Linear and nonlinear microwave properties of chemical vapor deposition (CVD)-grown graphene are characterized by incorporating a coplanar waveguide (CPW) transmission-line test structure. The intrinsic linear transport properties (S-parameters) of the graphene sample are measured and extracted via a deembedding procedure and then fitted with an equivalent circuit model up to 10 GHz. A statistical uncertainty analysis based on multiple measurements is implemented to esti- mate the error of the extracted graphene linear parameters as well. Nonlinear properties (second- and third-order harmonics as a function of fundamental input power) of the sample are also measured with a fundamental input signal of 1 GHz. Clear harmonics generated from graphene are observed, while no obvious fundamental power saturation is seen. The measured nonlinearity is applied in a graphene patch antenna case study to understand its influence on potential applications in terms of third-order intermodulation levels.

This thesis focuses on the structures of plated through holes in organic substrate, and discusses the high-frequency electrical characteristics of various plated through hole structures. This thesis consists of four parts. The first part introduces various kinds of vias in multilayer substrate. This content includes substrate drilling processes and capabilities, and discussions on plated through hole structures and their manufacture concerns. The second part focuses on actual measurement of plated through holes, and introduces high-frequency double-side probing technique. The difference from traditional high-frequency coplanar probing measurement is also discussed. The third part focuses on the high-frequency simulation by full-wave software ¡V Ansoft HFSS, and discusses the effects of various excited source and model structures on simulations. Part4 focuses on developing the broadband equivalent circuit model based on the physical structures, and discusses the electrical characterization of different plated through holes, and provides the related design concept.

Batteries have imparted momentum to the process of transition towards a green future. However, mass application of batteries is obstructed due to their explosive nature, a trait specific to Li-Ion batteries. To cater to an efficient battery utilization, an introduction of a battery management system would provide an ultimate solution. This thesis deals with different aspects crucial in designing a battery management system for high energy as well as high power applications. To build a battery management system capable of predicting battery behavior, it is necessary to analyze the dynamic processes happening inside the battery. Hence, a battery equivalent circuit model is proposed in this thesis as well as proper analysis is done in MATLAB to project a generic structure applicable to all Li-Ion chemistries. The model accounts for all dynamic characteristics of a battery including non-linear open circuit voltage, discharge current and capacity. Effect of temperature is also modeled using a cooling system. The model is validated with test current profiles. Less than 0.1% error between measured and simulated voltage profiles indicates the effectiveness of the proposed model to predict the runtime behavior of the battery. Furthermore, the model is implemented with the energy as well as the power battery pack. State of charge calculations are performed using the proposed model and the coulomb counting method and the results indicate only a 4% variance. Therefore, the proposed model can be applied to develop a real-time battery management system for accurate battery states estimation.

<p>This thesis investigates simulation of synchronous machines using a novel Magnetic Equivalent Circuit (MEC) model. The proposed model offers sufficient detail richness for design calculations, while still keeping the simulation time acceptably short.</p><p>Different modeling methods and circuit alternatives are considered. The selected approach is a combination of several previous methods added with some new features. A detailed description of the new model is given. The flux derivative is chosen as the magnetic flow variable which enables a description with standard circuit elements. The model is implemented in dq-coordinates to reduce complexity and simulation time. A new method to reflect winding harmonics is introduced.</p><p>Extensive measurements have been made to estimate the traditional dq-model parameters. These in combination with analytical calculations are used to determine the parameters for the new MEC model.</p><p>The model is implemented using the Dymola simulation program. The results are evaluated by comparison with measurements and FEM simulations. Three different operation cases are investigated; synchronous operation, asynchronous start and inverter fed operation. The agreement with measurements and FEM simulations varies, but it is believed that it can be improved by more work on the parameter determination.</p><p>The overall conclusion is that the MEC method is a useful approach for detailed simulation of synchronous machines. It enables proper modeling of magnetic saturation, and promises sufficiently detailed results to enable accurate loss calculations. However, the experience is that the complexity of the circuits should be kept at a reasonable low level. It is believed that the practical problems with model structure, parameter determination and the simulation itself will otherwise be difficult to master.</p>

