Optimization of a Multilevel Inverter Design Used for Photovoltaic Systems under Variable Switching Controllers

Abstract

Among multilevel inverters (MLIs), two-level inverters are the most common. However, this inverter type cannot maintain total harmonic distortion (THD) due to its limited number of levels. Reductions in THD are inversely proportional to the number of levels where increased output occurs in diverse ways, and the use of fewer components with low harmonic distortion is necessary for such reductions. This work proposes a seven-level (7L) MLI design with a small number of components and low harmonic distortion. The proposed MLI is combined with switched capacitor (SC) cells to promote output levels and at the same time to boost the input voltage. The connections between the capacitor and the source are based on the series to parallel topology, where the charging and discharging of the SC cells are caused by fluctuations in their connection. The output of the SC cell is combined with an H-bridge inverter controlled by a proposed PWM controller. The simulation result of the SC 7L inverter was completed using LTspice software. A comparison of the proposed topology with that of other current MLI led to better validation results. The proposed design shows a reduction in the THD with fewer components. The cost and size of the proposed inverter is minimal due to the smaller number of components. Ohmic load and inductive ohmic load were used as loads for the system.