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 pre-existing grid background harmonics using only the line current measurement, and provides superior line current harmonic performance. This PWM control scheme has been verified by both simulations and real-time experiments on a 10kVA/208V CSR prototype.