Fuel cell technology has undergone significant development in the past 15 years, spurred in part by its unique energy conversion characteristics; directly converting chemical energy to electrical energy. As fuel cell technology has past through the prototype/pre-commercialisation development, there is increasing interest in manufacturing and application issues. Of the six different fuel cell types pursued commercially, the Proton Exchange Membrane (PEM) fuel cell has received the greatest amount of research and development investment due to its suitability in a variety of applications. A particular application, to which state-of-the art PEMFC technology is suited, is backup/uninterruptible power supply (UPS) systems, or stand-by power systems. The most important feature of any backup/UPS system is reliability. Traditional backup power systems, such as those utilising valve regulated lead acid (VRLA) batteries, employ remote testing protocols that acquire battery state-of-health and state-of-charge information. This information plays a critical role in system management and reliability assurance. A similar testing protocol developed for a PEM fuel cell would be a valuable contribution to the commercialization of these systems for backup/UPS applications. This thesis presents a novel testing and analysis procedure, specifically designed for a PEM fuel cell in a backup power application. The test procedure electronically probes the fuel cell in the absence of hydrogen. Thus, the fuel cell is in an inactive, or passive, state throughout the testing process. The procedure is referred to as the passive state dynamic behaviour (PSDB) test. Analysis and interpretation of the passive test results is achieved by determining the circuit parameter values of an equivalent circuit model (ECM). A novel ECM of a fuel cell in a passive state is proposed, in which physical properties of the fuel cell are attributed to the circuit model components. Therefore, insight into the physical state of the fuel cell is achieved by determining the values of the circuit model parameters. A method for determining the circuit parameter values of many series connected cells (a stack) using the results from a single stack test is also presented. The PSDB test enables each cell in a fuel cell stack to be tested and analysed using a simple procedure that can be incorporated into a fuel cell system designed for backup power applications. An experimental system for implementing the PSDB test and evaluating the active performance of three different PEM fuel cells was developed. Each fuel cell exhibited the same characteristic voltage transient when subjected to the PSDB test. The proposed ECM was shown to accurately model the observed transient voltage behaviour of a single cell and many series connected cells. An example of how the PSDB test can provide information on the active functionality of a fuel cell is developed. This method consists of establishing baseline performance of the fuel cell in an active state, in conjunction with a PSDB test and identification of model parameter values. A subsequent PSDB test is used to detect changes in the state of the fuel cell that correspond to performance changes when the stack is active. An explicit example is provided, where certain cells in a stack were purposefully humidified. The change in state of the cells was identified by the PSDB test, and the performance change of the effected cells was successfully predicted. The experimental test results verify the theory presented in relation to the PSDB test and equivalent circuit model.

In comparison with PWM converters, resonant converters are gaining increasing popularity for cases in which efficiency and power density are at a premium. However, the lack of an accurate small-signal model has become an impediment to performance optimization. Many modeling attempts have been made to date. Besides the discrete time-domain modeling, most continuous-time modeling approaches are based on fundamental approximation, and are thus unable to provide sufficient accuracy for practical use. An equivalent circuit model was proposed by Yang, which works well for series resonant converters (SRCs) with high Q (quality factor), but which is inadequate for LLC resonant converters. Furthermore, the model is rather complicated, with system orders that are as high as five and seven for the SRC and LLC converter, respectively. The crux of the modeling difficulty is due to the underlying assumption based on the use of a band-pass filter for the resonant tank in conjunction with a low-pass output filter, which is not the case for most practical applications. The matter is further complicated by the presence of a rectifier, which is a nonlinearity that mixes and matches the original modulation frequency. Thus, the modulation signal becomes intractable when using a frequency-domain modeling approach. This dissertation proposes an extended describing function modeling that is based on a Fourier analysis on the continuous-time-domain waveforms. Therefore, all important contributions from harmonics are taken into account. This modeling approach is demonstrated on the frequency-controlled SRC and LLC converters. The modeling is further extended to, with great accuracy, a charge-controlled LLC converter. In the case of frequency control, a simple third-order equivalent circuit model is provided with high accuracy up to half of the switching frequency. The simplified low-frequency model consists of a double pole and a pair of right-half-plane (RHP) zeros. The double pole, when operated at a high switching frequency, manifests the property of a well-known beat frequency between the switching frequency and the resonant frequency. As the switching frequency approaches the resonant frequency of the tank, a new pair of poles is formed, representing the interaction of the resonant tank and the output filter. The pair of RHP zeros, which contributes to additional phase delay, was not recognized in earlier modeling attempts. In the case of charge control, a simple second-order equivalent circuit model is provided. With capacitor voltage feedback, the order of the system is reduced. Consequently, the resonant tank behaves as an equivalent current source and the tank property is characterized by a single pole. The other low-frequency pole represents the output capacitor and the load. However, the capacitor voltage feedback cannot eliminate the high-frequency poles and the RHP zeros. These RHP zeros may be an impediment for high-bandwidth design if not properly treated. Based on the proposed model, these unwanted RHP zeros can be mitigated by either changing the resonant tank design or by proper feedback compensation. The accurate model is essential for a high-performance high-bandwidth LLC converter. / Doctor of Philosophy / For high-frequency power conversion, resonant converters are increasingly popular. However, the lack of an accurate small-signal model has become an impediment to performance optimization. The existing equivalent circuit model and its simplified circuit were based on fundamental approximation, where the resonant tank was deemed a good band-pass filter. These models work well for series resonant converters (SRCs) with high Q (quality factor), but are inadequate for LLC resonant converters. The crux of the modeling difficulty is due to the fact that the operation of this type of resonant converter is based on the use of a band-pass filter in conjunction with a low-pass filter. The matter is further complicated by the presence of a rectifier, which is a nonlinearity that mixes and matches the original modulation frequency. Thus, the modulation signal becomes intractable when using a frequency-domain modeling approach. This dissertation proposes an extended describing function modeling that is based on a Fourier analysis on the continuous-time-domain waveforms. Therefore, all important contributions from harmonics are taken into account. This modeling approach is demonstrated on the frequency-controlled SRC, frequency-controlled LLC converter, and charge-controlled LLC converter, and the resulting models are proven to be accurate at all frequencies. A simple equivalent circuit model is provided that targets the frequency range below the switching frequency. This simple, accurate model is able to predict the small-signal behaviors of the LLC converter with high accuracy at half of the switching frequency. At high modulation frequencies, the resonant converter behaves like a non-minimum phase system, which was neither recognized nor characterized before. This property can be represented by RHP zeros, and these RHP zeros may be an impediment for high-bandwidth design if not properly treated. Based on the proposed model, these unwanted RHP zeros can be mitigated by either changing the resonant tank design or by proper feedback compensation. Accurate modeling is essential for a high-performance high-bandwidth LLC converter.

