Analysis and comparison of bus ranking indices for balanced and unbalanced three-phase distribution networks

In this paper, the definition of the conventional bus voltage ranking index V/V_o is extended and generalized using symmetrical component to include unbalanced three-phase operations. The performance and accuracy of the conventional and the new ranking indices are compared with the well-known voltage sensitivity approaches ∂V/∂P and ∂V/∂Q for balanced and unbalanced three-phase distribution networks. Simulations based on the above mentioned four approaches are performed using the DIgSILENT PowerFactory to identify the weakest buses of the modified IEEE 13 node test feeder under balanced and unbalanced operating conditions. Finally, an application of the generalized index of V/V_o to improve voltage stability of unbalanced networks is demonstrated.