Research Of Voltage Stability Based On Synchronous Phasor Measurement Data

Recently the electrical transmission system has become more heavily loaded due to increased loads and larger inter-utility power transfers, while economic and environmental constraints have limited additions of new transmission and generation facilities. This has necessitated system operation much closer to its load ability limits. Consequently, we urgently need to solve the problem and achieve the automation of adjustments of the power system to enhance its dynamic supervisal ability and improve its security and stabilization level. The technology of synchronous phasor measurement and wide-area measurement system(WAMS) makes it possible that monitoring and controlling dynamic charactcristic of grids synchronously, which will greatly facilitate the research advancements of related applications in power systems. So, research based on voltage stability using synchronous phasor measurement data has become a popular and valuable subject.The voltage instability phenomena is described and explained in the paper. Approaches to voltage stability based on static and dynamic means are analyzed as well as the index calculation.The basic principle of phasor measurement unit and its application in many domains of power sysem is reviewed,such as dynamic, steady and secondary protection. Based on the research,this paper carries on the equivalent to the system with recursive least-squares procedure in two different forms.They are two-bus system equivalence in Thevenin's theorem and the equivalent model based on local network parameters.The index of voltage stability valuation is created and then the differences between two forms are compared.The results showed that with the increased load, two voltage stability index values based on the equivalent models are both decreased for the impedance module voltage stability index. The index calculated from the equivalent model based on the local area network parameters fell at a faster speed, and quickly close to zero approaching critical state. Therefore the system model based on the local network parameters is superior to the equivalent of Thevenin's equivalent model.The power distribution after the line fault under a state of emergency is carried out in-depth research in this paper, which pointed out that the existing methods are most based on the knowledge of the restoration of the power flow that the load-shedding program can be implemented. The calculate method for the transferred power based on the theorem of superposition is presented, which can calculate the transferred power rapidly at the moment the fault occurs. The method is that equal the branch which may be disconnection fault in the original network as a current source, and in accordance with the superposition of voltage and current, the transferred power in every other branched can be calculated quickly and accurately. The simulation results proved that this method is feasible.