Abstract not available

This thesis proposes a new bidirectional three-phase AC-DC power converter using matrix converter and Z-source inverter topologies. Advantages of the AC-DC matrix converter are the inherently controllable power factor, the tight DC voltage regulation, the wide bandwidth with quick response to load variation, the single-stage buck-voltage AC-to-DC power conversion; advantages of the z-source inverter are the increased reliability by allowing the shoot-through between upper and lower power switches of one inverter leg, insensitivity to DC bus voltage due to the extra freedom of controlling DC-link voltage. The proposed Matrix-Z-source converter (MZC) marries up both advantages of AC-DC matrix converter and Z-source inverter. It can achieve voltage-boost DC-AC inversion capable of variable voltage variable frequency (VVVF) AC output; it can achieve voltage-buck AC-DC rectification capable of inherent control over AC current phase angle and DC output regulation with a (VVVF) AC source supply. Both foresaid performance in DC-AC inversion and AC-DC rectification can be implemented in a simple open-loop control manner. Three constraints of VSI, in the bidirectional AC-DC power conversion, are the peak AC voltages are always less than DC-link voltage, closed-loop control has to be employed when DC regulation and/or AC current phase angle control are required, and AC voltage is sensitive to the variation of the DC-link voltage in DC-AC inversion. The voltage-boost inversion and/or voltage-buck rectification of MZC overcomes the first constraint; thus MZC enables the AC machine voltage increased higher than DC-link voltage hence advantages of running AC machine at relatively high voltages are enabled. The direct DC voltage regulation and inherent AC-current-phase-angle control of MZC overcomes the second constraint in an open-loop manner; hence a simplified system design is obtained with sufficient room for the further improvement by closed-loop control schemes. The extra freedom in controlling DC-link voltage of MZC overcomes the third constraint hence a DC source voltage adaptable inverter is obtained. This thesis focuses on the study of the feasibility of the proposed MZC through theoretical analysis and experimental verification. At first, the proposed MZC is conceptually constructed by examining the quadrant operation of AC-DC matrix converter and Z-source inverter. After the examination of the operating principles of both AC-DC matrix converter and Z-source inverter, the configuration of MZC is then proposed. The MZC has two operating modes: DC-AC inversion and AC-DC rectification. Circuit analysis for both operating modes shows that the new topology does not impose critical conflict in circuit design or extra restriction in parameterization. On the contrary, one version of the proposed MZC can make full advantage of Z-source network components in both operating modes, i.e. a pair of Z-source inductor and capacitor can be used as low-pass filter in AC-DC rectification. The modulation strategy, average modeling of system, and features of critical variables for circuit design of the proposed MZC were examined for each operating mode. Simulations of the proposed MZC and its experimental verification have been presented. Analytical models of conduction and switching losses of the power-switch network in different operating mode have shown that the losses in the MZC compare favorably with conventional VSI for a range of power factor and modulation indices.

This dissertation focuses on design and implementation of a highly linear and low flicker-noise receiver front-end based on the direct conversion architecture for multiband applications in a CMOS technology. The dissertation consists of two parts: One, implementation of a highly linear RF receiver front-end and, two, implementation of a low flicker-noise RF receiver front-end based for direct conversion architecture. For multiband applications, key active components, highly linear LNAs and mixers, in the RF front-end receiver have been implemented in a 0.18um CMOS process. Theoretical approaches are analyzed from the perspective of implementation issues for highly linear receiver system and are also compared with measured results. Highly linear LNAs and mixers have been analyzed in terms of noise, linearity and power consumption, etc. For a low flicker-noise receiver front-end based on direct conversion architecture, the design of differential LNA and various low flicker-noise mixers are investigated in a standard 0.18um CMOS process. A differential LNA which shows high linearity was fabricated with a low flicker-noise mixer. Three low flicker-noise mixers were designed, measured and compared to the-state-of-the-arts published by other research institutes and companies.

