Optimal Modulation Strategy for Ripple Current Reduction of DC-Link Capacitor in Multidrive Systems

This article proposes a modulation method that significantly reduces the ripple current of the dc-link capacitor in multidrive systems. It is based on the derived analytical model for the capacitor ripple current with an arbitrary number of drives connected in parallel at the dc-link side. The effects of different parameters (including load, power factor, modulation ratio, and switching frequency) on the modulation method in multiple drives are analyzed. Both the low-frequency and high-frequency current components are minimized by the optimal phase shifts of the modulation signal and the carrier signal. The cases with three drives for the optimal phase shifts corresponding to different parameter configurations are given. Benchmark studies of multidrives systems with 2–20 drives reveal that the total capacitor root mean square current is reduced to 34.3%–15.9%. Proof-of-concept experimental results verify the theoretical analysis and the effectiveness of the proposed method.