Tesi sul tema "Electric power"

The latest generation of AC-fed traction drives, employing high-speed switching devices, is able to control the reactive power drawn from the overhead line by each equipment. If the conditions at each locomotive or train could be fed back to a central control point, it is possible for a centrally located controller to calculate optimal values for the reactive power in each drive and to send those commands back to the individual equipment. In this thesis, AC railway power flows are optimised in real time and the results are used to achieve some particular system objective via control of the PWM equipment as mobile reactive power compensators. The system voltage profile and the total power losses can be improved while the overall power factor at the feeder substation is also made nearer to unity. For off-line simulation purposes, high execution speeds and low storage requirements are not generally significant with the latest computer hardware. However, this real-time control employs on-line optimising controllers, which need embedded power solvers running many times faster than real time. Thus, a fast and efficient algorithm for AC railway power flow calculation was developed. The proposed scheme is compared to a conventional reactive power compensation, e.g. SVC, and found to be less expensive to implement. Several test cases for AC electric railway systems are examined. The centralised area control system leads to the best improvement where an existing fleet of diode or thyristor phase-angle controlled locomotives is partially replaced with PWM ones, compared to that obtained without compensation or to classical track-side Var compensation methods. From these results, the potential for PWM locomotives to improve overall system performance is confirmed.

Abstract Iran is a very vast country with about 80 million population that they are really fragmented. Providing electricitypower for all the society which is duty of power ministry of Iran according to the resources and facilities. The thesis gives an overview of production of electrical energy in Iran and how the production is divided ondifferent energy sources. At the present time there are 197 power plants are producing electricity to supportthe country that they are combination of 8 kind of different power plants which are thermal power plants, gaspower stations, combined cycles, hydro power plants, biogas plants, wind power stations, solar plants andnuclear power stations. During the last decade Iran took care of renewable energy sources to produce electricitythat cause wind power plants and solar power plants can take a small share from the total production. Althoughthey are not play a serious role yet but the policy of the country is improving these kind of power plants. Foreach source the production principle is described briefly by help of a diagram and also there is a table of allpower plants which are included details of each power plant like: name of power plant, state (location) , year ofinstallation, nominal power, gross power, efficiency, consumption (fuel, water,…) and so on. For each kind ofpower plants there is a bar chart which compares the nominal power of all power plants at a glance and alsothere is a map that the location of each station has been marked on. Total data for production in a year has been presented. Also there is a list of power plants which they are underconstruction and will be ready in future. For transmitting electricity power in the country there are four kind of transmission lines which are: 400 KV, 230KV, 132 KV and 66 KV. The development of each kind of transmission lines since 1963 is presented in a table anda chart. Also Iran has export and import electricity with 8 neighbor countries like: Iraq, Afghanistan, Azerbaijan,Turkmenistan, Turkey, Pakistan, Armenia and Nakhjavan. The range of exchange since 1993 is shown in a tableand a chart.

In 2003 the European Commission introduced the Directive 2003/54/EC and Regulation 1228/2003/EC which increased the focus on the liberalization of the European electricity market. The international electricity trade has increased and created new challenges related to cross-border transmission and compensation mechanisms. The focus of the report has been to discuss the development of the electricity market in Europe, and the status of international exchange. The report also discusses the concept of cross-border trade and transit, and investigates a proposed ITC model and whether correct investment incentives are given. Price data from the main power exchanges in Europe indicate that the market is experiencing increasingly integration and efficiency. There has also been a trend towards market based congestion management methods. Regional markets have successfully developed in Spain and Portugal (the Iberian market) and between France, Belgium and The Netherlands (the Trilateral Market Coupling, TLC). Further plans for regional coupling are also underway (see chapter 5. The most common definition of transit is the one adopted by ETSO (Association of European Transmission System Operators), where transit is defined as the minimum between exports and imports. This definition could create opportunities for market participants to manipulate transit income (discussed in chapter 5.3). The Inter-TSO compensation (ITC) model used in this report is based on the With-and-Without transit algorithm. The model only focuses on costs and load flow, and do not include market incentives or evaluation of benefits. The model bases the compensation calculation on the transit term, which can lead to misguided identification of network responsibility. Two scenarios were compared with a base case scenario in order to identify possible investment incentives. The first scenario included a situation where one of the cross-border lines in the network was constrained. Results from this simulation indicate that the transmission system operators involved would experience increased ITC payment, and therefore not receive investment incentives. The TSOs involved would benefit from the bottleneck in form of increased revenue (assuming Cost-Of-Service regulation). In the second scenario an extra cross-border line was implemented, and the situation was compared to the base case. The results from this simulation show that the TSOs involved would receive a positive effect in form of reduced ITC cost. The ITC mechanism would in this case be in line with the European Commission’s Regulation 1228/2003/EC, and give the involved TSOs correct investment incentives. The lack of correlated results in these two cases indicates that the ITC mechanism (in this case modeled by the WWT algorithm) cannot be regarded as relevant from an investment incentive perspective (more information found in chapter 7.3).

