The utilization of renewable energy resources such as wind and solar energy for electric power supply has received considerable attention in recent years due to adverse environmental impacts and fuel cost escalation associated with conventional generation. At the present time, wind and/or solar energy sources are utilized to generate electric power in many applications. Wind and solar energy will become important sources for power generation in the future because of their environmental, social and economic benefits, together with public support and government incentives. <p>The wind and sunlight are, however, unstable and variable energy sources, and behave far differently than conventional sources. Energy storage systems are, therefore, often required to smooth the fluctuating nature of the energy conversion system especially in small isolated applications. The research work presented in this thesis is focused on the development and application of reliability and economic benefits assessment associated with incorporating wind energy, solar energy and energy storage in power generating systems. A probabilistic approach using sequential Monte Carlo simulation was employed in this research and a number of analyses were conducted with regards to the adequacy and economic assessment of generation systems containing wind energy, solar energy and energy storage. The evaluation models and techniques incorporate risk index distributions and different operating strategies associated with diesel generation in small isolated systems. Deterministic and probabilistic techniques are combined in this thesis using a system well-being approach to provide useful adequacy indices for small isolated systems that include renewable energy and energy storage. The concepts presented and examples illustrated in this thesis will help power system planners and utility managers to assess the reliability and economic benefits of utilizing wind energy conversion systems, solar energy conversion systems and energy storage in electric power systems and provide useful input to the managerial decision process.

The utilization of renewable energy resources such as wind and solar energy for electric power supply has received considerable attention in recent years due to adverse environmental impacts and fuel cost escalation associated with conventional generation. At the present time, wind and/or solar energy sources are utilized to generate electric power in many applications. Wind and solar energy will become important sources for power generation in the future because of their environmental, social and economic benefits, together with public support and government incentives. <p>The wind and sunlight are, however, unstable and variable energy sources, and behave far differently than conventional sources. Energy storage systems are, therefore, often required to smooth the fluctuating nature of the energy conversion system especially in small isolated applications. The research work presented in this thesis is focused on the development and application of reliability and economic benefits assessment associated with incorporating wind energy, solar energy and energy storage in power generating systems. A probabilistic approach using sequential Monte Carlo simulation was employed in this research and a number of analyses were conducted with regards to the adequacy and economic assessment of generation systems containing wind energy, solar energy and energy storage. The evaluation models and techniques incorporate risk index distributions and different operating strategies associated with diesel generation in small isolated systems. Deterministic and probabilistic techniques are combined in this thesis using a system well-being approach to provide useful adequacy indices for small isolated systems that include renewable energy and energy storage. The concepts presented and examples illustrated in this thesis will help power system planners and utility managers to assess the reliability and economic benefits of utilizing wind energy conversion systems, solar energy conversion systems and energy storage in electric power systems and provide useful input to the managerial decision process.

The Turkish TSO (TEIAS) has been leading a project that aims the synchronous interconnected operation of the Turkish Power System and the ENTSO-E CESA (former UCTE) System. For this purpose, this study concentrates on the specific problems related to the electromechanical systems of large size hydroelectric power plants regarding low frequency inter area oscillations, which are prone to occur once the interconnected operation is established. The expected frequency of inter area oscillations after interconnected operation is close to 0.15 Hz, which is in the frequency range of the speed governing structures of turbines, as explained in the first two sections of the thesis. In the third section, the nonlinear turbine governor model used throughout the study is explained. In the following part, the governor parameter tuning study with regard to the defined performance objectives is explained. Afterwards, the effect of the retuned governor settings of the sample hydroelectric power plants on a simple multi machine power system is shown. Following that, the system wide effect of removing the sources of negative damping, which are strongly dependent on the governor settings of the major hydroelectric power plants of the Turkish Power System, is shown. In the final part, conclusions are made on the operation of the hydroelectric power plants regarding the frequency stability of the system after synchronous interconnected operation of the Turkish Power System and the ENTSO-E CESA System.

