Le travail présenté dans cette thèse est une contribution au dimensionnement et à la commande d’un générateur de type Cascade de Machines Asynchrones à Double Alimentation. Le modèle de la machine pour les simulations est basé sur une représentation modulaire qui découle du modèle de Park de deux machines asynchrones doublement alimentées distinctes, en respectant deux systèmes de référence. Le modèle dynamique est ensuite étendu pour décrire la machine dans un repère unifié. Cette représentation est cruciale pour le dimensionnement de la machine et la synthèse de la commande. Le domaine de fonctionnement de la cascade en régime permanent est exploré. Une méthode analytique générique est proposée pour établir les plages de puissances active-réactive. Les courbes limites sont définies par rapport aux grandeurs nominales de la machine. L’étude prend en compte l’effet de saturation du circuit magnétique. Il est prouvé que la capacité en puissance de la machine est déterminée par les valeurs maximales des courants statoriques et peut être soumise à plusieurs limitations. L’approche analytique est testée et validée par des mesures expérimentales. Deux cas sont considérés pour la commande de la cascade : un générateur raccordé au réseau et un générateur autonome. Pour la connexion au réseau l’application visée est les éoliennes de grande puissance. Une nouvelle méthode pour l’extraction de la puissance maximale d’une éolienne à vitesse variable est proposée. Le système est contrôlé dans le but de fournir une puissance maximale quasi-constante indépendamment des fluctuations du vent. En plus de l’optimisation de la puissance, le facteur de puissance est également ajusté selon les normes de raccordement standard imposées par les services système, et les limites de fonctionnement de l’unité intégrée. Une commande vectorielle sans capteur de tension, basée sur une orientation suivant un flux virtuel, est appliquée pour la régulation découplée des puissances active et réactive. Pour le fonctionnement en mode isolé, l’application visée est la génération électrique pour système avionique embarqué. Deux réseaux de distribution sont traités : réseau AC à fréquence fixe et réseau DC. Dans les deux cas, la commande est élaborée dans le but de maintenir une tension de sortie constante. Le fonctionnement de la cascade alimentant une charge triphasée déséquilibrée est également étudié. Des schémas de contrôle servant à la compensation du déséquilibre des tensions statoriques sont développés. Deux méthodes de compensation sont proposées : l’une basée sur le principe de deux repères tournants et l’autre sur un correcteur répétitif. Les approches présentées sont validées par simulation avec Matlab/Simulink et par expérimentation. / This thesis is a contribution to the power sizing and the control of a Cascaded Doubly Fed Induction Generator (CDFIG). The machine model for simulation is based on a modular representation, derived from the Park model of two distinct Doubly Fed Induction Machines expressed in their own reference frames. The dynamic model of the cascaded machine is then extended to be described in a unified reference frame. This representation is convenient for the sizing of the machine and for the design of the controller. The steady state power operating margins of the cascaded machine are investigated. A generic analytic method is suggested to derive the active-reactive power domain. The limit curves are defined in terms of the rated quantities of the machine. The study takes into account the magnetic circuit saturation effect. It is proven that the power capability of the machine is determined by the stator current maximum values and is subject to several limitations. The analytical approach is tested and validated by experimental measurements. The CDFIG is controlled in grid-connected and standalone operation modes. In grid-connected application, the attention is paid to high power wind generation systems. A new maximum power tracking of a variable speed wind turbine is suggested. The generating plant is carried to provide a quasi-constant maximum power regardless wind fluctuations. In addition to active power optimization the power factor is adjusted according to the grid code requirements and the operating domain of the integrated unit. A virtual flux oriented vector control is applied for the decoupled regulation of active and reactive powers, leading to grid voltage sensorless operation. In standalone operating mode, the study treats in particular the embedded aircraft power system generation. Two distribution networks are considered: constant frequency AC network and DC network. In both cases, the control aims to maintain a constant output voltage. The operation of the CDFIG supplying unbalanced three-phase load is further explored. Control schemes to cope with unbalanced stator voltage conditions are developed. Two compensation methods are elaborated: the first dealing with dual rotating frames and the second is based on repetitive controller. Simulations with Matlab/Simulink software and experiments validate the control approaches.

