Η παρούσα διδακτορική διατριβή εντάσσεται στο πλαίσιο που αφορά στο πεδίο ελέγχου συστημάτων ισχύος και ειδικότερα στην εφαρμογή προηγμένων μεθόδων στην ανάλυση και τον έλεγχο στρεφόμενων ηλεκτρικών μηχανών οδηγούμενων από ηλεκτρονικές διατάξεις ισχύος. Ειδικότερα, λαμβάνοντας υπόψη τα ακριβή μη γραμμικά μοντέλα των μετατροπέων ισχύος και των ηλεκτρικών μηχανών, αναλύεται η μορφή και η συμπεριφορά των ολοκληρωμένων συστημάτων που χρησιμοποιούνται για την οδήγηση των μηχανών και αποδεικνύεται ότι τα μοντέλα αυτά μπορούν να περιγραφούν με τη γενική παθητική Hamiltonian μορφή. Οι ηλεκτρονικές διατάξεις ισχύος που μελετώνται είναι ο μετατροπέας ΣΡ/ΣΡ ανύψωσης τάσης και ο τριφασικός μετατροπέας σε λειτουργία ανορθωτή και μετατροπέα, ενώ επίσης μελετώνται οι μηχανές ΣΡ ξένης διέγερσης και με διέγερση σε σειρά καθώς επίσης και η τριφασική επαγωγική μηχανή. Έχοντας αναπτύξει τα πλήρη μοντέλα, προτείνεται ένας νέος μη γραμμικός νόμος ελέγχου κατάλληλος για τη γενική παθητική Hamiltonian μορφή των συστημάτων τα οποία περιλαμβάνουν διακοπτικούς μετατροπείς ισχύος. Μια εκτενής μη γραμμική μαθηματική ανάλυση αποδεικνύει ότι ο προτεινόμενος νόμος ελέγχου εγγυάται ευστάθεια και σύγκλιση στο επιθυμητό σημείο ισορροπίας για το σύστημα κλειστού βρόχου. Ο έλεγχος αυτός εφαρμόζεται για τον έλεγχο κινητήρων ΣΡ οδηγούμενων από μετατροπέα ΣΡ/ΣΡ ανύψωσης τάσης καθώς και στην τριφασική επαγωγική μηχανή. Η ανάλυση και η εφαρμογή του ελέγχου οδηγεί στην ανάγκη για επεκτάσεις στη μορφή του ώστε να αυξηθεί η σθεναρότητά του ως προς τις αρχικές συνθήκες, να βελτιωθεί η μεταβατική του συμπεριφορά και να εφαρμοστεί κατάλληλα σε τριφασικούς μετατροπείς ισχύος ώστε να εγγυάται συγκεκριμένες λειτουργίες όπως γραμμική διαμόρφωση. Με την εφαρμογή του ελέγχου στην επαγωγική μηχανή, προτείνεται μια πλήρης σχεδίαση που λειτουργεί είτε βασιζόμενη στη λογική του προσανατολισμένου πεδίου, είτε πλήρως ανεξάρτητα από αυτή, ενώ μελετάται και η συμπεριφορά του σε καταστάσεις εξασθένησης πεδίου. Τέλος, η λογική του ελέγχου επιβεβαιώνεται σε ένα σύστημα ανεμογεννήτριας συνδεδεμένης στο δίκτυο μέσω πλήρους συστήματος μετατροπέων ισχύος με διασύνδεση συνεχούς ρεύματος. Σε όλες τις περιπτώσεις παρουσιάζονται προσομοιώσεις και κατά το δυνατό πειραματικά αποτελέσματα μέσω κατάλληλων εργαστηριακών διατάξεων. / The present PhD dissertation is addressed in the research field of control of power systems and more precisely in providing advanced methods for the analysis and control of electrical machines driven by power devices. Particularly, taking into account the accurate nonlinear models of the power converters and the electrical machines, the structure and the behavior of the complete models used for machine driving are analyzed based on the generalized Hamiltonian-passive form. The power converters discussed are the DC/DC boost converter and the three-phase power converter used as a rectifier or an inverter, while the separately-excited and the series-connected DC motors along with the three-phase induction machine are studied as well. After providing the complete dynamic models, a new nonlinear control scheme suitable for the generalized Hamiltonian-passive systems with switching devices is proposed. Using an extended mathematical analysis, it is proven that the proposed controller guarantees stability and convergence to the desired equilibrium for the closed-loop system. The proposed control application is tested for DC drive systems fed by DC/DC boost converters as well as for induction motor systems fed by AC/DC/AC converters. The control analysis and application leads to the extension of the control structure in order to increase the robustness with respect to the initial conditions, to improve the transient performance and to be suitably applied in three-phase power converter systems, guaranteeing simultaneously certain operating constraints such as linear modulation. For the case of the induction motor control, a complete form of the controller is proposed that acts either in the frame of field-orientation or independently from it, while the controller is also studied in field-weakening conditions. Finally, the controller performance is studied in a wind generating system connected to the grid through a full-scale power converter. In all cases, simulation results are presented while experimental results are provided where possible by using suitable laboratory testbeds.