Le volume des convertisseurs électroniques de puissance devient lié, dans une part importante aux composants passifs qui le constituent. En particulier, les condensateurs de découplage constituent une part non négligeable de ce volume. En outre, les évolutions technologiques des composants passifs et particulièrement la densité d'énergie des condensateurs de découplage s'accroit beaucoup moins vite que la densité de puissance des composants actifs auxquels ils sont associés (transistors de puissance). D'autre part, la technologie à film plastique utilisée représente une masse non recyclable qu'il est essentiel de minimiser. Leur rôle est néanmoins fondamental pour le fonctionnement de l'ensemble. Une réduction trop importante de leur valeur conduit à une augmentation de perturbations conduites et rayonnées, voire à une instabilité non contrôlée du bus de tension du véhicule. Cette instabilité, pouvant générer des surtensions importantes, pourrait conduire à une destruction du variateur. Dans certains cas, cette démarche de dimensionnement est compliquée par le fait que d'autres systèmes abonnés au bus source de tension continue participent également aux perturbations conduites, en particulier un deuxième variateur triphasé à découpage. Dans ce cas, un partage du même condensateur de découplage peut-être envisagé. Ceci dit, on est confronté à deux problèmes couplés : - D'une part, le dimensionnement des condensateurs reste lié au courant efficace (du point de vue de l'auto échauffement aussi bien que de l'ondulation de tension qui est également liée à la capacité, autre critère dimensionnant) qu'ils seront amenés à supporter. Il est donc souhaitable de mettre en œuvre des stratégies de réduction de ce courant. - D'autre part, la faible résistance série a tendance à réduire de manière importante le facteur d'amortissement de l'impédance de bus continu vue par l'entrée de l'onduleur. Il convient alors de s'assurer de la maîtrise de la résonance du bus dans une telle situation. Ce travail de recherche explore deux approches complémentaires permettant de minimiser la taille des condensateurs requis et de maîtriser les ondulations de tension à l'entrée du convertisseur : - Développer une stratégie de modulation aussi satisfaisante que possible pour le pilotage d'un onduleur triphasé classique à deux niveaux et trois bras de pont. La contrainte supplémentaire, liée aux risques de résonnance du bus continu, doit être analysée et sera un des objectifs des travaux proposés. - Etudier l’impact que peut avoir une stratégie de modulation sur l’ensemble de la chaine de traction électrique. Des contraintes additionnelles liées à la stratégie de modulation d'un variateur de vitesse automobile sont aussi prises en comptes comme par exemple : - La compensation des effets non-linéaires qui sont dus au comportement de l’onduleur de tension ; - La minimisation du stress exercé sur le condensateur de découplage partagé de manière commune entre deux onduleurs de tension, en termes d’ondulation de tension à ses bornes et de la valeur efficace du courant absorbé. Les résultats théoriques ont été validés expérimentalement sur deux bancs de tests : un premier dédié pour des essais à faible puissance sur une charge passive et un deuxième, monté au site de Lardy de Renault, dédié pour des essais à haute puissance sur une charge réaliste. / The volume of the electronic power converters becomes linked, in a large part, to the passive component which constitute it. In particular, the decoupling capacitors are a significant part of this volume. Moreover, the technological evolutions of the passive components and in particular the energy density of the decoupling capacitors increase much less rapidly than the power density of the active components to which they are associated. On the other hand, the plastic film technology used represents a non-recyclabl mass which it is essential to minimize. The role of the film capacitor is nevertheless fundamental for the functioning of the whole inverter. Too much reduction of their value leads to an increase in conducted and radiated disturbances, or to an uncontrolled instability of the vehicle DC bus voltage. This instability, which can generate significant overvoltages, could lead to a destruction of the switching power devices of the voltage source inverter. In some cases, this design approach could become complicated when other systems could be connected t the same DC voltage source bus, such as a second voltage source inverter. Hence, the same DC link capacitor is shared between the two inverters. Thus, it becomes much solicited and conducted disturbances may be generated. That said, we are confronted with two coupled problems. On the one hand, the design of the capacitors remains linked to the RMS current. It is therefore desirable to implement strategies to reduce this current. On the other hand, the low series resistance tends to reduce significantly the damping factor of the DC bus impedance seen by the input of the inverter. Hence, it is then necessary to ensure control of the resonance of the bus in such a situation. This research explores two complementary approaches to minimize the size of the required capacitors an to control the voltage ripples at the input of the converter: - Develop a P WM strategy that is as satisfactory as possible for controlling a conventional two-level three-phase inverter. The additional constraint, related to the resonance risks of the DC bus, must be analyzed and is one of the objectives of the proposed works. - Study the impact of P WM strategies on the entire electrical traction chain. Additional constraints related to the P WM strategy are also taken into account such as - Compensation for non-linear effects due to the behavior of the voltage inverter; - Minimization of the stress exerted on the decoupling capacitor commonly shared between two voltage source inverters in terms of voltage ripple across its terminals and the rms value of the absorbed current. Theoretical and simulation results have been validated experimentally on two test benches: one dedicated for low power tests on a passive load and the second one, mounted at the Lardy site of Renault, dedicated for hi h ower tests on a dynamic electrical machine.

