Carrier-based PWM strategies for the comprehensive capacitor voltage balance of multilevel multileg diode-clamped converters

Abstract

This paper presents four carrier-based PWM strategies for diode-clamped converters of any number of levels and any number of legs (phases). These carrier-based PWM strategies guarantee the dc-link capacitor voltage balance in every switching cycle without the need of additional hardware and with low dc-link capacitance values for any modulation index and load, provided that the sum of leg currents equals zero. The performance of the presented carrier-based PWM strategies, in terms of dc-link capacitor voltage balance and total harmonic distortion in the output line-to-line voltages, is evaluated through simulation, showing a tradeoff between the simplicity of the carrier-based PWM implementation and its total harmonic distortion performance.