Insulation Online Monitoring for Critical Components inside SiC based Medium Voltage Converter Prototype

Comparing with Si based ones, SiC based converters can achieve much higher voltage rating and power density. Therefore, electric field intensity inside SiC based converters can become significant and initial surface discharges, which usually occur along the exposed metal or insulator to air interfaces. Although converters should be surface discharge free by design, it is hard to guarantee discharge free throughout the entire converter lifecycle, mainly due to the air properties change and insulation degradation. Since surface discharges should be prevented before any catastrophic failure occurs, insulation online monitoring, especially for critical components, can have great value for converter system operation and maintenance. In this paper, novel fiber-optic acoustic sensor and silicon photomultiplier based sensor are developed to realize surface discharge online monitoring inside converters. Both sensors are compact in size with high isolation level, thus they can be integrated into the SiC based medium voltage converter prototype easily. Based on experimental results, it demonstrates that the proposed sensors have good sensitivity, high immunity to the Electromagnetic Interference and can be applied inside converters for insulation online monitoring along multiple regions. This paper could provide some useful exploration about insulation online monitoring for future SiC based medium and high voltage converters.