Organic photovoltaic (OPV) cells are advanced, newly emerging technologies that are lightweight, mechanically flexible devices with highthroughput processes from low cost material in a variety of colors. Rathnayake et al. of Western Kentucky University have developed a nanostructure-based OPV cell. Presented in this thesis is a model and simulation of a generalized PV powered system that can predict the performance of solar arrays in various environmental conditions. The simulation has been carried out in Matlab/Simulink, and upon entering the cell’s parameters, it provides key electrical characteristics such as the cell’s I-V curve and efficiency information. The total system that is simulated consists of three elements: a universal two-cell solar array that can account for partial shading and manufacturing variation, a current-controlled power converter, and an energy storage device with charging and discharging capabilities.

Les convertisseurs de puissance sont largement utilisés de nos jours dans des applications qui demandent une grande autonomie énergétique, comme par exemple ceux qui sont alimentés par des batteries. En particulier, les amplificateurs de type Class-D sont fréquemment utilisés dans les applications audio. Ces amplificateurs commutés ont une architecture ressemblante à celle d'un convertisseur DC-DC, ce qui les permet d'avoir une efficacité énergétique élevée. Cependant, leur inconvénient majeur est la forte émission en perturbations électromagnétiques (EM). Cela peut causer des problèmes de conformité avec les normes de compatibilité électromagnétique (CEM), ou bien perturbé le bon fonctionnement des applications électroniques qui l'entour. Pour cela, ils existent de nombreuses études qui permettent de réduire les émissions d'un amplificateur de Class D. Cependant, cela n'est pas suffisant pour retirer le filtre de CEM. Il est donc nécessaire d'optimiser ces filtres et de faciliter leurs conceptions. Ceci est le but de la présente thèse et il est divisé en quatre grandes parties. La première partie commence par développer une technique de modélisation dans le domaine fréquentiel. Cette technique qui est basée sur la détermination et la manipulation des matrices d'impédances a comme but de simuler et prédire les perturbations EM générées par un amplificateur de Class D. Tous les aspects théoriques de la méthode ont été développés. Ensuite, une application pratique sur un système de Class D dédié à la téléphonie mobile nous a permis de valider la méthode jusqu'à une fréquence de 100 MHz. Un amplificateur de Class D est une source de perturbation aussi bien sur les rails d'alimentation que sur les rails de sortie. Pour cela, le filtre de CEM est nécessaire sur les rails de l'alimentation comme il y est en sortie. Néanmoins, un filtre correctement construit doit être conçu en prenant en compte l'impédance de la charge qui est la batterie dans ce cas. Pour cela, la deuxième partie a pour objectif la mesure de l'impédance de la batterie sur la gamme de fréquence considérée. Ainsi, une technique de mesure d'impédance de batterie en utilisant un impédance mètre est développée. Ensuite, une application expérimentale sur un convertisseur DC-DC et une batterie nous a permis de valider la procédure de mesure. La troisième partie s'est focalisée sur l'optimisation du filtre de CEM. Le modèle fréquentiel développé dans la première partie est intégré dans une boucle d'optimisation basée sur un algorithme génétique. L'optimisation inclus plusieurs critères dans sa fonction objective qui sont l'augmentation de la capacité du filtre à réduire les émissions EM, la diminution des pertes supplémentaires due à l'utilisation du filtre et finalement le gain du filtre dans la bande de fréquence du signal audio. Cette étude est poursuivie par une validation expérimentale. La quatrième et la dernière partie étudie et quantifie les impacts du filtre de CEM sur la qualité audio de l'amplificateur. En effet, le filtre de CEM est l'un des chemins propagation du signal audio. Par suite, tout comportement non linéaire du filtre conduit à la distorsion du signal audio. Pour cela, cette partie est dédiée à la modélisation et la simulation des composants passifs contenant un matériau magnétique. En particulier, l'étude s'est focalisée sur la modélisation des perles de ferrite en utilisant le modèle de matériaux magnétiques Jiles-Aterthon. Les résultats de simulations sont comparés avec la mesure dans le domaine temporel et fréquentiel. En plus, le calcul du taux de distorsion harmonique nous a permis de valider le modèle sur une large plage d'amplitude. / Switching power management circuits are widely used in battery powered embedded applications in order to increase their autonomy. In particular, for audio applications, Class-D amplifiers are a widespread industrial solution. These, have a similar architecture of a buck converter but having the audio signal as reference. The switching nature of these devices allows us to increase significantly the power efficiency compared to linear audio amplifiers without reducing the audio quality. However, because of the switching behavior, Class-D amplifiers have high levels of electromagnetic (EM) emissions which can disturb the surrounding electronics or might not comply with electromagnetic compatibility (EMC) standards. To overcome this problem much architecture appeared in the state of the art that reduces the emissions, however, this has never been enough to remove electromagnetic interference (EMI) filters. It is then useful to optimize these filters, thus, it has been set as the goal of this PhD thesis. The latter has been divided to four main axes which can be resumed by the following. First, this work started by developing a frequency domain modeling method in order to simulate and predict the EMI of Class-D amplifiers in the final application. The method is based on system to block decomposition and impedance matrix modeling and manipulation. After providing all the theoretical background, the method has been validated on integrated differential Class-D amplifier. The experimental measurements have permitted to validate the method only up to 100MHz. However, this is sufficient to cover the conducted EMC frequency band. Second, the EMI at the supply rails of Class-D amplifiers has been treated. As the battery is often the same power supply for all applications in an embedded system, an EMI filter or a decoupling capacitor is needed to prevent the noise coupling by common impedance. Designing this filter needs the knowledge of the battery impedance at the desired frequencies. Therefore the present work dealt also with measuring the high frequency impedance of a battery. Afterwards, an experimental validation has been carried on with a DC-DC converter and a Class-D amplifier. The developed model allows a virtual test of the switching device in the final application. However, it is more useful if the model is able to help the system integrator in designing filters. Thus, third, the model has been implemented in an optimization loop based on a genetic algorithm in order to optimize the filter response, and also, reduce the additional power losses introduced by an EMI filter. The optimization search space has been limited to the components available on the market and the optimization result is given as component references of the optimal filter referring to the optimal solution found. This procedure has been validated experimentally. Finally, EMI filters often are constituted by magnetic components such as ferrite beads or inductors with magnetic cores. Thus, introducing the EMI filter in the audio path, adds a nonlinear behavior in the audio frequency band. Designing a high quality EMI filter require taking into account this phenomenon and studying its impact of the original amplifier audio performance. Therefore, the Jiles-Atherton model for magnetic materials has been used for ferrite bead modeling. Hereafter, the impact on the time and frequency domain signals has been simulated and compared to measurements. Finally, the total harmonic distortion (THD) has been computed for different signal amplitudes and compared to the THD measured using an audio analyzer. Accurate results have been obtained on a wide range of signal amplitudes. As a conclusion, this work aimed to design optimal EMI filters for Class-D amplifiers. Thus, we dealt with improving their EMI response, reducing their additional power losses and evaluating their impact on the audio quality.

