Real-time load-side control of electric power systems

Two trends are emerging from modern electric power systems: the growth of renewable (e.g., solar and wind) generation, and the integration of information technologies and advanced power electronics. The former introduces large, rapid, and random fluctuations in power supply, demand, frequency, and voltage, which become a major challenge for real-time operation of power systems. The latter creates a tremendous number of controllable intelligent endpoints such as smart buildings and appliances, electric vehicles, energy storage devices, and power electronic devices that can sense, compute, communicate, and actuate. Most of these endpoints are distributed on the load side of power systems, in contrast to traditional control resources such as centralized bulk generators. This thesis focuses on controlling power systems in real time, using these load side resources. Specifically, it studies two problems.

(1) Distributed load-side frequency control: We establish a mathematical framework to design distributed frequency control algorithms for flexible electric loads. In this framework, we formulate a category of optimization problems, called optimal load control (OLC), to incorporate the goals of frequency control, such as balancing power supply and demand, restoring frequency to its nominal value, restoring inter-area power flows, etc., in a way that minimizes total disutility for the loads to participate in frequency control by deviating from their nominal power usage. By exploiting distributed algorithms to solve OLC and analyzing convergence of these algorithms, we design distributed load-side controllers and prove stability of closed-loop power systems governed by these controllers. This general framework is adapted and applied to different types of power systems described by different models, or to achieve different levels of control goals under different operation scenarios. We first consider a dynamically coherent power system which can be equivalently modeled with a single synchronous machine. We then extend our framework to a multi-machine power network, where we consider primary and secondary frequency controls, linear and nonlinear power flow models, and the interactions between generator dynamics and load control.

(2) Two-timescale voltage control: The voltage of a power distribution system must be maintained closely around its nominal value in real time, even in the presence of highly volatile power supply or demand. For this purpose, we jointly control two types of reactive power sources: a capacitor operating at a slow timescale, and a power electronic device, such as a smart inverter or a D-STATCOM, operating at a fast timescale. Their control actions are solved from optimal power flow problems at two timescales. Specifically, the slow-timescale problem is a chance-constrained optimization, which minimizes power loss and regulates the voltage at the current time instant while limiting the probability of future voltage violations due to stochastic changes in power supply or demand. This control framework forms the basis of an optimal sizing problem, which determines the installation capacities of the control devices by minimizing the sum of power loss and capital cost. We develop computationally efficient heuristics to solve the optimal sizing problem and implement real-time control. Numerical experiments show that the proposed sizing and control schemes significantly improve the reliability of voltage control with a moderate increase in cost.

Strategic Optimization Techniques For FRTU Deployment and Chip Physical Design

Combinatorial optimization is a complex engineering subject. Although formulation often depends on the nature of problems that differs from their setup, design, constraints, and implications, establishing a unifying framework is essential. This dissertation investigates the unique features of three important optimization problems that can span from small-scale design automation to large-scale power system planning: (1) Feeder remote terminal unit (FRTU) planning strategy by considering the cybersecurity of secondary distribution network in electrical distribution grid, (2) physical-level synthesis for microfluidic lab-on-a-chip, and (3) discrete gate sizing in very-large-scale integration (VLSI) circuit. First, an optimization technique by cross entropy is proposed to handle FRTU deployment in primary network considering cybersecurity of secondary distribution network. While it is constrained by monetary budget on the number of deployed FRTUs, the proposed algorithm identi?es pivotal locations of a distribution feeder to install the FRTUs in different time horizons. Then, multi-scale optimization techniques are proposed for digital micro?uidic lab-on-a-chip physical level synthesis. The proposed techniques handle the variation-aware lab-on-a-chip placement and routing co-design while satisfying all constraints, and considering contamination and defect. Last, the first fully polynomial time approximation scheme (FPTAS) is proposed for the delay driven discrete gate sizing problem, which explores the theoretical view since the existing works are heuristics with no performance guarantee. The intellectual contribution of the proposed methods establishes a novel paradigm bridging the gaps between professional communities.

