A Dual Modulation Waveform PWM Combined With Phase-Shifted Carriers in Stacked Multicell Converter

This article proposes a hybrid dual modulation waveform pulsewidth modulation (DMW-PWM) strategy for 5L-SMC. The driver signals of each cell are generated by comparing dual modulating waves and two phase-shifted carriers, respectively. The voltage natural-balancing characteristic of both the floating capacitors and dc-link capacitors with the proposed DMW-PWM is derived. The proper active voltage balance control strategy is also presented to regulate the voltages of neutral point and floating capacitors. With this strategy, the voltage balancing of dc-link capacitors and floating capacitors is achieved simultaneously with the complete elimination of low-frequency ripples in neutral point. Compared with the conventional DMW-PWM method (also called the fast processing modulation method), the proposed method has a smaller voltage fluctuation in floating capacitors, better dynamic performance, lower switching frequency, and simply digital implementation. The superiority of the proposed method is verified by experimental results.