In response to the global climate change and environmental protection needs, more and more nations take renewable energies as one of the major future energy policies for its characteristics of clean, low greenhouse gas emission and self-productivity. Among Taiwan¡¦s many renewable energy development, wind energy is always on the list. Wind energy will not only avoid the problems of carbon dioxide which cause greenhouse effect, but also refrain pollution caused by fossil fuel or nuclear energy. The induction generator is a fundamental component of a wind machine. It¡¦s electric port and control can be classified into single fed control and double fed control. Through various comparisons of control and operation, double fed control seems to be more stable at present. Double fed induction generator may continuously produce power at island state without the supply of reactive power from parallel capacitor or the synchronous generator. which is the biggest advantage than single fed induction. , In other words, double fed induction generator may supply power independently. The induction generator is a time-varying and non-linear component. So the traditional rule of scalar control is not adopted in the thesis. The induction generator can be linearized by using vector control, and the power flow can also be directed with the control of its composition of rotor current vector and the controller is designed under the above methodology. The thesis aims to simulate, analyze and compare the steady and transient states of single fed and double fed wind generators with the purposes a more through understanding of the controller and its operation.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Please refer to full text for abstract.

The ability of liberalised electricity markets to trigger investment in the generation capacity required to maintain an acceptable level of security of supply risk has been - and will continue to be - a topic of much debate. Like many capital intensive industries, generation investment suffers from long lead and construction times, lumpiness of capacity change and high uncertainty. As a result, the ‘boom-and-bust’ investment cycle phenomenon, characterised by overcapacity and low prices, followed by power shortages and high prices, is a prominent feature in the debate. Modelling the dynamics of generation investment in market environments can provide insights into the complexities involved and address the challenges of market design. Further, many governments who preside over liberalised energy markets are developing policies aimed at promoting investment in renewable generation. Of particular interest is the mix and amount of generation investment over time in response to policies promoting high penetrations of variable output renewable power such as wind. Consequently, improved methods to calculate expected output, costs and revenue of thermal generation subject to varying load and random independent thermal outages in a power system with a high wind penetration are needed. In this interdisciplinary project engineering tools are applied to an economic problem together with knowledge from numerous other disciplines. A dynamic simulation model of the aggregated Great Britain (GB) generation investment market has been developed. Investment is viewed as a negative feedback control mechanism with current and future energy prices acting as the feedback signal. Other disciplines called upon include the use of stochastic processes to address uncertainties such as future fuel prices, and economic theory to gain insights into investor behaviour. An ‘energy-only’ market setting is used where generation companies use a classical NPV approach together with the Value at Risk criterion for investment decisions. Market price mark-ups due to market power are also accounted for. The model’s ability to simulate the market trends witnessed in GB since early 2001 is scrutinised with encouraging findings reported. A reasonably good agreement of the model with reality, gives a degree of confidence in the realism of future projections. An advancement to the dynamic model to account for expected high wind penetrations is also included. Building on the initial model iteration, the short-term energy market is simulated using probabilistic production costing based on theMix of Normals distribution technique with a residual load calculation (load net of wind output). Wind speed measurement data is combined with the outputs of atmospheric models to assess the availability of the GB wind resource and its relationship with aggregate load. Simulation results for 2010-40 suggest that the GB system may experience increased generation adequacy risk during the mid to late the 2020s. In addition, many new investments are unable to recover their fixed costs. This triggered an investigation into the design of a capacity mechanism within the context of the modelling environment. In light of the ongoing GB market electricity market reform debate, two mechanisms are tested; a strategic reserve tender and a marketwide capacity market. The goal of these mechanisms is to mitigate generation adequacy risk concerns by achieving a target winter peak de-rated capacity margin.