Dissertations / Theses on the topic 'Current commutation'

Compared to conventional AC-circuit breakers, a DC-breaker has to act fast and force the current down to zero. Many different DC-breaker topologies are available, and this thesis is focused on the hybrid DC-breaker comprising a mechanical switch and high power semiconductors. The main part of this thesis is focused on the current commutations in the hybrid DC-breaker. The two current commutations: from the mechanical switch to the semiconductor branch, and from the semiconductor to the metal oxide varistor, have completely different characteristics. When the mechanical switch opens, the metallic contacts separate and an electric arc is formed. As the voltage across the arc is higher than the voltage across the semiconductors, the current is pushed over to the semiconductor branch. The undesired stray inductance in the loop limits the current derivative and slows down the commutation. As the contacts keep separating, the arc voltage increases and eventually all current is conducted by the semiconductor and the arc ceases. For a hybrid DC-breaker, the worst case is a solid ground fault, as the fast rising current results in high current levels and makes the commutation from the mechanical switch to the semiconductor both difficult and slow. However, the fast rise of the current can be used to enhance the commutation by using coupled inductors in the two parallel branches. When the fault current rises in the semiconductor branch, the mutual coupling of the inductors causes the current in the mechanical switch to decrease and helps the commutation. The result is that the commutation time decreases with decreasing fault impedance, and makes the solid ground fault easier to handle. The commutation from the semiconductor to the metal oxide varistor is controlled by the turn-off of the semiconductor. When the semiconductor is turned off, it pulls the current down to zero with a rather constant current derivative regardless of the surrounding circuit and the system current is taken over by the metal oxide varistor. Hence, any inductance in the commutation loop will result in an over-voltage proportional to this inductance on top of the varistor voltage. By connecting a smaller metal oxide varistor, as a snubber, close to the semiconductor, the over-voltage can be controlled and the commutation from the snubber to the metal oxide varistor will be driven by the voltage difference between the two varistors. It is shown that for a 12 kV DC-system, a possible design of the mechanical switch in the hybrid DC-breaker comprises two contact gaps in series and opens with a velocity of 11 m/s. It has been experimentally verified that when starting the commutation at 4 kA, the commutation takes less than 700 us and is over before the switch has opened 1 mm. The thesis also contains proposed designs for an 80 kV DC-breaker that can be used as a modular solution for higher system voltages. For this higher voltage, the design will be a choice of the combination between the number of contact gaps in series and the opening velocity of the mechanical switch.<br>Till skillnad från konventionella brytare i växelspänningssystem behöver en brytare för likström (DC) reagera fortare och tvinga ner strömmen. Det finns många olika topologier för hur man kan designa en DC-brytare, men denna avhandling fokuserar på en hybridbrytare som består av en mekanisk kontakt och halvledarkomponenter. Huvuddelen av denna avhandling fokuserar på kommuteringen av strömmar mellan hybridbrytarens grenar. Brytförloppet består av två kommuteringar: från den mekaniska kontakten till halvledarna och från halvledarna till en metalloxidvaristor och dessa två kommuteringar har helt olika karakteristik. När den mekaniska kontakten öppnar bildas en ljusbåde. Eftersom ljusbågsspänningen är högre än spänningsfallet över halvledarna, flyttas strömmen över till halvledargrenen. Den oönskade induktansen som finns i kretsen kommer begränsa kommuteringen och förlänga tiden det tar att flytta strömmen från den mekaniska kontakten till halvledarna. Tack vare att den mekaniska kontakten öppnar med hög hastighet förlängs ljusbågen och ljusbågsspänningen fortsätter att öka tills all ström flyttats över till halvledarna och ljusbågen slocknar. För hybridbrytaren är ett solitt jordfel det värsta felfallet eftersom den snabbt ökande felströmmen leder till en svårare och mer utdragen kommutering till halvledarna. Den höga strömderivatan kan dock utnyttjas genom att installera två kopplade spolar i serie med den mekaniska kontakten och halvledarna. När strömmen ökar i halvledargrenen skapar den kopplade induktansen en motspänning som leder till en minskad ström genom den mekaniska kontakten och snabbar på kommuteringen. Resultatet är att kommuteringstiden blir kortare ju snabbare felströmmen växer. Kommuteringen från halvledarna till varistorn styrs av halvledarkomponenternas karakteristik. När halvledaren stänger av tvingas strömmen ner med en näst intill konstant derivata oberoende av komponenterna i kretsen och strömmen tas över av varistorn. Den oönskade induktansen i kretsen kommer då ge upphov till en överspänning proportionell till induktansen som ökar kraven på halvledaren. Genom att installera en liten varistor nära halvledaren kan överspänningen kontrolleras och kommuteringen kommer istället drivas av spänningsskillnaden mellan de två varistorerna. För ett 12 kV likströmssystem är en möjlig design av den mekaniska kontakten att ha två kontaktgap i serie och en öppningshastighet på 11 m/s. Experiment har verifierat att om kommuteringen startar vid 4 kA tar den midre än 700 us och är avslutad innan kontakten öppnats 1 mm. Avhandlingen innehåller även förslag på hur en 80 kV brytare kan designas för att användas som en modul i system med högre spänning. I det fallet är designen en avvägning mellan antalet kontakter i serie och öppningshastigheten på kontakten.<br><p>QC 20170519</p>

Current research and the price of semiconductors are making Matrix Converter topologies more attractive and practically viable for many applications. One of the key benefits claimed for the matrix approach is the possibility of greater power density due to the absence of a DC link. To capitalise on this it is necessary to make the input filter small by having a sufficiently high switching frequency. In order to arrive at optimised solutions in terms of filtering, heatsinking and packaging, it is important to have accurate models to predict power circuit losses as a function of operating point and switching frequency. This aim of this thesis is to further the understanding of Matrix Converter current commutation with a focus on switching losses. The commutation process is analysed in detail and a complete loss model for Matrix Converter circuits is developed. The use of circuit simulation software in the prediction of switching losses is investigated and comparisons are made with experimentally measured results. The loss model is used to compare Matrix Converter losses with a functionally equivalent sinusoidal front end inverter. A review of soft switching techniques for Matrix Converter circuits is given. A new auxiliary resonant soft switching Matrix Converter is presented which overcomes many of the problems of the previously proposed circuits. The design, construction and testing of a 6kW prototype soft switching Matrix Converter is presented to evaluate the feasibility of the topology.

