Mid-range voltage dynamics modeling with the load controls present

In this paper a dynamical model relevant for voltage studies is introduced and illustrated on a small study system. The interaction of the natural systems voltage response with the slowly acting, discrete voltage controls is defined leading to a hybrid, nonlinear state space model of the closed loop system. Since such a detailed model is not practical for large scale power systems, a reduced order model is proposed relevant for the mid-range voltage dynamics studies, under the assumption that the mechanical variables are asymptotically stable. The case is illustrated when the instability is purely due to voltage problems.