Η παρούσα διπλωματική εργασία παρουσιάζει τα Ευφυή Συστήματα ελέγχου και τις εφαρμογές τους στον έλεγχο συστημάτων ηλεκτρικής ενέργειας. Τα διάφορα είδη Σταθεροποιητών Συστημάτων Ισχύος (ΣΣΙ) παρουσιάζονται επίσης. Τα ηλεκτρικά συστήματα είναι δυναμικά συστήματα και υποβάλλονται συνεχώς σε διαταραχές. Είναι σημαντικό οι διαταραχές αυτές να μην οδηγούν το σύστημα σε αστάθεια. Για αυτόν το λόγο, πρόσθετα σήματα που προέρχονται από την απόκλιση ταχύτητας, την απόκλιση διέγερσης και την ροπή επιτάχυνσης εισάγονται στους ρυθμιστές τάσης. Η συσκευή που παρέχει αυτά τα σήματα αναφέρεται ως Σταθεροποιητής Συστημάτων Ισχύος. Η χρήση των Σταθεροποιητών Συστημάτων Ισχύος είναι πολύ συχνή στη λειτουργία των μεγάλων συστημάτων ηλεκτρικής ενέργειας. Οι συμβατικοί Σταθεροποιητές Συστημάτων Ισχύος που χρησιμοποιούν την αντιστάθμιση προήγησης-καθυστέρησης φάσης, όπου οι ρυθμίσεις κέρδους σχεδιάζονται για τις συγκεκριμένες συνθήκες λειτουργίας, δίνουν φτωχές επίδοσεις υπό τις διαφορετικές συνθήκες φόρτισης. Επομένως, είναι πολύ δύσκολο να σχεδιαστεί ένας σταθεροποιητής που θα μπορούσε να επιτύχει καλές επιδόσεις σε διάφορες συνθήκες λειτουργίας των συστημάτων ηλεκτρικής ενέργειας. Σε μία προσπάθεια να καλυφθεί ένα ευρύ φάσμα των συνθηκών λειτουργίας,τα Ευφυή Συστήματα ελέγχου έχουν προταθεί ως πιθανή λύση για να υπερνικηθεί αυτό το πρόβλημα. Σε αυτήν την εργασία, μια συστηματική προσέγγιση στο σχέδιο ελέγχου Ασαφούς λογικής προτείνεται. Παρουσιάζεται η μελέτη του Σταθεροποιητή Συστημάτων Ισχύος Ασαφούς λογικής για την αύξηση της ευστάθειας ενός συστήματος μιας μηχανής συνδεδεμένης σε άπειρο ζυγό. Προκειμένου να ολοκληρωθεί η αύξηση της ευστάθειας, η απόκλιση ταχύτητας και η επιτάχυνση του ρότορα της σύγχρονης γεννήτριας λαμβάνονται ως είσοδοι στον ελεγκτή ασαφούς λογικής. Αυτές οι μεταβλητές έχουν σημαντική επίδραση στην απόσβεση των μηχανικών ταλαντώσεων των αξόνων των γεννητριών. Τα σήματα ευστάθειας υπολογίστηκαν χρησιμοποιώντας την ασαφή συνάρτηση συμμετοχής ανάλογα με αυτές τις μεταβλητές. Το Simulink/Μatlab χρησιμοποιήθηκε στην εφαρμογή της μελέτης. Η απόδοση του συστήματος με το Σταθεροποιητή Συστημάτων Ισχύος Ασαφούς λογικής συγκρίνεται με το σύστημα με το συμβατικό Σταθεροποιητή Συστημάτων Ισχύος καθώς και με το σύστημα χωρίς Σταθεροποιητή Συστημάτων Ισχύος. / In this thesis the different types of intelligent control systems and the various techniques used in power system stabilizers are considered. The power system is a dynamic system and it is constantly being subjected to disturbances. It is important that these disturbances do not drive the system to unstable conditions. For this purpose, additional signals derived from speed deviation, excitation deviation and accelerating power are injected into voltage regulators. The device to provide these signals is referred as power system stabilizer. The use of power system stabilizers has become very common in operation of large electric power systems. The conventional PSS which uses lead-lag compensation, where gain settings designed for specific operating conditions, is giving poor performance under different loading conditions. Therefore, it is very difficult to design a stabilizer that could present good performance in all operating points of electric power systems. In an attempt to cover a wide range of operating conditions, intelligent control systems have been suggested as a possible solution to overcome this problem. Inittialy in this thesis, an introduction of power system control and the different types of stabilizers is briefly described. Afterwards, the system modeling and power system stabilizer model is presented. Finally, a systematic approach to fuzzy logic control design is proposed. The study of fuzzy logic power system stabilizer for stability enhancement of a single machine infinite bus system is presented. In order to accomplish the stability enhancement, speed deviation and acceleration of the rotor synchronous generator are taken as the inputs to the fuzzy logic controller. These variables take significant effects on damping the generator shaft mechanical oscillations. The stabilizing signals were computed using the fuzzy membership function depending on these variables. Simulink Block Design and Matlab is utilized in implementing the study. The performance of the system with fuzzy logic based power system stabilizer is compared with the system having conventional power system stabilizer and system without power system stabilizer.

