Ce travail s’inscrit dans l’optique de prédimensionnement par optimisation déterministe en électronique de puissance. Nous nous focalisons principalement sur la problématique de la Compatibilité ElectroMagnétique que nous désirons inclure dans la démarche. Pour cela, nous considérons l’exemple d’un redresseur triphasé comportant des filtres CEM à la fois du côté triphasé et du côté continu. Un couplage de mode commun a lieu entre les deux filtres, ils doivent donc être conçus simultanément. Des modéles de dimensionnement du convertisseur et de ses différents composants (passifs, interrupteurs, refroidisseur) ont été élaborés. Dans la procédure d’optimisation, l’ensemble des variables de cette modélisation globale du convertisseur (valeur des éléments fonctionnels, stratégie de commande MLI et fréquence de découpage) impacte les émissions CEM conduites. Ainsi, le modèle de calcul CEM est intégré dans le déroulement du processus, qui vise à minimiser la masse du convertisseur. Grâce à cela nous obtenons une approche globale où les filtres CEM sont dimensionnés en parallèle avec le convertisseur, et non une fois que la conception de ce dernier soit terminée, comme c’est classiquement le cas.La variation de la fréquence de découpage durant l’optimisation a constitué le problème majeur. Nous avons dû développer des stratégies concernant la surveillance des spectres CEM pour arriver à diminuer drastiquement les temps de calcul. Nous avons aussi développé une formulation de la contrainte CEM et une stratégie de lancement automatique d’optimisations déterministes avec paramétrage initial aléatoire qui a permis aux dimensionnements d’aboutir. Tout au long de la thèse, l’accent a été mis sur la généricité des modèles, qu’ils touchent à la CEM ou aux autres points du dimensionnement, en vue de leur adaptabilité à d’autres cas d’application. / This thesis deals with the sizing of power electronics using deterministic optimization. In this way, methods to integrate the ElectroMagnetic Compatibility constraints in such process were studied. The case of a three-phase rectifier with EMC filters on both AC and DC sides was considered. A common-mode path creates an interaction between the two filters, thus they have to be sized together. Models of the converter and its components were developed for their sizing by deterministic optimizations. In such conception problem, all the parameters used for describing the system configuration (functional elements values, PWM command strategy and the switching frequency) influence the conducted EMC emissions. Therefore, the modeling of the EMC constraints was integrated in the optimization procedure, which aims the overall weight reduction. Thanks to that, a global approach where EMC filters are sized along with the converter was achieved, whereas it is usually done after the converter conception.The main challenge was the variation of the switching frequency in optimization. Strategies were developed regarding the automatic surveillance of the EMC spectrums in order to drastically reduce their computation times. An innovative formulation of the EMC constraints enabled the optimizations to converge. An automatic procedure for launching multiple deterministic optimizations with random initial parameters allowed us to obtain good optimization results, regarding the constraints and the global weight of the system. In this work, genericity of the modelling approach was a main concern, regarding EMC and the different sizing models. Therefore, the adaptation of the developed methods to other applications should be convenient.

