In this dissertation, new high frequency link power conversion systems for the fuel cell power conditioning are proposed to improve the performance and optimize the cost, size, and weight of the power conversion systems. The first study proposes a new soft switching technique for the phase-shift controlled bi-directional dc-dc converter. The described dc-dc converter employs a low profile high frequency transformer and two active full-bridge converters for bidirectional power flow capability. The proposed new soft switching technique guarantees soft switching over wide range from no load to full load without any additional circuit components. The load range for proposed soft switching technique is analyzed by mathematical approach with equivalent circuits and verified by experiments. The second study describes a boost converter cascaded high frequency link direct dc-ac converter suitable for fuel cell power sources. A new multi-loop control for a boost converter to reduce the low frequency input current harmonics drawn from the fuel cell is proposed, and a new PWM technique for the cycloconverter at the secondary to reject the low order harmonics in the output voltages is presented. The performance of the proposed scheme is verified by the various simulations and experiments, and their trade-offs are described in detail using mathematical evaluation approach. The third study proposes a current-fed high frequency link direct dc-ac converter suitable for residential fuel cell power systems. The high frequency full-bridge inverter at the primary generates sinusoidally PWM modulated current pulses with zero current switching (ZCS), and the cycloconverter at the secondary which consists of only two bidirectional switches and output filter capacitors produces sinusoidally modulated 60Hz split single phase output voltage waveforms with near zero current switching. The active harmonic filter connected to the input terminal compensates the low order input current harmonics drawn from the fuel cell without long-term energy storage devices such as batteries and super capacitors.

Les travaux présentés dans cette thèse s'inscrivent dans le cadre de l"algorithmique et de la combinatoire du texte et s'appliquent à la bio-informatique. Plus particulièrement, ils concernent la localisation de motifs pondérés modélisés par des matrices score-position dans un texte non pondéré. Ces travaux sont appliqués au problème biologique de la recherche de sites de fixation de facteurs de transcription dans un génome. Cette application contribue à la compréhension de la régulation des gènes. Nous nous sommes attaqués à deux problèmes complémentaires, la recherche d'une seule matrice dans un texte puis la recherche simultanée d'un ensemble de matrices. Pour accélérer les algorithmes existant, nous nous sommes inspiré des algorithmes de recherche de motifs exacts connus pour leur efficacité. La différence est que les matrices score-position sont des motifs probabilistes, utilisant des fonctions de score. Nous devons donc intégrer la distribution de ces fonctions dans les algorithmes de recherche. Concernant le premier problème nous proposons une extension de l'algorithme de Knuth, Morris et Pratt qui repose sur un pré-traitement du motif pour optimiser le parcours le long du texte. Concernant le second problème nous avons utilisé une structure d'indexation afin de factoriser l'ensemble des matrices. Cette structure tire partie des distributions de scores associées à chaque matrice. Dans les deux cas, nous traitons en amont une partie des données de départ. Nous avons choisi de pré-traiter les matrices par rapport à l'application bio-informatique car les sites de fixation de facteurs de transcription sont des données relativement stables dans le temps. Ces algorithmes ont été mis en oeuvre dans un logiciel disponible en ligne appelé TFMscan. Ils ont fait l'objet d'une validation à grande échelle sur les bases de données de facteurs de transcription Jaspar et Transfac.