M.Ing. / The increase in awareness of the environmental problems resulting from emissions released from vehicles have forced governments and car manufactures to invest more time in to the designing a vehicle that is an alternative to petrol driven vehicles. This dissertation aims to introduce a control strategy to manage the flow of energy of different power sources that may be found on a vehicle. Hybrid vehicles are a possible solution to reducing carbon emissions that play a part in global warming. In this dissertation, di erent hybrid vehicles are de ned and their components discussed in detail. The possibility of more than one energy source to power the vehicle introduces more exibility in terms of the drivetrain but this increases the complexity of the energy control management. The goal is to optimize the energy control management to reduce fuel consumption and therefore reduce emissions. Operating procedures for the various hybrid con gurations are discussed. Simulations of the Energy Management System of the hybrid electric vehicle are used to develop the control optimization algorithm. Various control optimization procedures are discussed. Satisfactory results from the simulations allow the implementation of the hybrid onto a platform entered into the South African Solar Challenge 2010, which covered a distance of 4000 km. The Energy Management system selected for the parallel hybrid electric vehicle demonstrated fuel savings, which meant a reduction in emissions, which is the goal of any hybrid vehicle. Further investigations include more intelligent controllers to adjust the parameters of the energy management controller to allow for adaptation to various driving conditions, e.g. urban and motorway driving.

With rapid depletion of fossil fuels and increasing environmental concerns, the trend to capture renewable energy, especially through wind energy resources, is increasing. The doubly fed induction generator (DFIG) is the most widely used generator for wind energy conversion because of its various advantages over other types of generators. In a DFIG, the rotor is fed through back to back converters via slip rings. The converters enable the generation control. This control property can be used to support reliable operation of a grid network system. Interarea oscillation has been a major factor in limiting power transfers in interconnected power systems. Poorly damped modes can trigger oscillatory instability, potentially leading to cascading blackouts in such systems. We consider a two-area system where DFIG based wind generation is integrated with conventional synchronous generators. A simple controller is proposed for the DFIG to improve damping of interarca oscillations. To support the proposition, case studies are conducted in Matlab/Simulink. The effectiveness of the proposed controller is then analyzed by eigenvalue analysis and verified with time domain simulation results. The results show that a properly tuned controller can increase the damping of dominant oscillatory mode by nearly 5% while improving the area transfer by about 200 MW of wind power. The results further show that with the proposed control strategy, damping of dominant oscillatory mode increased by more than 10%. / North Dakota State University. Graduate School / North Dakota State University. Department of Electrical and Computer Engineering

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / Power system stability simulations are of growing importance for studying the operational integrity of modern power systems, especially in developing economies where generating and transmission capacity lead the demand by relatively small margins. The relevant model topologies, i.e. for synchronous generators, automatic voltage regulators (AVR) and governor control systems, and the simulation software tools are well established. The MATLAB® Power System Blockset provides engineers with a versatile power system stability simulation environment, particularly where the focus is on individual units or small systems. In comparison with dedicated power system simulation tools such as DIgSILENT®, the MATLAB® environment features a superior set of advanced data processing and data analysis features. This includes features such as optimisation and parameter estimation functions. The main aim of this project is to make use of the MATLAB® package in a bid to test an alternative platform with which to estimate the synchronous machine parameters. Conditioning of field data can delay the process considerably, thus the secondary task of this thesis is to solve this issue by ensuring that only one platform is needed for the entire process starting in the field and ending in the modelling and parameter estimation environment within MATLAB®. In closing, the following points summarise the essential aims of this project: • An application using MATLAB® Script must be created that is responsible for importing and processing the data, so it is suitable for analysis purposes. The processing could include cropping, scaling and filtering of data. • Once the data has been imported it must be used with appropriate models to estimate for machine parameters. This will require the use of the Power Systems Blockset. The actual estimation process also requires the creation of an effective cost function, thus a number of different scenarios will have to be investigated before a solution can be found.