It is customary to obtain ac power from batteries through a power converter, where mains ac power is not readily available. Such a power converter is also needed in several mobile/ airborne/ space applications. Till recently this application is served by a H bridge inverter followed by a low frequency transformer and a passive low pass filter. The H bridge inverter employs high frequency pulse width modulation. The transformer is made of standard silicon steel. The filter is made of L and C elements. In such a converter the magnetics account for about 30% of cost and 50% of weight. Moreover the dc input current in such converters is discontinuous, leading to poor efficiency. There is need for an input filter as well. This thesis presents the development of an inverter with high frequency (hf) link. The power converter employs a boost front end resulting in continuous input current. The H bridge inverter employs phase modulation technique with soft switching features. The boost converter and the H bridge share power devices. The isolation transformer handles high frequency ac power and is compact. It is shown that the transformer size can be reduced by more than one order of magnitude. There is a rear end cycloconverter to reconvert the high frequency ac power into 50 Hz output power. Innovative pulse sequencing in the cycloconverter ensures loss-less switching. The pulse width modulation shifts the dominant harmonic frequency to double the switching frequency. The output LC filter is light. The converter can handle bidirectional power. The controller is digital. The overall concept was demonstrated through the 500 W prototype design. The proposed topology offers small size, low losses and continous input current. The controller is digital and offers totally software based compensation and settings. It is expected that on account of the small size and cost, this topology is likely to become more popular in the near future. The applications of such power converters will bring down the size and cost of UPS, solar inverters, wind mill inverters etc.