Distributed generation (DG) with a converter interface to the power grid is found in many of the green power resources applications. This dissertation describes a multi-objective control technique of voltage source converter (VSC) based on multilevel converter topologies, for integration of DG resources based on renewable energy (and non-renewable energy)to the power grid. The aims have been set to maintain a stable operation of the power grid, in case of di erent types of grid-connected loads. The proposed method provides compensation for active, reactive, and harmonic load current components. A proportional-integral (PI) control law is derived through linearization of the inherently non-linear DG system model, so that the tasks of current control dynamics and dc capacitor voltage dynamics become decoupled. This decoupling allows us to control the DG output currents and the dc bus voltage independently of each other, thereby providing either one of these decoupled subsystems a dynamic response that signi cantly slower than that of the other. To overcome the drawbacks of the conventional method, a computational control delay compensation method, which delaylessly and accurately generates the DG reference currents, is proposed. The rst step is to extract the DG reference currents from the sensed load currents by applying the stationary reference frame and then transferred into synchronous reference frame method, and then, the reference currents are modi ed, so that the delay will be compensated. The transformed variables are used in control of the multilevel voltage source converter as the heart of the interfacing system between DG resources and power grid. By setting appropriate compensation current references from the sensed load currents in control circuit loop of DG link, the active, reactive, and harmonic load current components will be compensated with fast dynamic response, thereby achieving sinusoidal grid currents in phase with load voltages while required power of loads is more than the maximum injected power of the DG resources. The converter, which is controlled by the described control strategy, guarantees maximum injection of active power to the grid continuously, unity displacement power factor of power grid, and reduced harmonic load currents in the common coupling point. In addition, high current overshoot does not exist during connection of DG link to the power grid, and the proposed integration strategy is insensitive to grid overload. / La Generació Distribuïda (DG) injectada a la xarxa amb un convertidor estàtic és una solució molt freqüent en l'ús de molts dels recursos renovables. Aquesta tesis descriu una técnica de control multi-objectiu del convertidor en font de tensió (VSC), basat en les topologies de convertidor multinivell, per a la integració de les fonts distribuïdes basades en energies renovables i també de no renovables.Els objectius fixats van encaminats a mantenir un funcionament estable de la xarxa elèctrica en el cas de la connexió de diferents tipus de càrregues. El mètode de control proposat ofereix la possibilitat de compensació de les components actives i reactives de la potencia, i les components harmòniques del corrent consumit per les càrregues.La llei de control proporcional-Integral (PI) s’obté de la linearització del model inherentment no lineal del sistema, de forma que el problema de control del corrent injectat i de la tensió d’entrada del convertidor queden desacoblats. Aquest desacoblament permet el control dels corrents de sortida i la tensió del bus de forma independent, però amb un d’ells amb una dinàmica inferior.Per superar els inconvenients del mètode convencional, s’usa un retard computacional, que genera les senyals de referència de forma acurada i sense retard. El primer pas es calcular els corrents de referència a partir de les mesures de corrent. Aquest càlcul es fa primer transformant les mesures a la referència estacionaria per després transformar aquests valors a la referència síncrona. En aquest punt es on es poden compensar els retards.Les variables transformades son usades en els llaços de control del convertidor multinivell. Mitjançant aquests llaços de control i les referències adequades, el convertidor és capaç de compensar la potencia activa, reactiva i els corrents harmònics de la càrrega amb una elevada resposta dinàmica, obtenint uns corrents de la xarxa de forma completament sinusoïdal, i en fase amb les tensions.El convertidor, controlat amb el mètode descrit, garanteix la màxima injecció de la potencia activa, la injecció de la potencia reactiva per compensar el factor de potencia de la càrrega, i la reducció de les components harmòniques dels corrents consumits per la càrrega. A més, garanteix una connexió suau entre la font d’energia i la xarxa. El sistema proposat es insensible en front de la sobrecarrega de la xarxa

As the costs of large-scale power generation and transmission rise, distributed generation is becoming a prevalent alternative used by a growing number of both residences and businesses. Distributed generation systems typically consist of two main components: a small-scale, often high-efficiency or renewable power source, such as a fuel cell, solar panel, or wind turbine, and a power electronic converter to convert the raw power produced by the source to a usable form. In North America, the majority of power used in residential and light commercial locations is provided in a form known as single-phase three-wire, or split-phase. This consists of two half-phase AC voltages, each of 110 to 120V rms, and one combined AC voltage of 220 to 240V rms. It is therefore necessary for distributed generation systems to supply power in this same form so that it can be used by standard loads such as lighting or appliances, and the excess power can be fed back into the distribution grid. The most common type of converter used to make this conversion is the voltage-sourced inverter (VSI). There are, however, some advantages to using a current-sourced inverter (CSI) instead. These include improved output voltage waveform quality, built-in voltage boost, and built-in overcurrent protection. However, there are also two obstacles that have prevented the adoption of current-sourced inverters to date. The first obstacle to the use of current-sourced inverters is that they require a DC current input to operate. Therefore, a circuit and control algorithm must be developed to produce a DC current from a low DC voltage source. The first part of this thesis deals with the generation of a suitable DC current. The second major obstacle to adopting current-sourced inverters is that no algorithm for producing single-phase three-wire outputs with a CSI presently exists in literature. The second part of this thesis develops such a switching algorithm, using a three-leg current-sourced inverter. The algorithm is demonstrated using simulation and experimental results, which show that the proposed system is able to successfully generate balanced output voltages under unbalanced loading conditions while equalizing switch utilization and minimizing output voltage ripple.

Denna rapport behandlar utveckling av en tvåhjulig balanserande robot. En PID-regulator är implementerad i en mikrokontroller, som även AD-omvandlar en sensorsignal, samt styr motorer via H-bryggor med pulsbreddsmodulering. I rapporten förklaras framtagning av diskret PID-regulator, processorkort, motorkort, val av komponenter och sensor för att mäta robotens vinkel mot ett vertikalplan. Roboten kan balansera stillastående, men behöver kompletteras ytterligare med hjulåterkoppling för att kunna balansera medan den kör. Roboten balanserar med mätdata från en mekanisk golvavkännare (potentiometer). Andra sorters sensorer diskuteras också, t ex accelerometer, gyro och optisk sensor. / This report explain the development of a two wheel balancing robot. A PID-regulator is implemented in a microcontroller, which also AD-converts a sensor signal, and generate pulse width modulated signals to drive H-bridges. It is discussed how to develop a discretisized PID regulator, microcontroller and H-bridge circuit boards, as well as how to chose components and suitable sensors for measuring the robots angle against a vertical plane. The robot is able to balance on its own when standing still, but it need to have feedback from its wheel position if it should be able to maintain balancing when moving. The robot use a mechanical floor feeler (potentiometer). Other sensors are also discussed, e g accelerometer, rate gyro and optical sensor.

