Overvoltage Mitigation of Medium Voltage Electric Drives with Long Cables using Multilevel-Converters and Passive Filters

Paper in proceedings, 2019

Variable-speed drives with long cables between the electrical machine and the power converters suffer from overvoltages at the connection terminals of the cables. These overvoltages which are caused by reflections of the PWM voltage pulses to the two ends of the cable are investigated in this paper. Suitable passive filters are proposed in order to mitigate the overvoltages to an acceptable level, which is not harmful for the devices of the system. Additionally, the use of multilevel power converters can help to minimize the size of the passive filters. The filter design for drives with up to 7-level converters is described in this paper and simulations results on LTspice are presented in order to validate the mathematical analysis.