<div>Cables play an important role in the design of a power system. DC cable design presents unique challenges due to the fact that space charge can accumulate within the dielectric over time. Space charge accumulation is a function of temperature, electric field, and dielectric properties. Of particular concern is that the space charge leads to electric fields that are sufficient to break down the cable, particularly during transient conditions such as voltage reversal.</div><div><br></div><div>In this research, a focus is on the development of a coupled thermal- and electricalequivalent-circuit model that is general and provides the ability to predict the electric fields and space charge accumulation within single and multi-conductor DC cables. In contrast to traditional analytical models, the approach is more general, allowing for exploration of a wide spectrum of geometries. In contrast to traditional numerical methods, including finite element or finite difference, apriori knowledge of the electric field behavior is used to discretize the dielectric into a small number of electric flux tubes. The electric field dynamics within each tube are then modeled using a first order nonlinear differential equation. The relatively coarse discretization enables the solution to be computed rapidly. This is useful in population-based design where a large number of candidate evaluations is necessary to explore a design space. The modeling approach has been validated using several examples presented in the literature. In addition, its usefulness has been highlighted in the optimization of a 20 kV cable wherein objectives include minimization of mass and loss. </div>

Following the positive reception of electric and hybrid transport solutions in the market, manufacturers keep developing their vehicles further, while facing previously undertaken challenges. Knowing the way lithium-ion batteries behave is still one of the key factors for hybrid electric vehicles (HEVs) development, especially for the requirements of the battery management system during their operation. Hence, this project focuses on the necessity of robust yet reasonably simple and cost-effective models of the battery for estimating the health status during the operation of the vehicles. With this aim, the procedure and models to calculate the state-of-health (SOH) indicators, internal resistance and capacity, are proposed and the results discussed. Two machine-learning based models are presented, a support vector machine (SVM) and a neural network (NN), together with one equivalent circuit model (ECM). The data used for training and validating the models comes from testing the batteries in the laboratory with standard performance tests and real driving cycles along the battery lifespan. However, data sets measured in actual heavy-duty vehicles during their operation for three years is also analysed and compared. With respect to this matter, a study of the battery materials, behaviour and operation attributes is carried out, highlighting the main aspects and issues that affect the development of the models. The inputs for the models are signals that can be measured on-board in the vehicles, as current, voltage or temperature, and other derived from them as the state-of-charge (SOC) calculated by the internal battery management unit. Time-series of the variables are used for simulation purposes. The management of signals and implementation of the models is done in the environment of Matlab-Simulink, using some of its in-built functions and other specifically developed. The models are evaluated and compared by means of the normalized root mean squared error (NRMSE) of the voltage output profile compared to that of the tested batteries, but also the error of the internal resistance calculations calculated from the voltage profile for the three models, and the internal parameters in case of the ECM. While despite the difficulties faced with the data, the models can eventually perform accurate estimations of the resistance, the results of the capacity estimations are omitted in the document due to the lack of useful information derived. Nevertheless, the calculation procedure and other considerations to take into account regarding the capacity estimation and data sets are undertaken. Finally, the conclusions about the data used, battery materials and methods evaluated are drawn, laying down recommendations as to design the performance tests following the conditions of the driving cycles, and indicating the higher general performance of the SVM respect the other two methods, while asserting the usefulness of the ECM. Moreover, the battery with NMC material composition is observed to be easier to predict by the models than LFP, also showing different evolution of its internal resistance.

