State-variable modelling of CLL resonant converters

The paper presents the derivation and application of state-variable models to high-order topologies of resonant converters. In particular, a 3rd order CLL resonant circuit is considered with bridge rectification and both a capacitive output filter (voltage output), and an LC output filter (current output). The state-variable model accuracy is verified against component-based simulation packages (Spice) and practical measurements, and it is shown that the resulting models facilitate rapid analysis compared to their integration-based counterparts (Spice, Saber), without the loss of accuracy normally associated with fundamental mode approximation (FMA) techniques. Moreover, unlike FMA, the models correctly predict the resonant peaks associated with harmonic excitation of the tank resonance. Subsequently, it is shown that excitation of the resonant tank by odd harmonics of the input voltage can be utilised to provide overcurrent protection in the event of an output short-circuit. Further, through judicious control of operating frequency, it is shown that 'inductive' zero voltage switching (ZVS) can still be obtained, facilitating reductions in gate-drive switching losses, thereby improving efficiency and thermal management of the supply under fault conditions. Although the results are ultimately generic to other converter counterparts, measured results from two prototype 36 V input, 11-14.4V output, 3rd - order CLL converters are included to practically demonstrate the attributes of the proposed analysis and control schemes

Integrated series transformer in cascade converters for photovoltaic energy systems

This paper proposes a novel configuration for photovoltaic applications based on a cascade converter topology. The series connection between modules is achieved through the magnetic core of the integrated series transformer, therefore an inherent isolation is provided without the requirement of a dc-dc conversion stage. Such isolation approach between each module allows operation at high voltage levels without harming the PV panel insulation. The main principles that support this proposal, as well as, simulation results are presented to validate the configuration.Peer ReviewedPostprint (author's final draft

Nonlinear mechanisms in passive microwave devices

Premi extraordinari doctorat curs 2010-2011, àmbit d’Enginyeria de les TICThe telecommunications industry follows a tendency towards smaller devices, higher power and higher frequency, which imply an increase on the complexity of the electronics involved. Moreover, there is a need for extended capabilities like frequency tunable devices, ultra-low losses or high power handling, which make use of advanced materials for these purposes. In addition, increasingly demanding communication standards and regulations push the limits of the acceptable performance degrading indicators. This is the case of nonlinearities, whose effects, like increased Adjacent Channel Power Ratio (ACPR), harmonics, or intermodulation distortion among others, are being included in the performance requirements, as maximum tolerable levels. In this context, proper modeling of the devices at the design stage is of crucial importance in predicting not only the device performance but also the global system indicators and to make sure that the requirements are fulfilled. In accordance with that, this work proposes the necessary steps for circuit models implementation of different passive microwave devices, from the linear and nonlinear measurements to the simulations to validate them. Bulk acoustic wave resonators and transmission lines made of high temperature superconductors, ferroelectrics or regular metals and dielectrics are the subject of this work. Both phenomenological and physical approaches are considered and circuit models are proposed and compared with measurements. The nonlinear observables, being harmonics, intermodulation distortion, and saturation or detuning, are properly related to the material properties that originate them. The obtained models can be used in circuit simulators to predict the performance of these microwave devices under complex modulated signals, or even be used to predict their performance when integrated into more complex systems. A key step to achieve this goal is an accurate characterization of materials and devices, which is faced by making use of advanced measurement techniques. Therefore, considerations on special measurement setups are being made along this thesis.Award-winningPostprint (published version

Building the analytical response in frequency domain of AC biased bolometers Application to Planck/HFI

Context: Bolometers are high sensitivity detector commonly used in Infrared astronomy. The HFI instrument of the Planck satellite makes extensive use of them, but after the satellite launch two electronic related problems revealed critical. First an unexpected excess response of detectors at low optical excitation frequency for {\nu} < 1 Hz, and secondly the Analog To digital Converter (ADC) component had been insufficiently characterized on-ground. These two problems require an exquisite knowledge of detector response. However bolometers have highly nonlinear characteristics, coming from their electrical and thermal coupling making them very difficult to modelize. Goal: We present a method to build the analytical transfer function in frequency domain which describe the voltage response of an Alternative Current (AC) biased bolometer to optical excitation, based on the standard bolometer model. This model is built using the setup of the Planck/HFI instrument and offers the major improvement of being based on a physical model rather than the currently in use had-hoc model based on Direct Current (DC) bolometer theory. Method: The analytical transfer function expression will be presented in matrix form. For this purpose, we build linearized versions of the bolometer electro thermal equilibrium. And a custom description of signals in frequency is used to solve the problem with linear algebra. The model performances is validated using time domain simulations. Results: The provided expression is suitable for calibration and data process- ing. It can also be used to provide constraints for fitting optical transfer function using real data from steady state electronic response and optical response. The accurate description of electronic response can also be used to improve the ADC nonlinearity correction for quickly varying optical signals.Comment: 20 pages, 10 figure