The aim of this work is to reduce the cost and size of a brushless dc motor (BLDC) drive as well as increase the reliability and ruggedness of that drive. Traditional BLDC drives use Voltage Source Inverters (VSI) that utilize hard switching, thereby generating switching losses and entail the use of large heatsinks. VSI needs a huge dc link capacitor that is inherently unreliable and is one of the most expensive components of a drive. Hence, a Current Source Inverter (CSI) is used to replace the hard switchings by natural turn-off, thereby eliminating the heatsinks as well as the large dc link capacitor. A controlled rectifier together with a large inductor act as the current source. The only disadvantage is the large value of the dc link inductor and the huge number of turns needed to achieve these values of the inductances lead to huge resistive losses. Therefore, it is shown that it is possible to replace the controlled rectifier and the large inductor with a suitable dc-dc converter based current source switching at high frequencies and a much smaller value of the dc link inductor. Switching at high frequencies makes it possible to reduce the value of the dc link inductor without increasing the current ripple. Hence, it is possible to have the advantages of using a CSI as well as reduce the value of the dc link inductor without a corresponding increase in the heat sink and snubber requirements.

The thesis Is concerned with the development of a separately excited DC machine In which gate turn-off thyristor devices with their associated firing and protective circuits are used to provide the static commutation of armature coil current. The developed machine has Its armature winding with 24 tapping points located on the stator and Interconnected In "Lop" configuration. The Initiation of the conduction periods of armature switching devices Is defined by a digital control logic circuit. In conjunction with an Incremental rotary encoder which provides the necessary feedback Information relating to shaft speed and shaft angular position. This Is arranged such that, under normal running conditions of the machine, the axis of the radial field of the armature winding maintains the normal space-quadrature relationship with that of the main field winding, giving the optimal torque angle of 000. Provision Is made, however, within the digital control circuit for controlled departure of the armature switch tapping points from the quadrature axis positions, and the effect of this, In Improving commutation Is Investigated. The effect of Interpoles Is also explored. On the basis of the analysis carried out, a proposal Is made for the future development of the machine employing a reduced number of armature switching devices without the need for Interpole windings.

Depuis la première observation de désaimantation ultra-rapide dans des films de Ni soumis à une excitation laser pulsée, on a assisté à un grand intérêt de comprendre l'interaction entre les impulsions laser ultra-courtes et l'aimantation. Ces études ont conduit à la découverte de la commutation toute optique de l'aimantation dans un alliage de film ferrimagnétique en utilisant des impulsions laser femtosecondes. La commutation toute optique permet un renversement de l’aimantation d’un matériau magnétique sans champ magnétique externe. La direction de l'aimantation résultante est donnée par la polarisation circulaire droite ou gauche de la lumière. La manipulation de l'aimantation par un faisceau laser a longtemps été limité à un seul type de matériau, mais ce mécanisme s'est avéré être un phénomène plus général qui s’applique à une grande variété de matériaux ferromagnétiques, y compris des alliages, des empilements et des hétérostructures, ainsi que des hétérostructures ferrimagnétiques synthétiques de terres-rares. Récemment, nous avons observé le même phénomène dans des films ferromagnétiques simples, ouvrant ainsi la voie à une intégration de l'écriture toute optique dans les dispositifs spintroniques. De plus, dans des matériaux de type [Co/Pt] ou [Co/Ni] avec une polarisation de spin élevée et une anisotropie magnétique perpendiculaire contrôlable, un mouvement de parois de domaines induit par un courant polarisé peut être observé dans des pistes magnétiques (couple spin-orbite ou couple de transfert de spin), ce qui présente un grand intérêt pour des applications spintroniques basse consommation et de densité élevée, telles que le concept de mémoire racetrack et la logique magnétique. Cependant, la densité de courant requise pour le mouvement des parois de domaines est encore trop élevée pour permettre la réalisation de dispositifs à faible puissance. Dans ce contexte innovant, la recherche effectuée dans le cadre de ma thèse s’est concentrée sur la manipulation de parois de domaines dans les pistes fabriquées à partir de films minces à forte anisotropie magnétique perpendiculaire en combinant à la fois les effets du courant polarisé et ceux de la commutation toute optique. Différents films minces ont été explorés afin d'étudier les effets combinés optiques dépendant de l'hélicité et des couples spin-orbite ou de transfert de spin sur le mouvement des parois de domaines. Nous avons montré que les parois de domaine peuvent rester piégées sous une hélicité circulaire du laser et dépiégées par une hélicité circulaire opposée, et la densité de courant polarisé seuil peut être considérablement réduite en utilisant un laser femtoseconde. Nos résultats sont prometteurs pour le développement de nouveaux dispositifs photoniques-spintroniques de faible puissance<br>Since the first observation of ultrafast demagnetization in Ni films arising from a pulsed laser excitation, there has been a strong interest in understanding the interaction between ultrashort laser pulses and magnetization. These studies have led to the discovery of all-optical switching (AOS) of magnetization in a ferrimagnetic film alloy of GdFeCo using femtosecond laser pulses. All-optical switching enables an energy-efficient magnetization reversal of the magnetic material with no external magnetic field, where the direction of the resulting magnetization is given by the right or left circular polarization of the light. The manipulation of magnetization through laser beam has long been restricted to one material, though it turned out to be a more general phenomenon for a variety of ferromagnetic materials, including alloys, multilayers and heterostructures, as well as rare earth free synthetic ferrimagnetic heterostructures. Recently, we have observed the same phenomenon in single ferromagnetic films, thus paving the way for an integration of all-optical writing in spintronic devices. Moreover, in similar materials, like [Co/Pt] or [Co/Ni] with high spin polarization and tunable perpendicular magnetic anisotropy (PMA), efficient current-induced domain wall (DW) motion can be observed in magnetic wires, where spin-orbit torque (SOT) or spin transfer torque (STT) provides a powerful means of manipulating domain walls, which is of great interest for several spintronic applications, such as high-density racetrack memory and magnetic domain wall logic. However, the current density required for domain wall motion is still too high to realize low power devices. This is within this very innovative context that my Ph.D. research has focused on domain wall manipulation in magnetic wires made out of thin film with strong perpendicular magnetic anisotropy combining both spin-polarized current and all-optical switching. Different material structures have been explored, in order to investigate the combined effects of helicity-dependent optical effect and spin-orbit torque or spin transfer torque on domain wall motion in magnetic wires based on these structures. We show that domain wall can remain pinned under one laser circular helicity while depinned by the opposite circular helicity, and the threshold current density can be greatly reduced by using femtosecond laser pulses. Our findings provide novel insights towards the development of low power spintronic-photonic devices

Cette étude analyse la commutation de blocage d'un igbt utilise en commutation quasi-résonnante a zéro de courant. Deux igbt de structure technologique différente ont été étudiés, le premier est à base non homogène et a couche tampon, le second à base homogène et contrôlé d'injection de charges par l'émetteur. L'évolution de la charge stockée dans la base du transistor bipolaire interne au blocage est suivie et analysée à l'aide de simulations et d'expérimentations. Différents éléments interviennent sur l'évacuation de la charge stockée donc sur les pertes au blocage, qu'ils soient propres au composant (coefficients d'injection ou durées de vie) ou a sa commande (maintien du canal lors de la conduction de la diode antiparallèle). Ce qui permet de comprendre pourquoi les pertes au blocage sont plus faibles en commutation a zero de courant qu'en commutation commandée. Une caractérisation électrique et thermique de l'igbt permet ensuite de quantifier l'influence des conditions de commutation sur les pertes au blocage. Des limites de fonctionnement sont ainsi définies, pour s'affranchir de l'emballement thermique, principale cause de destruction des igbt a couche tampon en zcs a fréquence de découpage élevée

