Optimal MW/MVAR dispatch and minimal load shedding strategy for improving voltage stability margin

This paper presents a methodology to improve the power system economical dispatch from a voltage stability margin perspective. The proposed method is based on active/reactive power redispatch for normal operation, and also minimum load shedding strategies in case of severe contingencies. The actions are taken in the direction provided by modal participation factors computed for generator and load buses. The objective of this method is to obtain a new generation schedule to provide higher security levels to the system, and to improve its voltage stability margin. The generators with negative impact on system margin, which are indicated by the modal index, are penalized on the objective function of the optimal power flow program used to run the redispatch process. Results of this work show that significant improvement on voltage stability margin, as well as on system reactive power reserves, can be achieved with respect to the conventional economical dispatch solution. It is also shown that the impact on generation cost can be minimized, by combining active and reactive redispatch options. In addition, this work presents a study to identify critical contingencies, for which is proposed an optimal load shedding strategy also based on modal participation factors. It is shown that this method can easily identify the most adequate buses for load shedding purposes, from the point of view of stability margin improvement.