Design of Damping Strategies for LC filter in medium voltage induction motor drives

This work presents the impact of an LC filter when implemented in a medium voltage (MV) induction motor connected to a NPC inverter through long cables. The main reason to implement a filter is to mitigate the harmonic components introduced by the inverter, that could damage the machine isolation, and to reduce the reflected wave created by the long cables. However, this strategy introduces a resonance, which can lead to instabilities in current control. This issue can be mitigated by introducing resistive elements, which causes additional losses. In order to avoid these losses, the filter resistors can be suppressed if an active damping strategy is used. In this work, a design method for passive and active damping based on capacitor current measurement is presented. The parameters are selected based on root locus method. Finally, a comparison between both strategies is described.