Surface discharges at superimposed medium frequency high voltage

Due to new technological possibilities decentral structures will characterize the future electrical energy grid. To ensure the energy transport and to increase the efficiency Medium-Frequency High-Voltage (MF-HV) transformers are used. With these inductive couplers the electrical isolation between loads, sources and the AC-distribution system is possible. In this process a superposition of the MF-HV generated by power electronic circuits and the power frequency voltage occurs. Figure 1 shows the calculated voltage waveforms of these Multi-Cell Solid-State Transformers for two different power electronic topologies (3LL and 2LL), which are described in [1]. The voltage consists of a 50 Hz component and medium frequency harmonics.