Voltage quality bounds of multilevel converters

Multilevel converters feature a staircase voltage waveform, resulting in a high voltage quality. By a practical time domain approach, upper and lower bounds of the voltage quality can be derived as closed form analytical expressions. The voltage quality bounds are introduced for single- and three-phase converters with an arbitrary number of voltage levels and for different modulation indices. PWM voltage quality comparison with the theoretical lower and upper bounds is useful for a fair assessment of different switching strategies and for an improved converter control. The analytic definitions for the voltage quality bounds allow the use in everyday engineering practice.