Advances in electronics, computer and information technology are fueling major changes in the area of power systems instrumentations. More and more microprocessor based digital instruments are replacing older type of meters. Extensive deployment of digital instruments are generating vast quantities of data which is creating information pressure in Utilities. The legacy SCADA based data management systems do not support management of such huge data. As a result utilities either have to delete or store the metered information in some compact discs, tape drives which are unreliable. Also, at the same time the traditional integrated power industry is going through a deregulation process. The market principle is forcing competition between power utilities, which in turn demands a higher focus on profit and competitive edge. To optimize system operation and planning utilities need better decision making processes which depend on the availability of reliable system information. For utilities it is becoming clear that information is a vital asset. So, the utilities are now keen to store and use as much information as they can. Existing SCADA based systems do not allow to store data of more than a few months. So, in this dissertation effectiveness of compression algorithms in compressing real time operational data has been assessed. Both, lossy and lossless compression schemes are considered. In lossless method two schemes are proposed among which Scheme 1 is based on arithmetic coding and Scheme 2 is based on run length coding. Both the scheme have 2 stages. First stage is common for both the schemes. In this stage the consecutive data elements are decorrelated by using linear predictors. The output from linear predictor, named as residual sequence, is coded by arithmetic coding in Scheme 1 and by run length coding in Scheme 2. Three different types of arithmetic codings are considered in this study : static, decrement and adaptive arithmetic coding. Among them static and decrement codings are two pass methods where the first pass is used to collect symbol statistics while the second is used to code the symbols. The adaptive coding method uses only one pass. In the arithmetic coding based schemes the average compression ratio achieved for voltage data is around 30, for frequency data is around 9, for VAr generation data is around 14, for MW generation data is around 11 and for line flow data is around 14. In scheme 2 Golomb-Rice coding is used for compressing run lengths. In Scheme 2 the average compression ratio achieved for voltage data is around 25, for frequency data is around 7, for VAr generation data is around 10, for MW generation data is around 8 and for line flow data is around 9. The arithmetic coding based method mainly looks at achieving high compression ratio. On the other hand, Golomb-Rice coding based method does not achieve good compression ratio as arithmetic coding but it is computationally very simple in comparison with the arithmetic coding. In lossy method principal component analysis (PCA) based compression method is used. From the data set, a few uncorrelated variables are derived and stored. The range of compression ratio in PCA based compression scheme is around 105-115 for voltage data, around 55-58 for VAr generation data, around 21-23 for MW generation data and around 27-29 for line flow data. This shows that the voltage parameter is amenable for better compression than other parameters. Data of five system parameters - voltage, line flow, frequency, MW generation and MVAr generation - of Souther regional grid of India have been considered for study. One of the aims of this thesis is to argue that collected power system data can be put to other uses as well. In particular we show that, even mining the small amount of practical data (collected from SRLDC) reveals some interesting system behavior patterns. A noteworthy feature of the thesis is that all the studies have been carried out considering data of practical systems. It is believed that the thesis opens up new questions for further investigations.

The research topics presented in this dissertation focus on validation of customer-level voltage synchrophasor data for transmission system analysis, detection and categorization of power system events as measured by phasor measurement units (PMUs), and identification of the influence of power system conditions (wind power, daily and seasonal load variation) on low-frequency oscillations. Synchrophasor data can provide information across entire power systems but obtaining the data, handling the large dataset and developing tools to extract useful information from it is a challenge. To overcome the challenge of obtaining data, an independent synchrophasor network was created by taking synchrophasor measurements at customer-level voltage. The first objective is to determine if synchrophasor data taken at customer-level voltage is an accurate representation of power system behavior. The validation process was started by installing a transmission level (69 kV) PMU. The customer-level voltage measurements were validated by comparison of long term trends and low-frequency oscillations estimates. The techniques best suited for synchrophasor data analysis were identified after a detailed study and comparison. The same techniques were also applied to detect power system events resulting in the creation of novel categories for numerous events based on shared characteristics. The numerical characteristics for each category and the ranges of each numerical characteristic for each event category are identified. The final objective is to identify trends in power system behavior related to wind power and daily and seasonal variations by utilizing signal processing and statistical techniques. / text

