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Multilevel inverters are being preferred over conventional two-level voltage source inverters in medium-voltage high-power applications. The cascaded H-bridge configuration of multilevel inverters is widely used because of its ability to generate near sinusoidal output waveforms, modular structure, simple power circuit and high reliability. The cascaded H-bridge inverter is an ideal choice for systems where isolated DC sources are readily available. The objective of this study is to extend the attractive features of the cascaded H-bridge voltage source invertes (VSI) to low-voltage and low-power applications. The details of the design of a power supply for distribution voltage levels are presented. The design is verified through simulation and experiments. A laboratory prototype of a 15-level MOSFET-based cascaded H-bridge inverter is designed and the experimental results are presented. The proposed inverter configuration is capable of generating low distortion, near-sinusoid stepped output voltage even with fundamental frequency switching. The total harmonic distortion (THD), switching losses, fault-tolerant feature of the proposed multilevel inverter-based power supply is compared with that of the conventional two-level inverter-based power supplies. The comparative results demonstrate the advantages of the proposed system over the conventional system.
Date of Publication: July 2012