Three-level boost inverter with capacitor voltage self-balancing and high conversion efficiency for low DC voltage systems

Currently, Z-source networks are widely employed to extend the output-voltage range of inverters operating at a low voltage DC source. However, these inverters are troubled by low power-conversion efficiency and an obvious current distortion due to the copper losses and core losses of the inductors. In addition, they have limited voltage levels. In this paper, a novel boost network composed of two power switches, two capacitors, and two diodes is proposed to overcome these shortcomings. Meanwhile, a corresponding modulation strategy is also set forth to achieve capacitor voltage self-balancing and to regulate the output AC voltage. Moreover, by adding more switched-capacitor cells, the range of the output voltage can be further improved, and the max DC/AC-voltage conversion ratio of the inverter with n cells is √3( n + 1)/3. At last, an inverter prototype with a 1 kW power rating is built, and the obtained results demonstrate that this inverter possesses the following superiorities: a wider range of output voltage, automatic balancing of the capacitor voltage, less current distortion, and high-efficiency power conversion.