Abstract
Neutral point potential oscillation at low frequency is an important issue in four pole neutral point clamped converter since this leads to the extra voltage stress on the split DClink capacitors. The detailed analysis indicates such oscillation is closely associated with the neutral point current at low frequency, so this paper explores their relationship, and presents the modulation techniques to eliminate the neutral point oscillation. This study also evaluates their performance with the conventional modulation techniques. Finally, the laboratory test results are presented to support the analysis.