Die Bundesregierung plant im Rahmen der Energiewende den Anteil von erneuerbaren Energien an der Stromerzeugung in Deutschland von heute rund 25% auf 80% bis zum Jahr 2050 auszubauen. Damit stehen auch dem Stromsektor in Sachsen grundlegende Veränderungen bevor. Derzeit leistet im Freistaat Sachsen die Braunkohle den größten Beitrag zur Elektrizitätsbereitstellung. Mit dem zunehmenden Ausbau an erneuerbaren Energien steigt der Anteil dargebotsabhängiger Energieträger. Daraus resultieren technische und wirtschaftliche Herausforderungen für das bestehende Energiesystem, wie z.B. die künftige Bereitstellung von Systemdienstleistungen. Mit diesen und weiteren Fragestellungen zur Transformation des Elektrizitätssystems haben sich Nachwuchswissenschaftler der TU Dresden in den vergangenen zwei Jahren im Rahmen des vom Europäischen Sozialfonds – ESF geförderten Projekts EnerSAX auseinander gesetzt. Neben der Erstellung einer Potenzialanalyse für Sachsen wurden sowohl technische Fragestellungen,wie z.B. die Auswirkungen der Integration erneuerbarer Energien auf die Übertragungs-, Verteilungs-und Niederspannungsnetze, als auch ökonomische Fragestellung, wie z.B. die künftige Ausgestaltung der Regelenergiemärkte, untersucht. Durch die Zusammenarbeit der Nachwuchsforscher aus den Bereichen der Elektrotechnik und Energiewirtschaft konnten so integrierte Lösungsansätze zur Ausgestaltung einer weitgehend auf erneuerbaren Energien beruhenden Energieversorgung mit dem Fokus auf Sachsen im transnationalen Kontext erarbeitet werden. Die wesentlichen Ergebnisse aus dem Projekt werden in diesem Buch vorgestellt.

This thesis describes the flexible voltage control of a multi-level-voltage-reinjection voltage source converter. The main purposes are to achieve reactive power generation flexibility when applied for HVdc transmission systems, reduce dynamic voltage balancing for direct series connected switches and an improvement of high power converter efficiency and reliability. Waveform shapes and the impact on ac harmonics caused by the modulation process are studied in detail. A configuration is proposed embracing concepts of multi level, soft-switching and harmonic cancellation. For the configuration, the firing sequence, waveform analysis, steady-state and dynamic performances and close-loop control strategies are presented. In order not to severely compromise the original advantages of the converter, the modulated waveforms are proposed based on the restrictions imposed mathematically by the harmonic cancellation concept and practically by the synthesis circuit complexity and high switching losses. The harmonic impact on the ac power system prompted by the modulation process is studied from idealistic and practical aspects. The circuit topology being proposed in this thesis is developed from a 12-pulse bridge and a converter used classically for inverting power from separated dc sources. Switching functions are deduced and current paths through the converter are analysed. Safe and steady-state operating regions of the converter are studied in phasor diagrams to facilitate the design of simple controllers for active power transfer and reactive power generations. An investigation into the application of this topology to the back-to-back VSC HVdc interconnection is preformed via EMTDC simulations.

Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη ενός συστήματος διασύνδεσης μιας ανεμογεννήτριας ονομαστικής ισχύος 1kW με το δίκτυο χαμηλής τάσης. Επιπλέον, πραγματεύεται τη σχεδίαση, κατασκευή και έλεγχο ενός τριφασικού αντιστροφέα που αποτελεί την τελευταία βαθμίδα πριν τη σύνδεση με το δίκτυο χαμηλής τάσης. Η εργασία αυτή εκπονήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών. Σκοπός είναι η διασύνδεση της ανεμογεννήτριας με το δίκτυο χαμηλής τάσης μέσω δύο βαθμίδων: ενός μετατροπέα ανύψωσης τάσης και ενός τριφασικού αντιστροφέα. Ο μετατροπέας ανύψωσης τάσης αποτελεί αντικείμενο μελέτης της διπλωματικής εργασίας του συνάδελφου Ιωάννη Γκαρτζώνη, ενώ στην παρούσα διπλωματική εργασία μελετάται και σχεδιάζεται ο τριφασικός αντιστροφέας. Αμφότερες οι διατάξεις περιλαμβάνουν ελέγχους κλειστού βρόχου, μέσω των οποίων απομαστεύεται η μέγιστη ισχύς από την ανεμογεννήτρια (έλεγχος μετατροπέα ανύψωσης) και διατηρείται σταθερή η τάση μεταξύ των δύο βαθμίδων, παρέχοντας ενεργό ισχύ στο δίκτυο υπό μοναδιαίο συντελεστή ισχύος (έλεγχος τριφασικού αντιστροφέα). Αρχικά παρουσιάζονται τα πλεονεκτήματα και μειονεκτήματα της χρήσης ανεμογεννητριών για την παραγωγή ηλεκτρικής ενέργειας και αναλύεται ο τρόπος με τον οποίο η αιολική ενέργεια μετατρέπεται σε ηλεκτρική. Επιπλέον, γίνεται μια σύντομη αναφορά στους τύπους των ανεμογεννητριών, καθώς και στους τρόπους λειτουργίας τους ως προς τη διασύνδεση με το δίκτυο. Στη συνέχεια γίνεται θεωρητική ανάλυση για κάθε βαθμίδα του συνολικού συστήματος. Ιδιαίτερη έμφαση δίνεται στη λειτουργία του τριφασικού αντιστροφέα και στην τεχνική παλμοδότησής του που ονομάζεται Ημιτονοειδής Διαμόρφωση του Εύρους των Παλμών (Sinusoidal Pulse Width Modulation - SPWM). Επίσης, εξάγονται σχέσεις βάσει των οποίων είναι δυνατό να παραμετροποιηθεί ο τριφασικός μετασχηματιστής με μεγάλη επαγωγή μαγνήτισης που έπεται του τριφασικού αντιστροφέα. Το επόμενο βήμα αποτελεί η προσομοίωση στο λογισμικό προσομοίωσης κυκλωμάτων Simulink του Matlab τόσο του τριφασικού αντιστροφέα σε ανοιχτό και σε κλειστό βρόχο, όσο και ολόκληρου του συστήματος διασύνδεσης. Ο κλειστός βρόχος αποτελεί ένα νέο και άμεσο έλεγχο της ισχύος που παρέχεται στο δίκτυο. Επιπρόσθετα, περιγράφεται ο σχεδιασμός και η κατασκευή όλων των κυκλωμάτων που απαιτούνται για τον τριφασικό αντιστροφέα, το φίλτρο και το μετασχηματιστή. Τέλος πραγματοποιούνται πειραματικές δοκιμές για να διαπιστωθεί η ορθή λειτουργία των βαθμίδων που κατασκευάστηκαν, να εντοπιστούν και δικαιολογηθούν τυχόν διαφορές μεταξύ της θεωρητικής ανάλυσης και των μετρήσεων στην πραγματική διάταξη, καθώς και για να εκτιμηθεί η απόδοση του συστήματος. / The present diploma thesis deals with the interconnection of 1kW wind generator to the low voltage grid. A three phase inverter is the last stage of the interconnection system. The design, construction and control of the three phase inverter is studied. This work was developed in the Laboratory of Electromechanical Conversion Energy at the Department of Electrical Engineering and Computer Technology of Polytechnic School in the University of Patras, Greece. The purpose of this thesis is the connection of the wind generator with the low voltage grid through two stages: a boost converter and a three phase inverter. Both stages are closed loop controlled and in this way the maximum power of the wind generator is supplied (control of the boost converter) and the voltage between the two stages remains constant, providing active power to the grid with unity power factor (control of the three phase inverter). Initially, the advantages and disadvantages of the use of wind generator are presented and the way that the wind energy is converted to mechanical energy and finally to electrical energy is analyzed. Moreover, it is given a short reference in the types of the wind generators used for connection to the grid. In addition, every stage of the whole system is analyzed. Especially, the function of the three phase inverter and the Sinusoidal Pulse Width Modulation-sPWM are studied. The three phase transformer, that follows the three phase inverter stage, is parameterized through equations that are described in this work. The next step in this thesis is the simulation with Simulink of Matlab. The three phase inverter is simulated in open and closed loop as well as the whole connection system of the wind generator to the low voltage grid. The closed loop control is a new and direct control of active and reactive power that are supplied to the grid. Furthermore, it is described the design and construction of all the circuits for the three phase inverter, the filter and the transformer. Finally, experiments are conducted in order to confirm the proper function of the stages that are constructed, to find differences between theory and reality and to estimate the efficiency factor of the system.

