The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Xin-rong Zhang - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic analysis of Representative Power generation cycles for low to medium temperature applications
International Journal of Energy Research, 2015Co-Authors: Lin Chen, Yan Zhao, Xin-rong ZhangAbstract:SUMMARY This study is focused on the analysis of Representative thermodynamic cycles for Power generation at low-to-medium temperatures (with the highest cycle temperature from 450 to 700 K). The natural working fluid of carbon dioxide is selected for the current tests and comparisons with suitable operation ranges. Energy balance and exergy loss models are established and applied to 10 selected Representative thermodynamic cycles. One modified efficiency parameter is also defined for better comparison of performances, which has considered the effects of both specific thermodynamic process and cycle complexity. Based on the modified efficiency parameter, it is found that Rankine cycle yields the highest performance at 450–500 K among the 10 Representative cycles, while regenerative Brayton cycle shows better behavior for 550–700 K. Detailed behaviors and optimal principals of regenerative Brayton cycles are also identified and compared in this study. Also, a new cycle is also proposed in this study, which combines the advantages of Rankine cycle and Brayton cycle. The new cycle is proved to have better work output potential but higher system complexity factor. In addition, based on the thermodynamic analysis, possible future directions of low-to-medium temperature Power cycles are summarized. It is hoped that the results can be of help for related Power generation system designs. Copyright © 2014 John Wiley & Sons, Ltd.
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Thermodynamic analysis of Representative Power generation cycles for low‐to‐medium temperature applications
International Journal of Energy Research, 2014Co-Authors: Lin Chen, Yan Zhao, Xin-rong ZhangAbstract:SUMMARY This study is focused on the analysis of Representative thermodynamic cycles for Power generation at low-to-medium temperatures (with the highest cycle temperature from 450 to 700 K). The natural working fluid of carbon dioxide is selected for the current tests and comparisons with suitable operation ranges. Energy balance and exergy loss models are established and applied to 10 selected Representative thermodynamic cycles. One modified efficiency parameter is also defined for better comparison of performances, which has considered the effects of both specific thermodynamic process and cycle complexity. Based on the modified efficiency parameter, it is found that Rankine cycle yields the highest performance at 450–500 K among the 10 Representative cycles, while regenerative Brayton cycle shows better behavior for 550–700 K. Detailed behaviors and optimal principals of regenerative Brayton cycles are also identified and compared in this study. Also, a new cycle is also proposed in this study, which combines the advantages of Rankine cycle and Brayton cycle. The new cycle is proved to have better work output potential but higher system complexity factor. In addition, based on the thermodynamic analysis, possible future directions of low-to-medium temperature Power cycles are summarized. It is hoped that the results can be of help for related Power generation system designs. Copyright © 2014 John Wiley & Sons, Ltd.
K.a. Clements - One of the best experts on this subject based on the ideXlab platform.
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Power system state estimation via globally convergent methods
IEEE Transactions on Power Systems, 2005Co-Authors: S. Pajic, K.a. ClementsAbstract:This paper introduces backtracking and trust region methods into Power system state estimation. The traditional Newton (Gauss-Newton) method is not always reliable particularly in the presence of bad data, topological or parameter errors. The motivation was to enhance convergence properties of the state estimator under those conditions, and together with QR factorization to make a globally convergent and reliable algorithm. The trust region formulation shows that such a model is more robust than the traditional Newton (Gauss-Newton) or Backtracking (line search) algorithm. Both algorithms have been programmed and applied to Representative Power networks, and the computational requirement has been found.
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Power System State Estimation via
2005Co-Authors: S. Pajic, K.a. ClementsAbstract:This paper introduces backtracking and trust region methods into Power system state estimation. The traditional Newton (Gauss-Newton) method is not always reliable partic- ularly in the presence of bad data, topological or parameter errors. The motivation was to enhance convergence properties of the state estimator under those conditions, and together with QR factorization to make a globally convergent and reliable algorithm. The trust region formulation shows that such a model is more robust than the traditional Newton (Gauss-Newton) or Backtracking (line search) algorithm. Both algorithms have been programmed and applied to Representative Power networks, and the computational requirement has been found.
