Low voltage solutions calculation for voltage stability analysis using energy methods

This paper proposes a method to identify unstable equilibrium points of interest to voltage stability margin determination, using energetic methods. To perform these point selections, the proposed method identifies the load buses which have the same voltage drops patterns (the so called voltages control islands). It is shown that load buses belonging to the voltage control island where the load has been increased, present equally small voltage levels at the voltage collapse point. It is said that the unstable equilibrium points associated to a same voltage island have similar energy levels. Therefore these buses can be associated to one of these unstable equilibrium points which can be treated as the unstable equilibrium point of interest. The results present some energy function values calculated for some sets of unstable equilibrium points of the IEEE 39 bus (New England) system