A torsional mode damping controller system is connected to a converter that drives an electrical machine mechanically connected to a train. The controller system includes an input interface configured to receive measured data related to variables of the converter or the electrical machine, and a controller connected to the input interface. The controller calculates at least one dynamic torque component along a section of a shaft of the train based on the data from the input interface, generates control data for the converter for damping a torsional oscillation in the mechanical drive train based on the at least one dynamic torque component, and sends the control data to the converter for modulating an active power exchanged between the converter and the electrical machine.