Due to growth of wind power, system operators are being challenged by the integration of large wind farms into their electrical power systems. Large scale wind farm integration has adverse effects on the power system due to its variable characteristic. These effects include two main aspects: voltage stability and active line flow. In this thesis, a novel techniques to forecast active line flow and select pilot bus are introduced with wind power integration. First, this thesis introduces a methodology to forecast congestion in the transmission line with high wind penetration. Since most wind resources tend to be located far away form the load center, the active line flow is one of the most significant aspects when wind farm is connected to electrical grid. By providing the information about the line flow which can contribute to transmission line congestion, the system operators would be able to respond such as by requesting wind power or load reduction. The second objective of this thesis is to select the weakest bus, called pilot bus, among all load buses. System reliability, especially voltage stability, can be adversely affected by wind variability. In order to ensure reliable operation of power systems with wind power integration, the index to select the pilot bus is developed, and further prediction of voltage profile at the pilot bus is fulfilled. The objective function to select the pilot bus takes account of the N-1 contingency analysis, loading margin, and reactive power sensitivity. Through on the objective function, the pilot bus is representative of all load buses as well as controllable by reactive power regulation. Predicting the voltage profile at the pilot bus is also useful for system operators to determine wind power output. / text

The object of this research is to optimize the overall power system performance using FACTS devices. Particularly, it is intended to improve the reliability, and the performance of the power system considering steady state operating condition as well as the system subjected to small and large disturbances. The methodology proposed to achieve this goal corresponds to an enhanced particle swarm optimizer (Enhanced-PSO) that is proven in this work to have several advantages, in terms of accuracy and computational effort, as compared with other existing methods. Once the performance of the Enhanced PSO is verified, a multi-stage PSO-based optimization framework is proposed for optimizing the power system reliability (N-1 contingency criterion). The algorithm finds optimal settings for present infrastructure (generator outputs, transformers tap ratios and capacitor banks settings) as well as optimal control references for distributed static series compensators (DSSC) and optimal locations, sizes and control settings for static compensator (STATCOM) units. Finally, a two-stage optimization algorithm is proposed to improve the power system performance in steady state conditions and when small and large perturbations are applied to the system. In this case, the algorithm provides optimal control references for DSSC modules, optimal location and sizes for capacitor banks, and optimal location, sizes and control parameters for STATCOM units (internal and external controllers), so that the loadability and the damping of the system are maximized at minimum cost. Simulation results throughout this research show a significant improvement of the power system reliability and performance after the system is optimized.

The purpose of the proposed research is to design a Decentralized Voltage/Stability Monitoring and Control System to counteract voltage violations and the impact of disturbances/contingencies on power system voltage stability. A decentralized voltage and stability control system is designed to coordinate the controls of the local secondary voltage control devices and necessary load shedding without requiring information about the rest of the system. The voltage/stability control can be formulated as a multi-objective optimization problem. The control objectives include, but are not limited to: minimization of system active/reactive losses; maximization of the system stability margin; and minimization of the control actions. The constraints of the optimization problem depend on the specifications of the actual system components. For the first time, margin sensitivities of the control actions are included in the control formulation. The concept of using margin sensitivity to evaluate the post-control load margin is presented as a fast and accurate way to assess potential voltage and stability control options. A system decomposition procedure is designed to define the disturbance-affected zone as an independent control subsystem. A normal constraint algorithm is adopted to identify the most suitable control solution in a shorter timeline than the typical utility voltage-control practice. Both steady-state and dynamic simulations are performed to compare the proposed system with typical utility control practices.

Thesis (M.Eng.)--University of Wollongong, School of Electrical, Computer & Telecommunications Engineering. / Typescript. Includes bibliographical references: leaf 143-147.