A control-oriented model of a Dual Clutch Transmission was developed for real-time Hardware In the Loop (HIL) applications, to support model-based development of the DCT controller. The model is an innovative attempt to reproduce the fast dynamics of the actuation system while maintaining a step size large enough for real-time applications. The model comprehends a detailed physical description of hydraulic circuit, clutches, synchronizers and gears, and simplified vehicle and internal combustion engine sub-models. As the oil circulating in the system has a large bulk modulus, the pressure dynamics are very fast, possibly causing instability in a real-time simulation; the same challenge involves the servo valves dynamics, due to the very small masses of the moving elements. Therefore, the hydraulic circuit model has been modified and simplified without losing physical validity, in order to adapt it to the real-time simulation requirements. The results of offline simulations have been compared to on-board measurements to verify the validity of the developed model, that was then implemented in a HIL system and connected to the TCU (Transmission Control Unit). Several tests have been performed: electrical failure tests on sensors and actuators, hydraulic and mechanical failure tests on hydraulic valves, clutches and synchronizers, and application tests comprehending all the main features of the control performed by the TCU. Being based on physical laws, in every condition the model simulates a plausible reaction of the system. The first intensive use of the HIL application led to the validation of the new safety strategies implemented inside the TCU software. A test automation procedure has been developed to permit the execution of a pattern of tests without the interaction of the user; fully repeatable tests can be performed for non-regression verification, allowing the testing of new software releases in fully automatic mode. / Un modello orientato al controllo di una trasmissione a doppia frizione (DCT) è stato sviluppato per applicazioni real-time Hardware In the Loop (HIL) come supporto allo sviluppo model-based della centralina elettronica di controllo (TCU, Transmission Control Unit). Il modello è un tentativo innovativo di riprodurre le dinamiche del sistema di attuazione, molto veloci, mantenendo un passo di simulazione sufficientemente grande per applicazioni real-time. Il modello comprende una descrizione dettagliata del circuito idraulico, delle frizioni, dei sincronizzatori e delle marce, e un modello semplificato del veicolo e del motore. Poiché l’olio che circola nel sistema ha un modulo di comprimibilità molto elevato, le dinamiche di pressione sono molto veloci, causando instabilità durante una simulazione real-time; lo stesso problema riguarda la dinamica delle servo valvole, a causa delle piccole masse degli elementi in movimento. Perciò, il modello è stato modificato e semplificato senza perdere validità fisica, per adattarlo alla necessità di una simulazione real-time. I risultati di simulazioni offline sono stati confrontati con misure effettuate in vettura per verificare la validità del modello sviluppato, che è stato poi implementato all’interno di un sistema HIL e connesso alla TCU. Una serie di test è stata eseguita al simulatore: test riguardanti guasti elettrici su sensori ed attuatori, guasti idraulici e meccanici su valvole, frizioni e sincronizzatori, e test applicativi comprendenti tutte le principali funzionalità del controllo. Essendo basato su leggi fisiche, il modello simula una reazione plausibile del sistema in ogni condizione. Il primo uso intensivo del simulatore ha portato alla validazione delle nuove strategie di safety implementate in TCU. Una procedura di automatizzazione dei test è stata sviluppata per permettere l’esecuzione di un pattern di test senza l’interazione dell’utente; test completamente ripetibili possono essere eseguiti per verifiche di non regressione, permettendo di testare nuove release software in modo completamente automatico.