Assessing Decision Making Skill in Complex and Dynamic Environments Using Representative and Simulated Tasks

Traditional decision making research has often focused on one's ability to choose from a set of prefixed options, ignoring the process by which decision makers generate courses of action (i.e., options) in-situ (Klein, 1993). In complex and dynamic domains, this option generation process is particularly critical to understanding how successful decisions are made (Zsambok & Klein, 1997). When generating response options for oneself to pursue (i.e., during the intervention-phase of decision making) previous research has supported quick and intuitive heuristics, such as the Take-The-First heuristic (TTF; Johnson & Raab, 2003). When generating predictive options for others in the environment (i.e., during the assessment-phase of decision making), previous research has supported the situational-model-building process described by Long Term Working Memory theory (LTWM; see Ward, Ericsson, & Williams, 2013). In the first three experiments, the claims of TTF and LTWM are tested during assessment- and intervention-phase tasks in soccer. To test what other environmental constraints may dictate the use of these cognitive mechanisms, the claims of these models are also tested in the presence and absence of time pressure. In addition to understanding the option generation process, it is important that researchers in complex and dynamic domains also develop tools that can be used by `real-world' professionals. For this reason, three more experiments were conducted to evaluate the effectiveness of a new online assessment of perceptual-cognitive skill in soccer. This test differentiated between skill groups and predicted performance on a previously established test and predicted option generation behavior. The test also outperformed domain-general cognitive tests, but not a domain-specific knowledge test when predicting skill group membership. Implications for theory and training, and future directions for the development of applied tools are discussed.

The Broken Mirror: Maternal Agency and Identity in Charles Dickens's Bleak House

This paper examined how Esther Summerson, Dickens’s ideal good mother, can be understood as a woman who has maternal agency and identity both as a character and as a narrator, and how she contrasts with other maternal characters in the novel, both major and minor. While more transgressive mothers, such as Lady Dedlock, Mrs. Jellyby and even Krook’s cat, are doomed to death, ineffectiveness and madness, Esther moves from a frozen, “unsexualized” state into a space of life and sexual possibility. In addition, Esther has agency and identity as a narrator since she shares the narration with a third-person male narrator. Esther becomes the one who speaks rather than the one who is spoken of, and her maternal, nurturing voice provides a balm for the often harsh, judgmental voice of the male narrator. As the narrator’s patriarchal voice dies away at the end, it is Esther’s maternal voice that survives.

Productivity growth and the structure of production

In this study, interactions between potential hierarchical value chains existing in the production structure and industry-wise productivity growths are sought. We applied generalized Chenery-Watanabe heuristics for matrix linearity maximization to triangulate the input-output incidence matrix for both Japan and the Republic of Korea, finding the potential directed flow of values spanning the industrial sectors of the basic (disaggregated) industry classifications for both countries. Sector specific productivity growths were measured by way of the Trönquvist index, using the 2000-2005 linked input-output tables for both Japan and Korea.

Do intelligent heating controls out-smart ordinary users?

Nearly a third of UK gas and electricity is used in homes, of which 80% is for space heating and hot water provision. Rising consumer bills, concerns about climate change and the surge in personal digital technology use has provoked the development of intelligent domestic heating controls. Whilst the need for having suitable control of the home heating system is essential for reducing domestic energy use, these heating controls rely on appropriate user interaction to achieve a saving and it is unclear whether these ‘smart’ heating controls enhance the use of domestic heating or reduce energy demand. This paper describes qualitative research undertaken with a small sample of UK householders to understand how people use new heating controls installed in their homes and what the requirements are for improved smart heating control design. The paper identifies, against Nielsen’s usability heuristics, the divergence between the householder’s use, understanding and expectations of the heating system and the actual design of the system. Digital and smart heating control systems should be designed to maximise usability so that they can be effectively used for efficient heating control by all users. The research highlights the need for development of new systems to readdress the needs of users and redefine the system requirements.

Random walk with restart over dynamic graphs

Random Walk with Restart (RWR) is an appealing measure of proximity between nodes based on graph structures. Since real graphs are often large and subject to minor changes, it is prohibitively expensive to recompute proximities from scratch. Previous methods use LU decomposition and degree reordering heuristics, entailing O(|V|^3) time and O(|V|^2) memory to compute all (|V|^2) pairs of node proximities in a static graph. In this paper, a dynamic scheme to assess RWR proximities is proposed: (1) For unit update, we characterize the changes to all-pairs proximities as the outer product of two vectors. We notice that the multiplication of an RWR matrix and its transition matrix, unlike traditional matrix multiplications, is commutative. This can greatly reduce the computation of all-pairs proximities from O(|V|^3) to O(|delta|) time for each update without loss of accuracy, where |delta| (<<|V|^2) is the number of affected proximities. (2) To avoid O(|V|^2) memory for all pairs of outputs, we also devise efficient partitioning techniques for our dynamic model, which can compute all pairs of proximities segment-wisely within O(l|V|) memory and O(|V|/l) I/O costs, where 1<=l<=|V| is a user-controlled trade-off between memory and I/O costs. (3) For bulk updates, we also devise aggregation and hashing methods, which can discard many unnecessary updates further and handle chunks of unit updates simultaneously. Our experimental results on various datasets demonstrate that our methods can be 1–2 orders of magnitude faster than other competitors while securing scalability and exactness.

