A carrier based PWM technique for capacitor voltage balancing of single-phase three-level neutral-point-clamped converters

In this paper is presented a PWM technique for single-phase neutral-point-clamped converters for capacitors voltage balancing. The technique is based on the injection of a common mode voltage signal into the sinusoidal modulating signals of the conventional carrier-based pulse width modulation. Although several strategies have been reported for such a problem by using the voltage signal injection, the proposed method is very simple with easy implementation. It is presented a set of equations to demonstrate how the injected voltage signal introduces a dc component on the neutral-point current, which can be controlled in order to allow the capacitors voltages balancing. Selected results have been used demonstrate the effectiveness of the proposed strategy.