Dynamical network systems are complex interconnected systems useful to describe many real world problems. The advances in information technology has led the current trend towards connecting more and more systems, creating "intelligent" systems, where the intelligence originates in the scale and complexity of the network. With the growing scale of networked systems comes also higher demands on performance and continuous availability and this creates the need for optimization and control of network systems. This thesis makes four important contributions in this area. In the first contribution, we consider a collaborative road freight transportation system. An efficiency measure for the road utilization in collaborative transportation scenarios is introduced, which evaluates the performance of collaboration strategies in comparison to an optimal central planner. The efficiency measure is used to study a freight transport simulation in Germany and taxi trips using real data from New York City. This is followed by a study of the optimal idling locations for trucks, and the optimal locations for distribution centers. These locations are then exploited in a simulation of a realistic collaborative freight transport system. The second contribution studies the important problem of gathering data that are distributed among the nodes in an anonymous network, i.e., a network where the nodes are not endowed with unique identifies. Two specific tasks are considered: to estimate the size of the network, and to aggregate the distribution of local measurements generated by the nodes. We consider a framework where the nodes require anonymity and have restricted computational resources. We propose probabilistic algorithms with low resource requirements, that quickly generate arbitrarily accurate estimates. For dynamical networks, we improve the accuracy through a regularization term which captures the trade-off between the reliability of the gathered data and a-priori assumptions for the dynamics. In the third contribution, a peer-to-peer network is utilized to improve a live-streaming media application. In particular, we study how an overlay network, constructed from simple preference functions, can be used to build efficient topologies that reduce both network latency and interruptions. We present necessary and sufficient convergence conditions, as well as convergence rate estimates, and demonstrate the improvements for a real peer-to-peer video streaming application. The final contribution is a distributed optimization algorithm. We consider a distributed multi-agent optimization problem of minimizing the sum of convex objective functions. A decentralized optimization algorithm is introduced, based on dual decomposition, together with the subgradient method for finding the optimal solution. The convergence rate is analyzed for different step size rules, constant and time-varying communication delays, and noisy communication channels. / Dynamiska nätverkssystem är komplexa sammankopplade system med många praktiska tillämpningar. Den snabba utvecklingen inom informationsteknologin har drivit trenden att sammankoppla större och större system till nätverk av "intelligenta" system, där intelligensen kommer från komplexiteten av nätverken. Med den ökande storleken på nätverkssystemen kommer också ökade krav på dess prestanda och tillgänglighet, vilket är drivkraften bakom utvecklingen av optimering och styrning av nätverkssystem. Den här avhandlingen presenterar fyra viktiga bidrag inom detta område. Det första bidraget handlar om kooperativ lastbilstransport. Först introduceras ett mått som mäter effektiviteten i systemet jämfört med en central planerare. Detta mått används sedan för att utvärdera vinsterna med kooperativa transporter, men används också för att utvärdera taxiförarnas vägval med verkliga data från New York City. Detta följs av en studie av de optimala vänteplatserna för lastbilar och de optimal placeringarna av distributionscentraler. Dessa positioner används sedan