Design of a Single-Phase Quasi-Z-Source Asymmetric Cascaded Half-Bridge Multilevel Inverter

In this paper, a single-phase quasi-z-source asymmetric cascaded half-bridge multilevel inverter (qZS-ACHBMLI) is proposed, featuring a novel control scheme to achieve desired AC output voltage levels. The proposed inverter has a modular design, allowing for easy extension of output voltage levels by adding additional power modules. Unlike other multilevel inverters (MLIs), the proposed topology is designed as a half-bridge, so it is possible to generate an AC output voltage at the desired voltage level with a minimum number of switches. This reduces the size, cost, and complexity of the circuit. Besides, the proposed control algorithm enables the generation of negative voltage levels with a half-bridge polarity changer circuit. However, in the negative half cycle, the output voltage drops to zero as the polarity changer circuit provides a shoot-through (ST) condition to increase the output voltage. The robustness of the proposed topology and control method is validated through experimental results obtained from a 500 W, five-level qZS-ACHBMLI prototype, controlled by a 32-bit NUCLEO-F401RE microcontroller. The experimental findings demonstrate a significant improvement in energy efficiency compared with competing topologies.