Voltage Balancing Control of Hybrid Stacked Multicell Converters Based on Modified Phase-Shifted PWM

The hybrid stacked multicell converter (HSMC) is a competitive converter in the low-voltage high-efficiency applications. Proper modulation and voltage balancing control are important for the operation of the HSMC, which may ensure the HSMC to obtain high-quality output and low power losses. A hybrid phase-shifted PWM (PS-PWM) with the modified reference signal is developed for nine-level HSMC (9L-HSMC), and the neutral point voltage can be naturally balanced in a fundamental cycle. Based on the hybrid PS-PWM, an active voltage balancing control is put forward for the flying capacitor (FC). The voltage balancing of FC is implemented by slightly modifying the reference signals to adjust the duty cycles of the high-frequency switches symmetrically. This method does not need complex calculations, and it can be easily extended to higher level HSMC and other FC-based configurations. The simulations are carried out to validate the merits of low power losses and superior power quality. A downscale experimental platform of a 9L-HSMC is a setup to verify the effectiveness of the proposed control strategy under both the steady state and the transient states.