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.
Includes bibliographical references (leaf 49).
In this dissertation, I describe the design and construction of a system which can transfer electric power wirelessly. This is accomplished using inductive, near-field, non-radiative coupling between self-resonant copper helices. In our first experiment, we transfered 60W of power over a distance of 2m with 45% efficiency. In our second experiment, we designed a system which can transfer power from a single source to two devices, each 2m away, with 60% total efficiency. We also developed a quantitative model of our helical resonators which predicted the resonant frequency with an accuracy of 5%.
by Robert Alexander Moffatt.
S.B.

Thesis: S.M., Massachusetts Institute of Technology, School of Engineering, Center for Computational Engineering, Computation for Design and Optimization Program, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 87-91).
This thesis examines two problems concerning the secure and reliable operation of the electric power grid. The first part studies the distributed operation of the electric power grid using the power flow problem, which is vital to the operation of the grid. The power flow problem is a feasibility problem for finding an assignment of complex bus voltages that satisfies the power flow equations and is within operational and safety limits. For reliability and privacy reasons, it is desirable to solve the power flow problem in a distributed manner. Two novel distributed algorithms are presented for solving convex feasibility problems for networks based on the Method of Alternating Projections (MAP) and the Projected Consensus algorithm. These algorithms distribute computation among the nodes of the network and do not require any form of central coordination. The original problem is equivalently split into small local sub-problems, which are coordinated locally via a thin communication protocol. Although the power flow problem is non-convex, the new algorithms are demonstrated to be powerful heuristics using IEEE test beds. Quadratically Constrained Quadratic Programs (QCQP), which occur in the projection sub-problems, are studied and methods for solving them efficiently are developed. The second part addresses the robustness and resiliency of state estimation algorithms for cyber-physical systems. The operation of the electric power grid is modeled as a dynamical system that is supported by numerous feedback control mechanisms, which depend heavily on state estimation algorithms. The electric power grid is constantly under attack and, if left unchecked, these attacks may corrupt state estimates and lead to severe consequences. This thesis proposes a novel dynamic state estimator that is resilient against data injection attacks and robust to modeling errors and additive noise signals. By leveraging principles of robust optimization, the estimator can be formulated as a convex optimization problem and its effectiveness is demonstrated in simulations of an IEEE 14-bus system.
by Ming Qing Foo.
S.M.

Solar power is one source of renewable energy that is well established but, in the UK, expensive per kilowatt due to low levels of insolation caused by cloud cover. To over- come the limitations of cloud cover, an aerostat for electrical power generation has been proposed in literature. The aerostat would float at an altitude of six kilometres, above the majority of cloud cover, and can receive around 3.3 times the annual insolation of a ground based system in the UK. The aim of this work is to further demonstrate the feasibility of such an aerostat concept. This is achieved by considering three areas of study: the solar array shape, the control system and the thermal analysis. The analysis of the solar array compares two configurations, a spherical cap and a stepped array, in terms of size, mass, power production and sensitivity to pointing error. The results show that a spherical cap array has a lower sensitivity to pointing error and, with the support structure required for a stepped array, a lower mass despite its larger surface area. The control system design takes a proposed system concept as its starting point and revises it. The system is sized and its Sun tracking and disturbance rejection performance is simulated. It is found that the system is capable of maintaining a pointing error of within 1.81◦ during tracking and of correcting disturbances. The thermal analysis extends previous models to include the effects of a ballonet used for gas pressure regulation. The model is validated against experimental data and shows a good agreement (r ≥ 0.9). The model is then applied to the aerostat concept and shows that the gas pressure can be maintained within acceptable bounds and that the solar array does not become hot due to solar heating. Overall, the results of this study increase confidence in the feasibility of the aerostat concept.

The exploitation of renewable energy sources is currently at the top of the agenda of many governments that are required to face the problem of the rising energy demand. In particular photovoltaics is considered one of the most promising technologies to meet the energy needs in the long term. However the effective exploitation of this source has always been hindered in many northern countries (like the UK) due to the weather conditions which are detrimental for the efficiency of photovoltaic generators. As a possible solution to this problem, this research presents the preliminary concept evaluation of an innovative power generator based on photovoltaic and lighter than air technologies (Aerostat for Electric Power Generation – AEPG). The generator consists of a helium filled platform tethered to the ground that would be used to locate a photovoltaic array at high altitude, ideally above the cloud coverage, in order to reduce the negative effect of the atmosphere and optimize the power production. The power produced at high altitude would then be transmitted to the ground via the mooring tether. First of all, the potential of this technology is evaluated in terms of the solar energy that can be collected at high altitude. The results obtained demonstrate that a generator located at an altitude between 6 km and 12 km could collect between 3.3 and 4.9 times the solar radiation that would fall on a ground based photovoltaic array. Furthermore the environmental conditions in which the system is due to operate are evaluated, employing standard atmospheric models and experimental wind speed datasets. An overview of the main parameters involved in the design is then provided and general considerations are discussed in order to narrow the range of values these different parameters can take. A simplified mathematical model is introduced to assess the performance of the system in steady state conditions and a set of design parameters is chosen to define a baseline configuration for the concept design. Moreover, a transient 3D analysis of the whole system is performed in order to check if the dynamic behaviour can constitute a show stopper. Finally the concept design of the AEPG is addressed and the most critical technical issues are identified. The location of the different subsystems is briefly discussed and a possible solution for the system layout is proposed. The study is completed with an initial sizing of the main components (structural in particular) in order to evaluate the different mass contributions and provide a preliminary assessment of the technical feasibility of the AEPG.