Optimal power flow (OPF) is the choice tool for determining the optimal operating status of the power system by managing controllable devices. The importance of the OPF approach has increased due to increasing energy prices and availability of more control devices. Existing OPF approaches exhibit shortcomings. Current OPF algorithms can be classified into (a) nonlinear programming, (b) intelligent search methods, and (c) sequential algorithms. Nonlinear programming algorithms focus on the solution of the Kuhn-Tucker conditions; they require a starting feasible solution and the model includes all constraints; these characteristics limit the robustness and efficiency of these methods. Intelligent search methods are first-order methods and are totally inefficient for large-scale systems. Traditional sequential algorithms require a starting feasible solution, a requirement that limits their robustness. Present implementations of sequential algorithms use traditional modeling that result in inefficient algorithms. The research described in this thesis has overcome the shortcomings by developing a robust and highly efficient algorithm. Robustness is defined as the ability to provide a solution for any system; the proposed approach achieves robustness by operating on suboptimal points and moving toward feasible, it stops at a suboptimal solution if an optimum does not exist. Efficiency is achieved by (a) converting the nonlinear OPF problem to a quadratic problem (b) and limiting the size of the model; the quadratic model enables fast convergence and the algorithm that identifies the active constraints, limits the size of the model by only including the active constraints. A concise description of the method is as follows: The proposed method starts from an arbitrary state which may be infeasible; model equations and system constraints are satisfied by introducing artificial mismatch variables at each bus. Mathematically this is an optimal but infeasible point. At each iteration, the artificial mismatches are reduced while the solution point maintains optimality. When mismatches reach zero, the solution becomes feasible and the optimum has been found; otherwise, the mismatch residuals are converted to load shedding and the algorithm provides a suboptimal but feasible solution. Therefore, the algorithm operates on infeasible but optimal points and moves towards feasibility. The proposed algorithm maximizes efficiency with two innovations: (a) quadratization that converts the nonlinear model to quadratic with excellent convergence properties and (b) minimization of model size by identifying active constraints, which are the only constraints included in the model. Finally sparsity technique is utilized that provide the best computational efficiency for large systems. This dissertation work demonstrates the proposed OPF algorithm using various systems up to three hundred buses and compares it with several well-known OPF software packages. The results show that the proposed algorithm converges fast and its runtime is competitive. Furthermore, the proposed method is extended to a three-phase OPF (TOPF) algorithm for unbalanced networks using the quadratized three-phase power system model. An example application of the TOPF is presented. Specifically, TOPF is utilized to address the problem of fault induced delayed voltage recovery (FIDVR) phenomena, which lead to unwanted relay operations, stalling of motors and load disruptions. This thesis presents a methodology that will optimally enhance the distribution system to mitigate/eliminate the onset of FIDVR. The time domain simulation method has been integrated with a TOPF model and a dynamic programming optimization algorithm to provide the optimal reinforcing strategy for the circuits.

Numerical modeling of fluid flow and dissolved species transport in the subsurface is a challenging task, given variability and measurement uncertainty in the physical properties of the rock, the complexities of multi-fluid interaction, and limited computational resources. Nonetheless, this thesis seeks to expand our modeling capabilities in the context of contaminant hydrogeology. We describe the numerical simulator CompFlow Bio and use it to model invasion of a nonaqueous phase liquid (NAPL) contaminant through the vadose zone and below the water table in a fractured porous rock. CompFlow Bio is a three-phase, multicomponent, deterministic numerical model for fluid flow and dissolved species transport; it includes capillary pressure and equilibrium partitioning relationships. We have augmented the model to include randomly generated, axis-aligned, discrete fracture networks (DFNs). The DFN is coupled with the porous medium (PM) to form a single continuum. The domain is discretized using a finite-volume scheme in an unstructured mesh of rectilinear control volumes (CVs). Herein we present the governing equations, unstructured mesh creation scheme, algebraic development of fracture intersection CV elimination, and coupling of PM CVs over a fracture plane to permit asperity contact bridged flow. We include: small scale two-phase water-air and NAPL-water simulations to validate the practice of intersection CV elimination; small scale simulations with water-air, NAPL-water, and NAPL-water-air systems in a grid refinement exercise and to demonstrate the effect of asperity contact bridged flow; intermediate scale 3D simulations of NAPL invading the saturated zone, based on the Smithville, Ontario, site; intermediate scale 2D and 3D simulations of NAPL invading the vadose zone and saturated zone with transient recharge, based on the Santa Susana Field Laboratory site, California. Our findings indicate that: the formulation provides a practical and satisfactory way of modeling three-phase flow in discretely fractured porous rock; numerical error caused by spatial discretization manifests itself as several biases in physical flow processes; that asperity contact is important in establishing target water saturation conditions in the vadose zone; and simulation results are sensitive to relative permeability-saturation-capillary pressure relationships. We suggest a number of enhancements to CompFlow Bio to overcome certain computational limitations.