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Behrooz Mirafzal / In this dissertation, a new topology for Direct-Drive Wind Turbines (DDWTs) with a new power electronics interface and a low-voltage generator design is presented. In the presented power electronics interface, the grid - side converter is replaced by a boost Current Source Inverter (CSI) which eliminates the required dc-bus capacitors resulting in an increase in the lifetime of DDWTs. The inherently required dc-link inductor for this topology is eliminated by utilizing the inductance of the Permanent Magnet Synchronous Generator (PMSG). The proposed three-phase boost CSI is equipped with Reverse-Blocking IGBTs (RB-IGBT) and the Phasor Pulse Width Modulation (PPWM) switching pattern to provide a 98% efficiency and high boost ratios ([superscript V]LL/V[subscript dc]) up to 3.5 in a single stage. In this dissertation, Phasor Pulse Width Modulation (PPWM) pattern for the boost – CSI is also modified and verified through simulation and experimental results. In order to realize potential capabilities of the boost inverter and to assist its penetration into renewable energy systems, the boost inverter dynamic behaviors are studied in this dissertation. Then, the developed models are verified using circuit simulations and experiments on a laboratory-scale boost – CSI equipped with RB-IGBTs. The developed dynamic models are used to study the stability of the boost – CSI through root locus of small signal poles (eigenvalues) as control inputs and load parameters vary within the boost inverter's operating limits. The dynamic models are also used to design the control schemes for the boost – CSI for both stand-alone and grid-tied modes of operation. The developed controllers of the boost – CSI are verified through simulation and experimental results. In this dissertation, the boost – CSI steady-state characterization equations are also developed and verified. The developed boost – CSI is used to replace the grid - side converter in a DDWT. A reliability analysis on the power electronics interface of an existing and developed topology is presented to demonstrate the increase in the mean time between failures. The boost – CSI enables conversion of a low dc voltage to a higher line-to-line voltage enabling the implementation of a low-voltage generator. This further enables a reduction in the number poles required in DDWT generators. The feasibility of the presented low-voltage generator is investigated through finite element computations. In this dissertation, a 1.5MW low-voltage generator designed for the proposed topology is compared with an existing 1.5MW permanent magnet synchronous generator for DDWTs to demonstrate the reduction in the volume, weight, and amount of permanent magnet materials required in the generator. The feasibility of the developed system is supported by a set of MATLAB/Simulink simulations and laboratory experiments on the closed-loop stand-alone and grid-tied systems.

Wind energy has been growing rapidly during recent years. This paper aims to estimate the impact of wind power generation on the Swedish wholesale electricity price, using monthly time series data over the periods 2000-2016. The error-correction model is used to measure the price effect by including other factors that influence the electricity supply and demand. Thefindings suggest that the impact of changes in wind power production on the wholesale priceof electricity is negative in the short-term. When the wind power production increases by 1%, the wholesale electricity price decreases with 0.08%. Furthermore, the magnitude of the coefficient increases to 0.10% in the long-term.

Made available in DSpace on 2017-07-10T15:14:31Z (GMT). No. of bitstreams: 1 DissertacaoRobersonParizotto.pdf: 2503168 bytes, checksum: db5f1a0599dffdd5ab378e0d828d8f19 (MD5) Previous issue date: 2014-02-21 / This project aimed to install a water pumping system with wind generator and evaluation of the performance of the same field, considering the availability of wind energy on site. The system was composed of a small wind turbine Horizontal axis Greatwatt the brand mounted on a self-supporting tower and a water pump from SHURflo brand model 8000, it was installed on CASA (Center for Analysis of Alternative Systems) project. Data on the local wind speed, the power generated by the wind turbine and the water flow pumped by the motor pump were collected. With these data it was possible to determine the wind energy in place, the energy generated by the wind turbine, the wind turbine performance and the relationship between energy generated and the pump flow. Thus, by determining the best times of incidence of wind where it was possible to evaluate the best time range for wind power generation and performance of the pump under the action of different levels of wind speed system. / Este projeto teve como objetivo a instalação de um sistema de bombeamento d água com gerador eólico e avaliação do desempenho do mesmo em campo, considerando a disponibilidade de energia eólica no local. O sistema foi composto de um aerogerador de pequeno porte de eixo horizontal da marca Greatwatt instalado sobre uma torre autoportante e uma bomba d água da marca SHURflo modelo 8000, o mesmo foi instalado no projeto CASA (Centro de Analises de Sistemas Alternativos). Foram coletados dados de velocidade do vento no local, a energia gerada pelo aerogerador e a vazão d água bombeada pela moto bomba. Com esses dados foi possível determinar a energia eólica no local, a energia gerada pelo aerogerador, o rendimento do aerogerador e a relação entre a energia gerada e a vazão da bomba. Com isso determinou-se os horários de melhor incidência de vento onde foi possível avaliar a melhor faixa de horário para geração de energia eólica e o desempenho do sistema de bombeamento sob a ação de diferentes patamares de velocidade do vento.

