utilizes four independent dc sources to generate the nine output voltage levels considering a reduced number of switching devices. The proposed inverter consists of main and auxiliary circuits. The main circuit is a single H-bridge circuit, which is responsible for output voltage polarity. The auxiliary circuit consists of a special combination of switching devices, which are used to synthesize the multilevel output voltage. The merits of the proposed MLI are: increased output voltage levels at reduced number of switching devices, low switching loss, low total harmonic distortion, low dv/dt stress on the switches, and hence, low ratings of the switching devices, and low cost. The effectiveness of the proposed MLI and its pulsewidth modulation switching pattern has been verified experimentally by using a laboratory prototype controlled by DSPACE-1103.