High-Frequency Current Transformer Design and Analysis for Partial Discharge Detection of Power Electronic Modules

In medium-voltage applications, silicon carbide has a promising future due to its higher switching speed, higher thermal conductivity, and higher voltage levels. Meanwhile, higher voltage levels and higher power density put severe stress on the insulation structure. Partial discharge (PD) is an important characterization for the performance of insulation structure. However, there is limited research on dedicated design for PD current sensing systems, and there is also a lack of analysis of the frequency-domain characteristics of PD and system noise. In view of this situation, first, the high-frequency current transformer (HFCT) system is proposed, and the circuit model is established to analyze the influence of parameters on the frequency response and gain. Second, based on the analysis, a special HFCT system was designed for the characteristics of PD of power electronic power modules, including signal front-end circuits, and the correctness of the theoretical analysis was verified by a vector network analyzer. The system was calibrated and proved to capture the 10-pC charge with relative accuracy. Finally, the PD detection experiment of the power module is carried out, and the proposed system can effectively detect the PD signal in the time domain.