[pt] No novo modelo para o setor elétrico brasileiro a operação do sistema é de responsabilidade do Operador Independente do Sistema enquanto que a propriedade do equipamento e os gastos com a sua manutenção são de responsabilidade do agente prestador do serviço ancilar.Desta forma, o lucro do agente prestador do serviço ancilar de potência reativa será função do custo deste serviço uma vez que a sua remuneração é previamente definida pelo agente regulador. Dentro desta ótica os riscos operacionais dos equipamentos de compensação de potência reativa, se não forem convenientemente mitigados,poderão aumentar os gastos com a manutenção e o pagamento de multa pela indisponibilidade do equipamento.Riscos operacionais são situações de sistema que estão fora da responsabilidade do agente mas que poderão reduzir o seu faturamento.Esta dissertação descreve os riscos operacionais e faz algumas sugestões para proteger o agente da redução do seu faturamento. / [en] In the new brazilian deregulated electrical network, system operation is under Independent System Operator responsibility while the ancillary service agent is the owner of the reactive power equipment and, as a consequence, is responsible for its maintenance costs. In the new model, the profit of the agent is a function of the maintenance costs because his payment is previously defined by the authorities. The operational risks of the reactive power equipments, if not conveniently mitigated, may increase the maintenance frequency and may also result in the payment of a fee due to the equipment unavailability.Operational risks are events in the electrical transmission system that are not under the responsibility of the agent but may reduce his profits. This report describes these operational risks and makes some suggestions to protect the agent against the reduction in his profits.

The modern day power system is witnessing a tremendous change. There has been a rapid rise in the distributed generation, along with this the deregulation has resulted in a more complex system. The power demand is on a rise, the generation and trans-mission infrastructure hasn't yet adapted to this growing demand. The economic and operational constraints have forced the system to be operated close to its design limits, making the system vulnerable to disturbances and possible grid failure. This makes the study of voltage stability of the system important more than ever. Generally, voltage stability studies are carried on a single phase equivalent system assuming that the system is perfectly balanced. However, the three phase power system is not always in balanced state. There are a number of untransposed lines, single phase and double phase lines. This thesis deals with three phase voltage stability analysis, in particular the voltage stability index known as L-Index. The equivalent single phase analysis for voltage stability fails to work in case of any unbalance in the system or in presence of asymmetrical contingency. Moreover, as the system operators are giving importance to synchrophasor measurements, PMUs are being installed throughout the system. Hence, the three phase voltages can be obtained, making three phase analysis easier. To study the effect of unbalanced system on voltage stability a three phase L-Index based on traditional L-Index has been proposed. The proposed index takes into consideration the unbalance resulting due to untransposed transmission lines and unbalanced loads in the system. This index can handle any unbalance in the system and is much more realistic. To obtain bus voltages during unbalanced operation of the system a three phase decoupled Newton Raphson load ow was used. Reactive power distribution in a system can be altered using generators voltage set-ting, transformers OLTC settings and SVC settings. All these settings are usually in balanced mode i.e. all the phases have the same setting. Based on this reactive power optimization using LP technique on an equivalent single phase system is proposed. This method takes into account generator voltage settings, OLTC settings of transformers and SVC settings. The optimal settings so obtained are applied to corresponding three phase system. The effectiveness of the optimal settings during unbalanced scenario is studied. This method ensures better voltage pro les and decrease in power loss. Case studies of the proposed methods are carried on 12 bus and 24 bus EHV systems of southern Indian grid and a modified IEEE 30 bus system. Both balanced and unbalanced systems are studied and the results are compared.