Along with increased oil prices and rising environmental issues, a demand for alternatives to combustion engine driven hydraulic applications has risen. In the field of mobile hydraulics, the hydraulic applications have traditionally been driven by the combustion engine of the vehicle on which they are mounted. By instead using a battery driven power pack the hydraulic application is able to operate without the engine running, saving fuel costs and reducing sound levels. In this thesis, the concept of using an electric-hydraulic power pack with a variable-speed electric motor and a fixed-displacement hydraulic pump to provide power to a truck-mounted loader crane is investigated. This concept is compared to an electric-hydraulic system imitating the conventional combustion engine system by using a fixed-speed electric motor connected to a variable-displacement pump. The use of a variable speed motor where the speed can be controlled electrically by a control unit creates possibilities of using different control strategies to improve the efficiency and responsiveness of the application. The efficiencies of the two electric-hydraulic systems are compared by constructing a physical test rig and performing measurements in a test lab. The tests have shown an increased efficiency of about 20 \% when using the variable speed configuration. Three different control strategies are also investigated and tested on a simulated model. The simulations show that very good responsiveness and robustness can be achieved by using a hydraulic flow feed forward controller with a complementary pressure feedback controller. Furthermore, by controlling the hydraulic flow to the heaviest of the crane loads entirely with the flow from the hydraulic pump, the hydraulic pressure can be reduced and energy efficiency increased.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 103-115).
The electric power grid is recognized as an essential modern infrastructure that poses numerous canonical design and operational problems. Perhaps most critically, the inherently large scale of the power grid and similar systems necessitates fast algorithms. A particular complication distinguishing problems in power systems from those arising in other large infrastructures is the mathematical description of alternating current power flow: it is nonconvex, and thus excludes power systems from many frameworks benefiting from theoretically and practically efficient algorithms. However, advances over the past twenty years in optimization have led to broader classes possessing such algorithms, as well as procedures for transferring nonconvex problem to these classes. In this thesis, we approximate difficult problems in power systems with tractable, conic programs. First, we formulate a new type of NP-hard graph cut arising from undirected multicommodity flow networks. An eigenvalue bound in the form of the Cheeger inequality is proven, which serves as a starting point for deriving semidefinite relaxations. We next apply a lift-and-project type relaxation to transmission system planning. The approach unifies and improves upon existing models based on the DC power flow approximation, and yields new mixed-integer linear, second-order cone, and semidefinite models for the AC case. The AC models are particularly applicable to scenarios in which the DC approximation is not justified, such as the all-electric ship. Lastly, we consider distribution system reconfiguration. By making physically motivated simplifications to the DistFlow equations, we obtain mixed-integer quadratic, quadratically constrained, and second-order cone formulations, which are accurate and efficient enough for near-optimal, real-time application. We test each model on standard benchmark problems, as well as a new benchmark abstracted from a notional shipboard power system. The models accurately approximate the original formulations, while demonstrating the scalability required for application to realistic systems. Collectively, the models provide tangible new tradeoffs between computational efficiency and accuracy for fundamental problems in power systems.
by Joshua Adam Taylor.
Ph.D.

Pakistan is among some countries which has a lot of potential to produce electricity. The country is geographically very rich in terms of various renewable resources which are low costing to produce electricity and at the same time more environment friendly. But still from last 15 years Pakistan has a series of crises in power sector and there is a shortfall because electricity demand is growing day by day and the resources to produce electricity are not used efficiently. This study covers how the country is producing electricity from different available resources, furthermore to address how to reduce shortfall using renewable resources. The main parameters covered by this study are electricity production and its consumption, and installed capacity from different power sources. Currently there are 81 different Power plants with installed capacity 24857 MW of electricity and some more power generating projects are in consideration in future to increase electricity production in the country.  Production units are shown in terms of bar charts which compares installed capacity of all power plants. Annual production data of different power plants and their generation history is also shown and explained in tables. Furthermore in our study, reasons of existing shortfall are explained and renewable resources like wind, hydel and solar potential of the country is specified, which will help to reduce existing shortfall. At the end, it is concluded that renewable resources importance is realizing in the country with time, as their contribution towards electricity generation is increasing, and are more beneficial, sustainable, economical and long lasting.