för att förbättra transportprestandan i ett kooperativt transportsystem. I det andra bidraget studeras informationsaggregering i anonyma nätverkssystem, det vill säga nätverk där noderna saknar unika identiteter. Två specifika problem hanteras: att estimera storleken på nätverket, och att sammanställa fördelningen av lokala mätvärden i nätverket. Noderna i detta nätverk kräver anonymitet, men antas också ha strikt begränsad beräkningskapacitet. Vi presenterar stokastiska algoritmer med låga beräkningskrav, som dessutom har snabb konvergens och som kan justeras till att ge godtycklig precision. För dynamiska nätverk förbättras prestandan genom att en regulariseringsterm används för att väga observerad data mot förväntat beteende hos systemet. I tredje bidraget analyseras ett peer-to-peer nätverk för direktsänd videodistribution. Speciellt studeras konvergensen av nätverkstopologin som genereras från lokala preferensfunktioner, och hur resultaten kan används för att minska fördröjningarna och avbrotten under videouppspelning. Vi ger nödvändiga och tillräckliga villkor för konvergens, samt karakteriserar gränsvärden för hur snabbt användare kan ansluta eller lämna nätverket utan att påverka prestandan. Det sista bidraget är en distribuerad optimeringsalgoritm. Problemet består i att minimera summan av konvexa funktioner för varje nod i ett nätverk. En decentraliserad optimeringsalgoritm presenteras som baseras på det duala optimeringsproblemet tillsammans med subgradient-metoden. Konvergenshastigheten analyseras för olika val av steglängder, konstanta samt tidsberoende kommunikationsfördröjningar och brusiga kommunikationskanaler. / <p>QC 20161020</p>

Diss. Stockholm : Kungliga Tekniska högskolan, 2008.

Termisk energi som solfångare producerar kan lagras i Borehole Thermal Energy Storage, BTES, när efterfrågan är låg, för att sedan användas när efterfrågan är hög. Målet med detta examensarbete är att utveckla en skalbar systemarkitektur för styrning och monitorering av en BTES prototyp, där ringarna som borrhålen utgör är indelade i olika temperaturhierarkier. De ringar som ligger närmare centrum av borrhålen har högre temperaturhierarki än de som ligger längre ut. Driftinformation från systemet ska kunna följas på en webbplats och temperaturdata från systemet ska sparas undan för lagring. Datakommunikationen består av en One-Wire buss som innehåller temperatursensorer och ett CAN-buss system för datakommunikation mellan sensor/aktuator-noder och server-nod. Utifrån sensordata bestäms reglering av ventiler. Driftinformation lagras i en databas och från denna databas presenteras informationen på en hemsida. Hemsidan innehåller en överblick av brunnparken där temperaturen i varje brunn kan utläsas. Regleralgoritmen uppfyller den sökta temperaturhierarkin där de högsta temperaturerna ska vara i centrum av brunnparken. Prototypen fungerar som en utvecklingsplattform och demonstrerande prototyp. / Thermal energy produced from solar collectors can be stored in Borehole Thermal Energy Storage, BTES, when demand is low for later usage when demand is high. The aim of this thesis is to develop a scalable system architecture for control and monitoring of a BTES prototype.The BTES prototype consist of 13 boreholes configured in a hierarchically manner in two circles and one core. The core is of the highest priority. The operational information is displayed on a website and stored in a database.The data communication consist of two One-wire buses and one CAN bus. The temperature sensors are connected to the One-Wire buses. The CAN bus consist of sensor/actuator nodes and a server node. Based on sensor data, a control loop configures the actuators. Operational data is stored in a database and visually presented on a website. The website displays an overview of all the boreholes where all of the sensors data can be read. The control algorithm runs successfully according to its hierarchically priorities. The prototype works as a developement platform and a demonstrating prototype.

