POWER SYSTEM DAMPING USING SPEED SIGNALS

Abstract

Excessive rotor oscillations, stemming from disturbances to synchronous generators, give rise to adverse operating conditions in a power system. These oscillations increase tie-line power losses and cause unnecessary controller action. Oscillatory action of the rotor gives rise to prolonged periods of frequency and voltage transients which, depending on the type of load, may present a serious operating problem. The ideal situation would be for the generator to have sufficient damping so that when it is subjected to a load change (or other type of disturbance), the new rotor position would be reached with a minimum of oscillations. One method of damping out these oscillations is to transfer a signal, related to the rotor frequency error, through a coupling element to the voltage regulator. This thesis presents a method for determining the parameters of this frequency feedback coupling element to obtain improved system camping. Results obtained from simulated models of the generator, controllers and the frequency feedback element agree very closely with those predicted by analytical means. a study carried out using state variable representation gave information with regard to the influence of the feedback element on system stability. The results obtained from this study indicate that a frequency error signal fed back into the voltage regulator of a synchronous generator gives a marked improvement in system damping provided that the settings of the frequency feedback element are compatible with existing controllers and external load conditions.