Subsynchronous resonance of a power station with two identical generating units

The paper investigates the effect of adding a second 1072 MVA turbogenerator to an existing one in a power station feeding a series capacitor compensated transmission line. In carrying out the investigation, the new two-generator system is modelled as one equivalent generator with increased capacity, and also as a multimachine system with two separate generators. A comparison of these models shows that, for this type of stability study and this transmission system configuration, there is no advantage gained in modelling the two generators separately rather than as one equivalent generator. The results further show that conditions can exist where the system is stable with one generator but unstable with two, and vice versa.