The advantages of synchronous generator with superconducting field winding can be stated as: (1) Reduction in losses, (2) Improved system performance, (3) High-Voltage armature feasibility, (4) Small size and weight. Some feasibility studies have been carried out, and currently some model machines for demonstration are under construction.The superconducting field winding which produces strong magnetic flux can be viewed as an energy storage and its application to power system stabilization has been proposed and the damping effect of power swing has been confirmed numerically.In this paper an improved control scheme for power system stabilization which has the function of voltage regulation by the control of field winding current, is proposed. Some numerical examples demonstrate that the proposed system is capable of suppressing the voltage fluctuation as well as damping power oscillation, significantly. Furthermore, the specifications of the superconducting generator necessary for the stabilization of a model power transmission system are estimated in detail. In the case of 1, 120MVA generator with 24MJ stored energy at 6kA rated field current, the maximum DC voltage is 3, 300V, the maximum rate of field current change (dI/dt) is 3, 500A/s and the maximum power exchanged between the field winding and the power system is 20MVA.