Impact of Modulation Strategies on the Reliability and Harmonics of Impedance-Source Inverters

Impedance-source inverters, e.g., quasi-Z-source inverter (qZSI), with various modulation strategies have been explored in the literature to improve the inverter performance from different perspectives, such as high voltage gain, minimal inductor current ripple, and high efficiency. The modulation strategies can also significantly affect voltage/current stresses, power losses, thermal loading, and harmonics. Thus, this article presents a detailed analysis of the modulation effect on the reliability and harmonic performance of qZSIs. A comparative evaluation of current stresses, power losses, thermal stresses, number of cycles to failure of the power devices, and the output current harmonics is performed for various modulation strategies. Such comparative analysis enables the researchers to select the appropriate modulation strategy for the qZSI for their applications. Analytical expressions of current stresses and power losses are extracted for selected modulation strategies. Simulations and experiments are carried out to validate the analysis and comparison.