A damping controller (136; 236), comprising: a damping module for damping torsional oscillation in a wound field synchronous generator machine (106; 206), wherein the damping module has a synchronous selective compensator for generating a synchronous torsional oscillation compensation signal, a synchronous notch filter for selecting an asynchronous torsional oscillation compensation signal, and an adder module operatively coupled to the synchronous selective compensator and the synchronous notch filter for combining the synchronous torsional oscillation compensation signal and the asynchronous torsional compensation signal, the synchronous notch filter comprising: a constant multiplier module coupled to a position sensor; a speed estimator module coupled to the position sensor; a high-pass filter module coupled to the speed estimator module; a first low-pass filter module coupled to the high-pass filter module; a second low-pass filter module coupled to the high-pass filter module; and an adder module coupled to the first and second low-pass filter modules for generating an output signal for compensating asynchronous torsional oscillations in the wound field synchronous generator machine; a multiplier module coupled to the first low-pass filter; a multiplier module coupled to the second low-pass filter; an adder module coupled to each of multiplier modules; and a third adder module coupled to the adder module and the high-pass filter module. a damping module for damping torsional oscillation in a wound field synchronous generator machine (106; 206), wherein the damping module has a synchronous selective compensator for generating a synchronous torsional oscillation compensation signal, a synchronous notch filter for selecting an asynchronous torsional oscillation compensation signal, and an adder module operatively coupled to the synchronous selective compensator and the synchronous notch filter for combining the synchronous torsional oscillation compensation signal and the asynchronous torsional compensation signal, the synchronous notch filter comprising: a constant multiplier module coupled to a position sensor; a speed estimator module coupled to the position sensor; a high-pass filter module coupled to the speed estimator module; a first low-pass filter module coupled to the high-pass filter module; a second low-pass filter module coupled to the high-pass filter module; and an adder module coupled to the first and second low-pass filter modules for generating an output signal for compensating asynchronous torsional oscillations in the wound field synchronous generator machine; a multiplier module coupled to the first low-pass filter; a multiplier module coupled to the second low-pass filter; an adder module coupled to each of multiplier modules; and a third adder module coupled to the adder module and the high-pass filter module. a constant multiplier module coupled to a position sensor; a speed estimator module coupled to the position sensor; a high-pass filter module coupled to the speed estimator module; a first low-pass filter module coupled to the high-pass filter module; a second low-pass filter module coupled to the high-pass filter module; and an adder module coupled to the first and second low-pass filter modules for generating an output signal for compensating asynchronous torsional oscillations in the wound field synchronous generator machine; a multiplier module coupled to the first low-pass filter; a multiplier module coupled to the second low-pass filter; an adder module coupled to each of multiplier modules; and a third adder module coupled to the adder module and the high-pass filter module.