Decision tree approaches to voltage security assessment

A decision tree methodology is proposed to tackle voltage security concerns under two distinct facets, namely preventive-wise and emergency-wise. Decision tree methodology in general consists of inferring information from a ‘learning set of states’, and of compressing while hierarchically organising this information in a tree fashion, in terms of salient parameters automatically selected by the method at its nodes. Subsequently, the tree may readily assess any already known or new state. For preventive voltage stability purposes, trees are built for a given contingency and the system robustness is assessed in terms of precontingency parameters. For emergency control purposes, on the other hand, each tree is built for a set of contingencies and the system robustness is assessed in terms of parameters observed just after a contingency occurrence. The proposed approaches are illustrated by means of two simulation studies: one carried out on the Brittany region of the EHV French system and the other on an academic type example. These studies explore feasibility aspects, highlight interesting features and suggest that the proposed approaches have indeed potential for real world applications.