Optimal Voltage-Balancing Compensator in the Modulation of a Neutral-Point-Clamped Converter

This paper presents an optimal voltage-balancing compensator for a particular type of modulation technique applied to the neutral-point-clamped converter. This modulation technique is able to completely eliminate low- frequency voltage oscillations in the neutral point. However, its dynamic for balancing voltages on the dc-link capacitors is slow. The proposed compensator generates an optimal offset for the modulation signals that improves significantly the voltage balancing issue for any operation condition of the converter. Furthermore, this strategy does not increase switching frequencies of the devices. The algorithm is tested and verified by simulation and experiment.