A Hybrid Control Method to Suppress the Three-Time Fundamental Frequency Neutral-Point Voltage Fluctuation in a VIENNA Rectifier

This paper presents a solution to the control of the third harmonic of the neutral point in a VIENNA rectifier. A hybrid method combining a dynamic adjustment factor with a voltage deviation control of the split dc link is proposed. The fluctuation of the neutral point has been analyzed and the reason for the third harmonic fluctuation has been described with a mathematic model. In addition to minimizing the third-harmonic component in the neutral-point voltage, the proposed control method also provides immunity to the influence of changes in the capacitor voltage. Furthermore, the significant fluctuation in the neutral-point voltage caused by asymmetric capacitor parameters or unbalanced load can be effectively reduced by using a hybrid control method combining additional adjustment coefficients. The feasibility and effectiveness of the proposed strategy have been verified using both simulation and experimental results.