La dérégulation du marché de l'électricité, qui concerne progressivement tous les pays d'Europe, modifie profondément l'approche technico-économique dans l'exploitation et l'optimisation des réseaux électriques. C'est dans ce nouveau contexte que les spécialistes des .réseaux électriques se voient de plus en 'plus confrontés à de nombreux défis. Le développement des dispositifs FACTS (Flexible AC Transmission System) ouvre de nouvelles perspectives pour une meilleure exploitation des réseaux par leur action continue et rapide _sur les différents paramètres du réseau. Toutefois, ces dispositifs, ne sont pas à l'abri d'éventuelles interactions entre eux mais aussi avec d'autres éléments du réseau tels que les charges dynamiques. Cette thèse, qui s'inscrit dans le cadre de l'analyse et l'amélioration de la sécurité dynamique des réseaux électriques, s'est focalisé sur l'impact de l'interaction des dispositifs FACTS avec les charges dynamiques. Dans ce travail, il a été démontré que les boucles d'amortissement des oscillations de puissance dimensionnées par les techniques classiques de sensibilité ne sont pas robustes vis-à-vis des variations des modèles de charge. Pour remédier ,à ces problèmes, une première méthode, basée sur la sensibilité des valeurs propres et tenant compte. des variations des modèles de charge, a été proposée. Deux autres méthodes plus robustes, basées sur les techniques LMI, ont été mises en oeuvre. La première, basée Sllr une représentation polytopique des systèmes incertains, convient au cas d'incertitudes non structurées. La deuxième, basée sur une représentation LPV (système linéaire à paramètres variants), permet de traiter le cas d'incertitudes structurées.

In conventional three-phase PWM (Pulse Width Modulation) current source converter based STATCOM (Static Synchronous Compensator) applications, DC link current is kept constant at a predefined value and the reactive power of STATCOM is controlled by varying modulation index. This control strategy causes unnecessary power losses especially when the reactive power of STATCOM is low. For this purpose, in order to reduce the active power drawn by STATCOM, the modulation index can be maximized by adjusting DC link current. Within the scope of this thesis, an adaptive control of DC link current will be designed and applied to a 0.4kV 50kVAr three phase current source converter based STATCOM so that the power losses can be reduced. The theoretical work will be compared and discussed with the experimental results.

This research work is devoted to the analysis, design and development of the first medium power Current-Source Converter (CSC) based distribution-type Static Synchronous Compensator (D-STATCOM) with simplest converter topology and coupling transformer connection. The developed CSC-D-STATCOM includes a +/-750kVAr full-bridge CSC employing Selective Harmonic Elimination Method (SHEM), a 250kVAr low-pass input filter at 1kV voltage level, and a &amp / #916 / /Y connected coupling transformer for connection to medium-voltage load bus. The power stage of CSC is composed of series connection of natural air-cooled high-voltage IGCT switched at 500 Hz for the elimination of four lowest current harmonic components (5th, 7th, 11th, 13th), and optimized fast recovery high voltage diode in each leg. Reactive power control is achieved by applying the phase shift angle control at fixed modulation index, which is implemented digitally on a DSP microcontroller. The developed system has been implemented for compensation of rapidly varying reactive power demand of coal mining excavators in Turkish Coal Enterprises. The field test results have shown that the proposed CSC D-STATCOM serves as a technologically new full substitute of conventional Voltage-Source Converter based D-STATCOM having complex transformer connections in view of relatively fast response in reactive power compensation, very low total demand distortion factors, complying with the IEEE Std. 519-1992 even for the weakest power systems, and acceptable efficacy figures.

This research work is devoted to the analysis, design and development of the Current-Source Converter (CSC) based distribution-type Static Synchronous Compensator (D-STATCOM) for low-voltage applications in reactive-power control in order to achieve i) faster transient response in reactive-power control, ii) lower current harmonic distortion, iii) lower power losses and iv) minimum storage elements in comparison with conventional solutions. The developed CSC-D-STATCOM includes a low-pass input filter and a three phase forced-commutated CSC which is composed of six insulated gate bipolar transistors (IGBT) with built-in series diodes. The analysis and the control of the CSC-D-STATCOM are carried out in dq-synchronous reference frame in order to obtain the reference current waveform which is to be generated by switching the IGBTs at 3kHz with the use of space vector modulation.

