Virtual Impedance-Based Selective Harmonic Compensation (VI-SHC) PWM for Current Source Rectifiers

To mitigate the line current harmonics of a high-power current source rectifier (CSR) system, the selective harmonic elimination (SHE) scheme is frequently used due to its low switching frequency and superior harmonic performance. However, the SHE scheme only focuses on the harmonics generated by the converter itself. It cannot cope with the line current harmonics caused by the background grid voltage harmonics. In this paper, a selective harmonic compensation scheme using the virtual impedance concept (VI-SHC) is presented. This method compensates for the preexisting grid background harmonics using only the line current measurement, and provides superior line current harmonic performance. The proposed method does not require measuring the grid voltage harmonics (which are typically low), does not rely on an accurate CSR system model, and therefore is very robust for practical implementation. Thi s PWM control scheme has been verified by real-time experiments on a CSR prototype.