Dans les domaines industriels et en particulier celui du transport, le nombre et la puissance des équipements électriques et électroniques embarqués est en constante augmentation. L’alimentation des équipements électriques et la commande de ces actionneurs nécessitent l’utilisation de convertisseurs d’électronique de puissance à découpage dont la nature perturbatrice n’est plus à démontrer. Afin de prendre en compte la CEM dès la phase de conception d’un produit, les constructeurs doivent disposer d’outils dédiés à la CEM ou à défaut de règles ou techniques de conception spécifiques. C’est dans l’optique de répondre à ces besoins que se sont orientés ces travaux de thèse.La première partie des travaux traite de la modélisation des perturbations conduites des organes de puissance d’une chaîne de traction : un ensemble convertisseur / machine synchrone à rotor bobiné. Cette étude a conduit à un modèle CEM générique d’une structure non isolée quelconque d’électronique de puissance. La deuxième partie a permis de développer une nouvelle méthode de calcul qui ouvre de réelles perspectives quant à la réduction des temps de calcul. Par l’observation et l’étude de signaux sur différents horizons temporels, une technique de reconstitution des perturbations de mode commun par convolution a été proposée. Une troisième partie, consiste à synthétiser les sources de perturbations grâce à l’élaboration de fonctions de transfert décrivant le comportement haute fréquence d’une cellule de commutation. Cette approche immédiatement exploitable en simulation numérique se distingue dans la mesure où elle permet de s’affranchir des non linéarités intrinsèques des composants semi-conducteurs<br>In the transport field, whether road, rail, marine or aeronautic, the number and power of embedded electric or electronic devices are constantly increasing. New features, often developed for passengers comfort, are responsible for this increase. Moreover, many actuators which were previously mechanical, thermal or hydraulic are replaced by electrical ones. Those new actuators need an electrical power supply which most of the time rely on power electronics. It is well known that this kind of device generate high levels of disturbances. In order to take into account the electromagnetic compatibility (EMC) at the design stage of a product, builders need tools adapted to EMC or specific conception rules. The work performed during this thesis is geared in order to meet these needs.The first part deals with the modeling of conducted electromagnetic interferences (EMI) of an electrical power train mainly composed by power electronics converter and a wound rotor synchronous machine. Thanks to this study, a generic model of any non-insulated structure of power electronics was developed. The second part consists in developing a new computing method which allows to reduce the time of computing. Based on the observation of signals on different time intervals, a reconstruction technique by convolution product is proposed and applied for a common mode current. The third part deals with the elaboration of sources of disturbances by transfer functions which describe the high frequency behavior of a switching cell. This modeling is directly implementable in a circuit simulation software as it allows to linearize the intrinsic non linear behavior of the semiconductor components

Cette thèse traite de la conception d’un convertisseur DC / DC destiné aux véhicules électriques et hybrides (2,5 kW, 400V/14V, 250kHz). Dérivé de la topologie LLC à résonance, ce convertisseur bénéficie des nombreux avantages propres à cette structure particulière. C’est ainsi que le prototype réalisé présente un rendement très élevé, une densité de puissance très forte avec des perturbations EMI très réduites. La première partie de cette thèse est consacrée à l’analyse théorique du circuit LLC afin de dégager un modèle de conversion et une stratégie de contrôle adaptée à l’application visée. Afin de conserver un rendement important sur une large plage de charge, une structure basée sur la mise en parallèle de deux modules LLC est proposée. Une nouvelle stratégie de contrôle à deux boucles est également proposée pour équilibrer le courant entre les deux modules. La seconde partie de la thèse fait appel à la simulation et à l’expérimentation. Il s’agit de minimiser la masse et l’encombrement tout en maximisant le rendement. Un composant magnétique spécial est conçu puis dimensionné pour intégrer le transformateur et diverses inductances de résonance. Ce convertisseur met également en œuvre un système de redressement synchrone robuste avec une compensation de phase, un module de puissance avec une résistance thermique très faible et un système de refroidissement efficace par air. Le rendement maximal mesuré est 95%. Le rendement demeure supérieur à 94% sur une plage de puissance s’étalant de 500 W à 2 kW. La densité de puissance est 1W/cm3. La CEM du convertisseur est développée dans cette thèse<br>In this dissertation, a 2.5kW 400V/14V, 250kHz DC/DC converter prototype is developed targeted for electric vehicle/hybrid vehicle applications. Benefiting from numerous advantages brought by LLC resonant topology, this converter is able to perform high efficiency, high power density and low EMI. A first part of this dissertation is the theoretical analysis of LLC: topology analysis, electrical parameter calculation and control strategy. To arrange high output current, this thesis proposes parallel connected LLC structure with developed novel double loop control to realize an equal current distribution. The second part concerns on the system amelioration and efficiency improvement of developed LLC. A special transformer is dimensioned to integrate all magnetic components, and various types of power losses are quantified based on different realization modes and winding geometries to improve its efficiency. This converter also implements a robust synchronous rectification system with phase compensation, a power semiconductor module, and an air-cooling system. The power conversion performance of this prototype is presented and the developed prototype has a peak efficiency of 95% and efficiency is higher than 94% from 500W to 2kW, with a power density of 1W/cm3. The CEM analysis of this converter is also developed in this thesis

Conselho Nacional de Desenvolvimento Científico e Tecnológico<br>A complete study of a topology resulting from a combination of two Forward structures, attached to the same magnetic core of a transformer and operating as a Full-Bridge converter is presented. In order to reduce the switching losses and the electromagnetic interference, a soft commutation cell that provides ZCS commutation of all the switches is implemented. This converter limits the current on the main switches at the load current because diverts the sinusoidal half cycle to a auxiliary switch. This way, a new Double Forward On-Off ZCS was developed.<br>Um estudo completo de uma topologia, resultante de uma combinação entre duas estruturas Forward, acopladas ao mesmo núcleo magnético de um transformador, e operando como um conversor Full-Bridge, é apresentado. Com o objetivo de reduzir as perdas por chaveamento e a interferência eletromagnética, uma célula de comutação não dissipativa, que fornece uma comutação ZCS para todas as chaves do conversor é implementada. Este conversor limita a corrente nas chaves principais ao valor da corrente nominal, pois desvia o semiciclo senoidal da corrente ressonante para uma chave auxiliar. Deste modo, um novo conversor Duplo Forward On-Off ZCS é obtido.<br>Mestre em Ciências

My diploma thesis deals with a specific dynamic model of DC motor with the parameters obtained from the calculation and from the program using the finite element method. It shows how much accurate results can be achieved in the model, if you use only the values which can be measured, recorded and calculated on the engine. This thesis contens three parts. First part describes the structure and function of DC motor and the basic principle and the use of FEM. Next is calculation analytical and numerical parameters. The search parameters include torque, resistance and inductance of armature winding, resistance and inductance of excitation windings. The last part is dedicated to creating a dynamic model. Results from the dynamic model and measured values are compared in the conclusion of my thesis.

