Characteristics and Identification of Partial Discharge for Insulation Structures in High Voltage IGBT Modules Under Positive Square Wave Voltage

The insulation of insulated gate bipolar transistor (IGBT) modules is one of the key constraint factors in module development. It is significant to realize the accurate measurement of partial discharge (PD) and its identification of the insulation weaknesses under positive square wave voltage. In this article, a PD experimental platform under this voltage is established. Three main possible insulation weaknesses of high voltage IGBT modules are selected as experimental samples, including chip, silicone gel, and the interface between direct bonded copper and silicone gel. Then, PD current waveforms of them are measured. To solve the interference caused by high du/dt at the rising/falling edge of voltage, a distortionless extraction method of PD pulses independent of any auxiliary detection equipment is proposed. Based on this method, the PD phase distributions of three samples are obtained and there are distinct differences among them. Thus, the PD types in high voltage modules can be identified effectively. In addition, qualitative explanations of the differences in the typical PD characteristics are presented. The proposed PD identification method is experimentally verified and can guide the insulation design and fabrication of high voltage IGBT modules.