El propósito de la presente tesis es el estudio de la disipatividad en sistemas no lineales discretos. Dicho trabajo de investigación presenta nuevas contribuciones en la teoría de control no lineal discreto basado en disipatividad y en el estudio de las propiedades de sistemas disipativos no lineales. Los resultados conseguidos se dividen en tres objetivos principales:1. La caracterización de sistemas disipativos múltiple entrada múltiple salida (MIMO) no lineales discretos de estructura general, lo que también se conoce como condiciones de Kalman-Yakubovich-Popov (KYP). Las condiciones de KYP ya existentes se extienden a una clase de sistemas disipativos discretos no lineales MIMO que son no afines en el control. La clase de sistemas disipativos estudiada se denomina disipatividad QSS. También se proporcionan condiciones necesarias y suficientes para la caracterización de sistemas conservativos QSS discretos no afines en el control.2. El problema de disipatividad por realimentación en sistemas no lineales discretos. Se proponen dos formas de abordar dicho problema:2.1. El problema de la disipatividad por realimentación a través de la relación fundamental de la disipatividad. Se da solución al problema de la disipatividad por realimentación para sistemas única entrada única salida (UEUS) discretos no lineales no afines en el control, mediante cuatro metodologías basadas en la igualdad fundamental de la disipatividad. Se proponen condiciones suficientes bajo las cuales la disipatividad por realimentación es posible.2.2. El problema de pasivización mediante las propiedades del grado relativo y la dinámica cero del sistema no pasivo original. El problema de transformarción de un sistema no pasivo a uno que lo es se resuelve mediante realimentación de estado para una clase de sistemas MIMO no lineales discretos afines en el control, usando las propiedades del grado relativo y la dinámica cero del sistema no pasivo original. Se puede considerar como una extensión al caso pasivo de los resultados ya existentes, referentes al problema de transformar un sistema que no es conservativo a uno que lo es mediante realimentación de estado.3. El problema de estabilización basado en disipatividad en sistemas no lineales discretos. El método de Moldeo de Energía e Inyección de Amortiguamiento (MEIA) se extiende a sistemas generales no lineales discretos UEUS, además de analizar algunas de las propiedades de estabilidad de una clase de sistemas disipativos y de sistemas que se pueden transformar a disipativos por realimentación. También, se establecen condiciones suficientes bajo las cuales dichos sistemas son estabilizables.Otros objetivos secundarios han sido alcanzados, como son: el estudio del grado relativo y la dinámica cero de sistemas pasivos no lineales discretos, algunas conclusiones acerca de la conservación de la pasividad bajo la interconexión por retroalimentación negativa y la interconexión paralela, algunas notas acerca de la conservación y pérdida de la disipatividad y pasividad con el muestreo, además, las propiedades en el dominio de la frecuencia de los sistemas disipativos se usan y se relacionan con algunos de los criterios de estabilidad basados en la respuesta en frecuencia más importantes. También, los métodos de control basados en disipatividad diseñados se aplican al problema de regulación de un modelo discreto con interpretación física: un convertidor buck, para el que se mejora la respuesta en lazo abierto.El hecho de haber tratado sistemas discretos generales nos ha permitido dar una serie de resultados para sistemas no lineales continuos no afines en el control. Dos problemas se han propuesto, principalmente: el estudio de la disipatividad por realimentación para sistemas no lineales no afines UEUS y el uso de los resultados de disipatividad por realimentación, con el fin de extender al caso no lineal no afín UEUS el método de estabilización de MEIA. / This dissertation is devoted to dissipativity-related concepts in the nonlinear discrete-time setting, and presents several new contributions which are not covered by the existing nonlinear discrete-time dissipativity-based control theory and the study of the properties of nonlinear discrete-time dissipative systems.The study of dissipativity given in this dissertation is concentrated in the state-space or internal description representation of systems. The results achieved are classified into three main goals or problems to solve, such as:1. The characterization of dissipative multiple-input multiple-output (MIMO) nonlinear discrete-time systems of general form, what is regarded as Kalman-Yakubovich-Popov (KYP) conditions. The KYP conditions existing in the literature are extended to a class of nonlinear MIMO dissipative discrete-time systems which are non-affine in the control input. The class of dissipativity characterized is regarded as QSS-dissipativity. Necessary and sufficient conditions for the characterization of QSS-lossless discrete-time systems which are non-affine in the control input are also given.2. The feedback dissipativity problem in the nonlinear discrete-time setting. Two approaches are proposed to deal with this topic:2.1. The feedback dissipativity problem through the fundamental dissipativity inequality. The feedback dissipativity problem is solved for single-input single-output (SISO) nonlinear discrete-time non-affine-in-the-control-input systems by means of four methodologies based on the fundamental dissipativity equality. Sufficient conditions under which feedback dissipativity is possible are proposed. 