Dissertation (DTech(Electrical Engineering))--Cape Peninsula University of Technology, 2012 / The confluence of the limited resources of fossil fuels (e.g. coal, oil and natural gas), environmental degradations leading to climate change, security of supplies and fossil fuels high costs have demanded a tremendous efforts on humanity to seek for a sustainable and unlimited natural energy sources. Amongst these renewable energy sources stands out solar energy because of its ubiquitousness. Solar energy is converted to DC electricity by the photovoltaic effect. Photovoltaic (PV) power systems installed in commercial and industrial buildings are a good example of distributed power generation. Here the energy consumption and production match and thus electricity taken from the grid during daytime peak hours can be reduced. This is beneficial as the transmission losses in the grid are avoided and also transmission need is reduced. The cost effectiveness of a solar energy system has hindered its wide adoption and deployment in terms of the initial capital cost even though it has a zero energy cost and very minimal operating and maintenance costs. Different governments have instituted many financial incentives for fast adoption of PV systems for both residential and commercial applications. However, all these incentives are not sustainable in the longer term forecast. For PV system to attain grid parity requires more than unsustainable approach of many governments providing time limited subsidies. The technical solution to the problem is to reduce the overall system cost through technical innovations. One such method is the adoption of transformerless inverter technology as the grid interface system. Transformerless inverter topology provides galvanic isolation through innovative inverter topology and switching strategies that eliminates problems created by not employing the service of transformer.

CAPES / O desenvolvimento de um conversor CC-CC de três portas é proposto neste trabalho. Através da combinação de um conversor bidirecional Ćuk e um transformador de alta frequência com um circuito retificador em ponte completa, duas portas de energia não isoladas e uma porta de energia isolada são obtidas. Um circuito LC série ressonante é empregado, resultando em comutação suave nos interruptores de potência. O conversor bidirecional Ćuk, controlado por modulação de largura de pulso (PWM) e o circuito tanque ressonante, controlado por modulação de frequência (PFM) acima da frequência de ressonância, permitem duas variáveis de controle para a topologia. Além disso, os interruptores de potência são compartilhados nas etapas de operação, reduzindo o número de componentes ativos. Regulação de suas portas é realizada para aplicações com elementos armazenadores de energia. São apresentados os modos de operação, a análise matemática e a estratégia de controle do conversor proposto. Os resultados experimentais são expostos para discutir a viabilidade da estrutura. / The development of a DC-DC three-port converter is proposed in this work. Through the combination of a bidirectional Ćuk converter and a high frequency transformer with a full-bridge rectifier circuit, two non-isolated energy ports and one isolated energy port are achieved. A LC series resonant circuit is employed, resulting in soft-switching in the power switches. The bidirectional Ćuk converter, controlled by pulse width modulation (PWM), and the tank resonant circuit, controlled by pulse frequency modulation (PFM) above the resonance frequency, allow two control variables for the topology. Furthermore, the power switches are shared for the operation of both circuits, reducing the number of active components. Port regulations are performed for applications with energy storage elements. Operation modes, math analysis and control strategy of the proposed converter are presented. Experimental results are exposed to discuss the feasibility of the structure.