This thesis addresses the problem of reactive power scheduling in a power system with several areas controlled by independent transmission system operators (TSOs). To design a fair method for optimizing the control settings in the interconnected multi-TSO system, two types of schemes are developed. First, a centralized multi-TSO optimization scheme is introduced, and it is shown that this scheme has some properties of fairness in the economic sense. Second, the problem is addressed through a decentralized optimization scheme with no information exchange between the TSOs. In this framework, each TSO assumes an external network equivalent in place of its neighboring TSOs and optimizes the objective function corresponding to its own control area regardless of the impact that its choice may have on the other TSOs. The thesis presents simulation results obtained with the IEEE 39 bus system and IEEE 118 bus systems partitioned between three TSOs. It also presents some results for a UCTE-like 4141 bus system with seven TSOs. The decentralized control scheme is applied to both time-invariant and time-varying power systems. Nearly optimal performance is obtained in those contexts.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Ronald G. Harley; Committee Member: David G. Taylor; Committee Member: Deepakraj M. Divan; Committee Member: Ganesh Kumar Venayagamoorthy; Committee Member: Thomas G. Habetler. Part of the SMARTech Electronic Thesis and Dissertation Collection.

M. Tech. Electrical Engineering / Investigates the growing consensus that significant advantages can be achieved through the automation of distribution feeder switches In order to ensure quality and reliability of supply to single phase consumers by electrical utilities, a need arose to minimize unbalance. it is then postulated the unbalance due to uneven distribution of single-phase loads at the secondary side of the distribution network can be minimized using automatic and remote sensing technology.

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018. / A smart grid is an intelligent power delivery system integrating traditional and advanced control, monitoring, and protection systems for enhanced reliability, improved efficiency, and quality of supply. To achieve a smart grid, technical challenges such as voltage instability; power loss; and unscheduled power interruptions should be mitigated. Therefore, future smart grids will require intelligent solutions at transmission and distribution levels, and optimal placement & sizing of grid components for optimal steady state and dynamic operation of the power systems. At distribution levels, feeder reconfiguration and Distributed Generation (DG) can be used to improve the distribution network performance. Feeder reconfiguration consists of readjusting the topology of the primary distribution network by remote control of the tie and sectionalizing switches under normal and abnormal conditions. Its main applications include service restoration after a power outage, load balancing by relieving overloads from some feeders to adjacent feeders, and power loss minimisation for better efficiency. On the other hand, the DG placement problem entails finding the optimal location and size of the DG for integration in a distribution network to boost the network performance. This research aims to develop Particle Swarm Optimization (PSO) algorithms to solve the distribution network feeder reconfiguration and DG placement & sizing problems. Initially, the feeder reconfiguration problem is treated as a single-objective optimisation problem (real power loss minimisation) and then converted into a multi-objective optimisation problem (real power loss minimisation and load balancing). Similarly, the DG placement problem is treated as a single-objective problem (real power loss minimisation) and then converted into a multi-objective optimisation problem (real power loss minimisation, voltage deviation minimisation, Voltage stability Index maximisation). The developed PSO algorithms are implemented and tested for the 16-bus, the 33-bus, and the 69-bus IEEE distribution systems. Additionally, a parallel computing method is developed to study the operation of a distribution network with a feeder reconfiguration scheme under dynamic loading conditions.