Αυτή η διπλωματική εργασία εξετάζει θέματα που αφορούν την παρεχόμενη ποιότητα ισχύος στα σύγχρονα ηλεκτρικά συστήματα. Θα εξετάσουμε την απόδοση ενός στατικού σύγχρονου αντισταθμιστή STATCOM, που λειτουργεί ως ρυθμιστής τάσης, σε ένα σύστημα αυτοδιεγειρόμενης επαγωγικής γεννήτριας που τροφοδοτεί μη γραμμικά φορτία. Εκτός της θεωρητικής ανάλυσης των συνιστωσών του εξεταζόμενου συστήματος, θα πραγματοποιήσουμε προσομοίωσή του, με τη βοήθεια του λογισμικού PSCAD/EMTDC, με σκοπό την εξαγωγή χρήσιμων συμπερασμάτων από τα παραγόμενα αποτελέσματα. Ειδικό ενδιαφέρον θα δοθεί εκτός από την απόδοση στη ρύθμιση της τάσης και στη συνολική αρμονική παραμόρφωση της τάσης και την επίδραση των αρμονικών στην ποιότητα ισχύος. / This diploma thesis studies issues concerning the provided power quality in modern power systems. We will examine the performance of a STATCOM (Static synchronous Compensator) based voltage regulator in a, self excited induction generator (SEIG) feeding non-linear loads system. Besides the theoretical analysis of each component of the examined system, we will simulate it with the help of a software program called PSCAD/EMTDC in order to get useful conclusions through the provided results. Specific attention will be given, besides the efficiency in voltage regulation, in total harmonic distortion and the effect harmonics cause in power quality.

Made available in DSpace on 2014-06-11T19:22:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-28Bitstream added on 2014-06-13T19:06:57Z : No. of bitstreams: 1 pina_ap_me_ilha.pdf: 797000 bytes, checksum: d243ccbbde4d3e77f76b36fd34886251 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este trabalho apresenta estudos referentes à modelagem do dispositivo FACTS STATCOM para posterior inclusão nas equações do Modelo de Sensibilidade de Potência multimáquinas. O objetivo final da modelagem é o estudo da estabilidade a pequenas perturbações de sistemas elétricos de potência. São considerados dois modelos para o dispositivo: um primeiro modelo permite apenas a compensação de potência reativa, enquanto que num segundo modelo é possível a compensação tanto de potência ativa como de potência reativa. Também são sugeridos controladores para o dispositivo FACTS STATCOM e, neste trabalho, estes controladores são descritos por blocos de primeira ordem. Com o equacionamento do sistema elétrico realizado, seu modelo é implementado computacionalmente para se efetuar simulações para se avaliar a estabilidade a pequenas perturbações. As simulações estão baseadas na análise no domínio do tempo e no domínio da frequência, utilizando os dois modelos desenvolvidos para o STATCOM. A partir dos resultados obtidos pelas simulações, análises são realizadas, e discutidos os principais aspectos referentes à estabilidade a pequenas perturbações de sistemas elétricos de potência / This work presents studies referred to the modeling of the FACTS STATCOM device to include in multi-machine Power Sensitivity Model equations. The aim is to study electrical system stability under small perturbations. Two models are considered for the device: the first one allows only the reactive power compensation, while the other one allows the reactive or active compensation. Controllers for the FACTS STATCOM device are also suggested, and in this work they are described by first order blocks. As the electrical system equations are finalized, the model is computationally implemented to effectuate simulations and evaluate the stability under small perturbations. The simulations are based on the time and frequency domain using the two models developed for the FACTS STATCOM device. Considering the results obtained by the simulations the analysis are realized and discussed the principal aspects referred to the electrical Power system stability under small perturbations

The Brazilian transmission system covers a large area, with a high concentration of consumer centres in the Southeast region and abundant hydro generation in the North. To connect these regions, some of the transmission lines might reach 2500 km length, creating a challenging situation. In this context, system planners have been defining the use of HVDC systems as the most feasible choice of transmission investment. It is so, recognized that the connections of power plants in the Northern region to the load centres in the Southeast will require a significant number of bipoles and, until the present moment, all the operational and planned HVDC lines are based on the converter technology known as LCC (Line Commutated Converter) and consequently subject to commutation failure. Currently, the Brazilian system has four LCC bipoles, with two other bipoles under construction. Although the Southeast grid is strong, the connection of two additional bipoles is a concern as the interaction between these inverters may cause strong effects on one another, a phenomenon known as multi-infeed interaction. In such a situation, the assessment of the system operation, possible outages and possible mitigation methods are of paramount importance. This document presents a different methodology for the analysis of the multi-infeed system mentioned and focuses on its validation by analysing operation under normal conditions and with the implementation of established mitigation methods. The investigation was carried out with EMT, power flow, short-circuit and electromechanical softwares in a very large AC system composed by 100 buses on EMT and full Brazilian system on the rest. The effects of faults were analysed and the areas containing the buses where a fault leads to multiple commutation failures were identified. / O sistema de brasileiro de transmissão abrange uma área ampla, com uma alta concentração de consumo na região Sudeste e abundante geração hidrelétrica no Norte. Para conectar essas regiões, algumas das linhas de transmissão podem alcançar comprimentos de 2500 km, criando uma situação desafiadora. Neste contexto, os planejadores de sistemas têm definido o uso de sistemas HVDC como a escolha mais viável de investimento em transmissão. É então reconhecido que as conexões de usinas na região Norte aos centros consumidores no Sudeste exigirão um número significativo de bipolos e, até o momento presente, todas as linhas HVDC operacionais e planejadas são baseadas na tecnologia de conversão conhecida como LCC (Line Commutated Converter) e consequentemente sujeito a falha de comutação. Atualmente, o sistema brasileiro tem quatro bipolos LCC, com outros dois bipolos em construção. Embora a rede do Sudeste seja considerada forte, a conexão de dois bipolos adicionais é uma preocupação, pois a interação entre esses inversores pode causar efeitos danosos uns sobre os outros, um fenômeno conhecido como interação multi-infeed. Em tal situação, a avaliação da operação do sistema, possíveis interrupções e possíveis métodos de mitigação são de suma importância. Este documento apresenta uma metodologia diferente para a análise do sistema multi-infeed mencionado e foca em sua validação, analisando a operação em condições normais e com a implementação de métodos de mitigação conhecidos. A investigação foi realizada com softwares EMT, de curto circuito, fluxo de potência e estabilidade eletromecância em um sistema CA muito grande composto por 100 barras em EMT e sistema brasileiro completo no resto. Os efeitos das falhas foram analisados e as áreas que contêm as barras onde uma falha leva a múltiplas falhas de comutação foram identificadas.

