Harmonic Current Suppression Strategy for the VIENNA Rectifier Based on Discrete Fourier Transform

When the three-phase grid voltage is distorted, the grid current total harmonic distortion (THD) will deteriorate accordingly in the VIENNA rectifier. This article proposes a current harmonic suppression strategy based on real-time discrete Fourier transform (DFT). The DFT is employed to extract the sine and cosine components of the grid current high-order harmonics, which are applied to the feedback loop of the dq rotating coordinate system. Independent control loops for high-order harmonic currents are introduced, and the references are set as 0 to suppress the corresponding harmonic currents. The difference between the control strategies of positive and negative sequence components is discussed. The proposed control method can be extended to other orders. In order to verify the validity of the proposed strategy, a 50 kW VIENNA rectifier prototype is designed and built. The experimental results show that the current THD is improved under grid voltage distortion over the entire load range.