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 …

I and i

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

The Design and Analysis of Experiments

计量经济分析 = Econometric analysis

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.

World energy outlook

Introduction to stochastic programming

The ongoing rapid increase in the integration of variable and uncertain renewable energy sources calls for enhancing the ways of providing flexibility to power grids. To this end, we propose an optimal approach for utilizing electric vehicle parking lots to provide flexibility at the distribution level. Accordingly, we present a day-ahead scheduling model for distribution system operators, where they can offer discounts on the network tariff to electric vehicle parking lot operators. This way, they will be encouraged to exploit the potential flexibility of electric vehicle batteries to assist in alleviating the steep ramps of system net-load. To determine the optimal discounts, the distribution system operator minimizes the network operating costs considering the network operational constraints, while the electric vehicle parking lot operators try to maximize their profits. Due to the contradictory objectives and decision hierarchy, the problem is an instance of Stackelberg games and can be formulated as a bi-level program, which is linearized and converted to a single-level mixed-integer linear program using strong-duality theorem and Karush–Kuhn–Tucker conditions. To validate the proposed model, comprehensive simulation studies are performed on a test distribution network. The simulation results show that implementing the model can reduce the peak-off-peak difference and peak-to-average ratio of the network net-load by up to 15% and 24%, respectively. • A framework to motivate EV parking lots (EVPLs) to provide services in distribution networks. • Introducing a MILP model for distribution network operation that utilises EVPLs’ flexibility. • The model finds the optimal financial discounts that incentivise EVPLs to reduce net-load ramp. • Proposing a linear model for accurate estimation of the EV battery degradation cost. • Using the Unscented Transformation method to capture the correlated data uncertainties. 

Leveraging the flexibility of electric vehicle parking lots in distribution networks with high renewable penetration

Due to the wide dependency on electricity in our daily life, it is highly desired to have an uninterrupted and reliable supply of electricity for domestic, commercial, transportation, industrial and healthcare purposes. An arc fault occurring in switchgear causes long duration power interruption, damage to the equipment and hazard to personnel. Several arc protection systems have been introduced during last decade, mostly relying on reactive protection techniques. This paper introduces some unique methods detecting incipient faults leading to arc-flash in medium voltage (MV) and low voltage (LV) switchgear and motor controlgear. In MV switchgear, low power arcing and insulation degradation can be detected by differential electric field sensor (D-dot) and Rogowski coil (RC), and thermal degradation is detected by thermal ionization detector (TID) in LV switchgear. On-site testing is included in this paper to validate the laboratory test results.

Predicting arc faults in distribution switchgears

Power systems require a certain amount of flexibility to meet varying demand and to be able to cope with unexpected events, and this requirement is expected to increase with the emergence of variable power generation. In this paper, we focus on gas engine power plant technology and the beneficial influence its flexible operation can have on a power system. The study introduces the concept of a combined-cycle gas engine power plant (CCGE), which comprises a combination of several gas-fired combustion engines and a steam turbine. The operation of CCGE is then comprehensively analyzed in electricity and reserve production in the South African power system and compared with combined-cycle gas turbine (CCGT) technology. Even though CCGE is a form of technology that has already been commercialized, it is rarely considered as a source of flexibility in the academic research. That is the notion providing the motivation for this study. Our core contribution is to show that the flexibility of CCGE can be valuable in power systems. The methodology is based on the unit-level model of the studied system and the solving of a day-ahead unit commitment problem for each day of the simulated 11-year period. The simulation studies reveal how a CCGE is able to offer system flexibility to follow hourly load variations and capacity to provide reserve power effectively.

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System-Level Value of a Gas Engine Power Plant in Electricity and Reserve Production

This paper presents a new method for managing concurrent duties and time in low-power wireless sensor cells that monitor electrical power systems. The method is based on the co-operation of two interrupt levels, one generated locally in every sensor that is part of the cell, the other generated as the response to a signal that is sent out by some base station. With this method very precise synchronization of concurrent duties can be achieved at a very low energy cost. The same signal can also be used to provide an accurate timestamp of events that the system will generate. Experiments show that the method is successful in the case that the duration between two subsequent concurrent duties is relatively short. For longer periods it is predicted that the deviation among clocks can cause problems. A solution to this is presented in the paper. This solution is based on dividing the duration between two concurrent duties into shorter steps that the sensors may utilize to keep the synchronization at a feasible level.

Managing concurrent duties and time of wireless sensors in electrical power systems

A novel fast enumeration based reliability assessment algorithm based on a probabilistic load flow approach considering nodal uncertainties is proposed in this paper. The frequency and duration indices for each load point and the expected energy not supplied as well as the expected interruption costs are derived with the proposed methodology. By reducing the number of necessary system states a huge decrease of computation time is achieved while maintaining an adequate degree of accuracy. In order to verify the accuracy and the computational expensiveness of the proposed algorithm a commercial available program is used to compare the calculation results of a utility driven sub transmission power system. It is demonstrated that a fast calculation of the load indices, including station originated outages, can be performed, based on uncertain nodal powers, for instance nodal injections from wind farms or other stochastic power system loads, with a high degree of accuracy.

Matti Lehtonen

Papers

Leveraging the flexibility of electric vehicle parking lots in distribution networks with high renewable penetration

Predicting arc faults in distribution switchgears

System-Level Value of a Gas Engine Power Plant in Electricity and Reserve Production

Managing concurrent duties and time of wireless sensors in electrical power systems

Enumeration based reliability assessment algorithm considering nodal uncertainties