Experimental research on high-power converters, particularly in an academic environment, faces severe infrastructural constraints. Usually, power source and loads of required ratings are not available. Further, more importantly, the energy consumption is huge. One possibility is to establish an experimental research platform, comprising of a network of high-power converters, through which power is circulated and which draws only the losses from the mains. This work deals with the establishment of a circulating power test set-up, comprising of two line-side PWM converters, inclusive of control and modulation methods for the two converters. Two types of circulating power test setups are developed. In the first setup, the converters are connected in parallel, on ac as well as dc sides, such that real and/or reactive power is circulated between them. In the second test setup, the dc buses of the converters are separated; hence, only reactive power circulation is possible. These setups are used to conduct heat-run tests with low energy expenditure on the PWM converters at various operating conditions up to power levels of 150 kVA. Further, these are used to validate analytically-evaluated thermal characteristics of high-power PWM converters. A safe thermal limit is derived for such converters in terms of apparent power (kVA) handled, power factor and switching frequency. The effects of voltage sag and of unequal current sharing between parallel IGBT modules on the safe thermal limit are studied. While the power drawn by the circulating-power setup from the grid is much lower than the ratings of the individual converters, the harmonic injection into the mains by the setup could be significant since the harmonics drawn by both converters tend to add up. This thesis investigates carrier interleaving to improve the waveform quality of grid current, drawn by the circulating-power test setup. The study of carrier interleaving is quite general and covers various applications of parallel-connected converters such as unity power factor rectification, static reactive power compensation and grid-connected renewable energy systems. In literature, carrier interleaving has been employed mainly for unity power factor rectifiers, sharing a common dc load equally. In such case, the fundamental components of the terminal voltages of the parallel converters are equal. However, when the power sharing between the two converters is unequal, or when power is circulated between the two converters, the terminal voltages of the two converters are not equal. A method to estimate rms grid current ripple, drawn by parallel-connected converters with equal and/or unequal terminal voltages, in a synchronous reference frame is presented. Further, the influence of carrier interleaving on the rms grid current ripple is studied. The optimum interleaving angle, which minimizes the rms grid current ripple under various applications, is investigated. This angle is found to be a function of modulation index of the converters in the equal terminal voltages case. In the unequal terminal voltages case, the optimum interleaving angle is shown to be a function of the average modulation index of the two parallel converters. The effect of carrier interleaving is experimentally studied on the reactive power circulation setup at different values of kVA and different dc bus voltages. The grid current ripple is measured for different values of interleaving angle. It is found experimentally that the optimum interleaving angle reduces the rms grid current ripple by between 37% and 48%, as compared without interleaving, at various operating conditions. Further, the reactive power circulation test set-up is used to evaluate and compare power conversion losses corresponding to different PWM techniques such as conventional space-vector PWM (CSVPWM), bus-clamping PWM (BCPWM) and advanced bus-clamping PWM methods for static reactive power compensator (STATCOM) application at high power levels. It is demonstrated theoretically as well as experimentally that an advanced bus-clamping PWM method, termed minimum switching loss PWM (MSLPWM), leads to significantly lower power conversion loss than CSVPWM and BCPWM techniques at a given average switching frequency.

It is necessary to judge the influences of producers on the electric compounds while creating electrical energy or during the regulation of those existing. These analyses are sorted out by so called studies of connectivity. These calculations analyze the degree of connection of the producer and the standby unit during a break-down. The results of this report are several recommendations for creating such unit and succeeding steps leading to secure the stability and safety of the electric compound operation. The aim of this thesis is to discuss about software for PC solutions for static and dynamic network model, to draft power outlet into a network of generating high voltage, to complete a study of connectivity with respect to all the distortion factor, as increased voltage, inrush current at startup, flicker, harmonic currents, interference ripple, contribution to short-circuit current, reactive power control options, and demands for compensation.

