A New Index of Voltage Stability Considering Distribution Network

This paper was to research on voltage stability considering distribution network. An equivalent system considering distribution network with high/medium voltage and an approach of online tracking of voltage stability margin of the equivalent system were proposed. By applying the theorem of voltage stability, it was derived that because of power loss caused by the distribution line in the equivalent system, voltage collapse occurred at the distribution bus before at the transmission bus. With little additional calculation, the online tracking voltage stability margin considering distribution network included the main effects taken by distribution network on voltage stability, and well matched the current actual voltage stability situation, so it was very helpful for operator to make decisions before voltage crisis in distribution network developing into transmission network. Simulation showed that the presented new voltage stability margin can effectively avoid voltage collapse in power grid resulted from voltage crisis in distribution network developing into transmission network.