Characteristics and Mechanism of Partial Discharge Behavior of Power Module Under Unipolar Square Voltage

Partial discharge (PD) is an important characterization parameter of the reliability state of the insulation system, and it is also one of the reasons why the insulation structure fails for the high-voltage power electronics module. However, the current research on the characteristics and mechanism of PD behavior in power modules is limited. In view of this situation, this article proposes a parameterized PD model of the power module and introduces the discharge stochastic theory and memory effect. Combined with the proposed high-frequency current transformer detection system and statistical methods, the PD behavior characteristics of the power module are systematically revealed. As the applied voltage increases, the mathematical expectation of the first PD and the second PD gradually approaches the rising edge, from 9.4 to 2.5 mu s, and the data standard deviation gradually shrinks, from 1.23 to 0.35. The increase in the voltage rise rate can also lead to similar characteristics. Besides, during 0%-50% phase-to-period ratio (PPR) and 50%-100% PPR periods, PD statistical data exhibits a certain symmetry in the phase distribution and asymmetry in the discharge repetition rate.