This paper investigates the various parameters that effect voltage stability in sub-transmission power networks. The paper first looks at contributions from equipment: generators, transmission lines, transformers, capacitors, SVCs and STATCOMs. The paper also looks at the effects of loads on voltage stability. Power flow solutions, PV and VQ curves are covered. The study models an existing voltage problem i.e., a long, radial, 115 kV sub-transmission network that serves a 65 MW load. The network model is simulated with the following voltage instability countermeasures: adding a capacitor, adding an SVC, adding a STATCOM, tying to a neighboring transmission system, adding generation and bringing in a new 230 kV source. Then, using the WECC heavy-winter 2012 power flow base case and Siemens PTI software, VQ and PV curves are created for each solution. Finally, the curves are analyzed to determine the best solution.

Applications of power electronics in power systems are growing very rapidly and changing the power system infrastructure in terms of operation speed and control. Even though applications of power electronics are wide spread, the cost and reliability of power electronics are the issues that could hinder their penetration in the utility and industrial systems. The demand for efficient and reliable converter controllers gave rise to modularized converter and controller design. The objective of this dissertation is to determine the appropriate partitioning and interface requirements between the system and application control layers for power electronic converters so that the minimum set of system layer to application layer control interfaces is compatible across all power electronic controllers. Previous work, using the Open System Architecture (OSA) concept has shown that there is a set of common functions shared by different converters at the low-level control layers. It has also shown that, depending on the application, there is a variation in control functions in application/middle control layers. This functional variation makes it difficult to define system functionality of power converters at upper control layers and further complicates the investigation into the partition requirements of system to application control layer. However, by analyzing the current or voltage affected by a converter in terms of orthogonal components, where each component or group of components is associated with a power-converter application, and the amount of required DC bus energy storage, a common functionality can be observed at the application control layer. Therefore, by establishing common functionality in terms of affected current or voltage components, a flexibility of operation can be realized at upper control layers that will be a major contribution towards standardizing the open system architecture. In order to a construct functional flexible power converter control architecture, the interface requirements to the system control layer and the partitioning between the system control layer and application control layer need to be explored. This will provide flexibility of system design methodology by reducing the number of constraints and enabling system designers to explore possible system architectures much more effectively.

L'augmentation des transits de puissance dans les réseaux d'énergie électrique ainsi que les contraintes environnementales ont conduit à l'introduction des dispositifs FACTS (Flexible AC Transmission Systems) pour l'amélioration de l'exploitation des réseaux. Ces dispositifs sont capables de remplir diverses fonctions comme le maintien de la tension, le contrôle des flux de puissance, l'amélioration de la stabilité du réseau, l'augmentation de la puissance transmissible maximale, etc. De plus, grâce à leur temps de réponse rapide, ils sont apparus comme des outils efficaces pour l'amortissement des oscillations électromécaniques très basses fréquences. Cette nouvelle fonction des dispositifs FACTS est d'autant plus importante que les réseaux mondiaux sont de plus en plus interconnectés, donc sensibles aux oscillations électromécaniques inter-régions. Cependant, le recours à de nombreux dispositifs FACTS dans un réseau nécessite d'étudier attentivement les éventuels problèmes d'interaction de régulation des dispositifs FACTS entre eux, mais aussi avec les autres éléments du réseau. Le travail réalisé dans le cadre de cette thèse traite des phénomènes dynamiques liés aux problèmes d'interaction résultant de l'insertion d'un ou plusieurs dispositifs FACTS shunt. Des indices de sensibilité et d'influence sont définis depuis les concepts de commandabilité et d'observabilité respectivement afin de prévoir l'importance des phénomènes d'interaction liés à l'insertion d'un dispositif FACTS et d'identifier les zones d'influence du dispositif FACTS. Ces indices sont appliqués à un réseau test 2 zones 4 machines et à un réseau réel simplifié 29 machines. Deux méthodes de coordination (méthode de type " minimax " et méthode linéaire quadratique décentralisée) sont mises en œuvre pour coordonner les dispositifs FACTS entre eux et avec les stabilisateurs de puissance (PSS - Power System Stabilizer) dans le réseau test 2 zones 4 machines.