2.2. The feedback passivity problem through the properties of the relative degree and zero dynamics of the non-passive system. The problem of rendering a system passive via state feedback is solved for a class of MIMO nonlinear discrete-time systems which are affine in the control input using the properties of the relative degree and the zero dynamics of the non-passive system. It is an extension to the passivity case of the results reported in the literature for the losslessness feedback problem. 3. The dissipativity-based stabilization problem in nonlinear discrete-time systems. The dissipativity-based controller design methodology of the Energy Shaping and Damping Injection (ESDI) is extended to general nonlinear SISO discrete-time systems, in addition to, the analysis of some stability properties of a class of dissipative and feedback dissipative SISO nonlinear discrete-time systems. Furthermore, sufficient conditions under which a class of feedback dissipative systems is stabilizable are proposed.Other secondary goals in the dissipativity properties exploration in discrete-time systems are achieved, mainly: the study of the relative degree and zero dynamics of passive nonlinear discrete-time systems, some conclusions about passivity preservation under feedback and parallel interconnections, some notes on the non-preservation and preservation of dissipativity, and its special case of passivity, under sampling, in addition, dissipativity frequency-domain properties have been used and related to some of the most important frequency-based feedback stability criteria. Furthermore, the feedback dissipativity and dissipativity-based control results are applied to solve the regulation problem in a discrete-time model with physical interpretation: the DC-to-DC buck converter, whose open-loop response is improved by means of the use of some of the stabilization methods proposed.The fact of treating general discrete-time systems has allowed us to extend some dissipativity-related definitions to the case of continuous-time nonlinear non-affine-in-the-input systems. Two main problems are presented, namely: the study of the feedback dissipativity problem for nonlinear non-affine SISO systems based upon the fundamental dissipativity equality, and the use of the feedback dissipativity results in order to extend the ESDI controller design method to the case of non-affine SISO nonlinear systems.

Las pilas de combustible son muy ventajosas debido a su alta eficiencia en la conversión de energía y nula contaminación. En esta tesis se realiza un extenso estudio sobre el control y diseño de sistemas de generación eléctrica basados en pilas de combustible. El núcleo principal de la misma son los sistemas híbridos con pilas de combustible y supercapacitores como elementos almacenadores de energía, orientado a aplicaciones automotrices. La determinación del Grado de Hibridización (i.e. la determinación del tamaño de la pila de combustible y del número de supercapacitores) se realiza mediante una metodología propuesta con el objetivo de satisfacer requisitos de conductibilidad y consumiendo la menor cantidad de hidrógeno posible.El proceso de diseño comienza con la determinación de la estructura eléctrica de generación del vehículo y utiliza un modelo detallado realizado en ADVISOR, una herramienta para modelado y estudio de sistemas híbridos. Se analiza el flujo de energía a través de los componentes del vehículo cuando el vehículo sigue diferentes ciclos de conducción estándares, mostrando las pérdidas en cada componente que degradan la eficiencia del sistema y limitan la recuperación de energía de frenado. Con respecto a la recuperación de energía, se ha definido y analizado un parámetro que cuantifica la cantidad de energía que realmente es reaprovechada: el ratio frenado/hidrógeno.Para controlar el flujo de energía entre la pila de combustible, los almacenadores de energía y la carga eléctrica, se proponen tres Estrategias de Gestión de Energía (EMS) para Vehículos Híbridos con Pila de Combustible (FCHVs) basadas en el mapa de eficiencia de la pila y se validan mediante un montaje experimental desarrollado para emular el sistema híbrido. Los resultados de consumo de hidrógeno