Η παρούσα διπλωματική εργασία έχει ως στόχο την αντιμετώπιση των ηλεκτρομηχανικών ταλαντώσεων οι οποίες εμφανίζονται σε μία σύγχρονη γεννήτρια παραγωγής Ηλεκτρικής Ενέργειας μετά από διαταραχές. Ο συμβατικός έλεγχος για τη διατήρηση της μηχανής σε συγχρονισμό μετά από ξαφνικές αλλαγές φορτίου, βραχυκυκλωμάτων, κλείσιμο διακοπτών ή οποιασδήποτε κατάστασης που μπορεί να προκαλέσει αστάθεια στο Σύστημα της Ηλεκτρικής Ενέργειας, γίνεται με χρήση ελεγκτικών διατάξεων Σταθεροποιητών Συστημάτων Ισχύος σε συνδυασμό με τον Αυτόματο Ρυθμιστή Τάσης (ΑΡΤ/ΣΣΙ). Σκοπός της εργασίας αυτής είναι να σχεδιαστούν και να ρυθμιστούν κατάλληλα οι διατάξεις αυτές, ώστε να εξασφαλίζεται η απόσβεση των ηλεκτρομηχανικών ταλαντώσεων που εμφανίζονται ανάμεσα στην γεννήτρια και το υπόλοιπο σύστημα. Στην εργασία αυτή, αρχικά γίνεται μια εισαγωγή στα είδη των ηλεκτρομηχανικών ταλαντώσεων και την ευστάθεια για δυναμικά Συστήματα Ηλεκτρικής Ενέργειας. Στη συνέχεια αναπτύσσεται το δυναμικό μοντέλο ενός απλού συστήματος μιας γεννήτριας άπειρου ζυγού βασισμένο στο απλοποιημένο μοντέλο 4ης τάξης της σύγχρονης μηχανής. Επειδή το μοντέλο αυτό είναι μη γραμμικό προχωράμε στην εξαγωγή του γραμμικοποιημένου μοντέλου που θα μας βοηθήσει για τον σχεδιασμό του κατάλληλου ελεγκτή. Αξιοποιώντας ιδιότητες του μοντέλου παρουσιάζεται μια συστηματική μέθοδος σχεδίασης του Σταθεροποιητή Συστήματος Ισχύος που είναι βασισμένη στη λογική των ολοκληρωτικών υπολοίπων. Τέλος με τη βοήθεια του λογισμικού SIMULINK του MATLAB προσομοιώνεται το σύστημα σύγχρονης γεννήτριας συνδεδεμένης σε άπειρο ζυγό, που ελέγχεται με την χρήση του Αυτόματου Ρυθμιστή Τάσης και του Σταθεροποιητή Συστήματος Ισχύος σε κατάσταση τυπικής φόρτισης. Εφαρμόζοντας διαταραχές στο σύστημα παρατηρείται η απόκριση του συστήματος και εκτιμάται η λειτουργία του ελεγκτή. / This thesis aims to address the electromechanical oscillations which appear in a synchronous generator after disturbances. The conventional control for maintaining the machine synchronized after sudden load changes, short circuits, switching or any condition which may cause instability phenomena, is achieved by the use of control circuits such as Power System Stabilizers combined with the Automatic Voltage Regulator ( PSS / AVR). The purpose of this work is to design and configure properly these control circuits to ensure the reduction of electromechanical oscillations that occur between the generator and the rest of the system. In the beginning this thesis, an introduction of the types of power system electromechanical oscillations and stability is being discussed. Afterwards, the dynamic model of a simple system of a generator infinite-bus based on simplified 4th order of synchronous machine is being developed. Due to the model nonlinearities, we export the linearized model which helps us to design a suitable controller. Taking into account the model properties, we provide a systematic method for designing a Power System Stabilizer based on the residues method. Finally, using the MATLAB-SIMULINK software, the synchronous generator infinite-bus system is simulated which is controlled by an Automatic Voltage Regulator and a Power System Stabilizer. After applying disturbances, the system response is driven and analyzed along with the controller functioning.