Neutral-Point Oscillation Suppression for Vienna Rectifier Based on Small DC-Link Capacitor

This paper replaces the traditional electrolytic capacitors with film capacitors on the DC side to increase system reliability, working life and power density of Vienna rectifier. However, the neutral-point oscillation would become more severe and higher frequency voltage ripples cannot be neglected due to the small DC-link film capacitors. A simplified strategy of feed-forward zero-sequence component injection is presented in this paper to solve this problem. Based on the mathematical average model, the feed-forward injection is adopted to suppress severe oscillation of the neutral point, while the closed-loop control is adopted to eliminate the DC offset in case of load unbalance. An accurate analytical expression of the neutral-point oscillation's each frequency harmonics is derived to accurately calculate the feed-forward duty cycle. The effectiveness of the utilized approach is verified on a simulation and laboratory prototype.