Review of the Synergies Between Computational Modeling and Experimental Characterization of Materials Across Length Scales

With the increasing interplay between experimental and computational approaches at multiple length scales, new research directions are emerging in materials science and computational mechanics. Such cooperative interactions find many applications in the development, characterization and design of complex material systems. This manuscript provides a broad and comprehensive overview of recent trends where predictive modeling capabilities are developed in conjunction with experiments and advanced characterization to gain a greater insight into structure-properties relationships and study various physical phenomena and mechanisms. The focus of this review is on the intersections of multiscale materials experiments and modeling relevant to the materials mechanics community. After a general discussion on the perspective from various communities, the article focuses on the latest experimental and theoretical opportunities. Emphasis is given to the role of experiments in multiscale models, including insights into how computations can be used as discovery tools for materials engineering, rather than to "simply" support experimental work. This is illustrated by examples from several application areas on structural materials. This manuscript ends with a discussion on some problems and open scientific questions that are being explored in order to advance this relatively new field of research.Comment: 25 pages, 11 figures, review article accepted for publication in J. Mater. Sc

Contributions on DC microgrid supervision and control strategies for efficiency optimization through battery modeling, management, and balancing techniques

Aquesta tesi presenta equips, models i estratègies de control que han estat desenvolupats amb l'objectiu final de millorar el funcionament d'una microxarxa CC. Es proposen dues estratègies de control per a millorar l'eficiència dels convertidors CC-CC que interconnecten les unitats de potència de la microxarxa amb el bus CC. La primera estratègia, Control d'Optimització de Tensió de Bus centralitzat, administra la potència del Sistema d'Emmagatzematge d'Energia en Bateries de la microxarxa per aconseguir que la tensió del bus segueixi la referència dinàmica de tensió òptima que minimitza les pèrdues dels convertidors. La segona, Optimització en Temps Real de la Freqüència de Commutació, consisteix a operar localment cada convertidor a la seva freqüència de commutació òptima, minimitzant les seves pèrdues. A més, es proposa una nova topologia d'equilibrador actiu de bateries mitjançant un únic convertidor CC-CC i s'ha dissenyat la seva estratègia de control. El convertidor CC-CC transfereix càrrega cel·la a cel·la, emprant encaminament de potència a través d'un sistema d'interruptors controlats. L'estratègia de control de l'equalitzador aconsegueix un ràpid equilibrat del SOC evitant sobrecompensar el desequilibri. Finalment, es proposa un model simple de degradació d'una cel·la NMC amb elèctrode negatiu de grafit. El model combina la simplicitat d'un model de circuit equivalent, que explica la dinàmica ràpida de la cel·la, amb un model físic del creixement de la capa Interfase Sòlid-Electròlit (SEI), que prediu la pèrdua de capacitat i l'augment de la resistència interna a llarg termini. El model proposat quantifica la incorporació de liti al rang de liti ciclable necessària per a aconseguir els límits de OCV després de la pèrdua de liti ciclable en la reacció secundària. El model de degradació SEI pot emprar-se per a realitzar un control predictiu de bateries orientat a estendre la seva vida útil.Aquesta tesi presenta equips, models i estratègies de control que han estat desenvolupats amb l'objectiu final de millorar el funcionament d'una microxarxa CC. Es proposen dues estratègies de control per a millorar l'eficiència dels convertidors CC-CC que interconnecten les unitats de potència de la microxarxa amb el bus CC. La primera estratègia, Control d'Optimització de Tensió de Bus centralitzat, administra la potència del Sistema d'Emmagatzematge d'Energia en Bateries de la microxarxa per aconseguir que la tensió del bus segueixi la referència dinàmica de tensió òptima que minimitza les pèrdues dels convertidors. La segona, Optimització en Temps Real de la Freqüència de Commutació, consisteix a operar localment cada convertidor a la seva freqüència de commutació òptima, minimitzant les seves pèrdues. A més, es proposa una nova topologia d'equilibrador actiu de bateries mitjançant un únic convertidor CC-CC i s'ha dissenyat la seva estratègia de control. El convertidor CC-CC transfereix càrrega cel·la a cel·la, emprant encaminament de potència a través d'un sistema d'interruptors controlats. L'estratègia de control de l'equalitzador aconsegueix un ràpid equilibrat del SOC evitant sobrecompensar el desequilibri. Finalment, es proposa un model simple de degradació d'una cel·la NMC amb elèctrode negatiu de grafit. El model combina la simplicitat d'un model de circuit equivalent, que explica la dinàmica ràpida de la cel·la, amb un model físic del creixement de la capa Interfase Sòlid-Electròlit (SEI), que prediu la pèrdua de capacitat i l'augment de la resistència interna a llarg termini. El model proposat quantifica la incorporació de liti al rang de liti ciclable necessària per a aconseguir els límits de OCV després de la pèrdua de liti ciclable en la reacció secundària. El model de degradació SEI pot emprar-se per a realitzar un control predictiu de bateries orientat a estendre la seva vida útil.This dissertation presents a set of equipment, models and control strategies, that have been developed with the final goal of improving the operation of a DC microgrid. Two control strategies are proposed to improve the efficiency of the DC-DC converters that interface the microgrid’s power units with the DC bus. The first strategy is centralized Bus Voltage Optimization Control, which manages the power of the microgrid’s Battery Energy Storage System to make the bus voltage follow the optimum voltage dynamic reference that minimizes the converters’ losses. The second control strategy is Online Optimization of Switching Frequency, which consists in locally operating each converter at its optimum switching frequency, again minimizing power losses. The two proposed optimization strategies have been validated in simulations. Moreover, a new converter-based active balancing topology has been proposed and its control strategy has been designed. This equalizer topology consists of a single DC-DC converter that performs cell-to-cell charge transfer employing power routing via controlled switches. The control strategy of the equalizer has been designed to achieve rapid SOC balancing while avoiding imbalance overcompensation. Its performance has been validated in simulation. Finally, a simple degradation model of an NMC battery cell with graphite negative electrode is proposed. The model combines the simplicity of an equivalent circuit model, which explains the fast dynamics of the cell, with a physical model of the Solid-Electrolyte Interphase (SEI) layer growth process, which predicts the capacity loss and the internal resistance rise in the long term. The proposed model fine-tunes the capacity loss prediction by accounting for the incorporation of unused lithium reserves of both electrodes into the cyclable lithium range to reach the OCV limits after the side reaction has consumed cyclable lithium. The SEI degradation model can be used to perform predictive control of batteries oriented toward extending their lifetime