Two separate mechanistic kinetic models have been developed for the hydrocracking of complex feedstocks. The first model is targeted for the hydrocracking of vacuum gas oil. The second one addresses specifically the hydrocracking of long-chain paraffins, but at a more fundamental level as compared to the first one. Both models are based on an exhaustive computer generated reaction network of elementary steps. In the first model, the dehydrogenation/hydrogenation steps occurring on the metal sites to generate/consume the reactive olefinic intermediates are assumed to be very fast so that the acid site steps are considered as the rate determining steps. The frequency factors for acid site steps are modeled using the single-event concept and the activation energies based on the nature of the reactant and product carbenium ions. This model utilizes a detailed composition of the vacuum gas oil characterized by 16 different molecular classes up to carbon number 40. These classes are divided into 45 subclasses by distinguishing the isomers of a class according to the number of methyl branches. The kinetic model is plugged into an adiabatic multi-bed trickle flow reactor model. The model contains 33 feedstock and temperature independent parameters which have been estimated from the experimental data. The model has been used to study the effect of the operating conditions on the yield and composition of various products. A sensitivity analysis of the distribution of isomers of a class among its different subclasses has been performed showing that the total conversion increases when the content of isomers with a higher degree of branching is increased in the feed. In the second model, the dehydrogenation/hydrogenation steps on the metal sites are also assumed to be rate determining. The rate coefficients for the dehydrogenation steps are modeled depending on the nature of the carbon atoms forming the double bond. The frequency factors for the acid site steps are modeled using the single-event concept. A more rigorous approach has been selected to model the activation energies of the acid site steps by implementing the Evans-Polanyi relationship. The 14 model parameters, which are independent of the temperature and feedstock composition, have been estimated from the experimental data. The model elucidates the effect of the relative metal/acid activity of the catalyst on the isomerization/cracking selectivities and on the carbon number distribution of the products.

The interaction of a bubble with solid surfaces, hydrophobic and hydrophilic, was investigated. When a bubble approaches towards a solid surface, a thin liquid film forms between them. The liquid in the film drains until an instability forms and film ruptures resulting in a three phase contact (TPC). Following rupture, the TPC line spreads on the solid surface. In the present study, glycerol-water solutions with varying percentages of water were used to investigate the effect of viscosity. Experiments were carried out with varying bubble size. The rupture and TPC line movement were recorded by high-speed digital video camera. The dependence of the TPC line movement on different parameters was investigated. The experimental results were compared with the existing theories for the TPC line movement. An empirical equation was developed to predict the TPC line movement. Formation or rupturing of the intervening film in case of a hydrophilic surfaces, which were glass surface cleaned by six cleaning techniques, was investigated. It was shown that a stable film forms for acid or alkali cleaning.

Η παρούσα διπλωματική εργασία πραγματεύεται την μελέτη και κατασκευή ενός κυκλώματος για την οδήγηση ενός κινητήρα μαγνητικής αντίδρασης. Σκοπός είναι η μελέτη και κατασκευή ενός κυκλώματος τριφασικού αντιστροφέα τάσης για τηνλειτουργία και τον έλεγχο των στροφών ενός κινητήρα μαγνητικής αντίδρασης. Αν θέλαμε νακάνουμε μια περιγραφή του κινητήρα μαγνητικής αντίδρασης και να δώσουμε έναν ορισμό,θα μπορούσαμε να πούμε ότι: «Ο κινητήρας μαγνητικής αντίδρασης βασίζει τη λειτουργίατου στη ροπή αντίδρασης (reluctance torque), ροπή αντίδρασης ονομάζεται η ροπή που επάγεται σε ένα σιδερένιο αντικείμενο όταν κάποιο εξωτερικό μαγνητικό πεδίο αναγκάζει το αντικείμενο αυτό να ευθυγραμμιστεί με το πεδίο. Αυτή η ροπή αναπτύσσεται επειδή το εξωτερικό μαγνητικό πεδίο επάγει ένα πεδίο στο σίδηρο του αντικειμένου, το οποίο τείνει ναευθυγραμμιστεί με το μαγνητικό πεδίο που το προκάλεσε.» Αρχικά μελετώνται οι βασικές αρχές λειτουργίας του κινητήρα μαγνητικής αντίδρασης. Αναλύεται τομαθηματικό μοντέλο που διέπει τη λειτουργία του και γίνεται αναφορά στη μορφή και τα βασικά κατασκευαστικά χαρακτηριστικά του. Επίσης γίνεται μια σύντομη αναδρομή στην ιστορία των κινητήρων μαγνητικής αντίδρασης καθώς και μία σύγκριση αυτού του είδους κινητήρα με άλλουςκινητήρες εναλλασσομένου ρεύματος. Και αναλύονται τα πλεονεκτήματά του που τον καθιστούνανταγωνιστικό προς αυτούς. Στη συνέχεια γίνεται μια θεωρητική ανάλυση του κυκλώματος του τριφασικού αντιστροφέα τάσηςπου κατασκευάσαμε, καθώς και όλων των υπολοίπων κυκλωμάτων που είναι αναγκαία για τηλειτουργία του. Επιπροσθέτως αναλύεται η μέθοδος παλμοδότησης των διακοπτικών στοιχείων τουαντιστροφέα τάσης που χρησιμοποιήσαμε , και είναι η «Ημιτονοειδής Διαμόρφωση Εύρους Παλμών» Στο επόμενο βήμα αναλύουμε τον τρόπο κατασκευής του κυκλώματος του τριφασικού αντιστροφέατάσης που ακολουθήσαμε καθώς και του πλήρους κυκλώματος παλμοδότησης του. Ενώ γίνεται καιαναλυτική περιγραφή του βιομηχανικού μικροελεγκτή πουχρησιμοποιήσαμε για την παραγωγή τωνπαλμών , με τη μέθοδο της «Ημιτονοειδούς Διαμόρφωσης Εύρους Παλμών» Τέλος παραθέτουμε παλμογραφήματα και μετρήσεις που προέκυψαν από τα πειράματα πουδιενεργήθηκαν αφότου κατασκευάσαμε το κύκλωμα οδήγησης του κινητήρα μαγνητικής αντίδρασης. / The purpose of this thesis is the analysis and construction of a three phase reluctance motor drive system. At first the special characteristics of the syncronous reluctance motors are analyzed. After that there is a theoretical analysis of the three phase inverter circuit, and finally is described the construction of the drive system

