Mains Current Distortion Suppression for Third-Harmonic Injection Two-Stage Matrix Converter

The third-harmonic injection two-stage matrix converter (3TSMC) not only possesses the advantages of a TSMC, but also enhances the input reactive power control capability. Due to the input current deviation caused by the voltage ripple across the input filter capacitors, the mains currents of the 3TSMC are distorted at sector boundaries. To improve mains current quality, this article proposes a mains current distortion suppression method for a 3TSMC, which adds a prefilter to the output side of the input voltage selector to reduce the input current harmonics. As a result, the input filter capacitor voltage ripple and the input current deviation are reduced. The details of design of the prefilter are explained mathematically. To compensate for the dc-link voltage variation after topology improvement, an algorithm based on calculation of the voltage drops across the prefilter inductors is proposed, which can further improve the mains current performance. The feasibility of the proposed method is verified by simulation and experimental results.