Design of filters used in grid-connected inverter applications involves multiple constraints. The filter requirements are driven by tight filtering tolerances of standards such as IEEE 519-1992–IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems and IEEE 1547.2-2008–IEEE Application Guide for IEEE Std 1547, IEEE Standard for Interconnecting Distributed Resources with Electric Power Systems. Higher order LCL filters are essential to achieve these regulatory standard requirements at compact size and weight. This objective of this thesis report is to evaluate design procedures for such higher order LCL filters. The initial configuration of the third order LCL filter is decided by the frequency response of the filter. The design equations are developed in per-unit basis so results can be generalized for different applications and power levels. The frequency response is decided by IEEE specifications for high frequency current ripple at the point of common coupling. The appropriate values of L and C are then designed and constructed. Power loss in individual filter components is modeled by analytical equations and an iterative process is used to arrive at the most efficient design. Different combinations of magnetic materials (ferrite, amorphous, powder) and winding types (round wire, foil) are designed and tested to determine the most efficient design. The harmonic spectrum, power loss and temperature rise in individual filter components is predicted analytically and verified by actual tests using a 3 phase 10 kW grid connected converter setup. Experimental results of filtering characteristics show a good match with analysis in the frequency range of interconnected inverter applications. The design process is stream-lined for the above specified core and winding types. The output harmonic current spectrum is sampled and it is established that the harmonics are within the IEEE recommended limits. The analytical equations predicting the power loss and temperature rise are verified by experimental results. Based on the findings, new LCL filter combinations are formulated by varying the net Lpu to achieve the highest efficiency while still meeting the recommended IEEE specifications. Thus a design procedure which can enable an engineer to design the most efficient and compact filter that can also meet the recommended guidelines of harmonic filtering for grid-connected converter applications is established.

Power converters have evolved from the classical low switching frequency thyristorised converters to the modern high-frequency switched mode converters employing fast power devices such as Insulated Gate Bipolar Transistors (IGBTs). This evolution has changed the way power is processed in all the four functional areas of power conversion namely, AC-DC, DC-DC, DC-AC and AC-AC. High frequency switching has made it possible to reduce the size of the converters by using smaller energy storage elements. Switched mode conversion applied to AC-AC power conversion results in the use of two approaches: An indirect (two stage) conversion with a rectifier and an inverter with a dc link storage and a direct conversion scheme with a matrix converter. Matrix converter is a potential candidate in certain applications where a compact power converter design is required. Two approaches in topology, namely direct and indirect matrix converters are well reported in the literature. This thesis looks at the analysis, modeling and control of matrix converters from the perspective of converter switching functions. The switching functions as proposed for the line frequency switching rectifiers and cycloconverters is extended to the high frequency switching pulse-width modulated inverters and rectifiers. The matrix converter modulation schemes are analysed and a fresh interpretation in terms of these switching functions is presented in this thesis. The application of the switching function based analysis also yields a better insight into popular space phasor moulation techniques employed in matrix converters such as indirect-space-phasor modulation. The topology of the matrix converter is simple. There are no energy storage elements. However, the control, modulation and protection processes are more complex than other converters. The complexities involved in the control, modulation, commutation and protection of the matrix converter necessitates a much more complex controller capable of carrying out these tasks fast and effectively. In this work, a versatile FPGA based digital controller is designed which is not only capable of carrying out all the modulation, control, commutation and protection requirements of the matrix converter but also, can simulate the converter and the load in real-time. The real-time simulation capabilities of the control and real-time simulation platform are demonstrated with a suitable example of dynamic system. The real-time models of the matrix converter feeding passive load are developed and demonstrated in comparison with offline simulation models. Matrix converters are buck-derived converters and hence the input currents are discontinuous. Hence design of an appropriate filter becomes necessary. Some guidelines are suggested to design an appropriate input filter considering the non-idealities of the source. Finally, hardware designs of suitably rated direct and indirect matrix converters are presented and some representative results are given.

Fabrication technology, based on MEMS processes, for constructing components for use in switched-mode power supplies are developed and presented. Capacitors, magnetic cores, and inductors based on sacrificial multilayer electroplating are designed, fabricated, and characterized. Characterization of the produced inductors' core losses at high frequency and high flux is presented, confirming the aptness of the featured microfabrication processes for reducing eddy current losses in magnetic cores. As well, the demonstration of the same inductors in DC/DC converters at high switching frequencies, up to 6 MHz, is presented. Initial work addressing the top-down development of a fully-integrated DC/DC converter is presented. As well, the comprehensive advancement of the central process - sacrificial multilayer electroplating - is presented, including the development of a second-generation automated multilayer electroplating system. The advanced sacrificial multilayer plating process is applied to produce microfabricated capacitors, which achieved in excess of 1.5 nF/mm² capacitance density, The fabrication of highly-laminated magnetic cores and power inductors based on sacrificial multilayer electroplating is presented, along with the design and development of a system for characterizing inductor behavior at high-frequency, high-flux conditions. The design and operation of both buck and boost DC/DC converters, switching at up to 6 MHz, built around these highly-laminated-core inductors are presented.

