Voltage stability assessment: Voltage control inadequacy problem

The problem of voltage control inadequacy in voltage control devices in a power system is revealed, when an inverse relationship between controlling and controlled variables exists. The voltage control inverse relationship could adversely affect the voltage profile in a power system, thus, it is necessary to determine the relationship between controlling variables and controlled voltages, which can be accomplished through the analysis of the elements in the voltage controlled sensitivity matrix. The analysis of these elements, besides determining the adequacy of voltage control actions, allows determining possible conflicts between controls which, if not considered, could limit the adequate adjustment of the voltage profile. The identification of voltage control inadequacy of an operating point allows assessing the impact of the voltage control inadequacy in voltage stability conditions through voltage stability indexes. The proposed strategy for voltage stability assessment is tested on a 5-bus power system. From this analysis, the impact on voltage stability conditions is non-dependent on the reverse relationship between controlling variables and controlled voltages, as long as the best strategy for control actions is stablished, when voltage control inadequacy is determined.