Common-mode resonance suppression for parallel CSC-fed high power medium voltage drives with multilevel modulation

In high power application, the parallel connected current source converters (CSC) are applied to increase the power region. This parallel connected CSC topology can lead to multilevel output current and improve the harmonic performance. However, the common-mode voltage (CMV), common-mode current (CMC) and circulating current in the parallel CSC-fed motor drive system can cause serious problems which should be taken into consideration. Moreover, the common-mode resonance is a potential problem due to the series connection of inductor and capacitor in the common-mode loop under adjustable motor speed. This paper investigates the causes of common-mode resonance in parallel CSC system compared with single CSC system thoroughly and a multilevel space-vector-modulation (SVM) based method applied in parallel CSC system is proposed to suppress the CMV and common-mode resonance. The effectiveness of the proposed method is verified on a transformerless parallel connected CSC-fed motor drive system by both simulation and experiment.