Quasi steady-state simulation diagnosis using Newton method with optimal multiplier

This paper deals with the quasi steady-state approximation of the long-term dynamics. This fast time simulation method assumes that the short-term dynamics are stable and can be replaced by their equilibrium equations. When the latter stop having a solution, the simulation undergoes a singularity. This paper proposes a method to identify which component(s) are responsible for the loss of equilibrium. The corresponding equations are identified using the Newton method with optimal multiplier. The method has been validated with respect to full time simulation. Very good results are shown on the Nordic-32 system, in cases where long-term voltage instability triggers loss of synchronism. The proposed method enhances time simulation at very low computational cost and can also help correcting model and/or operating point errors.