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Matti Lehtonen

Bio: Matti Lehtonen is an academic researcher from Aalto University. The author has contributed to research in topics: Fault (power engineering) & Electric power system. The author has an hindex of 40, co-authored 694 publications receiving 8559 citations. Previous affiliations of Matti Lehtonen include Razi University & New York University.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors introduce hot-spot and top-oil temperature thermal models for more accurate temperature calculations during transient states based on data received in a normal heat run test (i.e., the top oil in the tank of the transformer and the average winding-to-average oil gradient).
Abstract: The aim of this paper is to introduce hot-spot and top-oil temperature thermal models for more accurate temperature calculations during transient states based on data received in a normal heat run test (i.e., the top oil in the tank of the transformer and the average winding-to-average oil gradient). Oil viscosity changes and loss variation with temperature are taken into account. The new thermal models will be validated using experimental (fiber-optic test) results obtained at varying load current on a 250-MVA-ONAF-cooled unit, a 400-MVA-ONAF-cooled unit and a 605-MVA-OFAF-cooled unit. The results are also compared with the IEEE-Loading guide (1995) Annex G method.

285 citations

Journal ArticleDOI
TL;DR: A system-wide demand response management model to coordinate demand response provided by residential customers and flatten the total load profile that is subject to minimum individual cost of customers is presented.
Abstract: Demand response enabled by time-varying prices can propel the power industry toward a greater efficiency. However, a noncoordinated response of customers may lead to severe peak rebounds at periods with lower prices. In this regard, a coordinated demand response scheme can mitigate concerns about the peak rebounds. This paper presents a system-wide demand response management model to coordinate demand response provided by residential customers. The objective of the model is to flatten the total load profile that is subject to minimum individual cost of customers. The model is first formulated as a bi-level optimization problem. It is then casted into equivalent single-level problems, which are solved via an iterative distributed algorithm. Home load management (HLM) modules embedded in customers' smart meters are autonomous agents associated with the algorithm. In the algorithm, at first, HLM modules, in response to prices announced by the utility, optimize the daily operation of household appliances and send back the scheduled load profiles. Then, the total load profile is calculated and released by the utility. Thereafter, the HLM modules asynchronously update their schedule such that, given their least energy expenses, the most evenly distributed total load profile is achieved. The mutual interaction between the utility and HLM modules is continued to the point in which no further improvement is obtained. Convergence and optimality of the algorithm are proved.

231 citations

Journal ArticleDOI
TL;DR: In this paper, a mathematical model is devised to minimize daily network losses via applying hourly reconfigurations, which is a mixed integer second-order cone programming problem and is solved via MOSEK solver.
Abstract: Proliferation of renewable energy resources in distribution networks has captured distribution companies' attention towards more active management tools. Thanks to the smart grid paradigm, hourly network reconfiguration, which is still among immature ideas, can bring the activeness required to handle fluctuating output of renewable resources. The aim of this study is to analyze the worthiness of the hourly reconfiguration in the presence of renewable energy resources. For doing so, a mathematical model is devised to minimize daily network losses via applying hourly reconfigurations. The model is a mixed integer second-order cone programming problem and is solved via MOSEK solver. The electrical demand variations as well as renewable power generation fluctuations during a day are taken into account. The proposed method is applied to the Baran 33-bus system and the results including a great deal of sensitivity analyses on key parameters are presented and discussed.

206 citations

Journal ArticleDOI
TL;DR: In this paper, the authors established voltage sag distributions caused by faults at different voltage levels and experienced by low-voltage customers for four different power system areas, and the shares of different fault types at each voltage level and the sag propagation throughout the power system were taken into account.
Abstract: Voltage sag distributions caused by faults at different voltage levels and experienced by low-voltage customers were established for four different power system areas. The shares of different fault types at each voltage level and the sag propagation throughout the power system were taken into account. The results show that the origin of sags in urban and rural areas tends to be different. These data are needed when, for example, planning measures for sag mitigation in different parts of the power system.

156 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented a residential energy hub model for a smart home, where a residential combined heat and power (CHP) as a cogeneration technology, and a plug-in hybrid electric vehicle are employed in the model.

146 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal Article
TL;DR: This book by a teacher of statistics (as well as a consultant for "experimenters") is a comprehensive study of the philosophical background for the statistical design of experiment.
Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

13,333 citations

Book
01 Jan 2009

8,216 citations

Book ChapterDOI
01 Jan 1982
TL;DR: In this article, the authors discuss leading problems linked to energy that the world is now confronting and propose some ideas concerning possible solutions, and conclude that it is necessary to pursue actively the development of coal, natural gas, and nuclear power.
Abstract: This chapter discusses leading problems linked to energy that the world is now confronting and to propose some ideas concerning possible solutions. Oil deserves special attention among all energy sources. Since the beginning of 1981, it has merely been continuing and enhancing the downward movement in consumption and prices caused by excessive rises, especially for light crudes such as those from Africa, and the slowing down of worldwide economic growth. Densely-populated oil-producing countries need to produce to live, to pay for their food and their equipment. If the economic growth of the industrialized countries were to be 4%, even if investment in the rational use of energy were pushed to the limit and the development of nonpetroleum energy sources were also pursued actively, it would be extremely difficult to prevent a sharp rise in prices. It is evident that it is absolutely necessary to pursue actively the development of coal, natural gas, and nuclear power if a physical shortage of energy is not to block economic growth.

2,283 citations