This thesis work describes the implementation perspective of an integrated high efficiency DC-DC converter implemented in 65 nm CMOS. The implemented system employs the Buck converter topology to down-convert the input battery voltages. This converter offers its use as a power management unit in portable battery operated devices. This thesis work includes the description of a basic Buck converter along with the various key equations involved which describe the Buck operation as well as are used to deduce the requirements for the various internal building blocks of the system. A detailed description of the operation as well as the design of each of the building blocks is included. The implemented system can convert the input battery voltage in the range of 2.3 V to 3.6 V into an output supply voltage of 1.6 V. The system uses dual-mode feedback control to maintain the output voltage at 1.6 V. For the low load currents the PFM feedback control is used and for the higher load currents the PWM feedback control is used. This converter can supply load currents from 0 to 300 mA with efficiency above 85%. The static line regulation of the system is < 0.1% and the load regulation of the system is < 0.3%. A digital soft-start circuit is implemented in this system. The system also includes the capability to trim the output voltage in ~14 mV steps depending on the 4-bit input digital code.

This thesis work contains a litterature study about electrical motors in general and how PWM-patterns for brushless DC-motors can be made. A suitable method has been implemented as a simulation model in VHDL. A simulation model of a brushless DC-motor which describes the phasecurrents, torque and angular velocity has also been made. The motor model made simulations easier for the complete PWM-system. The design was synthesised and tested with a prototypeboard including a SPARTAN II FPGA. In order to test the design, a powerstage and a motor was included. The tests showed that the design was working as expected according to the previous simulations. A study about an alternative way to control a brushless DC-motor has also been made. This alternative is best suited when the generated back-EMK for the motor is sinusoidal. A simulation model for a part of a system like this has been made, and it has been synthesised in order to examine if it is possible to implement using a FPGA availible today.

In this thesis a predefined design parameters are used to present theoretical guidelines for design of low voltage, and low power DC-DC converter with high power efficiency and low levels of EMI (Electro-Magnetic Interference). This converter is used to alter the DC voltage supplied by the power source. Several DC-DC converters of different types and topologies are described and analyzed. Switched converter of buck topology is found to satisfy the design criteria most adequately and therefore is chosen as the solution for the task of the thesis. Three control schemes are analysed PWM (Pulse-Width Modulation), PFM (Phase-Frequency Modulation), and Sliding control. PWM is found to be most appropriate for implementation with this type of converter. Further, basic operation of the buck converter which includes two modes of operation CCM (Continuous-Conduction Mode) and DCM (Discontinuous-Conduction Mode) is described. Power losses associated with it are analysed as well. Finally several techniques for power conversion improvement are presented.

The purpose with the report is to show that it is possible to design a class-D amplifier, using a programmable FPGA mounted on a developing card from Xess and a H-bridge. The FPGA was programmed in VHDL which is the language the software from Xilinx use to implement a logical function into the FPGA The logical function corresponds to a modeling of the music signal and the modeling can be described as a comparator which compare the music signal with a triangle wave and as a out signal produce a pulse width modulated (PWM) signal. The report is also a review and evaluating of two different modulating technologies, AD- modeling and BD-modeling. A detailed part about how the H-bridge was designed and how it works. The result of this project is a working audio amplifier to a significant lower price than the products in todays market.

Class D amplifiers are becoming increasingly popular in audio devices. The strongest reason is the high efficiency which makes it advantageous for portable battery-driven products. Infineon Technologies is developing products in this area, and has recently filed a patent application regarding an implementation of a part of the class D amplifier. The aim of this Master’s thesis is to evaluate a digital open-loop implementation of a class D amplifier, using the pending patent solution, and discuss the differences from an analog closed-loop implementation. The focus has been on generating a high resolution PWM signal with a relatively low clock frequency. To achieve this, a hybrid of a counter and a self-calibrating tapped delay-line are used as a pulse generator. A model of the pulse generator was developed which made it possible to study how sampling frequency and different types of quantization affected quality parameters such as THD and SNR. With the results from the model two systems were implemented and simulated in HDL and as circuit schematics. The proposed digital open-loop class D amplifier was found to be useful in voice-band applications and for music. Since the open-loop structure suffers from poor rejection of power supply ripple, either error correction or a regulated power supply is needed. If much effort is put on the different parts of the amplifier the result can be really good but, depending on other constraints on the system, it may be simpler and less time consuming to use the analog circuit with feedback to achieve hi-fi quality. In summary, the combination of a counter and a self-calibrating tapped delay-line as a pulse generator is very useful in high resolution low-power systems. To avoid errors the delay-line and calibration can be made very accurate but with the expense of higher power consumption and area. However, the technique benefits from the small and fast logic devices available in deep sub-micron process technologies, which may finally lead to an advantage in power consumption and cost over the closed-loop analog solution.