This thesis presents a novel, fast, and accurate 3 steady-state power-flow analysis (PFA) tool for the real-time operation of the active distribution systems, also known as the active distribution networks (ADN), in the grid-tied and islanded operating modes. Three-phase power-flow models of loads, transformers, and multi-phase power lines and laterals are provided. This thesis also presents novel steady-state, fundamental-frequency, power-flow models of voltage-sourced converter (VSC)-based distributed energy resource (DER) units. The proposed models address a wide array of DER units, i.e., (i) variable-speed wind-driven doubly-fed asynchronous generator-based and (ii) single/three-phase VSC-coupled DER units. In addition, a computationally-efficient technique is proposed and implemented to impose the operating constraints of the VSC and the host DER unit within the context of the developed PFA tool. Novel closed forms for updating the corresponding VSC power and voltage reference set-points are proposed to guarantee that the power-flow solution fully complies with the VSC constraints. All the proposed DER models represent (i) the salient VSC control strategies and objectives under balanced and unbalanced power-flow scenarios and (ii) all the operating limits and constraints of the VSC and its host DER unit. Also, the slack bus concept is revisited, associated with the PFA, where a 3 distributed slack bus (DSB) model is proposed for the PFA and operation of islanded ADNs. Distributing the real and reactive slack power among several DER units is essential to provide a realistic power-flow approach for ADNs in the absence of the utility bus. The proposed DSB model is integrated with the developed 3 PFA tool to form a complete ADN PFA package. The new PFA tool, including the proposed DER and DSB models, is tested using several benchmark networks of different sizes, topologies, and parameters. Many case studies, encompassing a wide spectrum of DER control specifications and operating modes, are conducted to demonstrate (i) the numerical accuracy of the proposed models of the DER units and their operating constraints, (ii) the effectiveness of the proposed DSB model for the islanded ADN PFA, and (iii) the computational efficiency of the integrated PFA software tool irrespective of the network topology and parameters.

This thesis presents a novel, fast, and accurate 3 steady-state power-flow analysis (PFA) tool for the real-time operation of the active distribution systems, also known as the active distribution networks (ADN), in the grid-tied and islanded operating modes. Three-phase power-flow models of loads, transformers, and multi-phase power lines and laterals are provided. This thesis also presents novel steady-state, fundamental-frequency, power-flow models of voltage-sourced converter (VSC)-based distributed energy resource (DER) units. The proposed models address a wide array of DER units, i.e., (i) variable-speed wind-driven doubly-fed asynchronous generator-based and (ii) single/three-phase VSC-coupled DER units. In addition, a computationally-efficient technique is proposed and implemented to impose the operating constraints of the VSC and the host DER unit within the context of the developed PFA tool. Novel closed forms for updating the corresponding VSC power and voltage reference set-points are proposed to guarantee that the power-flow solution fully complies with the VSC constraints. All the proposed DER models represent (i) the salient VSC control strategies and objectives under balanced and unbalanced power-flow scenarios and (ii) all the operating limits and constraints of the VSC and its host DER unit. Also, the slack bus concept is revisited, associated with the PFA, where a 3 distributed slack bus (DSB) model is proposed for the PFA and operation of islanded ADNs. Distributing the real and reactive slack power among several DER units is essential to provide a realistic power-flow approach for ADNs in the absence of the utility bus. The proposed DSB model is integrated with the developed 3 PFA tool to form a complete ADN PFA package. The new PFA tool, including the proposed DER and DSB models, is tested using several benchmark networks of different sizes, topologies, and parameters. Many case studies, encompassing a wide spectrum of DER control specifications and operating modes, are conducted to demonstrate (i) the numerical accuracy of the proposed models of the DER units and their operating constraints, (ii) the effectiveness of the proposed DSB model for the islanded ADN PFA, and (iii) the computational efficiency of the integrated PFA software tool irrespective of the network topology and parameters.