This dissertation is to design the operation strategy and protective scheme of micro-grid systems with dispersed generation (DG). The industrial power system with cogeneration units and the distribution feeder with wind power generators were selected as the study micro-grids for computer simulation. The mathematical models of cogeneration units and wind generators were included in the computer simulation by considering the operation control modes of DGs. The micro-grid systems and the nearby utility networks were constructed to solve the power flows of the micro-grids with various operation scenarios of power generation and load demand. For the severe external fault contingencies, the micro-grids have to be isolated from the utility power system in time to prevent the tripping of critical loads and DGs. By considering the fault ride through capability of cogenerators and voltage tolerance curves of critical loads, the critical tripping time (CTT) of tie circuit breaker of the micro-grids was determined according to the transient stability analysis. To maintain the stable operation of the micro-grids after tie line tripping, the load shedding scheme was designed by applying the under frequency and under voltage relays to disconnect the proper amount of non-critical loads according to the governor responses of cogeneration units. For the micro-grid of distribution feeder with wind power generator, the STATCOM was used to provide adaptive reactive power compensation for the mitigation of voltage fluctuation due to the variation of wind speed and feeder loading. The STATCOM can also be applied for the support of terminal voltage of wind generator (WG) to enhance the transient response of the micro-grid. The CTT of tie circuit breaker was determined by considering the low voltage ride through (LVRT) capability and the critical fault cleaning time of WG. To achieve more effective islanding operation of the micro-grids, the artificial neural network (ANN) was applied to determine the proper timing for tie line tripping and the proper amount of load shedding by using the wind speed, feeder loading and the voltage of micro-grid system as the input of ANN. To verify the effectiveness of the proposed tie line tripping and load shedding scheme, different fault contingencies of the external utility network have been simulated by using the computer program for the transient stability analysis. It is found that the critical and voltage sensitive loads of the micro-grid can be maintained when the tie circuit breaker is activated to isolate the external fault in time and followed by the execution of load shedding scheme.

Στη παρούσα διπλωματική εργασία γίνεται ανάλυση και μοντελοποίηση ενός μικροδικτύου, που αποτελείται από μία φωτοβολταϊκή και μία αιολική μονάδα που τροφοδοτούν ένα ωμικο-επαγωγικό φορτίο και είναι συνδεδεμένες στο δίκτυο σε κοινό κόμβο εναλλασσόμενης τάσης. Το φωτοβολταϊκό σύστημα περιλαμβάνει έναν αντιστροφέα και έναν μετατροπέα συνεχούς τάσης σε συνεχή που ανυψώνει την τάση και παράλληλα είναι ανιχνευτής του σημείου μέγιστης ισχύος, ώστε να είναι μέγιστη η παραγόμενη ισχύς του συστήματος. Το αιολικό σύστημα μεταβλητών στροφών χρησιμοποιεί μια σύγχρονη μηχανή μόνιμου μαγνήτη (PMSG) και ένα σύστημα δύο μετατροπέων, πλήρους κλίμακας, πλάτη με πλάτη. Στις εξόδους των μετατροπέων χρησιμοποιήθηκαν κατάλληλα φίλτρα RL με στόχο την μείωση του αρμονικού περιεχομένου των τάσεων και των ρευμάτων εξόδου. Έγινε προσπάθεια να εφαρμοστεί μια στρατηγική ελέγχου, ώστε να ελεγχθούν κατάλληλα τα συστήματα με σκοπό την επίτευξη μέγιστης παραγωγής ισχύος. Τέλος, υλοποιήθηκε το παραπάνω σύστημα σε περιβάλλον Matlab/Simulink και έγινε προσομοίωση για διάφορες