Evaluation of Modulation Strategies for Single-Phase Quasi-Z-Source Inverter

Abstract

Quasi-Z-source inverter has the ability to provide boost and DC–AC conversion of the input voltage in a single stage. The impedance network of the quasi-Z-source inverters offers unique advantages such as lower component ratings, constant DC current from source and capability to handle wide input voltage. Cascaded multilevel inverters are preferred as they are transformerless and modular and provide lower harmonics. The advantages of both are combined in five-level quasi-Z-source cascaded multilevel inverter, and the various modulation strategies applied to it are investigated in this paper. This paper focuses on phase-shifted pulse width modulation with simple boost, maximum boost and maximum constant boost control, phase-shifted pulse width amplitude modulation and hybrid pulse width modulation. Simulation of single-phase five-level quasi-Z-source cascaded multilevel inverter with the above-mentioned strategies has been carried out in MATLAB/Simulink. A hardware prototype of the five-level qZS-CMI has been developed. The PS-PWAM pulses have been implemented through FPGA/Spartan 3E, and the results are validated.