Three-phase four-level inverter with capacitor voltage self-balancing and high DC-voltage conversion ratio

Multilevel inverters are widely employed in industry application due to their low voltage-variation rate and little current distortion. However, capacitor-voltage regulation adds the complexity of their modulation, and the low DC-voltage conversion ratio restricts their application in some specific occasions. Here, a new three-phase four-level inverter with switched-capacitor circuits and full-bridge circuits is proposed to address the above issues. In addition, a corresponding space-vector diagram is proposed to control the power switches of the inverter. In this space-vector diagram, each subsector includes only a switching sequence, which is simpler than the conventional one. Then, simulation and experimental platforms are established to demonstrate the validity of the proposed inverter. The obtained results show that the proposed inverter can meet the expected design requirements.