Wireless Power Transfer (WPT) systems transfer electric energy from a source to a load without any wired connection. WPTs are attractive for many industrial applications because of their advantages compared to the wired counterpart, such as no exposed wires, ease of charging, and fearless transmission of power in adverse environmental conditions. Adoption of WPTs to charge the on-board batteries of an electric vehicle (EV) has got attention from some companies, and efforts are being made for development and improvement of the various associated topologies. WPT is achieved through the affordable inductive coupling between two coils termed as transmitter and receiver coil. In EV charging applications, transmitter coils are buried in the road and receiver coils are placed in the vehicle. Inductive WPT of resonant type is commonly used for medium-high power transfer applications like EV charging because it exhibits a greater efficiency. This thesis refers to a WPT system to charge the on-board batteries of an electric city-car considered as a study case. The electric city-car uses four series connected 12V, 100A•h VRLA batteries and two in-wheel motors fitted in the rear wheels, each of them able to develop a peak power of 4 kW to propel the car. The work done has been carried out mainly in three different stages; at first an overview on the wired EV battery chargers and the charging methodologies was carried out. Afterwards, background of different WPT technologies are discussed; a full set of Figures of Merit (FOM) have been defined and are used to characterize the resonant WPTs to the variations in resistive load and coupling coefficient. In the second stage, the WPT system for the study case has been designed. In the third stage, a prototypal of the WPT system has been developed and tested. Design of the WPT system is started by assessing the parameters of the various sections and by estimating the impact of the parameters of the system on its performance. The design process of the coil-coupling has come after an analysis of different structures for the windings, namely helix and spiral, and different shapes for the magnetic core; further to the preliminary results that have shown the advantages of the spiral structure, a more detailed analysis has then been executed on this structure. The coil design has encompassed the determination of the inductive parameters of the two-coil coupling as a function of the coil distance and axial misalignment. Both the analysis and the design was assisted by a FEM-approach based on the COMSOL code. Design of the power supply stages of the WPT system has consisted of the assessment of values and ratings of a) the capacitors that make resonant the coil-coupling, b) the power devices of the PFC rectifier and of the high frequency inverter (HF) that feeds the transmitting coil, c) the power devices of the converters supplied by the receiver coil: the rectifier diode and the in-cascade chopper that feeds the battery in a controlled way. For the converters that operate at high frequency (inverter and the rectifier in the receiver section), power electronic devices of the latest generation (the so-called Wide Band Gap (WBG) devices) have been used in order to maximize the efficiency of the WPT system. A prototypal WPT battery charger was arranged by using available cards with the power and signal circuits. Relevant experimental activities were: a) measurement of the parameters of the coils, b) desk assembling of the prototype, and c) conducting tests to verify proper operation of the prototype. The thesis work includes also a brief overview of i) emerging topics on WPT systems such as on-line electric vehicle (OLEV), ii) shielding of the magnetic fields produced by a WPT system, and iii) standards on WPT operation. These three issues play a significant role in the advancement of the WPT technology. The thesis work has been carried out at the Laboratory of “Electric systems for automation and automotive” headed by Prof. Giuseppe Buja. The laboratory belongs to the Department of Industrial Engineering of the University of Padova, Italy.
I sistemi per il trasferimento di potenza wireless (WPT) trasferiscono energia elettrica da una sorgente ad un carico senza alcuna connessione via cavo. I sistemi WPT sono attraenti per molte applicazioni industriali grazie ai loro vantaggi rispetto alla controparte cablata, come l’assenza di conduttori esposti, la facilità di ricarica e la trasmissione senza rischi della potenza in condizioni ambientali avverse. L’adozione di sistemi WPT per la carica delle batterie di bordo di un veicolo elettrico (EV) ha ricevuto l'attenzione di alcune aziende, e sforzi sono stati fatti per lo sviluppo e il miglioramento delle varie topologie ad essi associate. Il WPT è ottenuto tramite l'accoppiamento induttivo tra due bobine, definite bobina trasmittente e bobina ricevente. Nelle applicazioni per la carica delle batterie, le bobine trasmittenti sono installate sotto il manto stradale mentre le bobine riceventi sono poste a bordo del veicolo. Il WPT induttivo di tipo risonante è comunemente utilizzato nelle applicazioni per il trasferimento di potenze medio-alte, come la carica degli EV, perché presenta una maggiore efficienza. Questa tesi tratta un sistema WPT per caricare le batterie di bordo di una city-car elettrica considerato come caso di studio. La city-car elettrica utilizza quattro batterie da 12V, 100A•h VRLA collegate in serie e due motori-ruota montati sull’assale posteriore, ognuno in grado di sviluppare una potenza di picco di 4 kW per la propulsione del veicolo. Il lavoro svolto è stato effettuato principalmente in tre fasi diverse; in un primo momento è stata effettuata una panoramica sui caricabatteria cablati per EV e sulle metodologie di ricarica. Successivamente, sono stati discussi i principi base di diverse tecnologie WPT; è stato definito un insieme di figure di merito (FOM) che sono state utilizzate per caratterizzare il comportamento dei WPT risonanti rispetto alle variazioni di carico resistivo e al coefficiente di accoppiamento. Nella seconda fase, è stato progettato il sistema WPT per il caso di studio. Nella terza fase, è stato sviluppato e sperimentato un prototipo del sistema WPT. La progettazione del sistema WPT è stata iniziata con una valutazione dei parametri delle varie sezioni e stimando l'impatto dei parametri del sistema sulle sue prestazioni. La progettazione della bobina di accoppiamento è stata effettuata dopo l'analisi di avvolgimenti con strutture diverse, ovvero elica e spirale, e con forme differenti del nucleo magnetico; a seguito dei risultati preliminari che hanno mostrato i vantaggi della struttura a spirale, è stata poi eseguita un'analisi più dettagliata su questa struttura. Il progetto della bobina ha compreso la determinazione dei parametri induttivi dell’accoppiamento in funzione della distanza e del disallineamento assiale delle bobine. Sia l'analisi che la progettazione sono state assistite da un approccio FEM basato sul codice COMSOL. La progettazione degli stadi di alimentazione del sistema WPT è consistita nella valutazione dei valori e dei dati di targa di a) i condensatori che rendono risonante l’accoppiamento tra le bobine, b) i dispositivi di potenza del raddrizzatore PFC e dell'inverter ad alta frequenza (HF) che alimenta la bobina di trasmissione, c) i dispositivi di potenza dei convertitori alimentati dalla bobina ricevente, segnatamente il raddrizzatore a diodi e il chopper collegato a valle che carica la batteria in modo controllato. Per i convertitori che operano ad alta frequenza (l’invertitore e il raddrizzatore della sezione ricevente), sono stati utilizzati dispositivi elettronici di potenza di ultima generazione (i cosiddetti dispositivi Wide Band Gap (WBG)) al fine di massimizzare l'efficienza del sistema WPT. E’ stato realizzato un caricabatteria WPT prototipale utilizzando schede elettroniche disponibili in Laboratorio con i circuiti di potenza e di segnale. Le relative attività sperimentali sono state: a) misurazione dei parametri delle bobine, b) assemblaggio a banco del prototipo, e c) esecuzione di prove sperimentali per verificare il corretto funzionamento del prototipo. Il lavoro di tesi comprende anche una breve panoramica su temi emergenti in materia di sistemi WPT come i) IL WPT dinamico, chiamato anche “on-line electric vehicle” (OLEV), ii) la schermatura dei campi magnetici prodotti da un sistema WPT, e iii) la normativa sui sistemi WPT. Questi tre temi svolgono un ruolo significativo nello sviluppo della tecnologia WPT. Il lavoro di tesi è stato effettuato presso il Laboratorio di “Sistemi elettrici per l'automazione e la veicolistica” diretto dal Prof. Giuseppe Buja. Il Laboratorio fa parte del Dipartimento di Ingegneria Industriale dell'Università degli Studi di Padova, Italia.