renewable sources integration through the optimization of the load for residential applications

Abstract This work presents the implementation of two different control strategies for the control of Microgrids a Model Predictive Control (MPC) technique coupled with a Mixed-Integer Linear Program (MILP) structure and a Rule Based Control (RBC) strategy both applied to a residential MicroGrid. The validation of the models has been performed with an experimental setup laid out in the laboratory of University of Rome - Tor Vergata. Results obtained show that MicroGrids connected to the main network have enough potential to support grid balancing actions, thus allowing for a greater penetration of renewable sources into the mix, and giving economic benefits for both end users and providers. In particular, using a MPC strategy major benefits can be obtained in terms of reduction of the unbalanced energy exchange with the main grid and a more efficient use of the micro-grid components

EcoBlock: Grid Impacts, Scaling, and Resilience

Widespread deployment of EcoBlocks has the potential to transform today's electricity system into one that is more resilient, flexible, efficient and sustainable. In this vision, the system will consist of self- su cient, renewable-powered, block-scale entities that can deliberately adjust their net power exchange and can optimize performance, maintain stability, support each other, or disconnect entirely from the grid as needed. This report is intended as an independent analysis of the potential relationships, both constructive and adverse, between EcoBlocks and the grid

Modeling and analysis of geothermal organic rankine cycle turbines coupled with asynchronous generators as a primary power source in islanded microgrids

Thesis (M.S.) University of Alaska Fairbanks, 2019Local renewable resources, such as geothermal hot springs, are being explored as prime electric power and heat sources in remote permanently islanded microgrids, and in some cases these renewable resources have already been implemented. In these types of remote areas, diesel electric generation is typically the prime source of power, even in areas where alternative resources are readily available, despite the high fuel cost due to transportation. This thesis shows that geothermal hot springs, when locally available, can provide primary power for these remote microgrids with temperatures as low as 20°C below the boiling point of water. The geothermal heat can be converted to electrical energy using an organic Rankine cycle turbine in combination with a self-excited induction generator. A steady-state energy balance model has been developed using MATLAB® and Simulink® for simulating greenfield and brownfield geothermal microgrids at Pilgrim Hot Springs, Alaska and Bergstagir, Iceland, respectively, to demonstrate viability of this microgrid design. The results of the simulations have shown that modest loads can be primarily powered off of these low temperature geothermal organic Rankine cycles over long time scales. As expected, more power is available during colder months when sink temperatures are lower, thus increasing the temperature differential. More research is needed to examine system response over shorter time scale transients, which are beyond the scope of this work