Fault-Tolerant Control of a Flux-switching Permanent Magnet Synchronous Machine

Je jasné, že nejúspěšnější konstrukce zahrnuje postup vícefázového řízení, ve kterém každá fáze může být považována za samostatný modul. Provoz kterékoliv z jednotek musí mít minimální vliv na ostatní, a to tak, že v případě selhání jedné jednotky ostatní mohou být v provozu neovlivněny. Modulární řešení vyžaduje minimální elektrické, magnetické a tepelné ovlivnění mezi fázemi řízení (měniče). Synchronní stroje s pulzním tokem a permanentními magnety se jeví jako atraktivní typ stroje, jejíž přednostmi jsou vysoký kroutící moment, jednoduchá a robustní konstrukce rotoru a skutečnost, že permanentní magnety i cívky jsou umístěny společně na statoru. FS-PMSM jsou poměrně nové typy střídavého stroje stator-permanentní magnet, které představují významné přednosti na rozdíl od konvenčních rotorů - velký kroutící moment, vysoký točivý moment, v podstatě sinusové zpětné EMF křivky, zároveň kompaktní a robustní konstrukce díky umístění magnetů a vinutí kotvy na statoru. Srovnání výsledků mezi FS-PMSM a klasickými motory na povrchu upevněnými PM (SPM) se stejnými parametry ukazuje, že FS-PMSM vykazuje větší vzduchové mezery hustoty toku, vyšší točivý moment na ztráty v mědi, ale také vyšší pulzaci díky reluktančnímu momentu. Pro stroje buzené permanentními magnety se jedná o tradiční rozpor mezi požadavkem na vysoký kroutící moment pod základní rychlostí (oblast konstantního momentu) a provozem nad základní rychlostí (oblast konstantního výkonu), zejména pro aplikace v hybridních vozidlech. Je předložena nová topologie synchronního stroje s permanentními magnety a spínaným tokem odolného proti poruchám, která je schopná provozu během vinutí naprázdno a zkratovaného vinutí i poruchách měniče. Schéma je založeno na dvojitě vinutém motoru napájeném ze dvou oddělených vektorově řízených napěťových zdrojů. Vinutí jsou uspořádána takovým způsobem, aby tvořila dvě nezávislé a oddělené sady. Simulace a experimentální výzkum zpřesní výkon během obou scénářů jak za normálního provozu, tak za poruch včetně zkratových závad a ukáží robustnost pohonu za těchto podmínek. Tato práce byla publikována v deseti konferenčních příspěvcích, dvou časopisech a knižní kapitole, kde byly představeny jak topologie pohonu a aplikovaná řídící schémata, tak analýzy jeho schopnosti odolávat poruchám.It has become clear that the most successful design approach involves a multiple phase drive in which each phase may be regarded as a single-module. The operation of any one module must have minimal impact upon the others, so that in the event of that module failing the others can continue to operate unaffected. The modular approach requires that there should be minimal electrical, magnetic and thermal interaction between phases of the drive. Flux-Switching permanent magnet synchronous machines (FS-PMSM) have recently emerged as an attractive machine type virtue of their high torque densities, simple and robust rotor structure and the fact that permanent magnets and coils are both located on the stator. Flux-switching permanent magnet (FS-PMSM) synchronous machines are a relatively new topology of stator PM brushless machine. They exhibit attractive merits including the large torque capability and high torque (power) density, essentially sinusoidal back-EMF waveforms, as well as having a compact and robust structure due to both the location of magnets and armature windings in the stator instead of the rotor as those in the conventional rotor-PM machines. The comparative results between a FS-PMSM and a traditional surface-mounted PM (SPM) motor having the same specifications reveal that FS-PMSM exhibits larger air-gap flux density, higher torque per copper loss, but also a higher torque ripple due to cogging -torque. However, for solely permanent magnets excited machines, it is a traditional contradiction between the requests of high torque capability under the base-speed (constant torque region) and wide speed operation above the base speed (constant power region) especially for hybrid vehicle applications. A novel fault-tolerant FS-PMSM drive topology is presented, which is able to operate during open- and short-circuit winding and converter faults. The scheme is based on a dual winding motor supplied from two separate vector-controlled voltage-sourced inverter drives. The windings are arranged in a way so as to form two independent and isolated sets. Simulation and experimental work will detail the driver’s performance during both healthy- and faulty- scenarios including short-circuit faults and will show the drive robustness to operate in these conditions. The work has been published in ten conference papers, two journal papers and a book chapter, presenting both the topology of the drive and the applied control schemes, as well as analysing the fault-tolerant capabilities of the drive.