Power electronic converters are widely used in industrial power conversion systems both for utility and drives applications. As the power level increases, the voltage level is increased accordingly to obtain satisfactory efficiency. During the last years, the voltage rating of fast switching high voltage semiconductors such as the Insulated Gate Bipolar Transistor (IGBT) has increased. Still, there is a need for series connection of switching devices. In this area of applications, the Multilevel Converter has shown growing popularity.

The fundamental advantages of the Multilevel Converter topologies are low distorted output waveforms and limited voltage stress on the switching devices. The main disadvantages are higher complexity and more difficult control.

In this thesis, Multilevel Converters are analysed for large motor drive applications. The main focus has been on converter losses, output waveform quality and control.

Analytical expressions for both switching and conduction losses for 4- and 5-level Diode Clamped Converters have been developed. The investigation shows that the losses can be reduced by utilizing a multilevel topology for a 1 MW drive. This work is presented in [46]. The same reduction in losses is proven for a 2300V/ 3 MW drive.

Analytical expressions for the harmonic losses in 3-level converters have been developed for 2 different Carrier Based PWM schemes, presented in [56], [57] and [58]. Also Space Vector PWM are investigated and compared by simulations, in addition to 4- and 5-level Carrier Based PWM.

DC-bus balancing in both 3- and 5-level converters is discussed. Balancing in 3- level converters can be achieved by proper control. Balancing in 5-level converters can be achieved by proper arrangement of isolated DC-supplies.

One 40kW 3-level converter and one 5kW 5-level converter has been designed and built. Experimental verification of the analytical and simulated results is shown.

