A study of frequency responses of generator electrical torques for power system stabilizer design

Frequency response methods based on the concept of damping torque enhancement have been successfully used in the design of practical power system stabilizers. Central to this approach is the calculation of the frequency response from the automatic voltage regulator input to the electrical torque of a generator without the effect of rotor angle feedback. This paper carries out a study to deepen the understanding of certain important properties of the frequency response. It is shown that the frequency response of a generator can be considered as having two components. One component, which depends only on the associated generator, is very significant and has a great effect on the overall frequency response; it has the important property that its shape is fixed independent of the operating condition of the associated generator. The other component depends on the associated generator as well as on the external system. However, this component is found to be not much affected by the dynamics of generators in the external system because of the diagonal dominance of the reduced admittance matrix of the modified network with generators lumped into it as dynamic admittances.