PWM Voltage Quality Bounds of a Single-Phase Multilevel Converter

The paper presents simple closed-form analytical expressions for a single-phase multilevel PWM converter voltage quality upper and lower bounds. Voltage ripple Normalized Mean Square is used as a converter voltage quality figure of merit. The accurate upper bound for synchronous switching is delivered by the asymptotic estimate that assumes infinitely high switching frequency. The approximate lower bound is figured out for the minimum amount of switching that is a single switching between any two adjacent voltage levels. Voltage ripple Normalized Mean Square criterion represents, in the first approximation, normalized additional eddy current iron core loss in electrical machine, transformer, or filter / coupling inductor caused by converter switching that is a dominant PWM loss mechanism for relatively high switching frequencies. Comparison with PWM voltage quality theoretical lower and upper bounds may be useful for making a fair assessment of different switching strategies.