• Multilevel inverters use more than one dc voltage source or split a single voltage
source with a capacitor voltage divider to produce multiple voltage levels on the
output of an inverter.
• Pulse-width modulation (PWM) provides amplitude control of the fundamental
output frequency. Although the harmonics have large amplitudes, they occur at
high frequencies and are filtered easily.
• Class D audio amplifiers use PWM techniques for high efficiency.
• The six-step inverter is the basic switching scheme for producing a three-phase ac
output from a dc source.
• A PWM switching scheme can be used with a three-phase inverter to reduce the
THD of the load current with modest filtering.
• Speed control of induction motors is a primary application of three-phase inverters.