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Globally convergent state estimation via the trust region method
2003 IEEE Bologna Power Tech Conference Proceedings, 2003Co-Authors: S. Pajic, K.a. ClementsAbstract:This paper introduces trust region methods into Power system state estimation. The traditional Newton (Gauss-Newton) method is not always reliable particularly in the presence of bad data, topological or parameter errors. The motivation was to enhance convergence properties of the state estimator under those conditions, and together with QR factorization to make a globally convergent and reliable algorithm. The trust region formulation shows that such a model is more robust then the traditional Newton (Gauss-Newton). The algorithm has been programmed and applied to Representative Power networks, and the computational requirement has been found.
Soren Jorgensen - One of the best experts on this subject based on the ideXlab platform.
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Power cycling test methods for reliability assessment of Power device modules in respect to temperature stress
IEEE Transactions on Power Electronics, 2018Co-Authors: Uimin Choi, Frede Blaabjerg, Soren JorgensenAbstract:Power cycling test is one of the important tasks to investigate the reliability performance of Power device modules in respect to temperature stress. From this, it is able to predict the lifetime of a component in Power converters. In this paper, Representative Power cycling test circuits, measurement circuits of wear-out failure indicators as well as measurement strategies for different Power cycling test circuits are discussed in order to provide the current state of knowledge of this topic by organizing and evaluating current literature. In the first section of this paper, the structure of a conventional Power device module and its related wear-out failure mechanisms with degradation indicators are discussed. Then, Representative Power cycling test circuits are introduced. Furthermore, on-state collector–emitter voltage $(V_{{\rm{CE\_ON}}})$ and forward voltage $(V_{F})$ measurement circuits for wear-out condition monitoring of Power device modules during Power cycling test are presented. Finally, different junction temperature measurement strategies for monitoring of solder joint degradation are explained.
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Power cycling test methods for reliability assessment of Power device modules in respect to temperature stress
IEEE Transactions on Power Electronics, 2018Co-Authors: Uimin Choi, Frede Blaabjerg, Soren JorgensenAbstract:Power cycling test is one of the important tasks to investigate the reliability performance of Power device modules in respect to temperature stress. From this, it is able to predict the lifetime of a component in Power converters. In this paper, Representative Power cycling test circuits, measurement circuits of wear-out failure indicators as well as measurement strategies for different Power cycling test circuits are discussed in order to provide the current state of knowledge of this topic by organizing and evaluating current literature. In the first section of this paper, the structure of a conventional Power device module and its related wear-out failure mechanisms with degradation indicators are discussed. Then, Representative Power cycling test circuits are introduced. Furthermore, on-state collector–emitter voltage $(V_{{\rm{CE\_ON}}})$ and forward voltage $(V_{F})$ measurement circuits for wear-out condition monitoring of Power device modules during Power cycling test are presented. Finally, different junction temperature measurement strategies for monitoring of solder joint degradation are explained.
Dejan J. Sobajic - One of the best experts on this subject based on the ideXlab platform.
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Neural-net based tangent hypersurfaces for transient security assessment of electric Power systems
International Journal of Electrical Power & Energy Systems, 1994Co-Authors: M. Djukanovic, Dejan J. SobajicAbstract:Abstract In this paper a new direct method for transient security assessment of multimachine Power systems is presented. A local approximation of the stability boundary is made by tangent hypersurfaces which are developed from Taylor series expansion of the transient energy function in the state space near a certain class of unstable equilibrium points (UEP). Two approaches for an estimation of the stability region are proposed: by taking into account the second order coefficients or alternatively, the second and third order coefficients of the hypersurfaces. Results for two Representative Power systems are described and a comparison is made with the hyperplane method, demonstrating the superiority of the proposed approach and its potential in real Power system applications. Neural-nets are used to determine the unknown coefficients of the hypersurfaces independently of operating conditions.