Lithium-ion batteries are complex systems and making a simulation model of them is always challenging. A method for producing an accurate model with high capabilities for predicting the behavior of the battery in a time and cost efficient way is desired in this field of work. The aim of this thesis has been to develop a method to be close to the desired method as much as possible, especially in two important aspects, time and cost. The method which is the goal of this thesis should fulfill the below five requirements: 1. Able to produce a generic battery model for different types of lithium-ion batteries 2. No or low cost for the development of the model 3. A time span around one week for obtaining the model 4. Able to predict the most aspects of the battery’s behavior like the voltage, SOC, temperature and, preferably, simulate the degradation effects, safety and thermal aspects 5. Accuracy with less than 15% error The start point of this thesis was the study of current methods for cell modeling. Based on their approach, they are divided into three categories, abstract, black box and white box methods. Each of these methods has its own advantages and disadvantages, but none of them are able to fulfill the above requirements. This thesis presents a method, called “gray box”, which is, partially, a mix of the black and white boxes’ concepts. The gray box method uses values for model’s parameters from different sources. Firstly, some chemical/physical measurements like in the case of the white box method, secondly, some of the physical tests/experiments used in the case of the black box method and thirdly, information provided by cell datasheets, books, papers, journals and scientific databases. As practical part of this thesis, a prismatic cell, EIG C20 with 20Ah capacity was selected as the sample cell and its electrochemical model was produced with the proposed method. Some of the model’s parameters are measured and some others are estimated. Also, the abilities of AutoLion, a specialized software for lithium-ion battery modeling were used to accelerate the modeling process. Finally, the physical tests were used as part of the references for calculating the accuracy of the produced model. The results show that the gray box method can produce a model with nearly no cost, in less than one week and with error around 30% for the HPPC tests and, less than this, for the OCV and voltage tests. The proposed method could, largely, fulfill the five mentioned requirements. These results were achieved even without using any physical tests/experimental data for tuning the parameters, which is expected to reduce the error considerably. These are promising results for the idea of the gray box which is in its nascent stages and needs time to develop and be useful for commercial purposes.

L’objectif de cette thèse est la conception de biocapteurs capables de détecter la présence de séquences d’ADN sans utilisation de marqueurs chimiques ou de traitement préalable de l’échantillon. Le principe de mesure utilise la spectroscopie d’impédance pour la détection du changement provoqué par la présence de la séquence ADN sur le biocapteur. Notre étude s’appuie sur des simulations analytiques et numériques pour définir les dimensions des capteurs adaptés aux mesures en basse fréquence ainsi que le développement d’un modèle de circuit équivalent qui prend en considération les effets d'interfaces. La fabrication du capteur a été réalisée en plusieurs étapes. Dans un premier temps, la conception et la fabrication en salles blanches ont été optimisées pour des structures interdigitées avec différentes géométries et différents types de substrat (Verre, Si, SiO2). Après la validation du modèle, par des mesures sur des solutions de conductivité étalon et sur plusieurs concentrations d’ADN, l’analyse des résultats nous a conduits à proposer une nouvelle structure à électrodes concentriques mieux adaptée aux mesures d’impédance en basses fréquences pour des milieux liquides. Deux prototypes de taille micrométriques, l’un à électrode interdigitée et l’autre à électrode concentrique ont été développés pour une étude comparative / The objective of this thesis is the conception of a biosensor able to detect the presence of DNA sequences without any use of chemical markers or a prior treatment of the samples. The measurements are performed using impedance spectroscopy technique to detect the changes caused by the presence of DNA sequences on the biosensor. Our study is based on analytic and numeric simulations, which allows us to define the dimensions of the sensors adapted to low frequency measurements and to propose an equivalent circuit model taking into account the effects of the electrical double layer. The sensor was manufactured in several steps. Initially, clean room design and manufacturing were optimized for interdigitated structures with different geometries and substrate types (Glass, Si, SiO2). The data analysis of the measurement on standard conductivity and on several DNA concentrations using interdigitated electrode biosensor, allows us to propose a new design with concentric electrodes which is more adapted to low frequency impedance measurement according to a comparative study between interdigitated and concentric electrodes