Charge Accumulation at High DC Voltage and Superimposed Medium Frequency AC Voltage

A big challenge for future electric grids is the energetic coupling of DC systems. This can be realized by Solid-State-Transformers with an operating medium frequency AC voltage generated by power electronic converters. The DC voltage and the superimposed medium frequency AC voltage stress the insulation system because of, for instance, partial discharges. In this paper, the results of the measurement of the charge accumulation by corona discharges at this composite voltage at a polyethylene surface are presented.