Les matériaux à changement de phase montrent la combinaison exceptionnelle d'un contraste énorme dans leurs propriétés physiques entre la phase amorphe et cristalline allié à une cinétique de changement de phase extrêmement rapide. La grande différence en résistivité permet leur application dans les mémoires numériques. De plus, cette classe de matériaux montre dans leur état vitreux des phénomènes de transport électronique caractéristiques. Le seuil de commutation dénote la chute de la résistivité dans l'état amorphe au delà d'un champ électrique critique. Le phénomène de seuil de commutation permet la transition de phase en appliquant des tensions relativement faibles. Au-dessous de cette valeur critique l'état désordonné montre une conductivité d'obscurité activée en température ainsi qu'une résistance - dans les cellules mémoires et les couches minces également - qui augmente avec le temps. Cette évolution de la résistivité amorphe entrave le stockage à plusieurs niveaux, qui offrirait la possibilité d'accroître la capacité ou la densité de stockage considérablement. Comprendre les origines physiques de ces deux phénomènes est crucial pour développer de meilleures mémoires à changement de phase. Bien que ces deux phénomènes soient généralement attribués aux défauts localisés, la connaissance de la distribution de défauts dans les matériaux amorphes à changement de phase est assez limitée. Cette thèse se concentre sur la densité des défauts mesurée dans différents verres chalcogénures présentant l'effet de seuil de commutation. Sur la base d'expériences de photo courant modulé (MPC) et de spectroscopie par déviation photothermique, un modèle sophistiqué des défauts a été développé pour GeTe amorphe (a-GeTe) mettant en évidence les états de la bande de valence et plusieurs défauts. Cette étude sur a-GeTe montre que l'analyse des données MPC peut être grandement améliorée en prenant en compte la variation de la bande de l'énergie interdite avec la température. Afin de mieux appréhender l'évolution de la résistivité amorphe, la présente étude porte sur l'évolution avec les recuits et le vieillissement de la résistivité, de l'énergie d'activation du courant d'obscurité, de la densité des défauts, du stress mécanique, de l'environnement atomique et de l'énergie de la bande interdite mesurée par des méthodes optiques sur les couches minces de a-GeTe. Le recuit d'un échantillon entraîne un élargissement de la bande interdite et de l'énergie d'activation du courant d'obscurité. De plus, la technique MPC a révélé une diminution des défauts profonds dans les couches minces de a-GeTe vieillies. Ces résultats illustrent l'impact de l'annihilation des défauts et de l'élargissement de la bande interdite sur l'évolution de la résistivité des matériaux à changement de phase amorphe. Cette thèse présente également une étude sur les alliages à changement de phase GeSnTe. En augmentant la concentration d'étain, on observe une décroissance systématique de la résistivité amorphe, de l'énergie d'activation du courant d'obscurité, de la largeur de bande interdite et de la densité des défauts, qui conduisent à une résistivité amorphe plus stables dans les compositions riches en étain comme a-Ge2Sn2Te4. L'étude sur les alliages GeSnTe montre que les matériaux à changement de phase ayant une résistivité amorphe plus stable présentent une faible énergie d'activation du courant d'obscurité. À l'exemple du Ge2Sn2Te4 et GeTe la présente étude montre un lien étroit entre l'évolution de la résistivité et la relaxation du stress mécanique. L'étude sur les verres chalcogénures montrent que les matériaux ayant un grand champ d'électrique de seuil, bien connu d'après la littérature, présentent aussi une grande densité de défauts. Ce résultat implique que l'origine du phénomène de seuil de commutation se trouve dans un mécanisme de génération à travers la bande interdite et de recombinaison dans les défauts profonds comme proposé par D. Adler.

Électronique de commutation pour l'essentiel, l'électronique de puissance met en œuvre des structures de convertisseurs ou la gestion des pertes par commutation pose problème. La commutation commandée lorsqu'elle est associée à des techniques d'aide a la commutation des interrupteurs, donne de bons résultats. Dans la gamme de puissance allant jusqu'a la dizaine de kilowatts, il existe une alternative à cette solution, que l'on désigne par le terme de quasi-résonance. L'étude présentée montre comment l'introduction de la commutation douce au sein de convertisseurs classiques permet d'obtenir d'aussi bonnes performances voire même meilleures, tout en simplifiant quelque peu la topologie des structures. Sa facilite de mise en œuvre est mise en évidence. La problématique du choix des interrupteurs est abordée. Un second problème pose par l'emploi de l'électronique de puissance et par la multiplication de convertisseurs, est la pollution du réseau auquel ils sont connectes. Afin de résorber cette pollution, des convertisseurs dits à absorption sinusoïdale (c. A. S. ) font l'objet d'études en tout points du globe. Une étude bibliographique leur est consacrée et une réalisation propre au laboratoire est détaillée. Ces convertisseurs fonctionnent en commutation commandée, aussi nous sommes nous attaches à développer des structures réalisant cette fonction de c. A. S. Tout en introduisant les techniques de commutation douce. Deux structures de flyback quasi-résonants, de 500 et 1300 w sont étudiées. Chacune consomme un courant sinusoïdal présentant un taux de distorsion inferieur à 10%. Une ébauche de modélisation de l'un de ces convertisseurs est également décrite

