A clustering validation based method for zone number determination in network partitioning for voltage control

The paper proposes a method for automatic determination of the best number of zones when partitioning a power network for voltage control. It combines four widely-used clustering validity indices to evaluate the validity of a series of network partitioning schemes obtained by a hierarchical clustering algorithm, each with a different number of zones. The zone number of the scheme with the highest validity is taken as the best number. A similar method is also used to select the proper definition of inter-zone distance used in network partitioning by the hierarchical clustering algorithm. Case studies on IEEE 57-bus and 118-bus systems show the detail of the proposed method.