Modulation Strategy for the 3TSMC to Suppress Mains Current Sector-Switching Distortions Under Capacitive Input Power Factor Angles

In this article, a modulation strategy is proposed for the third-harmonic injection two-stage matrix converter (3TSMC) to suppress the mains current sector-switching distortions under capacitive input power factor angles. First, it is revealed that when the 3TSMC operates under nonunity input power factors, the injection current has control errors after sector switching, which cannot be completely solved by optimizing the controller. Second, the mechanism that the injection current control errors lead to the mains current distortions is analyzed, and the shapes of distortions are summarized. Then, a novel switching pattern is introduced for the input voltage selector of the 3TSMC, which can weaken or even offset the distortions generated by the control errors under capacitive input power factor angles. The proposed modulation strategy inserts this switching pattern into the original switching sequence with a suitable duty cycle after sector switching, thus suppressing the distortions. Finally, experimental results are presented to verify the validity of the proposed modulation strategy.