An AC system’s voltage unbalance by a fundamental frequency negative sequence system is usually the main cause for the emission of non-characteristic harmonics by current source converters as used in conventional HVDC systems. This emission takes place on both sides of each 12-pulse converter. On the DC side mainly a 2nd harmonic voltage appears driving a 2nd harmonic current. The magnitude of this harmonic current can exceed the magnitudes of the characteristic harmonics even if no low order resonance exists. Further non-characteristic harmonics generated by the converter under such unbalanced supply voltage conditions have frequencies with a frequency distance to the characteristic harmonics of 2 times the fundamental frequency. The main technical drawbacks are the unintended coupling between both AC systems and the risk of thyristor over-stresses by DC current discontinuities at low power transfer levels. On both AC sides the largest 2 non-characteristic current harmonics generated by a 12-pulse HVDC converter under unbalanced supply voltage conditions are a negative sequence system of the fundamental harmonic and a positive sequence system of the 3rd harmonic. Also on the AC sides further harmonics are emitted by the converter with a order number distance of 2 to the orders of the characteristic harmonics. However, in practical AC system operation special attention has to be paid to the 3rd harmonic distortion level, in particular when low order resonance appears between the system impedance and the impedance of the converter station AC filters. In order to avoid the above mentioned problems, large smoothing reactors and sometimes large blocking filters are installed on the DC side and the voltage distortion on the AC sides is reduced by AC filters. However, these filters require an expensive high component rating if they are tuned to the 2nd or 3rd harmonic respectively. The work shows that a modification of the valve firing can reduce the levels of the 2nd and 3rd harmonic without investment into additional primary equipment. Furthermore, this offers the chance to reduce the minimum power transfer level since also the risk of an intermittent DC current can be reduced. A corresponding algorithm and a control strategy are proposed. However, the calculation of an appropriate firing pattern requires a detailed modelling of the processes within the converters, especially the formation of the harmonics and the harmonic transfer between AC and DC sides. The work proposes a component vector model for the calculation of the harmonics. This model assumes that each harmonic consists of a first component representing the ideal conversion process, a 2nd component representing the impact of different commutation angles and in the case of the modified firing a 3rd component considering the impact of the intended non-equidistant firing. The work shows, that the harmonic component vectors resulting from voltage unbalance and from firing modulation can be treated separately and superimposed linearly. The calculation of the harmonic component vectors is performed applying the method of switching functions. For the consideration of the commutation and firing angle differences the modelling of switching functions based on differential impulses is proposed. However, especially an accurate representation of the above mentioned 2nd component vector requires a correct calculation of the commutation angles and their valve-specific differences. The investigations of this work have revealed that the conventional method of calculating the commutation angles – assuming an ideal smoothed DC current - may not produce results of sufficient accuracy. This is especially true in the case of a high ripple of the DC current, e.g. smoothed with a small smoothing reactor. A small smoothing reactor is typical for HVDC back-to-back applications. Therefore a new analytical method for the calculation of the commutation angles has been developed which in particular considers the typical pulse form of the DC current and additionally the impacts of the voltage unbalance and of the proposed modification of the firing on the ripple shape of the DC current. Moreover, as this analytical method requires the instantaneous values of the DC current at the instants of valve firing, a further analytical method for the calculation of these discrete current values has been developed. The equations are valid under the same conditions as the new ones for calculation of the commutation angles, i.e. resistive-inductive AC system fundamental frequency impedances, any degree of DC current smoothing between ideal smoothing and a ripple at the limit for current discontinuities. Symmetrical conditions, supply voltage unbalances and non-equidistant firing as proposed are applied. It is shown that, using this method, also the discrete values of the DC current at the end of the commutation intervals can be determined. In practice one of these discrete current values indicates the minimum value during one period of the fundamental frequency. This offers the chance for a more exact analytical determination of the limit for the appearance of DC current discontinuities. For typical parameters of a back-to-back installation the new methods and the new analytical equations have been compared with simulation results showing excellent correlation for typical voltage unbalances of not more than 1...2% and firing angle differences of not more than 2.5°. This verification is performed for the harmonics, the commutation angles and the discrete values of the DC current at the firing instants as well.

Ce travail s'inscrit dans une démarche générale de réduction des perturbations électromagnétiques émises par les équipements électriques. Il s'agit d'étudier les perturbations conduites générées par les convertisseurs statiques haute fréquence moyenne puissance dans l'optique de réaliser un outil d'aide a la conception prenant en compte ces phénomènes. Notre étude utilise comme support deux alimentations continu-continu isolées (alimentation flyback et alimentation forward) représentatives des problèmes rencontres. Après un bref rappel sur les normes et sur les équipements correspondants, un capteur de courant adapte a l'étude des perturbations électromagnétiques dans les convertisseurs statiques est présenté. Un des objectifs de l'étude est de pouvoir prédéterminer par simulation le niveau de perturbations d'un convertisseur. Pour cela, il est nécessaire de disposer d'un modèle électrique pour chacun des ensembles qui le constitue. Les modèles développés dans ce document concernent le transformateur et les composants a semi-conducteur (diode et igbt). Afin que ces modèles soient simples et facilement intégrables a un logiciel de simulation de type circuit, des modèles comportementaux issus de la littérature sont utilises. Notre travail consiste à adapter ces modèles à notre étude, c'est à dire à obtenir une bonne représentation des composants dans la bande de fréquence 10khz-30mhz. Le comportement des alimentations flyback et forward est alors analyse, essentiellement par simulation. A partir d'un schéma élémentaire (composants idéaux) de l'alimentation, les différents éléments parasites sont ajoutes étape par étape. L'analyse des modifications observées dans le domaine temporel et fréquentiel permet de cerner les diverses origines des perturbations. Cette démarche est reprise avec l'introduction d'un écrêteur puis d'un calc non dissipatif. Les résultats obtenus par simulation sont compares aux résultats expérimentaux afin de valider l'ensemble de l'étude (modèles et résultats d'analyse). Enfin, divers moyens de reduction des perturbations sont analyses. Tout d'abord deux moyens de reduction a la source sont proposes. Puis diverses solutions de reduction des couplages sont présentées. Finalement, le filtrage est abordé et les diverses cellules usuelles sont étudiées et comparées

