Synchronous Machine Initialization For Unbalanced Network Conditions Within An Electromagnetic Transients Program

The Electromagnetic Transients Program (EMTP) offers two quite different algorithms for the representation of synchronous machine dynamics. The original [1) uses compensation [2], while the second [3, 4] is based on a Thevenin equivalent of the generator. It is shown that positive sequence initialization is inadequate if the electric network is even just slightly unbalanced (e.g., untransposed lines). Two new initialization procedures which also account for negative (and possibly zero) sequence armature quantities are now being used. Even cases of gross imbalance (e.g., one phase open) can now be handled easily. Sample digital computer calculations are presented, including simulations of the IEEE subsynchronous resonance (SSR) benchmark model using large time-steps.