A Method for Suppressing DC-Link Ripples of Multilevel Packed U-Cell Inverter by Compensate-Control Combination

Abstract

In order to suppress the influence of the DC-link ripples in the multilevel inverters, a compensate-control combination method for the Packed U-cell (PUC) multilevel inverter to suppress DC-link ripples is proposed in this paper. The method suppresses the influence of the DC-link ripples of the multilevel PUC inverter from the perspectives of controlling the stability of the capacitors voltage on the DC side and the feed-forward compensation of the DC-link voltage disturbance. A feed-forward compensation strategy for the DC-link voltage disturbance of the PUC inverter is proposed. This strategy is implemented by the modified voltage pulse duty ratio and is organically combined with the stability control of the PUC inverter’s capacitor voltage based on redundant level modulation. The proposed method further feed-forward compensates for the influence caused by the DC-link voltage disturbance in the pulse width modulation while ensuring the relative stability of the DC-side capacitor voltage. It can effectively reduce the low-order harmonics under the PUC inverter’s non-ideal operating conditions.

Keywords

• Capacitor voltage control
• current harmonic
• DC-Link ripples
• feed-forward compensation
• PUC inverter