Thesis (MScEng)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: This thesis presents the design and implementation of shunt active power filtering algorithms for unbalanced, non-linear loads. A three-phase four-wire topology is developed in the dqO space. Based on this development an accurate dynamic system model, taking into account the effect of the neutral inductor is developed. The synchronous reference frame technique is expanded to enable the isolation of the zero sequence current component into its instantaneous active and reactive current components. Additionally a prediction method is proposed that will enable the proper prediction of the reference currents in a threephase four-wire system. Two categories of reference current signal tracking algorithms are investigated; namely the predictive current controller and the sliding mode current controller. A compensating technique is proposed to compensate for the effects that sampling and computational time delay have on the performance of the system. Additionally, an investigation is done into the effect that dead-time has on the performance of the system, and based on this investigation a dead-time compensating strategy is proposed. Finally simulation and practical results are provided to validate the discussed theories.
AFRIKAANSE OPSOMMING: Hierdie verhandeling ondersoek die ontwerp en implementering van parralel gekoppelde aktiewe filter algoritmes vir ongebalenseerde, nie-lineêre laste. 'n Drie-fase vier-draad topologie, asook 'n korrekte model van die dinamiese sisteem, wat die effek van die neutraal induktor insluit, is ontwikkel in die dqO ruimte. Die sinchroon verwysing vlak tegniek is uitgebrei om die isolering van die nul sekwensie stroom in onderskeidelik die oombliklike aktiewe en reaktiewe stroom komponente te verdeel. Addisioneel is a vooruitskatting tegniek aanbeveel wat die beheerder in staat sal stelom voldoende die verwysing strome vooruit te skat in 'n drie-fase vier-draad stelsel. Twee katagoriee van verwysing stroom volging algoritmes is ondersoek, naamlik die afskatting stroom beheerder en die gleiende modus stroom beheerder. 'n Effektiewe kompensasie tegniek is voorgestel om die effek van tydvertraging as gevolg van monstering en verwerking te elimineer. Addisioneel is die effek van dooie-tyd ondersoek en gebasseer op hierdie ondersoek is 'n effektiewe dooie-tyd kompensasie tegniek voorgestel. Laastens is simulasies en praktiese resultate verskaf om die werking van die voorgestelde teorie te bevestig.

Thesis (MScIng)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: Electricity theft in South Africa has become a major problem. This led to several developments from both industries and research institutes to counter these actions. Since equipment is already installed and major capital has been invested to provide electricity for a broad spectrum of consumers, the challenge is to find a low cost solution harnessing current investments and technology to detect electricity theft more accurately. This thesis investigates into the electricity theft topic. Two different methods, Time Domain Pulse Reflectometry and a data driven platform based on the Theory of Constraints philosophy, were investigated to provide means to detect and determine the impact of illegal electricity usage. Both methods required detailed designs to conduct preliminary proof of concept tests in a laboratory environment. These methods are evaluated against their economical viability, possible practical implications and applications. This thesis presents a practical approach to electricity theft detection and provides the basic tools for management of this ever-increasing problem.
AFRIKAANSE OPSOMMING: Suid Afrika se elektrisiteit diefstal statistiek het die afgelope jare skrikwekkend gegroei. Dit het die industrie genoop om baie meer navorsing in die area te doen. Met reeds gevestigde toerusting en tegnologie om di´e energie medium so effektief moontlik te versprei, is die uitdaging juis om ’n ekonomiese oplossing te vind om reeds beskikbare tegnologie¨e meer doeltreffend aan te wend. Die doel van die tesis is om die gebied van elektrisiteit diefstal na te vors. Twee verskillende metodes is ondersoek, naamlik Tydgebied-pulse-reflektometrie en ’n informasie gebaseerde stelsel wat op die Randvoorwaarde Teorie gebaseer is, om effektief die omvang van elektrisiteit diefstal in ’n mikro, asook makro omgewing te bepaal. Die twee metodes is in ’n beheerde omgewing getoets sodat die konsepte wat ontwikkel is bewys kon word. Die metodes is ge-evalueer in terme van die ekonomiese lewensvatbaarheid daarvan met inagneming van die praktiese implikasies. Die tesis bied bestuur die nodige kennis om elektrisiteit diefstal in die praktyk doeltreffend die hok mee te slaan.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2009.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 18, 2009) Includes bibliographical references.

The trend towards development of More Electric Aircraft (MEA) has been driven by increased fuel fossil prices and stricter environmental policies. This is supported by breakthroughs in power electronic systems and electrical machines. The application of MEA is expected to reduce the aircraft mass and drag, thereby increasing fuel efficiency and reduced environmental impact. The starter-generator (S/G) scheme is one of the solutions from the MEA concept that brings the most significant improvement to the electrical power generation system. A S/G system is proposed from the possible solutions brought by the MEA concept in the area of electrical power generation and distribution. Due to the wide operating speed range, limited controller stability may be present. This thesis contributes to the control plant analysis and controller design of this MEA S/G system. The general control requirements are outlined based on the S/G system operation and the control structure is presented. The control plants are derived specifically to design the controllers for the S/G control scheme. Detailed small signal analysis is performed on the derived plant while taking into consideration the aircraft operating speed and load range. A safe range for the controller gains can then be determined to ensure stable operation throughout the S/G operation. Adaptive gain and a novel current limit modifier are proposed which improves the controller stability during S/G operation. Model predictive control is considered as an alternative control strategy for potential control performance improvements with the S/G system. The technical results and simulations are supported by Matlab®/Simulink® based models and validated by experimental work on a small scaled drive system.

