On-line Estimation and Correction of Voltage Stability Index as Slack Nodes Failure

Along with the widely application of the Wide— Area Measurement System in power system, voltage instability based on WAMS is becoming all increasingly important worldwide issue.By using the WAMS to collect the measured value of local voltage and current vector directly, we can realize the online estimate and instruction of the voltage stability degree of key node. Use this as a foundation, this paper analyses problems in the phase failure of slack node, puts forward that taking the voltage phase of the node, which has the nearest electrical distance from the slack node, as the reference phase; and according to the least square method based on historical data of WAMS two effective methods to correct and estimate the voltage andcurrent phasor of the key node, can also realize online correction and estimating of the voltage stability of the key node. The simulations show that this method is suitable for the surveillance of online static voltage stability of node and has certain feasibility.