Neste trabalho é proposto o desenvolvimento de um novo microinversor de estágio único para aplicação em sistemas fotovoltaicos. A topologia apresentada é baseada na combinação do conversor Cuk com uma estrutura de indutores chaveados para obtenção de um maior ganho estático e um circuito inversor em ponte completa conectado à rede. A estrutura de indutores chaveados apresentada nesse trabalho reduz esforços de tensão e corrente nas chaves semicondutoras. Com o objetivo de facilitar o controle, a etapa CC do microinversor opera em modo de condução descontínua (DCM). Para injetar corrente senoidal com baixa distorção harmônica à rede, é aplicado às chaves semicondutoras da etapa CC uma modulação por largura de pulso senoidal (SPWM). As chaves semicondutoras do circuito inversor em ponte completa são comandadas na frequência da rede, reduzindo perdas por chaveamento. Por se tratar de uma topologia inédita, são apresentados os modos de operação e a análise matemática do conversor CC-CC Cuk com alto ganho estático. Posteriormente, são realizadas a análise teórica e a estratégia de controle do microinversor proposto. Os resultados experimentais são expostos para discutir o funcionamento da topologia proposta, através de simulações e da implementação de um protótipo de 180 W. / The development of a novel single stage microinverter is proposed. The presented topology is based on the combination of the Cuk converter with a switched inductor structure to obtain a higher static gain, and a full-bridge inverter circuit. The presented switched inductor structure reduces voltage and current stresses on the power switches. In order of simplify the control, the stage CC of the microinverter operate in discontinuous conduction mode (DCM). To inject sinusoidal current with low harmonic distortion to the grid, a sinusoidal pulse width modulation (SPWM) is applied in the power switches. The switches of the full-bridge invertes are commanded in low frequency, in order to reduce switching losses. Operation modes and math analysis of the novel CC-CC converter are presented. Moreover, the math analysis and control strategy of proposed microinverter topology are exposed. Furthermore, experimental results are performed to analyze the proposed topology operation, by software simulations and implementation of a 180 W prototype.

CAPES / O desenvolvimento de um conversor CC-CC de três portas é proposto neste trabalho. Através da combinação de um conversor bidirecional Ćuk e um transformador de alta frequência com um circuito retificador em ponte completa, duas portas de energia não isoladas e uma porta de energia isolada são obtidas. Um circuito LC série ressonante é empregado, resultando em comutação suave nos interruptores de potência. O conversor bidirecional Ćuk, controlado por modulação de largura de pulso (PWM) e o circuito tanque ressonante, controlado por modulação de frequência (PFM) acima da frequência de ressonância, permitem duas variáveis de controle para a topologia. Além disso, os interruptores de potência são compartilhados nas etapas de operação, reduzindo o número de componentes ativos. Regulação de suas portas é realizada para aplicações com elementos armazenadores de energia. São apresentados os modos de operação, a análise matemática e a estratégia de controle do conversor proposto. Os resultados experimentais são expostos para discutir a viabilidade da estrutura. / The development of a DC-DC three-port converter is proposed in this work. Through the combination of a bidirectional Ćuk converter and a high frequency transformer with a full-bridge rectifier circuit, two non-isolated energy ports and one isolated energy port are achieved. A LC series resonant circuit is employed, resulting in soft-switching in the power switches. The bidirectional Ćuk converter, controlled by pulse width modulation (PWM), and the tank resonant circuit, controlled by pulse frequency modulation (PFM) above the resonance frequency, allow two control variables for the topology. Furthermore, the power switches are shared for the operation of both circuits, reducing the number of active components. Port regulations are performed for applications with energy storage elements. Operation modes, math analysis and control strategy of the proposed converter are presented. Experimental results are exposed to discuss the feasibility of the structure.