The aerospace industry is currently looking at options for fulfilling the technological development targets set for the next aircraft generations. Conventional engines and aircraft architectures are now at a maturity level which makes the realisation of these targets extremely problematic. Radical solutions seem to be necessary and Electric Distributed Propulsion is the most promising concept for future aviation. Several studies showed that the viability of this novel concept depends on the implementation of a superconducting power network. The particularities of a superconducting power network are described in this study where novel components and new design conditions of these networks are highlighted. Simulink models to estimate the weight of fully superconducting machines have been developed in this research work producing a relatively conservative prediction model compared to the NASA figures which are the only reference available in the literature. A conceptual aircraft design architecture implementing a superconducting secondary electrical power system is also proposed. Depending on the size of the aircraft, and hence the electric load demand, the proposed superconducting architecture proved to be up to three times lighter than the current more electric configurations. The selection of such a configuration will also align with the general tendency towards a superconducting network for the proposed electric distributed propulsion concept. In addition, the hybrid nature of these configurations has also been explored and the potential enhanced role of energy storage mechanisms has been further investigated leading to almost weight neutral but far more flexible aircraft solutions. For the forecast timeframe battery technology seems the only viable choice in terms of energy storage options. The anticipated weight of the Lithium sulphur technology is the most promising for the proposed architectures and for the timeframe under investigation. The whole study is based on products and technologies which are expected to be available on the 2035 timeframe. However, future radical changes in energy storage technologies may be possible but the approach used in this study can be readily adapted to meet such changes.

The trend towards more and all-electric apparatuses and more electrification will lead to higher electrical demand. Increases in electrical power demand can be provided by either higher currents or higher voltages. Due to "weight" and "voltage" drop, a raise in the current is not preferred; so, "higher voltages" are being considered. Another trend is to reduce the size and weight of apparatuses. Combined, these two trends result in the high voltage, high power density concept. It is expected that by 2030, 80% of all electric power will flow through "power electronics systems". In regards to the high voltage, high power density concept described above, "wide bandgap (WBG) power modules" made from materials such as "SiC and GaN (and, soon, Ga2O3 and diamond)", which can endure "higher voltages" and "currents" rather than "Si-based modules", are considered to be the most promising solution to reducing the size and weight of "power conversion systems". In addition to the trend towards higher "blocking voltage", volume reduction has been targeted for WBG devices. The blocking voltage is the breakdown voltage capability of the device, and volume reduction translates into power density increase. This leads to extremely high electric field stress, E, of extremely nonuniform type within the module, leading to a higher possibility of "partial discharge (PD)" and, in turn, insulation degradation and, eventually, breakdown of the module. Unless the discussed high E issue is satisfactorily addressed and solved, realizing next-generation high power density WBG power modules that can properly operate will not be possible. Contributions and innovations of this Ph.D. work are as follows. i) Novel electric field grading techniques including (a) various geometrical techniques, (b) applying "nonlinear field-dependent conductivity (FDC) materials" to high E regions, and (c) combination of (a) and (b), are developed; ii) A criterion for the electric stress intensity based upon accurate dimensions of a power device package and its "PD measurement" is presented; iii) Guidelines for the electrical insulation design of next-generation high voltage (up to 30 kV), high power density "WBG power modules" as both the "one-minute insulation" and PD tests according to the standard IEC 61287-1 are introduced; iv) Influence of temperature up to 250°C and frequency up to 1 MHz on E distribution and electric field grading methods mentioned in i) is studied; and v) A coupled thermal and electrical (electrothermal) model is developed to obtain thermal distribution within the module precisely. All models and simulations are developed and carried out in COMSOL Multiphysics.
Doctor of Philosophy
In power engineering, power conversion term means converting electric energy from one form to another such as converting between AC and DC, changing the magnitude or frequency of AC or DC voltage or current, or some combination of these. The main components of a power electronic conversion system are power semiconductor devices acted as switches. A power module provides the physical containment and package for several power semiconductor devices. There is a trend towards the manufacturing of electrification apparatuses with higher power density, which means handling higher power per unit volume, leading to less weight and size of apparatuses for a given power. This is the case for power modules as well. Conventional "silicon (Si)-based semiconductor technology" cannot handle the power levels and switching frequencies required by "next-generation" utility applications. In this regard, "wide bandgap (WBG) semiconductor materials", such as "silicon carbide (SiC)"," gallium nitride (GaN)", and, soon, "gallium oxide" and "diamond" are capable of higher switching frequencies and higher voltages, while providing for lower switching losses, better thermal conductivities, and the ability to withstand higher operating temperatures. Regarding the high power density concept mentioned above, the challenge here, now and in the future, is to design compact WBG-based modules. To this end, the extremely nonuniform high electric field stress within the power module caused by the aforementioned trend and emerging WBG semiconductor switches should be graded and mitigated to prevent partial discharges that can eventually lead to breakdown of the module. In this Ph.D. work, new electric field grading methods including various geometrical techniques combined with applying nonlinear field-dependent conductivity (FDC) materials to high field regions are introduced and developed through simulation results obtained from the models developed in this thesis.

