Grid Current Distortion Suppression for Unified Power Flow Controller Based on the 3TSMC

The third-harmonic injection two-stage matrix converter (3TSMC) can freely control the input reactive power, which makes it suitable for acting as a unified power flow controller (UPFC). However, when the 3TSMC-based UPFC produces reactive power, the grid currents suffer from distortions. This paper introduces a suppression strategy is for the grid current distortions in the 3TSMC-based UPFC. First, the overall structure and working principles are introduced for the UPFC based on 3TSMC. Second, the cause of grid current distortions is investigated. Then, the suppression strategy is introduced for the 3TSMC by temporarily pulse width modulating the switches which originally operate depending on the grid voltage. Finally, the effectiveness of the proposed strategy is proven by simulation results.