Common-mode voltage reduction for medium-voltage current source converters by optimizing switching sequences

Common-mode voltages (CMVs) can lead to premature failure of the motor insulation system in medium-voltage (MV) current source drives. This paper proposes a novel space-vector modulation (SVM) based gating strategy that can significantly reduce the peak CMV by optimizing the switching sequences for MV current source converters (CSCs). In the proposed method, the switching sequence of one side of the CSC is fixed and the sequence of the other side is selected to produce the minimum peak CMV. The optimization process is based on the CMV calculation for all the possible switching sequence combinations. To validate the proposed concept, different SVM based control schemes for CSCs are investigated. The results show the effectiveness of the proposed concept. In addition, the proposed strategy can be easily implemented in software and requires no extra hardware. By using this method, the CMV stress of the motor is reduced significantly and the size/weight for the common-mode choke can also be reduced.