Cette thèse s'inscrit dans un contexte de développement durable où les enjeux énergétiques consistent à concevoir des convertisseurs de puissance plus disséminés, donc avec une Spécification ambitieuse en termes de densités massique et volumique. Les composants à semiconducteur dit à grand Gap permettent l’augmentation de la fréquence de commutation et permettent un fonctionnement à plus haute température locale. Les commutations à front raides et à haute fréquence des transistors rendent le système plus sensible aux éléments parasites. Ceci perturbe en retour la commutation des transistors et génère des pertes joules supplémentaires. Dans ce contexte les travaux ont été effectués dans le cadre d’une cotutelle entre les laboratoires Ampère (INSA Lyon) et LN2 (Université de Sherbrooke), le but étant d’apporter des contributions à l’optimisation de la commutation des HEMTs GaN. Le premier axe des travaux consiste à mettre en place des stratégies de contrôle de vitesses de commutation en tension et en courant, par la grille, dans le but d’améliorer la signature CEM. Les circuits de contrôle proposés sont développés dans un premier temps en boucle ouverte puis dans un second temps en boucle fermée afin de compenser des non-linéarités (température, courant de charge et tension de fonctionnement). Les prototypes de contrôle de grille ont été testés à partir de composants discrets du marché. Des limites apparaissent, que l’intégration monolithique GaN doit corriger à terme, en particulier en atténuant fortement le problème des inductances parasites. Les analyses en simulation ont reposé sur l’adoption d’un modèle comportemental de HEMT GaN identifiable. Le deuxième axe des travaux consiste à vérifier de manière systémique différentes stratégies de contrôle de grille notamment pour la gestion du compromis entre pertes joule pendant les temps morts au sein d’un à bras d’onduleur et la performance fréquentielle des commutations. Aux termes de ces travaux, les systèmes de contrôles développés en boucle ouverte ont permis de ralentir les vitesses de commutation d’au moins 30 %, occasionnant une augmentation des pertes de commutation, dans un ordre de grandeur inférieur à 50 %. Due à la rapidité de commutation des HEMT GaN et aux limites des composants discrets du marché, le taux de réduction des vitesses de commutation obtenu avec la boucle fermée (taux de réduction inférieur à 20 %) est moins intéressant qu’avec la boucle ouverte. L’utilisation d’un circuit monolithique peut être une alternative pour augmenter le taux de réduction des vitesses de commutation en boucle fermée. Des résultats de simulation sous SPICE en vue du circuit monolithique sont à la base de cette hypothèse. Concernant le deuxième axe, l’application de commande multiniveaux de grille des transistors du bras d’onduleur a permis de réduire les pertes de conduction inverse et les pertes dues aux phénomènes de Cross Talk d’au moins 30 %<br>This thesis is part of the sustainable development context where the energy challenges rely on designing numerous and lumped power converters with good power density and high efficiency. New power semiconductor devices, namely wide band semiconductors (GaN, SiC) are used in designing the converters. The high frequency control of these converters makes the system more sensitive to parasitic elements. The latter elements disrupt the switching behavior of the transistors and generate additional losses. In this context this work was carried out in a cotutelle partnership between Ampère Laboratory in Villeurbanne and LN2 laboratory at the University of Sherbrooke; the aim being to make a contribution in optimizing the switching conditions of GaN HEMTs. The first work axis consists in managing the voltage and current switching speed through gate control strategies in order to improve the conducted EMI. Firstly, most of the proposed control circuits are developed in open-loop and then secondly in closed-loop in order to compensate the effects of non-linearities (with respect to temperature, load current and operating voltage). Concerning the development of control systems, it can be done first by the use of available discrete components, then by the alternative of the monolithic GaN integration which is considered in order to bring more speed and efficiency. Monolithic integration would also solve the problem of parasitic inductances. To facilitate the design of integrated circuits and control systems, the development of a behavioral model of HEMT GaN will serve as a modeling tool. The second axis of the work consists in experimentally validating well-adapted control system for the gate of the power transistor in order to master the transient behaviors of the power transistors. Namely it is necessary to allow a satisfying management of losses during dead time in a half bridge converter. At the end of this work, the control systems developed in open loop made it possible to slow the switching speeds by at least 30 % but causing an increase in switching losses up to 50% in some cases. Due to the fast switching speed of HEMT GaNs and the limitations of discrete components on the market, the reduction rate of switching speeds obtained with the closed loop (reduction rate less than 20%) is less attractive than that of the open loop. Using a monolithic circuit can be an alternative to increase the rate of reduction of closed loop switching speeds. SPICE simulation toward monolithic circuit are the basis of this hypothesis. Concerning the second axis, the application of multilevel gate voltage control of the transistors of half bridge made it possible to reduce the losses of reverse conduction and the losses due to the phenomena of Cross Talk by at least by 30 %

Direct current motors and stepping motors are very often used for electric drives in cars. The most frequent representatives of direct current motors are electric starter and wind- screen wiper motor. Stepping motors are very often used for electric regulating of outsides driving mirrors and seats. This study is focused on innovation and DC permanent magnet motor. The disadvanage of direct current motors is so called „sliding contact“. A possible compensation of direct current motor are EC (electronically commutator) motors that do not need sliding contact for their work.

碩士<br>高苑科技大學<br>電機工程研究所<br>96<br>The electromagnetic torque is an important indicator of the performance of electrical machinery, and the torque ripple generated in commutation period is the main drawback of BLDC motor, which deteriorates the precision of BLDC motor. Therefore the torque ripple reduction is the key technology in the control of BLDC motor. An analytical study was developed concerning the torque ripple under 4 kinds of PWM schemes due to phase commutation. Experiments were conducted to validate the analytical work and the PWM-ON type was confirmed to be the best scheme in four types PWM scheme, including PWM-ON, H_PWM-L_ON, ON-PWM, and H_ON-L_PWM.

碩士<br>大同工學院<br>電機工程研究所<br>86<br>Brushless DC Motors are driven by DC voltage and are commutated electronically. In most cases, the commutation of armature winding is down at a specified position, which is usually sensed by Hall effect sensors. In practical operation, the commutation is restricted by winding reactance, which causes current lagging with respect to the specified magnetic pole position at different velocities. Therefore, the torque developed will be reduced and the torque ripple occurred. In this thesis, an improved commutation method is proposed to advance the switching time of the applied voltage. A microcontroller and additional circuitry are used to calculate the required advanced angle instantly, therefore the relative position between armature current versus magnetic pole will remain the same in a wide range of the running velocities. So that the smooth torque can be obtained and dead speed can be avoided. Finally, a hardware scheme consists of microprocessor 8XC196MC and suitable peripheral circuits, and a flexible software controlled algorithm are established for experimentation, the results prove that the proposed system can be fulfilled the requirements.

碩士<br>國立交通大學<br>機械工程系所<br>103<br>Brushless DC motors (BLDCM) has the advantage of high efficiency, high reliability, less noise and maintenance free nature as compared with brushed DC motors. In general, BLDCM relies on the Hall Effect sensors to detect the rotor position for switching of inverter. However, in some extremely working environments such as electromagnetic interference (EMI) and high temperature surrounding, the Hall sensors are not suitable; the operating region is restricted. For high reliability required system, sensor failure may cause instability in the control system. Not only that, the space and costs reduction make sensorless drive more popular. Sensorless technique of permanent magnet motor can be classified into three categories: using motor back-EMF, using inductance and using flux linkage. For BLDCM, which always use motor back-EMF can further divided into three categories: direct back-EMF detection, in direct back-EMF detection and the techniques using model-based estimation. However, sensored and sensorless drive techniques both suffer from several error sources during implementation, resulting in commutation error. Commutation error is unavoidable unfortunately. This thesis analyzed in depth with current waveform under commutation error, non-ideal back-EMF, armature reaction and realized that current waveform is function of commutation error. A current integral method is proposed for commutation error compensation. This method compared two 30 degree current integration in one 60 degree conduction. The difference is caused by commutation error, and can feedback eliminated by PI controller. Let the motor having less noise, vibration and torque ripple. Experiment results showed that the proposed method is capable of running in different speed, load torque and speed variation operating with good performance.

碩士<br>國立中山大學<br>電機工程學系碩士班<br>107<br>This thesis derives the relationship between input and output of the AC/AC step-down inverter from the traditional Buck converter as the prototype. To suppress the surge voltage on inductor and IGBTs during the commutation of inductor current, this thesis analyzes the current loop of inductor and uses the three-step current commutation. While voltage fluctuation of system is happened, the controller compensates voltage by ac/ac inverter as the dynamic voltage regulator. Experiment tests are carried out by the laboratory prototype with ac/ac inverter. Using the programmable ac source to simulate voltage sag of system. Experimental results show that the dynamic voltage regulator can compensate load voltage and fix it to the nominal voltage in different load characteristics and power factors. Besides, it can suppress the surge voltage on inductor and IGBTs effectively.

