LAUSR

This article presents a direct carrier-based modulation scheme to mitigate the dc-link current ripple for a current source converter (CSC). Excessive dc-link current ripple increases system losses, causes current distortion, and leads to more electromagnetic interference, so, it should be mitigated. Compared with increasing dc-link inductor or switching frequency, it is more attractive to mitigate dc-link current ripple with modulation schemes. However, existing modulation schemes suffer from either high dc-link current ripple or shrink of modulation index range. To address this issue, this article analyzes the mechanism of mitigating the dc-link current ripple and proposes a new modulation scheme for a CSC. By employing two kinds of non-nearest three vectors to synthesize the reference current, the proposed scheme successfully extends the index range from [$\sqrt 3 /3$, 1] to [0, 1]. For easier implementation, its carrier-based modulation, which can automatically select the desired vectors and last predetermined dwell times, is also presented. Theoretical analyses show that the proposed scheme can mitigate the dc-link current ripple over the full index range for a CSC. The effectiveness of the proposed modulation scheme is verified experimentally with a CSC operating as a rectifier.