Low-frequency voltage ripples in the flying capacitors of the nested neutral-point-clamped converter

Abstract

The flying capacitors (FCs) of the nested neutral-point-clamped (NNPC) converter show an inherent voltage ripple at fundamental frequency. This ripple can be significantly large under some operating conditions of the converter. In this paper, the amplitudes of the low-frequency voltage ripples in the FCs are determined. An averaged model of the NNPC converter is introduced and used in the analysis. The amplitudes of the capacitor voltage ripples are provided using normalized variables so that this information can be used to size the FCs of the converter in different applications. The results of the analysis are validated experimentally in a laboratory prototype.