碩士<br>國立成功大學<br>電機工程學系碩博士班<br>97<br>The torque loop, known as the current control loop, plays an important role in the AC servo drive. Well-designed current control loop can provide a smooth and fast torque response to AC motor and efficiently protect the motor and drive’s hardware circuit. In addition, it also simplifies the control design and parameter tuning for the velocity loop and position loop. Sinusoidal commutation can be divided into two categories: three-phase current control and field oriented control (FOC). However, there is few existing literature focusing on systematically comparing the performance of the above two sinusoidal commutation techniques. The goal of this thesis is to study the current control based on the sinusoidal commutation for the permanent magnet synchronous motor. In order to compare the differences between three-phase current control and field oriented control, the Matlab/simulink software is used to construct a simulation system to discuss the dynamic response of current control, design of servo parameter, and robustness of controller. In addition to theoretic analysis, the dsPIC30F4011 by Microchip is employed in this thesis as a core of the control system to realize field oriented control by well-designed hardware circuits and software programs. A commercial 1 hp servo motor is used as the test platform to evaluate the performance of the servo drive developed in this thesis. According the experimental results, the servo drive developed in this thesis can control the servo motor with external load to perform acceleration/deceleration under the torque mode and the velocity mode.

This thesis deals with modeling, simulation and implementation of Load Commutated SCR based current source Inverter (LCI) fed squirrel cage induction motor drive with sinusoidal voltage and sinusoidal current. In the proposed system, the induction motor is fed by an LCI. A three level diode clamped voltage source inverter (VSI) is connected at the motor terminal with ac chokes connected in series with it. The VSI currents are controlled in such a manner that it injects the reactive current demanded by the induction motor and the LCI for successful commutation of the SCRs in the LCI. Additionally, it absorbs the harmonic frequency currents to ensure that the induction motor draws sinusoidal current. As a result, the nature of the motor terminal voltage is also sinusoidal. The concept of load commutation of the SCRs in the LCI feeding an induction motor load is explained with necessary waveforms and phasor diagrams. The necessity of reactive compensation by the active filter connected at the motor terminal for the load commutation of the thyristors, is elaborated with the help of analytical equations and phasor diagrams. The requirement of harmonic compensation by the same active filter to achieve sinusoidal motor current and motor voltage, is also described. Finally, to achieve the aforementioned induction motor drive, the VA ratings of the active filter (VSI) and the CSI with respect to VA rating of the motor, are determined theoretically. The proposed drive scheme is simulated under idealized condition. Simulation results show good steady state and dynamic response of the drive system. Load commutation of the SCRs in the LCI and the sinusoidal profile of motor current and voltage, have been demonstrated. As in LCI fed synchronous motor drives, a special mode of operation is required to run up the induction motor from standstill. As the SCRs of the LCI are load commutated, they need motor terminal voltages for commutation. At standstill these voltages are zero. So, a starting strategy has been proposed and adopted to start the motor with the aid of the current controlled VSI to accelerate until the motor terminal voltages are high enough for the commutation of the SCRs in the LCI. The proposed drive is implemented on an experimental setup in the laboratory. The IGBT based three level diode clamped VSI has been fabricated following the design of the standard module in the laboratory. A generalized digital control platform is also developed using a TMS320F2407A DSP. Two, three phase thyristor bridges with necessary firing pulse circuits have been used as the phase controlled rectifier and the LCI respectively. Appropriate protection scheme for such a drive is developed and adopted to operate the drive. Relevant experimental results are presented. They are observed to be in good agreement with the simulation results. The effect of capacitors connected at the output of the LCI in the commutation process of the SCRs in the LCI is studied and analyzed. From the analysis, it is understood that the capacitors form a parallel resonating pair with filter inductor and the motor leakage inductance, which results in an undesired oscillation in the terminal voltage during each of the commutation intervals leading to commutation failure. So, in the final system, the capacitors are removed to eliminate any chance of commutation failure of the SCRs in the LCI. It is shown by experiment that the commutation of the SCRs takes place reliably in the absence of the capacitors also. The commutation process is studied and analyzed without the capacitors to understand the motor terminal voltage waveform of the experimental results.

碩士<br>國立交通大學<br>電子工程系<br>89<br>Requests of wireless communication push the researches of front-end modules. The mixer is an important element of the front-end. In this thesis, we address our discussions at the noise and linearity analysis for the current commutating mixer, choosing the CMOS Gilbert cell as the analysis target. A simple mathematical and physical model, which indicates the elationship between the noise and linearity performance and the design arameters, such as the device dimension and biasing, is roposed to perform the analysis. Through the model, an instant prediction of the (noise/linearity) performance of the Gilbert cell mixers can be achieved. A comparison between the evaluation of the derivation result and the simulation result is also taken and a sufficient match is shown. Trade-off exists among all the figure-of-merits of the current-commutating mixer. A rough theoretical derivation is done and the simulation is taken to verify it. To shorten the design time and improve the portability, a digital mixer based on the architecture of the four-quadrant multiplier is also proposed in this thesis. The simulation results showed an adequate performance with the conversion gain of -12dB, $P_{1dB}$ of -0.2dBm, $IIP_3$ of 7dBm and power dissipation of about 4mW. The circuit is also fabricated in TSMC $0.35\mu m$ 1P4M standard CMOS process and though there's a quite large gap between the measurement and simulation esult, a reasonable reason is concluded to explain these problems. Exploiting the theoretical derivation previously and the proposed circuit, a general design guideline for the digital mixer is concluded. A conclusion and feasibility are provided finally.

