Coordinated steady-state voltage stability assessment and control

A framework for mid and long term small disturbance voltage stability assessment and control with dissimilar controls is presented. The parameter space includes parameters for loads, capacitor support and tap changing transformers. A general method is used to locate all the small disturbance characteristic points which contains saddle-node bifurcation, Hopf bifurcation and minimum damping points. The distances from the operating point to the global and/or local closest points in stability boundaries are used as security indices. A new function, defined in terms of multiple (local) minimum distances and the safe distance needed, is used to evaluate the security margin and find the most effective control actions to increase the security margin. All these methods are tested and illustrated in a given example system