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

Compared with the direct matrix converter and the two-stage matrix converter (TSMC), the third-harmonic injection TSMC (3TSMC) has significant advantages in the input reactive power control range and the maximum linear voltage transfer ratio. However, for nonunity input power factor operations and high-mains-frequency applications, there are input current distortions in the 3TSMC. Further analysis reveals that the actual injection current cannot track the reference without error in the conventional harmonic current injection circuit, resulting in the current distortions. Therefore, an improved circuit is proposed, which is based on the asymmetric H-bridge and does not need extra energy storage components or current sensors. The injection current in the improved circuit can follow the reference without error by injection current modulation, which means that the input current distortions are suppressed significantly. All theoretical considerations are verified by experimental results taken on a 3-kVA prototype.