Multi-level Inverters For High-Power Industrial Drives

This paper presents a comparative analysis of three multi-level inverter (MLI) topologies — Neutral-Point Clamped (NPC), Flying Capacitor (FC), and Cascaded H-Bridge (CHB) — for driving high-power three-phase induction motors in the 1–10 MW class. Five-level configurations of each topology were modelled in MATLAB/Simulink and evaluated under identical load conditions (4-kW, 400-V, 50-Hz induction motor) with Phase-Shifted PWM and Level-Shifted PWM modulation strategies. The output voltage total harmonic distortion (THD), switching losses, conduction losses, and component count were compared across a modulation index range of 0.3 to 1.0. The CHB inverter achieved the lowest THD of 3.8% at a modulation index of 0.9, meeting the IEEE 519 harmonic limit without additional filtering. Switching losses were 20% lower in the CHB topology due to lower device voltage stress. The NPC topology offered the most compact solution for back-to-back converter configurations, while the FC design provided inherent fault tolerance through redundant switching states. These findings guide topology selection for specific industrial drive requirements.