Modelling the generation of customised poetry in Jess

The present paper presents an application that composes formal poetry in Spanish in a semiautomatic interactive fashion. JASPER is a forward reasoning rule-based system that obtains from the user an intended message, the desired metric, a choice of vocabulary, and a corpus of verses; and, by intelligent adaptation of selected examples from this corpus using the given words, carries out a prose-to-poetry translation of the given message. In the composition process, JASPER combines natural language generation and a set of construction heuristics obtained from formal literature on Spanish poetry.

Ordonnancement des opérations dans une unité d’extrusion

Les travaux de ce mémoire traitent du problème d’ordonnancement et d’optimisation de la production dans un environnement de plusieurs machines en présence de contraintes sur les ressources matérielles dans une usine d’extrusion plastique. La minimisation de la somme pondérée des retards est le critère économique autour duquel s’articule cette étude car il représente un critère très important pour le respect des délais. Dans ce mémoire, nous proposons une approche exacte via une formulation mathématique capable des donner des solutions optimales et une approche heuristique qui repose sur deux méthodes de construction de solution sérielle et parallèle et un ensemble de méthodes de recherche dans le voisinage (recuit-simulé, recherche avec tabous, GRASP et algorithme génétique) avec cinq variantes de voisinages. Pour être en totale conformité avec la réalité de l’industrie du plastique, nous avons pris en considération certaines caractéristiques très fréquentes telles que les temps de changement d’outils sur les machines lorsqu’un ordre de fabrication succède à un autre sur une machine donnée. La disponibilité des extrudeuses et des matrices d’extrusion représente le goulot d’étranglement dans ce problème d’ordonnancement. Des séries d’expérimentations basées sur des problèmes tests ont été effectuées pour évaluer la qualité de la solution obtenue avec les différents algorithmes proposés. L’analyse des résultats a démontré que les méthodes de construction de solution ne sont pas suffisantes pour assurer de bons résultats et que les méthodes de recherche dans le voisinage donnent des solutions de très bonne qualité. Le choix du voisinage est important pour raffiner la qualité de la solution obtenue. Mots-clés : ordonnancement, optimisation, extrusion, formulation mathématique, heuristique, recuit-simulé, recherche avec tabous, GRASP, algorithme génétique

Entrepreneurship: a long way to go

Entrepreneurship education has emerged as one popular research domain in academic fields given its aim at enhancing and developing certain entrepreneurial qualities of undergraduates that change their state of behavior, even their entrepreneurial inclination and finally may result in the formation of new businesses as well as new job opportunities. This study attempts to investigate the Colombian student´s entrepreneurial qualities and the influence of entrepreneurial education during their studies.

Un aporte a la comprensión de las estrategias emergentes en las organizaciones a través del concepto de improvisación y la metáfora musical

Este trabajo se inscribe en uno de los grandes campos de los estudios organizacionales: la estrategia. La perspectiva clásica en este campo promovió la idea de que proyectarse hacia el futuro implica diseñar un plan (una serie de acciones deliberadas). Avances posteriores mostraron que la estrategia podía ser comprendida de otras formas. Sin embargo, la evolución del campo privilegió en alguna medida la mirada clásica estableciendo, por ejemplo, múltiples modelos para ‘formular’ una estrategia, pero dejando en segundo lugar la manera en la que esta puede ‘emerger’. El propósito de esta investigación es, entonces, aportar al actual nivel de comprensión respecto a las estrategias emergentes en las organizaciones. Para hacerlo, se consideró un concepto opuesto —aunque complementario— al de ‘planeación’ y, de hecho, muy cercano en su naturaleza a ese tipo de estrategias: la improvisación. Dado que este se ha nutrido de valiosos aportes del mundo de la música, se acudió al saber propio de este dominio, recurriendo al uso de ‘la metáfora’ como recurso teórico para entenderlo y alcanzar el objetivo propuesto. Los resultados muestran que 1) las estrategias deliberadas y las emergentes coexisten y se complementan, 2) la improvisación está siempre presente en el contexto organizacional, 3) existe una mayor intensidad de la improvisación en el ‘como’ de la estrategia que en el ‘qué’ y, en oposición a la idea convencional al respecto, 4) se requiere cierta preparación para poder improvisar de manera adecuada.

