Power electronic systems could be unstable due to the interaction between converters. Impedance-based stability analysis is an effective approach to predict stability and to provide design criteria. Therefore significant are impedance measurement techniques, which have been well established for DC systems, but need to be improved for AC systems nevertheless. This paper proposes a novel AC impedance measurement method which injects bipolar pulse at current zero-crossing point. Compared with existing methods, it enhances accuracy and reduces distortion. Simulation and experimental results demonstrate the effectiveness of the novel method.
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