son comparados con dos referencias: el consumo correspondiente al caso del vehículo sin hibridización y el caso óptimo con el menor consumo para el vehículo propuesto. El consumo óptimo se calcula mediante una metodología propuesta que, a diferencia de otras, evita la discretización de las variables de estado.Para operar el sistema eficientemente, la pila de combustible es controlada mediante una metodología de control, basada en Control de Matriz Dinámica (DMC). Esta metodología de control utiliza como variables de control el voltaje de compresor y una nueva variable propuesta: la apertura de una válvula proporcional ubicada a la salida del cátodo. Los objetivos de control son controlar el exceso de oxígeno en el cátodo y el voltaje generado por la pila. Se analiza tanto en régimen estacionario como transitorio las ventajas de emplear esta nueva variable de control y se muestran resultados de funcionamiento por simulación del controlador ante perturbaciones en la corriente de carga.Por otro lado, se aborda el diagnóstico y el control tolerante a fallos del sistema basado en pila de combustible proponiendo una metodología de diagnóstico basada en las sensibilidades relativas de los fallos y se muestra que la estructura de control con las dos variables propuestas tiene buena capacidad de rechazo a fallos en el compresor cuando se controla el exceso de oxígeno en el cátodo. / The use of fuel cell systems based on hydrogen is advantageous because of their high efficiency in the energy conversion and null emissions. In this thesis, an extensive study about the control and design of electrical generation systems based on fuel cells is performed. The main focus is in hybrid systems composed of fuel cells and supercapacitors as energy storage elements, oriented to automotive applications. The determination of the hybridization degree (i.e. the determination of the fuel cell size and the number of supercapacitors) is performed through a proposed methodology with the objective to fulfil the conductibility requirements and to consume the lowest amount of hydrogen.The process of design starts with the determination of the electrical structure and utilizes a detail model developed using ADVISOR, a MATLAB toolbox for modelling and studying hybrid vehicles. The energy flow between the vehicle components is analyzed when the vehicle is tested with different Standard Driving Cycles, showing how the losses in each component degrade the efficiency of the system and limit the energy recovery from braking.With regard to the energy recovery, a parameter to quantify the amount of energy that is actually reused is defined and analyzed: the braking/hydrogen ratio.To control the energy flow between the fuel cell, the energy storage system, and the electrical load in Fuel Cell Hybrid Vehicles (FCHVs), three Energy Management Strategies (EMSs) based on the fuel cell efficiency map are presented and validated through an experimental setup, which is developed to emulate the FCHV. The resulting hydrogen consumptions are compared with two references: the consumption of the pure fuel cell case, a vehicle without hybridization, and the optimal case with the minimum consumption. The optimal consumption for a given vehicle is determined through a methodology proposed that, unlike other previous methodologies, avoids the discretization of the state variables.To operate the fuel cell system efficiently, the system is controlled through a proposed control technique, which is based on Dynamic Matrix Control (DMC). This control technique utilizes the compressor voltage as control variable and also a new proposed variable: the opening area of a proportional valve at the cathode outlet. The control objectives are the control of the oxygen excess ratio at the cathode and the fuel cell voltage. The advantages of this new control variable are analyzed both in steady state and transient state. Simulation results show and adequate performance of the controller when a series of step changes in the load current is applied.On the other hand, the diagnosis and fault-tolerant control of the fuel cell-based system is approached. A diagnosis methodology based on the relative fault sensitivity is proposed. The performance of the methodology to detect and isolate a set of proposed failures is analyzed and simulation results in an environment developed to include the set of faults are given. The fault-tolerant control is approached showing that the proposed control structure with two control variables has good capability against faults in the compressor when the oxygen excess ratio in the cathode is controlled.

Proefschrift Rijksuniversiteit Groningen. / Datum laatste controle: 02-07-1997. Met lit.opg. en index. - Met een samenvatting in het Nederlands.

No description available.

Proefschrift Rijksuniversiteit Groningen. / Met lit. opg. - Met een samenvatting in het Nederlands.