The main goal of this thesis is to develop an active thermal management control scheme for multi-phase current mode buck converters in order to improve the long term reliability of the converters. A thermal management unit (TMU) with independent linear compensators for the thermal loops is incorporated into the existing digital controller to regulate the current through each phase so that equal temperature distribution is achieved across all phases. A lumped parameter thermal model of the multi-phase converter is built as the basis of the TMU. MATLAB simulation results are used to verify the TMU concept. Experimental results from a digitally controlled 12 V to 1 V, 50 A, 250 kHz four-phase peak current mode buck converter demonstrate the effectiveness of the proposed thermal management technique in the presence of uneven air flow. The steady-state performance, dynamic transient load performance, effect of gate drive voltage and efficiency measurements are investigated and discussed.

The main goal of this thesis is to develop an active thermal management control scheme for multi-phase current mode buck converters in order to improve the long term reliability of the converters. A thermal management unit (TMU) with independent linear compensators for the thermal loops is incorporated into the existing digital controller to regulate the current through each phase so that equal temperature distribution is achieved across all phases. A lumped parameter thermal model of the multi-phase converter is built as the basis of the TMU. MATLAB simulation results are used to verify the TMU concept. Experimental results from a digitally controlled 12 V to 1 V, 50 A, 250 kHz four-phase peak current mode buck converter demonstrate the effectiveness of the proposed thermal management technique in the presence of uneven air flow. The steady-state performance, dynamic transient load performance, effect of gate drive voltage and efficiency measurements are investigated and discussed.

Significant advances in modern ac/ac power converter technologies and demands of industries have reached beyond standard ac/ac power converters with voltage-source inverters fed from diode rectifiers. Power electronics converters have been matured to stages toward compact realization, increased high-power handling capability, and improving utility interface. Modern ac/ac power converter topologies with various control strategies have been introduced for the further improvements, such as matrix converters, current-fed converters, PWM rectifiers, and active power filters. In this dissertation, several new converter topologies are proposed in conjunction with developed control schemes based on the modern ac/ac converters which enhance performance and solve the drawbacks of conventional converters. In this study, a new fault-tolerant PWM strategy is first proposed for matrix converters. The added fault-tolerant scheme would strengthen the matrix converter technology for aerospace and military applications. A modulation strategy is developed to reshape output currents for continuous operation, against fault occurrence in matrix converter drives. This study designs a hybrid, high-performance ac/ac power converter for high power applications, based on a high-power load commutated inverter and a mediumpower voltage source inverter. Natural commutation of the load commutated inverter is actively controlled by the voltage source inverter. In addition, the developed hybrid system ensures sinusoidal output current/voltage waveforms and fast dynamic response in high power areas. A new topology and control scheme for a six-step current source inverter is proposed. The proposed topology utilizes a small voltage source inverter, to turn off main thyristor switches, transfer reactive load energy, and limit peak voltages across loads. The proposed topology maximizes benefits of the constituent converters: highpower handling capability of large thyristor-based current source inverters as well as fast and easy control of small voltage source inverters. This study analyzes, compares, and evaluates two topologies for unity power factor and multiple ac/ac power conversions. Theoretical analyses and comparisons of the two topologies, grounded on mathematical approaches, are presented from the standpoint of converter kVA ratings, dc-link voltage requirements, switch ratings, semiconductor losses, and reactive component sizes. Analysis, simulation, and experimental results are detailed for each proposed topology.

In this dissertation the ac-link universal power converters, which are a new class of power converters, are introduced and studied in detail. The inputs and outputs of these converters may be dc, ac, single phase, or multi-phase. Therefore, they can be used in a variety of applications, including photovoltaic power generation, wind power generation, and electric vehicles. In these converters the link current and voltage are both alternating and their frequency can be high, which leads to the elimination of the dc electrolytic capacitors and the bulky low-frequency transformers. Therefore, the ac-link universal power converters are expected to have higher reliability and smaller size. Moreover, these converters are soft switching, which results in negligible switching losses and minimized current and voltage stress over devices. In the first part of the dissertation, the parallel ac-link universal power converter is studied in detail. This converter is an extension of the buck-boost converter. The series ac-link universal power converter, which is dual of the parallel ac-link universal power converter, is proposed in the second part of this dissertation. This converter is an extension of the Cuk converter. A modified configuration with fewer switches, named sparse ac-link universal power converter is proposed in the third part of this dissertation. The sparse ac-link universal power converters can appear as parallel or series. The performance of all these configurations is evaluated through simulations and experiments.