Este trabalho propõe uma metodologia de projeto de controladores para o amortecimento de oscilações eletromecânicas de baixa frequência em sistemas elétricos de potência. O problema de controle é estruturado na forma de desigualdades matriciais, as quais permitem a busca por uma solução numérica para o problema de controle. Os controladores de amortecimento baseados na realimentação dinâmica de saída, gerados por metodologias de projeto na forma de desigualdades matriciais, geralmente apresentam ordem elevada. Além disso, projetos considerando sistemas de potência de médio porte demandam elevado tempo computacional. Nesse contexto, o presente trabalho propõe uma metodologia de projeto capaz de gerar controladores de ordem reduzida. A metodologia proposta adota um índice de desempenho que possibilita a redução do tempo computacional demandado no projeto. O índice de desempenho adotado para o sistema em malha fechada é a energia do sinal de saída do sistema. Essa energia corresponde à integral do valor quadrático do sinal adotado como saída do sistema. A metodologia proposta permite especificar um índice de desempenho apenas para aos modos de resposta de interesse do sistema, contornando as limitações das metodologias baseadas em posicionamento regional de polos. A relação entre o valor da energia do sinal de saída do sistema e seu fator de amortecimento é estabelecida por meio de uma equação algébrica. Neste trabalho, a metodologia é aplicada na geração de controladores de amortecimento para geradores síncronos. Entretanto, o procedimento proposto é genérico o suficiente para ser aplicado a outros tipos de geradores (gerador de indução empregado em unidades eólicas, por exemplo), a dispositivos FACTS (do Inglês, Flexible AC Transmission System) assim como a outros tipos de sistemas dinâmicos. A metodologia gerou um controlador eficaz para um caso onde a formulação baseada no tradicional posicionamento regional de polos é incapaz de gerar um controlador que assegure uma boa margem de estabilidade para o modo de resposta de interesse. / This work proposes a methodology for the design of controller to damp low frequency electromechanical oscillations in power systems. The control problem is structured in the form of matrix inequalities, which allows obtaining a numerical solution for the control problem. The damping controllers based on dynamic output feedback, generated by design methodologies in the form of matrix inequalities, usually presents high order. In addition, the design of this controller, considering large power systems, usually requires excessive computational effort. In this context, this work proposes a methodology for the design of reduced order controllers. The proposed methodology employs a performance index that is less costly in terms of computational effort when compared to the one with the traditional regional pole placement. The adopted performance index for the closed loop system is the energy of the system output. This energy corresponds to the integral of the signal squared regarding the system output. The proposed methodology allows specifying a performance index only for the response modes of interest, overcoming the limitations of the methodologies based on regional pole placement. The relation between the energy value of the output signal of the system and its damping factor is established by means of an algebraic equation. In this paper, the methodology is applied to generate damping controller for synchronous generators. However, the proposed procedure is general enough to be applied to other kinds of power plants (wind generation, for example), to FACTS devices, as well as to other dynamic systems. The methodology has generated an effective controller for a case where the formulation based on the regional pole placement is unable to generate a controller which assures a good stability margin for the response mode of interest.

Este trabalho propõe uma metodologia de projeto de controladores para o amortecimento de oscilações eletromecânicas de baixa frequência em sistemas elétricos de potência. O problema de controle é estruturado na forma de desigualdades matriciais, as quais permitem a busca por uma solução numérica para o problema de controle. Os controladores de amortecimento baseados na realimentação dinâmica de saída, gerados por metodologias de projeto na forma de desigualdades matriciais, geralmente apresentam ordem elevada. Além disso, projetos considerando sistemas de potência de médio porte demandam elevado tempo computacional. Nesse contexto, o presente trabalho propõe uma metodologia de projeto capaz de gerar controladores de ordem reduzida. A metodologia proposta adota um índice de desempenho que possibilita a redução do tempo computacional demandado no projeto. O índice de desempenho adotado para o sistema em malha fechada é a energia do sinal de saída do sistema. Essa energia corresponde à integral do valor quadrático do sinal adotado como saída do sistema. A metodologia proposta permite especificar um índice de desempenho apenas para aos modos de resposta de interesse do sistema, contornando as limitações das metodologias baseadas em posicionamento regional de polos. A relação entre o valor da energia do sinal de saída do sistema e seu fator de amortecimento é estabelecida por meio de uma equação algébrica. Neste trabalho, a metodologia é aplicada na geração de controladores de amortecimento para geradores síncronos. Entretanto, o procedimento proposto é genérico o suficiente para ser aplicado a outros tipos de geradores (gerador de indução empregado em unidades eólicas, por exemplo), a dispositivos FACTS (do Inglês, Flexible AC Transmission System) assim como a outros tipos de sistemas dinâmicos. A metodologia gerou um controlador eficaz para um caso onde a formulação baseada no tradicional posicionamento regional de polos é incapaz de gerar um controlador que assegure uma boa margem de estabilidade para o modo de resposta de interesse. / This work proposes a methodology for the design of controller to damp low frequency electromechanical oscillations in power systems. The control problem is structured in the form of matrix inequalities, which allows obtaining a numerical solution for the control problem. The damping controllers based on dynamic output feedback, generated by design methodologies in the form of matrix inequalities, usually presents high order. In addition, the design of this controller, considering large power systems, usually requires excessive computational effort. In this context, this work proposes a methodology for the design of reduced order controllers. The proposed methodology employs a performance index that is less costly in terms of computational effort when compared to the one with the traditional regional pole placement. The adopted performance index for the closed loop system is the energy of the system output. This energy corresponds to the integral of the signal squared regarding the system output. The proposed methodology allows specifying a performance index only for the response modes of interest, overcoming the limitations of the methodologies based on regional pole placement. The relation between the energy value of the output signal of the system and its damping factor is established by means of an algebraic equation. In this paper, the methodology is applied to generate damping controller for synchronous generators. However, the proposed procedure is general enough to be applied to other kinds of power plants (wind generation, for example), to FACTS devices, as well as to other dynamic systems. The methodology has generated an effective controller for a case where the formulation based on the regional pole placement is unable to generate a controller which assures a good stability margin for the response mode of interest.