Numerical modeling of fluid flow and dissolved species transport in the subsurface is a challenging task, given variability and measurement uncertainty in the physical properties of the rock, the complexities of multi-fluid interaction, and limited computational resources. Nonetheless, this thesis seeks to expand our modeling capabilities in the context of contaminant hydrogeology. We describe the numerical simulator CompFlow Bio and use it to model invasion of a nonaqueous phase liquid (NAPL) contaminant through the vadose zone and below the water table in a fractured porous rock. CompFlow Bio is a three-phase, multicomponent, deterministic numerical model for fluid flow and dissolved species transport; it includes capillary pressure and equilibrium partitioning relationships. We have augmented the model to include randomly generated, axis-aligned, discrete fracture networks (DFNs). The DFN is coupled with the porous medium (PM) to form a single continuum. The domain is discretized using a finite-volume scheme in an unstructured mesh of rectilinear control volumes (CVs). Herein we present the governing equations, unstructured mesh creation scheme, algebraic development of fracture intersection CV elimination, and coupling of PM CVs over a fracture plane to permit asperity contact bridged flow. We include: small scale two-phase water-air and NAPL-water simulations to validate the practice of intersection CV elimination; small scale simulations with water-air, NAPL-water, and NAPL-water-air systems in a grid refinement exercise and to demonstrate the effect of asperity contact bridged flow; intermediate scale 3D simulations of NAPL invading the saturated zone, based on the Smithville, Ontario, site; intermediate scale 2D and 3D simulations of NAPL invading the vadose zone and saturated zone with transient recharge, based on the Santa Susana Field Laboratory site, California. Our findings indicate that: the formulation provides a practical and satisfactory way of modeling three-phase flow in discretely fractured porous rock; numerical error caused by spatial discretization manifests itself as several biases in physical flow processes; that asperity contact is important in establishing target water saturation conditions in the vadose zone; and simulation results are sensitive to relative permeability-saturation-capillary pressure relationships. We suggest a number of enhancements to CompFlow Bio to overcome certain computational limitations.

Στις μέρες μας, τα Συστήματα Ηλεκτρικής Ενέργειας περιλαμβάνουν μονάδες παραγωγής και φορτία που χρησιμοποιούν συσκευές με ηλεκτρονικά ισχύος σε ολοένα και αυξανόμενο βαθμό. Αυτό έχει σαν αποτέλεσμα να εμφανίζονται στο δίκτυο μη ημιτονοειδείς κυματομορφές τάσεων και ρευμάτων. Ως γνωστόν, υπό ημιτονοειδείς συνθήκες ο υπολογισμός της ενεργού ισχύος, της αέργου ισχύος και του συντελεστή ισχύος αρκούν για την κατανόηση της ροής ενέργειας ενός συστήματος. Παρ’όλα αυτά, σε μη ημιτονοειδείς συνθήκες οι κλασσικές έννοιες της ενεργού και αέργου ισχύος δεν είναι χρήσιμες. Στόχος της συγκεκριμένης διπλωματικής εργασίας είναι η ανάδειξη αυτού του προβλήματος καθώς και η θεμελίωση της θεωρίας στιγμιαίας ισχύος, η οποία αποτελεί βασική θεωρία ανάλυσης των σύγχρονων τριφασικών συστημάτων. / Nowadays, power systems include production units and loads using power electronic devices in an increasing rate. Thus,non sinusoidal voltages and currents appear in the network. In sunusoidal conditions the calculation of active power, reactive power and power factor are sufficient for understanding the energy flow of the system. Although, in non-sinusoidal conditions the classical theory is not sufficient to describe the energy flow in the system. The purpose of this thesis is to highlight this problem and present the instantaneous power theory, which is the basic theory of modern analysis of three phase systems.