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.

Probabilistic Risk Assessment of MV Insulator Flashover Under Combined AC and Lightning-Induced Overvoltages

Abstract: The effect of lightning-induced overvoltages is more profound in overhead distribution lines due to their limited height and low insulation level. Consequently, there is a high risk of line insulation flashover when exposed to lightning-induced overvoltages. This paper presents a probabilistic method to assess the risk of insulator flashover in medium-voltage overhead lines due to lightning-induced overvoltages. In order to accomplish this, a modified Gaussian cumulative distribution function has been used to predict the probability of single-phase, two-phase, and three-phase flashover of insulators under combined ac- and lightning-induced overvoltages. The validity of the modified probabilistic model is confirmed through experiments carried out in the high-voltage laboratory. Next, Monte Carlo simulations were performed on the simplified Rusck's model to generate the distribution of peak lightning-induced overvoltages. Finally, the risk of insulator flashover is calculated based on the distributions of lightning-induced overvoltages and insulator flashover voltages. The proposed procedure could be considered beneficial to select the optimum insulation level required against lightning-induced overvoltages by distinguishing between single-phase and multiphase flashover faults.

High-resolution modeling of elevator power consumption

Abstract: This paper proposes a framework for modeling the instantaneous power consumption of individual elevators and elevator groups based on passenger traffic. Though elevators have a key role in the modern urban society, they have remained as rather neglected appliances in the energy efficiency research. To accelerate the energy efficiency studies of elevators, this paper has two major contributions. First, we propose means to model the instantaneous power consumption of individual elevators and elevator groups and analyze the reliability of these means versus the complexity of the modeling. Second, we present an elevator group control scheme to organize the elevator dispatching according to the simulated passenger traffic. When combined, these methods yield enhanced predictions about the energy and power consumption of elevators in a specific type of building with measured or simulated movement of occupants.

A User-Friendly Transactive Coordination Model for Residential Prosumers Considering Voltage Unbalance in Distribution Networks

Abstract: Designing transactive energy (TE) markets in distribution systems has been a hot topic due to the increased presence of residential prosumers. In the literature, several residential market platforms have been proposed; however, they usually have two main drawbacks: 1) ignoring the effect of single-phase distributed energy resources on the voltage unbalance (VU) in active distribution networks to develop a transactive coordination model that will effectively mitigate the VU and 2) inability in providing a user-friendly strategy for home occupants to adjust the willingness to pay/accept of responsive assets according to their comfort and economic purposes. This article amends the shortcomings by proposing a network-constrained TE model to coordinate residential prosumers with the main goal of satisfying households’ preferences as well as mitigating distribution system problems. The case study is then carried out demonstrating that the proposed TE-concept-based coordination of residential prosumers is aligned with customers’ preferences (comfort and economic purposes) and concerns (plug-in electric vehicle battery life) and could effectively decrease the VU.

Optimal Allocation of Inverter-Based WTGS Complying With Their DSTATCOM Functionality and PEV Requirements

Abstract: Recently, the integration of inverter-based wind turbine generation systems (WTGS) and plug-in electric vehicles (PEV) has remarkably been expanded into distribution systems throughout the world. These distributed resources could have various technical benefits to the grid. However, they are also associated with potential operation problems due to their stochastic nature, such as high power losses and voltage deviations. An optimization-based approach is introduced in this paper to properly allocate multiple WTGS in distribution systems in the presence of PEVs. The proposed approach considers 1) uncertainty models of WTGS, PEV, and loads, 2) DSTATCOM functionality of WTGS, and 3) various system constraints. Besides, the realistic operational requirements of PEVs are addressed, including initial and preset conditions of their state of charge (SOC), arriving and departing times, and various controlled/uncontrolled charging schemes. The WTGS planning paradigm is established as a bi-level optimization problem which guarantees the optimal integration of multiple WTGS, besides optimized PEV charging in a simultaneous manner. For this purpose, a bi-level metaheuristic algorithm is developed for solving the planning model. Intensive simulations and comparisons with various approaches on the 69-bus distribution system interconnected with four PEV charging stations are deeply presented considering annual datasets. The results reveal the effectiveness of the proposed approach.

I and i

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 …

The Design and Analysis of Experiments

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

World energy outlook

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.