Die Bundesregierung plant im Rahmen der Energiewende den Anteil von erneuerbaren Energien an der Stromerzeugung in Deutschland von heute rund 25% auf 80% bis zum Jahr 2050 auszubauen. Damit stehen auch dem Stromsektor in Sachsen grundlegende Veränderungen bevor. Derzeit leistet im Freistaat Sachsen die Braunkohle den größten Beitrag zur Elektrizitätsbereitstellung. Mit dem zunehmenden Ausbau an erneuerbaren Energien steigt der Anteil dargebotsabhängiger Energieträger. Daraus resultieren technische und wirtschaftliche Herausforderungen für das bestehende Energiesystem, wie z.B. die künftige Bereitstellung von Systemdienstleistungen. Mit diesen und weiteren Fragestellungen zur Transformation des Elektrizitätssystems haben sich Nachwuchswissenschaftler der TU Dresden in den vergangenen zwei Jahren im Rahmen des vom Europäischen Sozialfonds – ESF geförderten Projekts EnerSAX auseinander gesetzt. Neben der Erstellung einer Potenzialanalyse für Sachsen wurden sowohl technische Fragestellungen,wie z.B. die Auswirkungen der Integration erneuerbarer Energien auf die Übertragungs-, Verteilungs-und Niederspannungsnetze, als auch ökonomische Fragestellung, wie z.B. die künftige Ausgestaltung der Regelenergiemärkte, untersucht. Durch die Zusammenarbeit der Nachwuchsforscher aus den Bereichen der Elektrotechnik und Energiewirtschaft konnten so integrierte Lösungsansätze zur Ausgestaltung einer weitgehend auf erneuerbaren Energien beruhenden Energieversorgung mit dem Fokus auf Sachsen im transnationalen Kontext erarbeitet werden. Die wesentlichen Ergebnisse aus dem Projekt werden in diesem Buch vorgestellt.

Die Bundesregierung plant im Rahmen der Energiewende den Anteil von erneuerbaren Energien an der Stromerzeugung in Deutschland von heute rund 25% auf 80% bis zum Jahr 2050 auszubauen. Damit stehen auch dem Stromsektor in Sachsen grundlegende Veränderungen bevor. Derzeit leistet im Freistaat Sachsen die Braunkohle den größten Beitrag zur Elektrizitätsbereitstellung. Mit dem zunehmenden Ausbau an erneuerbaren Energien steigt der Anteil dargebotsabhängiger Energieträger. Daraus resultieren technische und wirtschaftliche Herausforderungen für das bestehende Energiesystem, wie z.B. die künftige Bereitstellung von Systemdienstleistungen. Mit diesen und weiteren Fragestellungen zur Transformation des Elektrizitätssystems haben sich Nachwuchswissenschaftler der TU Dresden in den vergangenen zwei Jahren im Rahmen des vom Europäischen Sozialfonds – ESF geförderten Projekts EnerSAX auseinander gesetzt. Neben der Erstellung einer Potenzialanalyse für Sachsen wurden sowohl technische Fragestellungen,wie z.B. die Auswirkungen der Integration erneuerbarer Energien auf die Übertragungs-, Verteilungs-und Niederspannungsnetze, als auch ökonomische Fragestellung, wie z.B. die künftige Ausgestaltung der Regelenergiemärkte, untersucht. Durch die Zusammenarbeit der Nachwuchsforscher aus den Bereichen der Elektrotechnik und Energiewirtschaft konnten so integrierte Lösungsansätze zur Ausgestaltung einer weitgehend auf erneuerbaren Energien beruhenden Energieversorgung mit dem Fokus auf Sachsen im transnationalen Kontext erarbeitet werden. Die wesentlichen Ergebnisse aus dem Projekt werden in diesem Buch vorgestellt.