Analysis of subsynchronous torsional interaction with power electronic converters

This paper extends previously proposed methods for frequency-domain analysis of subsynchronous oscillation phenomena in synchronous machines. Particular attention is given to the case where a current-controlled voltage-source converter is located electrically nearby. It is shown that the converter can contribute with significant positive electrical damping. Negative electrical damping is normally contributed only in the frequency region where the converter acts as a negative resistance. This region. can be reduced or eliminated by proper design of the current controller.