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- Type of Document: Ph.D. Dissertation
- Language: Farsi
- Document No: 40963 (05)
- University: Sharif University of Technology
- Department: Electrical Engineering
- Advisor(s): Ranjbar, Ali Mohammad; Feuillet, Reneh
- Abstract:
- oltage stability is a dynamic phenomenon. The time frame of interest for voltage stability phenomenon may vary from a few seconds to tens of minutes. Therefore, voltage stability may be either a short-term or a long-term phenomenon. The past proposed voltage stability protection schemes have major drawbacks in both static and dynamic aspects. To mitigate the drawbacks of the previously proposed voltage stability protection schemes in both static and dynamic domains two system protection schemes are proposed. In static domain, the proximity to the collapse point(i.e. proximity is measured by a voltage stability indicator) as well as the instability mechanism (i.e. determination of the most sensitive remedies and most critical locations) cannot be determined properly in a wide area basis, by the previously proposed protection schemes. In the first part of this thesis a comprehensive wide area voltage stability protection scheme is proposed in static domain. In the proposed scheme the voltage stability protection scheme is modeled as an optimal control problem and then the model is modified to implement remedial actions in such a way that the power system cascading is reduced or eliminated. Based on the post contingency conditions, the proposed method executes the most sensitive remedies in order to restore the power system from a cascaded collapse and make it immune against severe contingencies. To determine the proximity to the stability boundary a new voltage stability indicator is proposed in a wide area basis. Since the main cause of voltage instability is the lack of reactive power support, the proposed indicator measures the proximity to the stability boundary by monitoring the system ability in providing reactive power support. To determine the instability mechanism the current approach is the calculation of the normal vector to the stability boundary. Normal vector suffers from the uncertainty about the convexity of the stability boundary. Therefore in the proposed system protection scheme, another method based on the Lagrange multipliers is proposed. To reduce the risk of cascading event the contingency screening and analysis is modeled via Benders Decomposition technique. i The previously proposed wide area schemes in dynamic domain are not well adapted to the severity of contingency. In other words, less effort has been done to include prediction and adaptivity features. Therefore in the second part of this thesis an adaptive under-voltage load shedding scheme is proposed based on the model predictive control theory. In both static and dynamic schemes it is assumed that the required measurements are available via the new measuring technologies like Phasor Measurement Units as the main part of the Wide Area Measurement System. System protection schemes proposed in this thesis could be implemented in a decentralized manner in which the network is divided into distinct voltage and reactive power control areas. Therefore a modified algorithm is proposed to determine the voltage control areas and associate pilot nodes
- Keywords:
- Voltage Stability ; Dynamic Analysis ; Static Analysis ; Wide Area Protection
Digital Object List-
محتواي پايان نامه - view
Bookmark- Front matter
- Abstract
- Acknowledgements
- Dedication
- Table of Contents
- List of Tables
- List of Figures
- List of Symbols
- Introduction
- Wide Area Phenomena and System Protection Schemes
- Static Aspects of Voltage Stability
- System Protection Scheme for Mitigation of Voltage Collapse
- Dynamic Aspects of Voltage Stability
- MPC-Based Under-Voltage Load Shedding
- Conclusion and Recommendation
- Bibliography
- Appendices
- Wide Area Measurement System
- Data of Test Cases