La disrupción: el punto de partida de la resiliencia o del fracaso empresarial (reflexiones desde la ingeniería)

La perdurabilidad empresarial ha sido un tema recurrente en la literatura sobre dirección de empresas. A pesar de los avances, la liquidación de las empresas aumenta permanentemente. Buscando alternativas de mejora se estudia el caso de dos empresas cuadragenarias dedicadas a prestar servicios de consultoría en ingeniería eléctrica y civil que, en condiciones de crisis, implementaron acciones que les permitieron, no sólo mantenerse en el mercado sino también fortalecer su estructura financiera. Los resultados demostraron que un enfoque equilibrado caracterizado por la toma oportuna de decisiones y la definición e implementación de estrategias de negocio efectivas constituyen herramientas óptimas para asegurar un mayor grado de resiliencia empresarial.

El exceso de confianza y el statu quo dentro de la estructuración de capital: una perspectiva de las finanzas corporativas del comportamiento

El presente artículo, presenta un análisis de las decisiones de estructuración de capital de la compañía Merck Sharp & Dome S.A.S, desde la perspectiva de las finanzas comportamentales, comparando los métodos utilizados actualmente por la compañía seleccionada con la teoría tradicional de las finanzas, para así poder evaluar el desempeño teórico y real. Incorporar elementos comportamentales dentro del estudio permite profundizar más sobre de las decisiones corporativas en un contexto más cercano a los avances investigativos de las finanzas del comportamiento, lo cual lleva a que el análisis de este artículo se enfoque en la identificación y entendimiento de los sesgos de exceso de confianza y statu quo, pero sobre todo su implicación en las decisiones de financiación. Según la teoría tradicional el proceso de estructuración de capital se guía por los costos, pero este estudio de caso permitió observar que en la práctica esta relación de costo-decisión está en un segundo lugar, después de la relación riesgo-decisión a la hora del proceso de estructuración de capital.

la influencia de la felicidad en las decisiones de inversión de activos de largo plazo para una muestra de siete gerentes financieros en la ciudad de Bogotá en el año 2016.

El presente artículo contribuye con la investigación de las Finanzas Corporativas del Comportamiento, rama de las finanzas corporativas que considera que el individuo que toma decisiones financieras no es completamente racional y que por hecho existen sesgos psicológicos que influyen en sus decisiones. Este documento se enfoca, desde el punto de vista conceptual y también mediante el análisis de un estudio de campo, en la influencia de la felicidad en las decisiones de inversión en activos de largo plazo para un grupo de siete gerentes ubicados en la ciudad de Bogotá en el año 2016. En el documento se abarca el concepto general de las finanzas corporativas del comportamiento, se define la felicidad y se presentan sub-variables determinantes para la felicidad del individuo como lo son: salud, balance vida/trabajo, educación y habilidades, conexiones sociales y medio ambiente. Finalmente se presenta cómo éstas afectan a los gerentes financieros en sus decisiones de acuerdo a la investigación realizada.

Assessing Household Food Waste in Italy: A Methodology for Detecting Drivers and Quantities

It has been estimated that one third of edible food destined for human consumption is lost or wasted along the food supply chain globally. Much of the waste comes from Global North, where consumers are considered as the bigger contributors. Different studies tried to analyze and estimate the Household Food Waste (HFW), especially in UK and Northern Europe. The result is that accurate studies at national level exist only in UK, Finland and Norway while no such studies are available in Italy, except for survey- based researches. Though, there is a widespread awareness that such methods might be not able to estimate Food Waste. Results emerging from literature clearly suggest that survey estimate inferior amounts of Food Waste as a result, if compared to waste sorting and weighting analysis or to diary studies. The hypothesis that household food waste is under-estimated when gathered through questionnaires has been enquired into. First, a literature review of behavioral economics and heuristics has been proposed; then, a literature review of the sector listing the existing methodologies to gather national data on Household Food Waste has been illustrated. Finally, a pilot experiment to test a mixed methodology is proposed. While literature suggests that four specific cognitive biases might be able to affect the reliability of answers in questionnaires, results of the present experiment clearly indicate that there is a relevant difference between how much the individual thinks to waste and he/she actually does. The result is a mixed methodology based on questionnaire, diary and waste sorting, able to overcome the cons of each single method.