Voltage Stability Analysis using an Optimal Thevenin Equivalent Estimation Method for varying Reactive Power in a Power System
Vishal Kumar Singh1, S. V. Jayaram Kumar2
1Vishal Kumar Singh, Student Electrical and Electronics Engineering, Gokaraju Rangaraju Institute of Engineering and Technology (JNTU-H), Nizampet, Hyderabad, India.
2Dr. S V Jayaram Kumar, Professor, Department of Electrical and Electronics Engineering, Gokaraju Rangaraju Institute of Engineering and Technology (JNTU-H), Nizampet, Hyderabad, India.

Manuscript received on 09 April 2019 | Revised Manuscript received on 14 May 2019 | Manuscript published on 30 May 2019 | PP: 1485-1490 | Volume-8 Issue-1, May 2019 | Retrieval Number: A9284058119/19©BEIESP
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© The Authors. Blue Eyes Intelligence Engineering and Sciences Publication (BEIESP). This is an open access article under the CC-BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Abstract: A voltage stability method using Thevenin equivalent method has been proposed. The change in reactive power in the system introduces voltage swells or sags in the system and vice-versa giving rise to a phenomena called Voltage Stability. Our proposed method will do away with the problems associated with short circuit faults, circuit breakers action, load-switching, etc., and thus voltage instability. The idea is to obtain Thevenin equivalent parameters of the system and replacing it with the same (Eth and Xth) so that the voltage of the system remains constant during all the possible mishaps mentioned above at different places in a power system. The proof of the proposed method is shown by the simulation obtained in MATLAB/Simulink, for a two generator system and also verifying it mathematically with the proposed algorithm. The quadratic approximation/curve fitting helps us finding the optimal solution. This proposed system finds its application in various power systems containing renewable energy sources where power flow is not constant from these sources to the grid and hence causing the voltage of the main system to fluctuate. Replica of such a WINDHUB system has been examined and results show that power quality of the system can be improved by using the Thevenin’s model and shunt capacitors on a medium length transmission line.
Index terms: Voltage Stability, Reactive Power, Thevenin Equivalent, Quadratic Curve Fitting, AQ bus, PV Curve

Scope of the Article: Optimal Design of Structures