A Novel Common-Mode Voltage Suppression Strategy for Current Source Converter

The problem of common-mode voltage (CMV) in current source converter (CSC) has been concerned with the development and application of CSC, such as in the transformerless motor drive system. Using a common-mode (CM) choke is a popular solution to suppressing CMV. The high-frequency harmonics of the CMV can be eliminated by the CM filter. However, the low-order harmonics cannot be eliminated effectively, especially at low modulation index, which may cause CM resonance and increase the size of the choke. In this article, a novel virtual space vector modulation method is proposed, which constructs virtual space vectors by the original vectors. The average value of the CMV produced by each virtual vector is zero. The proposed method can reduce the amplitude and third-order harmonic component of the CMV. In addition, the number of switching transitions in a switching sequence of the proposed method is the same as the conventional five-segment space vector modulation. The suppression effects of different methods on the low-order harmonics of CMV are compared through simulation and experiments, and the effectiveness of the proposed methods is verified.