μεταβολές στην ακτινοβολία, την ταχύτητα του ανέμου και το φορτίο. Σκοπός ήταν η μελέτη της συμπεριφοράς της δεδομένης στρατηγικής ελέγχου που εφαρμόστηκε και η εξαγωγή συμπερασμάτων. Στο πρώτο κεφάλαιο ορίζεται η κατανεμημένη παραγωγή μέσω της διαφοροποίησής της από την κεντρικοποιημένη και παρουσιάζονται οι λόγοι της πρόσφατης επανεμφάνισής της. Επίσης, αναλύονται τα πλεονεκτήματα και τα μειονεκτήματα αυτών και τέλος εισάγεται η έννοια του μικροδικτύου και τα βασικά χαρακτηριστικά του. Στο δεύτερο κεφάλαιο γίνεται αναφορά στις μονάδες παραγωγής ενός μικροδικτύου και τις διαθέσιμες τεχνολογίες. Δίνεται έμφαση στις ανεμογενήτριες, τα φωτοβολταϊκά και συστήματα συμπαραγωγής αναλύοντας τα τεχνικά χαρακτηριστικά και την αρχή λειτουργίας τους. Στο τρίτο κεφάλαιο ορίζονται οι μονάδες μετατροπής ενέργειας, δηλαδή οι ηλεκτρονικοί μετατροπείς ισχύος. Εξετάζονται οι διάφορες κατηγοριοποιήσεις αυτών και αναφέρονται τα διάφορα είδη των ημιαγωγών ισχύος από τα οποία αποτελούνται. Τέλος, αναλύονται οι τύποι των ηλεκτρονικών μετατροπέων ισχύος που χρησιμοποιήθηκαν στο υπό μελέτη σύστημα. Στο τέταρτο κεφάλαιο γίνεται η εξαγωγή των μαθηματικών εξισώσεων που περιγράφουν το σύστημα καθώς και αναλυτική περιγραφή των τεχνικών και μεθοδων που χρησιμοποιήθηκαν για τον έλεγχο. Τέλος, στο πέμπτο κεφάλαιο δίνονται τα αποτελέσματα της προσομοίωσης υπό τη μορφή διαγραμμάτων καθώς και τα συμπεράσματα της μελέτης. / In the current thesis an analysis and modeling of a microgrid is conducted. The microgrid consists of one photovoltaic and one wind unit which are feeding an R-L load and are connected in a common node to the grid. The photovoltaic system includes an inverter and a Dc to Dc converter that elevates the voltage and at the same time is a maximum power point tracker. The variable speed wind turbin uses a permanent magnet synchronous generator (PMSG) and a system of two full scale, back to back converters. Proper RL filters were used in the outputs of the converters in order to reduce the harmonic content of the voltage and current output. An attempt was made to implement a control strategy in order to control the system appropriately with the aim of achieving production of maximum power. Finally, this particular system was implemented in a Matlab/Simulink environment and simulated for various changes in radiation, wind speed and load. The aim was to study the behavior of the given control strategy applied and to come to a conclusion. In the first chapter the distributed generation is defined through its diversification from the centralized one and the reasons for its recent revival are presented. In addition, the advantages and disadvantages of these are analyzed, and finally the concept of microgrid is introduced along with its main characteristics. In the second chapter a reference of the production units of a microgrid and the available technologies is made. Emphasis is placed on wind turbines, photovoltaic and cogeneration systems by analyzing their technical features and their principal of operation. In the third chapter there is the specification of the energy conversion units, namely the electronic power converters. Their various classifications are examined and the different types of power semiconductors of which they consist are mentioned. Finally, there is an analysis of the types of converters used in the system being tested. In the fourth chapter the extraction of the mathematical equations that describe the system is made, along with a detailed description of the techniques and methods used for its control. Finally, in the fifth chapter the results of the simulation are provided in the form of diagrams along with the conclusions of the study.