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Learning tangent hypersurfaces for fast assessment of transient stability
[1993] Proceedings of the Second International Forum on Applications of Neural Networks to Power Systems, 1Co-Authors: M. Djukanovic, Dejan J. Sobajic, Yoh-han PaoAbstract:A new direct method for transient security assessment of multimachine Power systems is presented. A local approximation of the stability boundary is made by tangent hypersurfaces which are developed from Taylor series expansion of the transient energy function in the state space nearby a certain class of unstable equilibrium points (UEP). Two approaches for an estimation of the stability region are proposed by taking into account the second order coefficients or alternatively, the second and third order coefficients of the hypersurfaces. Results for two Representative Power systems are described and a comparison is made with the hyperplane method, demonstrating the superiority of the proposed approach and its potential in real Power system applications. Artificial neural networks are used to determine the unknown coefficients of the hypersurfaces independently of operating conditions. >
Lin Chen - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic analysis of Representative Power generation cycles for low to medium temperature applications
International Journal of Energy Research, 2015Co-Authors: Lin Chen, Yan Zhao, Xin-rong ZhangAbstract:SUMMARY This study is focused on the analysis of Representative thermodynamic cycles for Power generation at low-to-medium temperatures (with the highest cycle temperature from 450 to 700 K). The natural working fluid of carbon dioxide is selected for the current tests and comparisons with suitable operation ranges. Energy balance and exergy loss models are established and applied to 10 selected Representative thermodynamic cycles. One modified efficiency parameter is also defined for better comparison of performances, which has considered the effects of both specific thermodynamic process and cycle complexity. Based on the modified efficiency parameter, it is found that Rankine cycle yields the highest performance at 450–500 K among the 10 Representative cycles, while regenerative Brayton cycle shows better behavior for 550–700 K. Detailed behaviors and optimal principals of regenerative Brayton cycles are also identified and compared in this study. Also, a new cycle is also proposed in this study, which combines the advantages of Rankine cycle and Brayton cycle. The new cycle is proved to have better work output potential but higher system complexity factor. In addition, based on the thermodynamic analysis, possible future directions of low-to-medium temperature Power cycles are summarized. It is hoped that the results can be of help for related Power generation system designs. Copyright © 2014 John Wiley & Sons, Ltd.
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Thermodynamic analysis of Representative Power generation cycles for low‐to‐medium temperature applications
International Journal of Energy Research, 2014Co-Authors: Lin Chen, Yan Zhao, Xin-rong ZhangAbstract:SUMMARY This study is focused on the analysis of Representative thermodynamic cycles for Power generation at low-to-medium temperatures (with the highest cycle temperature from 450 to 700 K). The natural working fluid of carbon dioxide is selected for the current tests and comparisons with suitable operation ranges. Energy balance and exergy loss models are established and applied to 10 selected Representative thermodynamic cycles. One modified efficiency parameter is also defined for better comparison of performances, which has considered the effects of both specific thermodynamic process and cycle complexity. Based on the modified efficiency parameter, it is found that Rankine cycle yields the highest performance at 450–500 K among the 10 Representative cycles, while regenerative Brayton cycle shows better behavior for 550–700 K. Detailed behaviors and optimal principals of regenerative Brayton cycles are also identified and compared in this study. Also, a new cycle is also proposed in this study, which combines the advantages of Rankine cycle and Brayton cycle. The new cycle is proved to have better work output potential but higher system complexity factor. In addition, based on the thermodynamic analysis, possible future directions of low-to-medium temperature Power cycles are summarized. It is hoped that the results can be of help for related Power generation system designs. Copyright © 2014 John Wiley & Sons, Ltd.