Damping of Torsional Shaft Oscillations in Two Interacting Neighbouring Turbogenerators

Abstract

This paper investigates the damping of torsional oscillations in a power station with two identical 1072 MVA generating units connected to an infinite bus through a series capacitor compensated transmission line. It considers a single common controlled shunt reactor to damp torsional oscillations of both turbogenerator shafts. To overcome the mathematical difficulties arising from having to use a high order model of the power system, together with powerful techniques for controller design, the order of the system model is firstly reduced by considering an 'equivalent' single generator and then applying a known model reduction method to this 'equivalent' generator's model. The transient response of the complete unreduced system is then evaluated when the two generator units are equipped with this single common controlled shunt reactor (1SR) and compared against the case when each generator unit has its own separate controlled shunt reactor (2SR). The results show that torsional oscillations in the turbogenerator shafts of such a multimachine system can be damped by the action of a single common controlled shunt reactor; nevertheless, a system where each turbogenerator is equipped with its own individual shunt reactor shows better overall system behavior.