Abstract
This paper investigates the effect of neutral point potential oscillation on four pole neutral point clamped converter. The detailed derivation indicates such oscillation is closely associated with neutral point current, so this paper presents a modulation technique to effectively eliminate this neutral point current. Besides, an offset injected method is also taken into consideration, and a comparison between both schemes will be presented for an optimal oscillation elimination. Finally, the laboratory test results will be supported the aforementioned analysis.