Partial discharge measurement and analysis in high voltage IGBT modules under DC voltage

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.