Novel Modular Multilevel Inverter Structures with Reduced Components for Medium Voltage Applications

Multilevel inverters (MLIs) are increasingly prominent in medium-voltage and high-power applications due to their ability to produce output voltages with reduced harmonic distortion and lower device blocking voltage. By employing isolated voltage sources, clamping diodes, and flying capacitors, MLIs generate terminal voltages in incremental steps, mimicking a sinusoidal waveform. However, the cascaded structure often requires a higher number of power components as voltage levels increase, resulting in elevated implementation costs. To address these challenges, this article introduces two novel modular MLI structures that utilize fewer semiconductor switches and DC sources to achieve the desired voltage levels efficiently. Each structure employs four DC sources and a reduced number of switches to synthesize stepped voltages at the load terminals, providing a cost-effective and modular solution. The feasibility of the proposed structures is demonstrated through a detailed comparison with recent reduced-component MLI configurations in terms of controllable switches, gate isolators, current-conducting switches, and power loss. The designs are validated using MATLAB/Simulink simulations, and their practicality is confirmed through real-time performance analysis using a laboratory prototype. The results show strong agreement between simulated and experimental findings, confirming the proposed designs' effectiveness.