Test Cases Library of Power System Sustained Oscillations

Natural oscillation case ND_7 (Back to the homepage)

This case contains two sources, i.e. generators 45 and 159, with different contributions into a single unstable local mode.


System model:

  • All generators are in GENCLS model.
  • Parameter D for generators 45 and 159 equals -0.5 and -0.5, respectively.
  • Parameter D for all other generators equals 4.
  • All loads are in constant MVA model.

  • Disturbance:

  • A three-phase short circuit is added at bus 159 at 0.5s and cleared after 0.05s.

  • Small signal analysis:

  • The local mode at 1.41Hz has a negative damping of -0.40%.
  • Mountain View

    Figure 1. WECC 179-bus power system

    The specifics of the cases ND_6 and ND_7 is as follows. Sensitivity of real part of the associated eigenvalue to variation of damping coefficient D for generator 159 is two times higher than that for generator 45. Thus, the contribution in negative damping of generator 159 is twice comparing to generator 45 in case ND_7 despite they have the same values of D.