Current Harmonic Reduction in DC-Link Capacitors of a Regenerative Cascaded H-Bridge Converter

This paper proposes a new approach to reduce current harmonics in the power cell dc-link capacitors of a regenerative cascaded H-bridge (regen-CHB) converter. In order to suppress the 2nd carrier band dominant harmonic current injected into dc-link capacitor, a pulse width modulation (PWM) carrier shifted angle optimization is proposed. This proposed method is based on an optimization ideology, which can promote dc-link capacitor’s performance on ripple current rating and power loss. The theoretical analysis of dc-link capacitor current harmonics and corresponding optimization ideology for the problem is studied in this paper. Compared to the other existing methods for dc-link capacitor current ripple suppression, the proposed method requires no online parameter update and realtime computation. The simulation results show a noticeable elimination of dominant current harmonics which reduces rms current and current ripples of the dc-link capacitors significantly.