Insulation performance of high voltage IGBT modules is one of the key attributes in power system applications. However

the existing standards of IGBT devices and research on the evaluation of insulation performance of high voltage IGBT modules are insufficient; for example

partial discharge resistance under DC voltage blocking condition is not considered. In this paper

a new test was proposed to allow the measurement of partial discharges in all the components of IGBT modules under DC voltage. The topology of the measuring circuit is arranged in the polarity discrimination way to exclude the interference

and the voltage and discharge current waveforms during the partial discharge process are measured by the wideband time domain measurement technique. According to the proposed test

the discharge phenomenon of the IGBT modules below the rating voltage were detected. A comprehensive waveform analysis on the voltage and discharge current was performed

and the influence of the applied voltage on the waveform parameters was obtained. The waveform parameters are influenced by the applied voltage and insulation structure

which enables the discrimination of the causes of the observed partial discharge in the IGBT module under DC voltage by the waveform analysis technique. Based on the waveform analysis technique

the types and causes of the observed partial discharges were discussed and inferred

and the correctness of the inference was further verified by observation. The proposed test and waveform analysis technique provide the possibility to evaluate and distinguish partial discharges in the high voltage IGBT module under DC voltage

which may be helpful to insulation performance evaluation and insulation defect diagnosis in high voltage IGBT module.