Modelling and analysis of asynchronous and synchronous torques in split-phase induction machines

In this thesis, the nature of asynchronous and synchronous torques in a split-phase induction machine is investigated and quantified. The equivalent circuit for this type of machine is derived using the rotating field theory. It is extended to include harmonic effects. Using this model, winding harmonics and permeance harmonics may be calculated independently of each other so that the model can be used to analyse asynchronous torques from winding harmonics as well as synchronous torques from permeance harmonics. These are calculated separately. The asynchronous torques appear as perturbations in the steady-state torque-speed curve while the synchronous torques only appear at specific speeds. The synchronous torques are superimposed onto the torque-speed curves to model both effects together. The model predictions are compared against test results using purpose-built experimental machines together with production machines. These have varying rotor bar number and skew. Different methods are used to assess the synchronous torques. It is found that measuring synchronous locking torque is not a straightforward matter; however, reasonable agreement is found between calculation and measurement. The work highlights the need for the correct choice of stator and rotor slot numbers together with the effect skew has on reducing the synchronous and asynchronous locking torques

Integrated design of high performance pulsed power converters : application to klystron modulators for the compact linear colider (CLIC)

Ce travail de recherche présente l’étude, conception et validation d’une topologie de convertisseur de puissance pulsé qui compense la chute de tension pour des modulateurs de type klystron de haute performance. Cette topologie est capable de compenser la chute de tension du banc de condensateur principal et, en même temps, de faire fonctionner le modulateur avec une consommation de puissance constante par rapport au réseau électrique. Ces spécifications sont requises par le projet Compact Linear Collider (CLIC) pour les modulateurs klystron de son Drive Beam. Le dimensionnement du système est effectué à partir d’un outil d’optimisation globale développé à partir des modèles analytiques qui décrivent les performances de chaque composant du système. Tous les modèles sont intégrés dans un processus optimal intermédiaire de conception qui utilise des techniques d’optimisation afin de réaliser un dimensionnement optimal du système. Les performances de cette solution optimale intermédiaire sont alors évaluées à l’aide d’un modèle plus fin basé sur des simulations numériques. Une technique d’optimisation utilisant l’approche «space mapping» est alors mise en oeuvre. Si l’écart entre les performances prédites et les performances simulées est important, des facteurs de correction sont appliqués aux modèles analytiques et le processus d’optimisation est relancé. Cette méthode permet d’obtenir une solution optimale validée par le modèle fin en réduisant le nombre de simulations. La topologie finale sélectionnée pour le cahier des charges du modulateur CLIC est validée expérimentalement sur des prototypes à échelle réduite. Les résultats valident la méthodologie de dimensionnement et respectent les spécifications.This research work presents the study, design and validation of a pulsed power converter topology that performs accurate voltage droop compensation for high performance klystron modulators. This topology is capable of compensating the voltage droop of the intermediate capacitor bank and, at the same time, it makes possible a constant power consumption operation of the modulator from the utility grid. These two main specifications are required for the Compact Linear Collider (CLIC) Drive Beam klystron modulators. The dimensioning of the system is performed by developing a global optimization design tool. This tool is first based on developed analytical models describing the performances of each system subcomponent. All these models are integrated into an intermediate design environment that uses nonlinear optimization techniques to calculate an optimal dimensioning of the system. The intermediate optimal solution performances are then evaluated using a more accurate model based on numerical simulation. Therefore, an optimization technique using «space mapping» is implemented. If differences between predicted performances and simulated results are non-negligible, correction factors are applied to the analytical models and the optimization process is launched again. This method makes possible to achieve an optimal solution validated by numerical simulation while reducing the number of numerical simulation steps. The selected final topology for the CLIC klystron modulator is experimentally validated using reduced scale prototypes. Results validate the selected methodology and fulfill the specifications