Impact of load modeling on small signal stability investigations

In this paper fundamental investigations concerning the influence of load modeling on small signal stability investigations of power systems are presented. For this purpose the effect of different voltage- and frequency-dependent static load models on oscillation damping and frequency was examined by means of a single-machine infinite-bus system. Frequency domain calculations as well as time domain simulations were carried out. Results are presented by both providing the eigenvalues of the electromechanical oscillation modes and by plotting the electromechanical transients of relevant system quantities after a disturbance. It has been found that an increasing voltage- and frequency-dependency of the load model increases the damping and decreases the eigenfrequency of generator rotor oscillations. The reasons for these influences are discussed and analyzed whereas special attention is paid to the interpretation of the load model's impact on oscillation damping.