On Angle References in Long-Term Time-Domain Simulations

In power system dynamic models, the complex network equations and the various phasors are projected onto reference axes. After a short critical review of commonly chosen reference axes, this letter proposes to use the center-of-inertia at the previous integration time step. This approach is shown to combine the advantages of the center-of-inertia with a sparser Jacobian structure and an easier handling of network splits.