To Örebro University

Inverters are a bridge for DC resources that want to supply AC loads. They can be connected to different resources such as batteries or solar panels on their DC side, and through their AC terminal, get connected to different types of AC loads and supply them. Due to the high flexibility in the layout design of multilevel inverters, these inverters are used widely in various applications. One of the most common applications of multi-level inverters is in microgrids, where DC resources with different characteristics and most probably, unstable voltage exists. In general voltage output of inverters, are problematic and might be not close to an ideal sinusoid. Using different types of resources for connecting them to the DC side of inverters, causes different harmonics that their amplitude and THD changes in the different situation. Considering real-world DC resources, where their voltage might change suddenly or overtime, the problem of controlling harmonics and THD dynamically is more significant. In this paper for overcoming these harmonics under instability, a new comprehensive algorithm has been introduced by using a closed-loop PI controller in multi-carrier power width modulation switching that can control the selected harmonics, or lower the produced THD, in both steady DC voltage and unstable situations such as voltage unbalancing of DC resources.