Natural oscillation case ND_4 (Back to the homepage)
This case contains single source, one unstable inter-area mode and two poorly damped local and inter-area modes, where the oscillation source is generator 11.
System model:
Disturbance:
Small signal analysis:
![Mountain View](source\wecc179_4nd.jpg)
Figure 1. WECC 179-bus power system
Fig. 2 illustrates the case ND_4, where 0.70 Hz mode has negative damping and two other modes (one local and one inter-area) are slightly damped.
![Mountain View](source\Spectra_NO_case4.jpg)
Figure 2. Spectra of oscillations for the case ND_4
![Mountain View](source\Rotor_Angles_NO_case4.jpg)
Figure 3. Rotor angles in the case ND_4. Blue curve is the angle of generator 11 creating negative damping