Research On Improved Assessment Method And Application Of Thevenin Equivalent Based On Measurement Data

Into the21st century, grid interconnection and power needs are growing rapidly, and gradually into the bulk power grid, high pressure, high voltage, large units, long-distance transmission of the times, troubled network is an important factor in the development of voltage stability, due to voltage instability caused by the collapse of the grid collapse accident at home and abroad on many occasions. We enjoy the benefits of a large network era, but also concerned about the voltage stability problem. In-depth study of voltage stability analysis, to reduce or even avoid the occurrence of voltage instability.Grid interconnection, more and more complex network topology, all nodes consider the whole network based voltage stability has become increasingly difficult, and often need to focus on those important load nodes. In order to simplify the complexity of the grid, the researchers consider the use of Thevenin equivalent of the grid can be simplified, it will simplify the complex network into a simple two-node system that allows researchers to the need for voltage stability of the analysis and evaluation of the node to respond quickly. With further research, Thevenin equivalent method is accurate and the advantages of simple steps gradually revealed, so that the method become a hot research.This paper presents a fully differential variable reaction parameters based on changes in the modified Thevenin equivalent recursive estimation algorithm, to obtain the load node voltage and current phasors, all derived a set of linear differential equations, Thevenin parameters in response to differential forms changes. While the node voltage and current characteristics, based on measurement data to calculate the grid node side equivalent impedance, as initial start of the algorithm, based on initial start fully differential solution of linear equations, the grid can Thevenin current time equivalent parameters of track calculations, the method not only overcomes the traditional algorithm assumes that the existing two moments before and after the Thevenin equivalent parameters to bring the same error, but also in the selection of initial start to improve, making the algorithm simpler. Secondly, The algorithm derivation process does not exist0/0model, inhibition of the parameter drift problem. Secondly, the use of node impedance modulus margin and load margin with voltage stability analysis and evaluation of system nodes and networks. Finally, a simple DC system, examples IEEE14, IEEE39, IEEE57verify the validity of the recursive estimation algorithm and the correctness of, for the study of voltage stability can provide a new research method.