A Direct Carrier-Based Modulation Scheme With Full Index Range for DC-Link Current Ripple Mitigation of a Current Source Converter
Lei Ming, Wenlong Ding, Poh Chiang Loh, Zhen Xin
Abstract
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 [ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sqrt 3 /3$</tex-math></inline-formula> , 1] to <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[0, 1]</xref> . 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.