An AC system’s voltage unbalance by a fundamental frequency negative sequence system is usually the main cause for the emission of non-characteristic harmonics by current source converters as used in conventional HVDC systems. This emission takes place on both sides of each 12-pulse converter. On the DC side mainly a 2nd harmonic voltage appears driving a 2nd harmonic current. The magnitude of this harmonic current can exceed the magnitudes of the characteristic harmonics even if no low order resonance exists. Further non-characteristic harmonics generated by the converter under such unbalanced supply voltage conditions have frequencies with a frequency distance to the characteristic harmonics of 2 times the fundamental frequency. The main technical drawbacks are the unintended coupling between both AC systems and the risk of thyristor over-stresses by DC current discontinuities at low power transfer levels. On both AC sides the largest 2 non-characteristic current harmonics generated by a 12-pulse HVDC converter under unbalanced supply voltage conditions are a negative sequence system of the fundamental harmonic and a positive sequence system of the 3rd harmonic. Also on the AC sides further harmonics are emitted by the converter with a order number distance of 2 to the orders of the characteristic harmonics. However, in practical AC system operation special attention has to be paid to the 3rd harmonic distortion level, in particular when low order resonance appears between the system impedance and the impedance of the converter station AC filters. In order to avoid the above mentioned problems, large smoothing reactors and sometimes large blocking filters are installed on the DC side and the voltage distortion on the AC sides is reduced by AC filters. However, these filters require an expensive high component rating if they are tuned to the 2nd or 3rd harmonic respectively. The work shows that a modification of the valve firing can reduce the levels of the 2nd and 3rd harmonic without investment into additional primary equipment. Furthermore, this offers the chance to reduce the minimum power transfer level since also the risk of an intermittent DC current can be reduced. A corresponding algorithm and a control strategy are proposed. However, the calculation of an appropriate firing pattern requires a detailed modelling of the processes within the converters, especially the formation of the harmonics and the harmonic transfer between AC and DC sides. The work proposes a component vector model for the calculation of the harmonics. This model assumes that each harmonic consists of a first component representing the ideal conversion process, a 2nd component representing the impact of different commutation angles and in the case of the modified firing a 3rd component considering the impact of the intended non-equidistant firing. The work shows, that the harmonic component vectors resulting from voltage unbalance and from firing modulation can be treated separately and superimposed linearly. The calculation of the harmonic component vectors is performed applying the method of switching functions. For the consideration of the commutation and firing angle differences the modelling of switching functions based on differential impulses is proposed. However, especially an accurate representation of the above mentioned 2nd component vector requires a correct calculation of the commutation angles and their valve-specific differences. The investigations of this work have revealed that the conventional method of calculating the commutation angles – assuming an ideal smoothed DC current - may not produce results of sufficient accuracy. This is especially true in the case of a high ripple of the DC current, e.g. smoothed with a small smoothing reactor. A small smoothing reactor is typical for HVDC back-to-back applications. Therefore a new analytical method for the calculation of the commutation angles has been developed which in particular considers the typical pulse form of the DC current and additionally the impacts of the voltage unbalance and of the proposed modification of the firing on the ripple shape of the DC current. Moreover, as this analytical method requires the instantaneous values of the DC current at the instants of valve firing, a further analytical method for the calculation of these discrete current values has been developed. The equations are valid under the same conditions as the new ones for calculation of the commutation angles, i.e. resistive-inductive AC system fundamental frequency impedances, any degree of DC current smoothing between ideal smoothing and a ripple at the limit for current discontinuities. Symmetrical conditions, supply voltage unbalances and non-equidistant firing as proposed are applied. It is shown that, using this method, also the discrete values of the DC current at the end of the commutation intervals can be determined. In practice one of these discrete current values indicates the minimum value during one period of the fundamental frequency. This offers the chance for a more exact analytical determination of the limit for the appearance of DC current discontinuities. For typical parameters of a back-to-back installation the new methods and the new analytical equations have been compared with simulation results showing excellent correlation for typical voltage unbalances of not more than 1...2% and firing angle differences of not more than 2.5°. This verification is performed for the harmonics, the commutation angles and the discrete values of the DC current at the firing instants as well.:1 Einleitung und Ziel der Arbeit 1.1 Einführung in die Problematik 1.2 HGÜ-Systeme als Quelle von Strom- und Spannungsharmonischen 1.3 Netzspannungsunsymmetrien 1.4 Abgrenzung der betrachteten technischen Systeme 1.5 Beweggründe für die Betrachtung 1.6 Zielstellungen 2 Erkenntnisstand und Analyse der Aufgabenstellung 2.1 Harmonische 2.2 Aktive Kompensation von Harmonischen 2.3 Diskrete Werte des Zwischenkreisstromes am Beginn und Ende der Kommutierungsintervalle 2.4 Kommutierungswinkel 3 Grundlagen 3.1 Methodischer Ansatz 3.2 Allgemeine Voraussetzungen, Annahmen und Festlegungen 3.3 Maßgebliche Impedanzen für die Stromaufteilung 3.4 Maßgebliche Impedanz für die gleichstromseitigen Stromharmonischen 3.5 Leerlauf-Klemmenspannung des Stromrichters 3.6 Kommutierungsspannung 3.7 Nummerierungssystem der Ventile 3.8 Überlappungsformen der Kommutierungsintervalle 3.9 Komplexer Spannungsunsymmetriefaktor 3.10 Anwendung und Modifikation von Schaltfunktionen 3.11 Verifikation der Ergebnisse 4 Harmonische auf der Gleichstromseite 4.1 Bildungsgesetz 4.2 Charakteristische Harmonische 4.3 Nichtcharakteristische Harmonische infolge unsymmetrischer Netzspannungen 4.4 Nichtcharakteristische Harmonische infolge Ansteuermodifikation 5 Diskreter Wert des Zwischenkreisstromes im Zündzeitpunkt 5.1 Vorgehensweise 5.2 Lösungsansatz 5.3 Konstante Gegenspannung 5.4 Reale Gegenspannung des HGÜ-Stromrichters 5.5 Berücksichtigung von Resistanzen 5.6 Unsymmetrische Netzspannungen 5.7 Ansteuermodifikation 5.8 Unsymmetrische Netzspannungen und gleichzeitige Ansteuermodifikation 5.9 Ergebnisse 6 Kommutierungswinkel 6.1 Vorgehensweise 6.2 Konstante Gegenspannung 6.3 Reale Gegenspannung des HGÜ-Stromrichters 6.4 Berücksichtigung von Resistanzen 6.5 Unsymmetrische Netzspannungen 6.6 Ansteuermodifikation 6.7 Unsymmetrische Netzspannungen und gleichzeitige Ansteuermodifikation 6.8 Ergebnisse 7 Vertiefende Betrachtung der nichtcharakteristischen Harmonischen auf der Gleichstromseite 7.1 Vorbemerkungen 7.2 Unsymmetrische Netzspannungen 7.3 Ansteuermodifikation 7.4 Spannungsunsymmetrie und gleichzeitige Ansteuermodifikation 7.5 Ergebnisse 8 Harmonische auf der Netzseite 8.1 Bildungsgesetz 8.2 Charakteristische Harmonische 8.3 Nichtcharakteristische Harmonische 9 Betrachtungen zur aktiven Kompensation 9.1 Vorbemerkungen 9.2 Betrachtungsumfang 9.3 Grundlagen 9.4 Konzeptioneller Vorschlag für die Kompensation der 2. Stromharmonischen 9.5 Betrachtung der Drehstromseite 9.6 Vorschlag zur Weiterentwicklung des Konzeptes 9.7 Berechnungsbeispiel zur Kompensation der 2. Harmonischen im Zwischenkreis 9.8 Ergebnisse und Schlussfolgerungen 10 Zusammenfassung 11 Literatur 12 Formelzeichen und Abkürzungen 13 Anlagenverzeichnis