DC microgrid simulation and control

However, one of the primary challenges in the microgrid is controlling power electronic devices when it is coordinated with the utility grid. The control system in the microgrid has the main objectives, to ensure supply power to the critical loads, to connect and disconnect the load in case of any fault occurring in the microgrid. This thesis investigates different types of strategies used to control and manage a microgrid; also, the report considers inverter control in islanded mode. This thesis explores the ideas for controlling a microgrid in terms of voltage control in both centralized and decentralized configurations. In more detail, simulations were carried out on two control strategies; inverter control, and frequency control. The inverter control method having the ability to bring the stable and efficient electricity to microgrid system has attracted much consideration in recent years. The droop controller had the capability to autonomously perform equal power sharing and maintain stability in islanded mode of operation. There are many existing dc microgrid around the world. Kythnos Island microgrid is one of those existing microgrid, which can supply 12 houses within the island by using the inverter controller, as the utility grid is located far away from the microgrid. However, this island is either ac or dc loads, so some inverters and converters will be involved in the network. The investigation used MATLAB /SIMULINK to simulate the microgrid network. Which done by implementing the controller in the both ac and dc load. The performance measures such as power sharing accuracy between the microgrid and diesel generator will be obtained. The diesel generators used as a backup in the case of any fault occur in the microgrid. The network simulations at different dc and ac loads will be simulating by using Simulink. This then used to calculate the efficiency of the whole network through the Simulink. Then how efficiency is can be used to upgrade the network as future scope. Active and reactive power in the droop control has been commonly reported on and has been shown to work over a series of the condition of the network. The PQ inverter improves the performance of microgrid in islanded mode; however, the result demonstrates that the inverter controller performed well in the simulation of the Kythnos microgrid network. The efficiency of the LVDC indicates that inverter controller with the ac load performance higher efficiency compared to the dc loads

Sistema de gestión de energía para una estación de carga de vehículos cero emisiones basado en MPC

This work is within the lines of research of the Automática y Robótica Industrial group from the Ingeniería de Sistemas y Automática Department at University of Seville. In particular, it aims at serving as a base for the group contribution to the zero-emission vehicle recharging station future project, which will be held by the Excellent Research Group ENGREEN with the collaboration of researches from the whole Escuela Técnica Superior de Ingeniería. Due to environmental goals of ENGREEN, besides inspiring the use of electric and hydrogen-based vehicles, the charging station will consume renewable energy coming from solar power. The use and management of energy storage system such as hydrogen is crucial because of uncertainty in energy production and consumption. Predictive controllers, well-known as MPC, are used in this work for the resolution of such a complex and multi-objective energy flow problem in that system. Throughout this report, the microgrid is simulated in different generation and consumption scenarios, showing how a scheduler MPC, using both continuous and logic variables, and a reference tracking MPC, using only continuous variables, allow for optimal and efficient solutions. The software Simµgrid, developed by the group itself some years ago, is used over MATLAB/Simulink with Yalmip toolbox and solver CPLEX for the scheduler MPC and the solver quadprog without Yalmip for the reference tracking MPC. The work described above is expected to be used in the future as a starting point for a more complex and detailed management of zero-emission vehicles charging process.Este trabajo se encuentra dentro de las líneas de investigación del grupo Automática y Robótica Industrial del Departamento de Ingeniería de Sistemas y Automática de la Universidad de Sevilla. En concreto, trata de sentar las bases de la aportación de dicho grupo al futuro proyecto de estación de recarga de vehículos cero emisiones que llevará a cabo la Unidad de Excelencia ENGREEN, con componentes de toda la Escuela Técnica Superior de Ingeniería. Debido a los fines medioambientales de dicha unidad de excelencia, además de impulsar el uso del vehículo eléctrico y del basado en hidrógeno, la estación de recarga hará uso de fuentes de energía renovable como la solar. La incertidumbre en la producción y consumo de energía hace necesario el empleo de sistemas de almacenamiento de energía como el hidrógeno y su consiguiente gestión. El flujo de potencia en estos sistemas es un problema de control complejo y multiobjetivo para cuya resolución se emplean en este trabajo técnicas de control predictivo, o más conocido como MPC. A lo largo de esta memoria se describen las simulaciones de la microrred con diferentes escenarios de generación y consumo, mostrando cómo un MPC planificador, usando tanto variables continuas como lógicas, y otro de seguimiento, usando sólo variables continuas, permiten obtener una solución óptima y eficiente. Para ello se usa MATLAB/Simulink sobre el software Simµgrid, desarrollado en años anteriores por el propio grupo de investigación, con el toolbox Yalmip y el solver CPLEX para el MPC planificador y el solver quadprog sin Yalmip para el MPC de seguimiento. Lo anterior pretende emplearse en un futuro como punto de partida para una gestión más compleja y detallada del proceso de recarga de vehículos cero emisiones.Universidad de Sevilla. Máster en Ingeniería Electrónica, Robótica y Automátic