Dentre as fontes de energia renováveis utilizadas para geração de energia elétrica a que mais se destaca atualmente e a energia eólica. 0 crescente índice de penetração da geração eólica na matriz energética dos sistemas de potencia impõe a necessidade da revisão de conceitos anteriormente estabelecidos sobre a estabilidade de sistemas de potencia, uma vez que ainda não e perfeitamente compreendida a influencia de uma maior integração deste recurso no comportamento dos sistemas de potencia. Este trabalho tem como foco o estudo da estabilidade de sistemas com aerogeradores de velocidade fixa equipados com geradores de indução de rotor em gaiola. E estudada a estabilidade angular de um sistema de geração eólica equipado com aerogeradores desta natureza. O problema da estabilidade foi decomposto em três partes: estabilidade estática, estabilidade dinâmica e estabilidade transitória. São definidos os modelos dos componentes do aerogerador para cada um dos estudos realizados. A topologia adotada á a máquina Barramento Infinito (MBI), na qual o restante do sistema de potência a representado pelo seu equivalente de Thevenin. Esta topologia típica de analise de estabilidade de sistemas de potencia e adotada por permitir a obtenção de resultados analíticos para as analises estática e dinâmica. A analise transitória se dá através de simulações computacionais. A fim de manter um caráter mais geral para os resultados as simulações são realizados com três aerogeradores de características distintas. Os resultados obtidos permitem uma melhor compreensão da influencia sobre a estabilidade do sistema de geração eólica dos parâmetros de rede do sistema de potencia como: potencia de curto-circuito do ponto de conexão comum com o sistema de potencia, relação X/R da linha de transmissão e do capacitor de compensação de fator de potencia. / Among the renewable energy sources used to generate electric power one of the most important at this time is the wind power. The growing penetration index of wind power in the power systems energetic matrix leads to the necessity of a reevaluation of the concepts previously established about the stability of power systems, since the influence of a major integration of this resource in the behavior of power systems is not perfectly understood. This work focuses on the stability study of wind power systems equiped with fixed-speed squirrel-cage induction generators. The angular stability of a wind generation system equipped with wind generators of this nature is studied. The stability problem was decomposed in three parts: static stability, dynamic stability and transient stability. The models of the components of the wind generator are defined for each of the studies. The considered topology was an Induction Generator Infinite Bus System (IBM), where the rest of the power system is represented by it’s Thévenin equivalent. This is a typical topology in power systems stability analysis and is adopted in this work aiming at obtaining analytical and general stability results. The transient analysis is performed by computer simulations. In order to provide more generatily to the stability results, all simulations are conducted with three wind generators with distinct characteristics. The obtained results allow a better comprehension about the influence, on the stability of wind power systems, of power system network parameters as: short-circuit capacity of the common connection point with the power system, the X/R relation of the transmission line and the power factor compensation capacitor.

Dentre as fontes de energia renováveis utilizadas para geração de energia elétrica a que mais se destaca atualmente e a energia eólica. 0 crescente índice de penetração da geração eólica na matriz energética dos sistemas de potencia impõe a necessidade da revisão de conceitos anteriormente estabelecidos sobre a estabilidade de sistemas de potencia, uma vez que ainda não e perfeitamente compreendida a influencia de uma maior integração deste recurso no comportamento dos sistemas de potencia. Este trabalho tem como foco o estudo da estabilidade de sistemas com aerogeradores de velocidade fixa equipados com geradores de indução de rotor em gaiola. E estudada a estabilidade angular de um sistema de geração eólica equipado com aerogeradores desta natureza. O problema da estabilidade foi decomposto em três partes: estabilidade estática, estabilidade dinâmica e estabilidade transitória. São definidos os modelos dos componentes do aerogerador para cada um dos estudos realizados. A topologia adotada á a máquina Barramento Infinito (MBI), na qual o restante do sistema de potência a representado pelo seu equivalente de Thevenin. Esta topologia típica de analise de estabilidade de sistemas de potencia e adotada por permitir a obtenção de resultados analíticos para as analises estática e dinâmica. A analise transitória se dá através de simulações computacionais. A fim de manter um caráter mais geral para os resultados as simulações são realizados com três aerogeradores de características distintas. Os resultados obtidos permitem uma melhor compreensão da influencia sobre a estabilidade do sistema de geração eólica dos parâmetros de rede do sistema de potencia como: potencia de curto-circuito do ponto de conexão comum com o sistema de potencia, relação X/R da linha de transmissão e do capacitor de compensação de fator de potencia. / Among the renewable energy sources used to generate electric power one of the most important at this time is the wind power. The growing penetration index of wind power in the power systems energetic matrix leads to the necessity of a reevaluation of the concepts previously established about the stability of power systems, since the influence of a major integration of this resource in the behavior of power systems is not perfectly understood. This work focuses on the stability study of wind power systems equiped with fixed-speed squirrel-cage induction generators. The angular stability of a wind generation system equipped with wind generators of this nature is studied. The stability problem was decomposed in three parts: static stability, dynamic stability and transient stability. The models of the components of the wind generator are defined for each of the studies. The considered topology was an Induction Generator Infinite Bus System (IBM), where the rest of the power system is represented by it’s Thévenin equivalent. This is a typical topology in power systems stability analysis and is adopted in this work aiming at obtaining analytical and general stability results. The transient analysis is performed by computer simulations. In order to provide more generatily to the stability results, all simulations are conducted with three wind generators with distinct characteristics. The obtained results allow a better comprehension about the influence, on the stability of wind power systems, of power system network parameters as: short-circuit capacity of the common connection point with the power system, the X/R relation of the transmission line and the power factor compensation capacitor.