Single-Carrier Phase-Disposition PWM Implementation for Multilevel Flying Capacitor Converters

Abstract

This letter proposes a new implementation of phase-disposition pulse-width modulation (PD-PWM) for multilevel flying capacitor (FC) converters using a single triangular carrier. The proposed implementation is much simpler than conventional PD-PWM techniques based on multiple trapezoidal-shaped carriers, generates the same results as far as natural capacitor voltage balance is concerned and offers better quality line-to-line voltages when compared to phase-shifted PWM. The proposed algorithm is based on reshaping the reference signal to fit within the range of a single carrier and assigning each crossing of the reference signal with the carrier to a particular pair of switches at any time. The proposed algorithm is suitable for digital implementation taking maximum benefit from the PWM units available in the processor. Simulation and experimental results are presented from the five-level FC converter to verify the proposed PD-PWM implementation.