Neste trabalho é proposto o desenvolvimento de um novo microinversor de estágio único para aplicação em sistemas fotovoltaicos. A topologia apresentada é baseada na combinação do conversor Cuk com uma estrutura de indutores chaveados para obtenção de um maior ganho estático e um circuito inversor em ponte completa conectado à rede. A estrutura de indutores chaveados apresentada nesse trabalho reduz esforços de tensão e corrente nas chaves semicondutoras. Com o objetivo de facilitar o controle, a etapa CC do microinversor opera em modo de condução descontínua (DCM). Para injetar corrente senoidal com baixa distorção harmônica à rede, é aplicado às chaves semicondutoras da etapa CC uma modulação por largura de pulso senoidal (SPWM). As chaves semicondutoras do circuito inversor em ponte completa são comandadas na frequência da rede, reduzindo perdas por chaveamento. Por se tratar de uma topologia inédita, são apresentados os modos de operação e a análise matemática do conversor CC-CC Cuk com alto ganho estático. Posteriormente, são realizadas a análise teórica e a estratégia de controle do microinversor proposto. Os resultados experimentais são expostos para discutir o funcionamento da topologia proposta, através de simulações e da implementação de um protótipo de 180 W. / The development of a novel single stage microinverter is proposed. The presented topology is based on the combination of the Cuk converter with a switched inductor structure to obtain a higher static gain, and a full-bridge inverter circuit. The presented switched inductor structure reduces voltage and current stresses on the power switches. In order of simplify the control, the stage CC of the microinverter operate in discontinuous conduction mode (DCM). To inject sinusoidal current with low harmonic distortion to the grid, a sinusoidal pulse width modulation (SPWM) is applied in the power switches. The switches of the full-bridge invertes are commanded in low frequency, in order to reduce switching losses. Operation modes and math analysis of the novel CC-CC converter are presented. Moreover, the math analysis and control strategy of proposed microinverter topology are exposed. Furthermore, experimental results are performed to analyze the proposed topology operation, by software simulations and implementation of a 180 W prototype.

The need for efficiency, reliability and continuous operation has lead over the years to the development of fault-tolerant electrical drives for various industrial purposes and for transport applications. Permanent-magnet synchronous machines have also been gaining interest due to their high torque-to-mass ratio and high efficiency, which make them a very good candidate to reduce the weight and volume of the equipment.<p><p>In this work, a multidisciplinary approach for the design of fault-tolerant permanent-magnet synchronous machine drives is presented. <p><p>The drive components are described, including the electrical machine, the IGBT-based two-level inverter, the capacitors, the sensors, the controller, the electrical source and interfaces. A literature review of the failure mechanisms and of the reliability model of most of these components is performed. This allows understanding how to take benefit of the redundancy generally introduced in fault-tolerant systems.<p><p>A necessary step towards fault tolerance is the modelling of the electrical drive, both in healthy and faulty operations. A general model of multi-phase machines (with a number of phases equal to or larger than three) and associated converters is proposed. Next, control algorithms for multi-phase machines are derived. The impact of a closed-loop controller upon the occurrence of faults is also examined through simulation analysis and verified by experimental results.<p><p>Condition monitoring of electrical machines has expanded these last decades. New techniques relying on various measurements have emerged, which allow a better planning of maintenance operations and an optimization of the uptime of electrical machines. Regarding drives, a number of sensors are inherently present for control and basic protection functions. The utilization of these sensors for advanced condition monitoring is thus particularly interesting since they are available at no cost. <p><p>A novel fault detection and isolation scheme based on the available measurements (phase currents, DC-link voltage and mechanical position) is developed and validated experimentally. Change-detection algorithms are used for this purpose. Special attention is paid to sensor faults as well, what avoids diagnosis errors.<p><p>Fault-tolerant control can be implemented with passive and active approaches. The former consists in deriving a control scheme that gives acceptable performance for all operating conditions, including faulty conditions. The latter consists in applying dedicated solutions upon the occurrence of faults, i.e. by reconfiguring the control. Both approaches are investigated and implemented. <p><p>Finally, design considerations are discussed throughout the thesis. The advantages and drawbacks of various topologies are analyzed, which eventually leads to the design of a five-phase fault-tolerant permanent-magnet synchronous machine. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished