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Nous proposons dans cette thèse, différents outils de réglage de tension et de gestion de la puissance réactive en fonction des conditions de raccordement des éoliennes au réseau électrique. Trois cas figure sont étudiés : raccordement direct sur un poste source de distribution, raccordement des éoliennes réparties dans un réseau de distribution et raccordement d’un ensemble de parcs éoliens au réseau de transport.Un algorithme de réglage basé sur l’asservissement de la puissance réactive est proposé pour le raccordement direct d'un parc sur un poste source. Un réglage coordonné de tension en présence de régleur en charge est proposé (D-RCT) pour le raccordement des éoliennes reparties dans un réseau de distribution. On propose aussi une version plus décentralisée du réglage coordonné (D2-RCT) qui pourrait être implantée sous forme de système multi-agents intelligents (SMA). Un system de control multi-niveaux est proposé pour le raccordement d’un ensemble de parcs éoliens au réseau de transport. Il permet de répondre de manière optimale à une demande puissance réactive envoyée par le gestionnaire du réseau de transport. Les différents types de réglages proposés sont basés sur des algorithmes d’optimisation multi-objectifs. Afin de valider en temps réel le bon fonctionnement des stratégies de réglages développées ainsi que leurs modes de communication, une implantation expérimentale sous simulateur temps réel RT-Lab a été effectuée. Enfin, les résultats des simulations montrent l’amélioration de l’intégration de la production décentralisée dans les réseaux électriques / In this PhD dissertation, we propose various voltage and reactive power regulation algorithms for different connection types of the wind farm to the power network. Three connection types are considered here: a wind farm connected directly to the distribution network, dispersed wind turbines connected to the distribution network and a set of wind farms connected to the transmission system.A closed loop controller (Wind Farm Controller) is proposed in case of a directly connected wind farm to the distribution network.A coordinated voltage control in the presence of on load tap changer (D-CVC) is proposed in case of dispersed wind turbines connected to the distribution network. We also propose a more decentralized version of D-CVC named D2-CVC; this version can be also implemented under multi-agent system (MAS).A multi-level control system is proposed in case of a set of wind farms connected to the transmission system. It allows the wind farms to optimally participate at reactive power balancing in transmission network. All the proposed voltage algorithms are based on a multi-objective optimization function. The experimental implementation of these regulation algorithms is run under RT-Lab real-time simulator. It allows validating their real-time operation and their communication modes before the implementation on a real site.The results of the current thesis show the improvement of distributed generation integration in the power system network

Small signal oscillation has been always a major concern in the operation of power systems. In a generator, the electromechanical coupling between the rotor and the rest of the system causes it to behave in a manner similar to a spring mass damper system. Following any disturbance, such as sudden change in loads, actuations in the output of turbine and faults etc. it exhibits an oscillatory behaviour around the equilibrium state. The use of fast acting high gain AVRs and evolution of large interconnected power systems with transfer of bulk power across weak transmission links have further aggravated the problem of these low frequency oscillations. Small oscillations in the range of about 0.1Hz to 3.5Hz can persist for long periods, limiting the power transfer capability of the transmission lines. These oscillations can be reduced by incorporating auxiliary controllers on generator excitation system. Power System Stabilizers (PSSs) were developed to produce additional damping by modulating the generator excitation voltage. Designing effective PSS for all operating conditions especially in large interconnected power systems still remains a difficult and challenging task. More and more power electronic based controllers have been and will be used in power systems. Many of these controllers such as Static Var Compensators (SVCs), Static Synchronous Compensators (STATCOMs) and Unified Power Flow Controllers (UPFCs) etc., are incorporated in power transmission networks to improve its operational capability. In addition, some of the energy storage systems such as Battery Energy Storage systems (BESS), Super conducting Magnetic Energy Storage System (SMES) as well large non-conventional energy sources are also increasingly being integrated with the power grid. With large integration of these devices, there is a significant impact on system stability, more importantly on small signal oscillatory instability of the power system. This thesis primarily focuses on impact of such devices on small signal oscillatory stability of the power systems. More specifically in this thesis small signal stability analysis of a Single Machine Infinite Bus (SMIB) system with a grid connected wind powered Permanent Magnet Synchronous Generator (PMSG) has been presented. A SMIB system has been purposely chosen so that general conclusions can be obtained on the behaviour of the embedded STATCOM/Energy Source (ES) system on system stability. With a better understanding of the impact of such a system it would be probably possible to analyze more complicated multimachine power system and their impact on system stability. Small signal model of the complete system which comprises the generator, transmission network, inter connecting STATCOM, the wind power generator and all associated controllers has been developed. The performances of the system following a small disturbance at various operating conditions have been analyzed. To obtain quantitative estimates of the damping and synchronizing torques generated in the system, expressions for damping and synchronizing torque clients have been developed. With these analyses, the relative impact of the STATCOM and STATCOM with ES on system performance have been assessed. It is shown that with active and reactive power modulation capabilities effective and efficient control of small signal oscillations in power systems can be achieved.

