Simulation of low frequency undamped oscillations in large power systems

New techniques were applied to the analysis of spontaneous power oscillations that occur in the Mid-Continent Area Power Pool (MAPP). System natural frequencies below one hertz were calculated along with the relative velocity deviations of major generating units at each frequency. Operating data was used to determine which of these low natural frequencies correspond to system oscillations. Simulation of the spontaneous oscillation was obtained using a dynamic stability program by giving each generator an initial velocity deviation proportional to the previously calculated relative velocity deviations for that frequency. The oscillation was also obtained by suddenly dropping load in one area of the dynamic model and picking it up in another area. A number of simulations were carried out to about twenty seconds or approximately three cycles of the natural frequency to investigate dynamic stability limits under various conditions. Quantitative calculations of synchronizing power flow capability between areas were used to evaluate the effects of operating and design changes.