Research On The Applications Of Synchronized Phasor On Protection,Control Of Power System And Its Algorithms

With the scale of the power system increasingly large and the extent of power system interconnection increasingly greater, the unstability of power system caused by disturbances or contingencies may affected broader region than before. Once the out-of-step detection devices misoperate, it may causes enormous losses. For this reason, the traditional pre-setting asynchronous oscillation detection criteria based on local information cannot adapt to this situation. But the electrical information of lager area so much even the whole power system can be obtained using synchronized phasor measurement technology. And this can help us to consider the out-of-step detection & islanding from a higher viewpoint.In this paper, the asynchronous state identification criteria widely used in practice like U cos?) criterion and impedance step by step discriminant is firstly analysised. It is indictated that the present criterion is mainly deduced based on the two-generator-system. Specifically, the U cosc? criterion is based on the hypothesis that the magnitudes of the two generators are equal; the impedance step by step discriminant relies on the parameters calculated off-line. Then, an real-time detection criterion based on PMU information is presented to overcome the aforementioned defects. It can match all the conditions of the model of two equivalent generators losing synchronization. And it is immun to the changes of operation and topology of power system as well as of which the parameters setted easily. At last, the proposed criterion is tested on the IEEE 3-generator-9-bus system using PSCAD. It is demonstrated that the presented criterion can distinct asynchronous oscillation from synchronous oscillation precisely.According to the complexity of current power system, the model of two or even more equivalent generators losing synchronization often appears in power system. In addition, the boundary of the areas may be fuzzy and areas may connect with each other by more than one transmission line. In this situation, the traditional asynchronous state identification criteria based on two-generator-system cannot perform well. So in this paper, another islanding sheme based on coherent generators recognization using PMU information is proposed. The presented islanding sheme firstly uses non-negative matrix factorization (NMF) algorithm to reduce the dimension of the matrix of the generator speed. And then, generators are classified into coherent groups by applying K-mean clustering to the reduced matrix. After this, tie-lines to be opened in order to create the islands are determined by means of concepts based on graph theory, Dijkstra's shortest electrical distance and active power imbalance. A reduced frequency response model is employed to determine the power imbalance limits on each island. The 39 bus-New England System is used to test proposed islanding scheme showing its capability to avoid systems collapse.