What are multilevel inverters and why are they used?

Multilevel inverters synthesize output voltage using multiple DC levels, producing a staircase waveform closer to sinusoidal than two-level inverters. Common topologies: Neutral-Point-Clamped (NPC), Flying Capacitor, and Cascaded H-Bridge. Advantages include: lower harmonic content (reduced filter size), lower dv/dt stress on motor insulation, lower switching losses (each device switches at line frequency), and ability to use lower-voltage devices for high-voltage applications. Used in medium-voltage drives, FACTS devices, and large solar inverters.