Optimal Modulation Strategy for Current-Source Converter to Reduce DC-Link Current Ripple

As one of the most important performance indices of a current-source converter, dc-link current ripple is closely related to the modulation strategy. Excessive dc-link current ripple not only reduces the system efficiency but also increases the total harmonic distortion of grid current and leads to more electromagnetic interference. To get around this problem, optimizing the modulation strategy is more attractive compared with increasing the inductor or switching frequency. To this end, based on the detailed analysis of the mechanism to reduce the dc-link current ripple and the inherent deficiency of the current ripple continuous increase phenomenon between two adjacent sequences, in this article, a novel modulation strategy by employing an optimized switching sequence according to the modulation index is proposed. By applying the proposed modulation strategy, the current ripple is effectively reduced in the full range of the modulation index. Furthermore, the proposed scheme is easy to implement in practice without increasing the switching frequency or inductor. Finally, the selected experimental results confirm the validity of the theoretical analysis.