This Bachelor thesis has been written at the Blekinge Institute of Technology. This thesis concentrates on the wind power and their components, also the large wind farm is studied. The electrical power is generated by using the power in wind to drive a wind turbine to produce mechanical power. This mechanical power can be converted into electrical power by using electrical induction generators. There are two types of the wind turbines, the horizontal axis and vertical axis wind turbine, where the horizontal axis wind turbine is mostly used and was studied in this thesis. The rotor can be placed in two directions: an upwind rotor where the blade of turbine faces to the wind, so it operates more smoothly and transmit more power. The other type is a downwind rotor which orients itself with respect for the wind direction. Moreover, the tower shadow makes the blade to flex, consequently resulting in fatigue, noise, and reduces output of the power. The modern wind turbine has been built with an odd number of blades which is important for the stability of the turbine. The rotor with an odd number of blades can be considered to be similar to a disc when calculating the dynamic properties of the machine. The main idea of this thesis is to study the wind power in general and large wind parks specifically. The Horns Rev wind park was taken as an example of a wind park in Denmark and the Gotland wind park as an example of a wind park in Sweden too. Into account, the distance between wind turbine in the wind direction cannot be too small. If the wind turbines are located to close to each other, the wind will be more and more turbulent after it passes through each single wind turbine. This would lead to that wind turbines downstream in the wind park, and it might even have to shut down due to that mechanical loading gets to high during strong conditions. This is due to the fact that when wind passes through the rotor of the wind turbine it gets very turbulent and the wind speed is decreased. The minimum length of the rotor should be approximately 5-7 rotor diameters to avoid that issue. Gotland Energy AB (GEAB) considered, that high voltage direct current light would be the only realistic way to solve the technical problems for the high amount of wind power in-feed. One result is that The stability of voltage during transient events, has become much better by using the high voltage direct current light so that the output current stability from the asynchronous generators have been improved, which reduces the stresses on the AC grid and on the mechanical construction of the windmills. / In general the wind turbines with three blades accommodated a thicker root are used. It is obvious that, the less number of blades on the wind turbine, the cost of material and manufacturing will be lower. It is worthy to mentioned that, the modern wind turbine has been built with an odd number of blades. When the length of the blade increases the deflection of blade tip due to axial wind force also increase as well. So without consider the increase in length of blade may lead to dangerous situation of collision of tower and blade. Moreover, by increasing the number of blades cost of the system would increased as well. The limit of transfer for the AC transmission system depends on the distance from shore and is therefore physically limited by this. AC large wind parks that are placed at a long distance from the shore, which means AC long transmission line, and more drop voltage A solution to AC long transmission line, it could be to decrease the offshore frequency and use a low frequency AC networks. There is a suggestion by for instance (Schütte, Gustavsson and Ström 2011). The usages of a low frequency system are in electrified railway systems, where the frequency ranges from 16.67 Hz to 25 Hz. However, the network of a low frequency would allow a simpler design of the offshore WTs and The aerodynamic rotor of a large WT operates at maximum revolutions at 15-20 rpm. The lower frequency would then allow a smaller gear ratio for turbines with a gearbox, or decrease the poles number for WTs with direct driven generators. This would lead to lighter and cheaper turbines. One of the disadvantages by using a low frequency system is the size of transformer would be increased, and hence, the costs of transformer will increased too. The operator of the grid, Gotland Energy AB (GEAB) considered, that HVDC light would be the only realistic way to solve the technical problems for the high amount of wind power in-feed. The experiences have supported expected improvements in the characteristics for example: - Stability in the system arose. - Reactive demands, power flows, as well as voltage level in the harmonic and system were reduced. - Flicker problems were eliminated with the installation of HVDC light and transient phenomena disappeared. Moreover, Overall experiences of Gotland Energy AB (GEAB) are that the control of power flow from the converters makes the AC grid easier to observe than a conventional AC network and the power variations do not stress the AC grid as much as in normal network. Voltage quality has been better with the increased wind power production. A topic to study in the future is the consequences of blackouts in power supply with many wind power farm. / 004676396018

L’intégration de l’énergie éolienne, qui est une ressource renouvelable très utilisée, n’est pas toujours facile pour le micro-réseau urbain. Dans cette thèse, une éolienne urbaine basée sur une machine synchrone à aimants permanents (MSAP) est étudiée pour être intégrée dans un micro-réseau urbain à courant continu. Un état de l'art concernant les énergies renouvelables, les micro-réseaux à courant continu et les stratégies de contrôle de la production d'énergie éolienne, est réalisée. Basé sur un modèle d’éolienne urbaine répondant à la demande du système électrique, qui se compose d’un émulateur de vent et de pales, un MSAP et un convertisseur DC/DC, cette thèse propose des méthodes de poursuite du point de puissance maximale satisfaisant à l’obligation de produire de l’énergie dans la mesure du possible. Une stratégie de contrôle à puissance limitée répond correctement. De simples à complexes, quatre algorithmes MPPT, P&O à pas fixe, P&O à pas variable avec la méthode Newton-Raphson améliorée, P&O à pas variable à base de logique floue et une méthode indirecte de type lookup table, sont étudiés et implémentés pour être comparés à l’aide de trois profils de vitesse du vent. Par expérimentation, les algorithmes MPPT et PLC sont comparés, analysés et discutés. Résumant tous les résultats expérimentaux, la méthode lookup table peut gérer toutes les exigences du mode de fonctionnement MPPT en présentant la meilleure performance, mais, dans le mode de fonctionnement PLC, la P&O à base de logique floue présente les meilleures performances. / The integration of the wind power, which is one mostly used renewable resource, is always one challenger for urban microgrid. In this thesis, one urban wind turbine based on a permanent magnet synchronous machine (PMSM) is studied in order to be integrated into a DC urban microgrid. A state of the art concerning the renewable energies, DC microgrid, and control strategies of wind power generation is done. Based on a model of urban wind turbine fitting the demand of urban electric system, which consists of an emulator of wind speed and blades, a PMSM and a DC/DC converter, this thesis proposes the maximum power point tracking (MPPT) methods satisfying the requirement of producing energy as much as possible, and power limited control (PLC) strategies answering the demand of flexible energy production. From simple to complex, four MPPT algorithms including Perturbation and Observation (P&O) fixed step-size method, P&O with improved Newton-Raphson method, P&O with fuzzy logic method and lookup table method are studied and implemented to be compared with each other using three wind velocity profiles. According to the experience about MPPT subject, four PLC algorithms are introduced and implemented to be analyzed and compared with each other with one power demand profile calculated randomly. Summarizing all experimental results, the lookup table method can handle all requirement of MPPT operating mode supplying the best performance, however, in the condition of more flexible power demand operating mode, the combination of P&O and fuzzy logic method presents the best performance and potential which can be achieved in future works.

This thesis investigates the impact of resonant overvoltages and their origin. Series and parallel resonances are present in any electrical grid. The frequency of which this resonance occurs is called resonance frequency. For parallel resonance, which is mainly being studied in this thesis, a high impedance peak can be found at the resonance frequency. This impedance peak in conjunction with a harmonic rich current cause a kind of temporary overvoltages called resonant overvoltages. The harmonic content of the current is high following a fault clearing in the grid, due to transformer saturation. The resonance frequency is heavily dependent on the amount of reactance present in the grid, which entail that a change in reactance causes a change in the resonance frequency. The electromagnetic transient tool PSCAD has been used to investigate resonant overvoltages following transformer energization caused by faults and switching in Stockholm. Secondly, a model was created of a grid connecting off-shore wind power to the mainland via long AC submarine transmission cables. These cables, having a high capacitance, lower the resonance frequency. Faults in this model were simulated to investigate the phenomenon of resonant overvoltages in such a grid. This was especially interesting due to Swedens planned expansion of wind power in the Baltic sea. While resonant overvoltages were found in Stockholm they were not deemed significant due to their low magnitude and longevity. However, severe resonant overvoltages were found in the off-shore wind farm model. The worst resonant overvoltages had a maximum amplitude of the 2nd order harmonic voltage of 130 kV which, while eventually damped, were significant for up to 50 periods. Lastly, the phenomenon of an increased resonance frequency during the saturation of a transformer was studied. The most severe resonant overvoltages occured in a model where the frequency scans showed a resonance frequency of 98 Hz. Indicating, caution needs to be had during EMT-studies of resonant overvoltages while choosing what resonance frequency to study.

The submitted diploma thesis describes particular types of European energetic exchanges, focuses in depth on principles market in Czech Republic and studies the price development on spot and futures markets. The main idea of this work is to focus on renewable energy sources (RES) and their influence on energetic markets. At first, operational and reliability properties of RES are explained and then their development support is analyzed. Last chapters focus on how the power grid is impacted by RES that are hardly predictable source with local production characteristic. There are also outlined problems originating from irregular production that are linked to a surplus of electric energy, but also on energy shortage caused by bad weather. These problems influence international commerce and reduce the capacity of cross-border profiles.

The thesis concerns of the possibility by using alternative decentralized sources of energy. The first chapter describes current energy situation in the Czech Republic and consideration of future electrical energy consumption and the coverage by the renewable sources. Another part of this chapter describes each types of renewable energy with their advantages and disadvantages related to the Czech Republic. In the second chapter are introduced inputs which are appropriate for the plan of energetic system. The following theoretical chapter deals with each types of alternative energy sources using renewable source including the possibility of the installation and plan for the building. These alternative sources are sorted out by the way of using renewable sources of energy. The theoretical-practical fourth chapter concerns of the heating by the heat pump. For the detailed description was chosen the heat pump which is currently denote as appropriate alternative source of heat in household. With appropriate plan, which the thesis deals with, is this alternative source considered as proper investment. In the last chapter was assembled programme for creating models of energetic flux and calculation for the plan of heating by the heating pump air/water. This model is taken for concrete buildings related to exact outdoor temperature from previous years in concrete locality. In the end was realized validation of the software with the real measurement in concrete building.

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.