A preliminary study on the Thevenin equivalent impedance for power systems monitoring

It is an important task to accurately estimate the Thevenin equivalent impedance seen from a load bus for power systems monitoring and control. The purpose of this paper is to investigate the mechanism and characteristics of the Thevenin equivalent impedance in a nonlinear circuit. A general model is introduced for investigating the Thevenin equivalent impedance in an analytical manner. Two typical approaches are presented to approximate the Thevenin equivalent impedance. A simple three bus system is employed to test the two approximate methods. In the simulations, three types of load models, i.e. constant impedance, constant current and constant power, are discussed, respectively, for the load inside the equivalent network. Some interesting phenomena have been observed, and these findings could be likely to bring a new idea to determine the Thevenin impedance for power systems, in an analytical manner.

[1]  Christian Rehtanz,et al.  Design Aspects for Wide-Area Monitoring and Control Systems , 2005, Proceedings of the IEEE.

[2]  M. Begovic,et al.  Use of local measurements to estimate voltage-stability margin , 1997, Proceedings of the 20th International Conference on Power Industry Computer Applications.

[3]  Hsiao-Dong Chiang,et al.  CPFLOW: a practical tool for tracing power system steady-state stationary behavior due to load and generation variations , 1995 .

[4]  Thomas J. Overbye,et al.  Improved techniques for power system voltage stability assessment using energy methods , 1991 .

[5]  T. Carlsen,et al.  Voltage stability condition in a power transmission system calculated by sensitivity methods , 1990 .

[6]  Yang Wang,et al.  A new node voltage stability index based on local voltage phasors , 2009 .

[7]  Jean Claude Maun,et al.  Comparison of Thevenin's Equivalent based Methods to Monitor Voltage Stability , 2008 .

[8]  B. Gao,et al.  Voltage Stability Evaluation Using Modal Analysis , 1992, IEEE Power Engineering Review.

[9]  Weixing Li,et al.  On impedance matching and maximum power transfer , 2010 .

[10]  Miroslav Begovic,et al.  Voltage Stability Protection and Control Using a Wide Area Network of Phasor Measurements , 2002, IEEE Power Engineering Review.

[11]  F. Gubina,et al.  Local voltage-stability index using tellegen's Theorem , 2007, 2007 IEEE Power Engineering Society General Meeting.

[12]  F. Gubina,et al.  A new concept of voltage-collapse protection based on local phasors , 2003, 2003 IEEE Power Engineering Society General Meeting (IEEE Cat. No.03CH37491).

[13]  S. Corsi,et al.  A Real-Time Voltage Instability Identification Algorithm Based on Local Phasor Measurements , 2008, IEEE Transactions on Power Systems.

[14]  Claudio A. Caiiizares.  ON BIFURCATIONS, VOLTAGE COLLAPSE AND LOAD MODELING , 1995 .

[15]  P. Kessel,et al.  Estimating the Voltage Stability of a Power System , 1986, IEEE Power Engineering Review.

[16]  Mohammed H. Haque.  On-line monitoring of maximum permissible loading of a power system within voltage stability limits , 2003 .

[17]  Tongwen Chen,et al.  Investigation on the thevenin equivalent parameters for online estimation of maximum power transfer limits , 2010 .