Thesis (M.S. in Operations Research)--Naval Postgraduate School, March 2004.
Thesis advisor(s): Javier Salmeron, R. Kevin Wood. Includes bibliographical references (p. 69-70). Also available online.

Electric quality is a common concept for a energy delivery without interference. In time with he development of the technology which produce more complex devices connected to the lectric mains increase the demands on a electric delivery without interference. The purpose ith this report was to investigate the electric quality to chosen places at the combined power nd heating plant of E.ON in Händelö. The degree thesis is performed at the company ES lektroSandberg which have their manning/crew at Händelö. From the analyse it was suppose o show the result and give proposal to any problem that may arise. The last 10-15 years it’s been a great focus on harmonics and its influence on the electric ains. It’s easy to make the conclusion that harmonics are a great problem in our electric ains but it isn’t always like that. Certainly a net which shows a lot of harmonics can be a roblem but the greatest problem in the electric mains is the variation of voltage. That’s the eason why this report doesn’t only limits to harmonics but also includes other factors in elation to electric quality. The measurements are performed with a power quality analyser C.A 8334, from the company A Mätsystem AB. The duration for the measurements are 24 hours. When the measurements ere done, the data transfers to the PC where it can be analysed. he report begins with a general theory to give such a good platform as possible for the nalysis and the conclusion. After the theory the companies are presented. This follows by an ccount of the results that power quality analyser received. The report ends with a conclusion nd a discussion about the result. The conclusion treats interesting problems where it’s essential to inspect more in the process. hrough the result it can be concluded that the level of harmonics are pretty low in the plants. t result shows that the levels of harmonics are greatest at the converters which should not e such a surprise. In the transient analysis you will find several big transients which could ead to damages on equipments if they are not designed for big transients. The discussion does lso presents some proposals to carry through in future on the plants of Händelö.
Elkvalite är ett samlingsnamn för störningsfri energileverans. I takt med att eknikutvecklingen producerar mer komplexa apparater anslutna till elnätet så ökar kraven på törningsfri elleverans. Syftet med rapporten var att sätta sig in i begreppet elkvalite för att edan undersöka elkvaliten på utvalda platser vid E.ONs kraftvärmeverk på Händelö. xamensarbetet är utfört hos företaget ES ElektroSandberg som har bemanning på Händelö. tifrån analysen var det meningen att resultat skulle redovisas samt att eventuella tgärdsförslag ges. De senaste 10-15 åren har det fokuserats mycket på övertoner och dess inverkan på elnätet när an talar om elkvalite. Det är då lätt att dra slutsatsen att övertoner skulle vara ett stort roblem i våra elnät men så är inte fallet. Visserligen kan ett nät som uppvisar större mängder ara ett problem men det största problemen i elnäten är de spänningsvariationer som erhålls. ärför har det i rapporten inte bara fokuserats på övertoner utan på fler störningsmoment som ehandlar elkvalite. Mätningar har utförts med en inlånad nätanalysator C.A 8334, från företaget CA Mätsystem B. Mätningarna har skett under ett dygn där data sedan överförts till en dator för att sedan unna analyseras. Rapporten inleder med övergripande teori för att ge en så bra plattform som möjligt för nalysen och slutsatsen. Efter teorin presenteras företagen. Detta följs av en redovisning av de resultat som nätanalysatorn erhöll. Slutligen avslutas rapporten med en slutsats och diskussion ring resultatet. Slutsatsen behandlar vissa problematiseringar där det är nödvändigt att granska mer rocessmässigt. Generellt är det inga större övertonsnivåer i de ställverk där mätningar har tförts. Övertonsnivån är störst vid frekvensomriktarna vilket inte var någon överraskning. I ransientanalysen påträffas flera stora transienter som kan medföra skador på utrustningar om e inte är dimensionerade för stora transienter. I diskussionen presenteras också förslag till framtidaarbeten inom anläggningen.

Disturbances in the services provided by the infrastructuresystems—e.g. electric power supplies and communications—can have serious implications for everyday life,economic prosperity and national security. The disturbances canbe initiated by natural disasters, adverse weather, technicalfailures, human errors, sabotage, terrorism or acts of war. Theaim of this thesis is to study methods for proactivevulnerability analysis of electric power delivery networks(i.e. to analyze their sensitivity to threats and hazards), andto formalize vulnerability as a theoretical concept.

The thesis consists of three papers. In the first paper, wediscuss concepts and perspectives for developing a methodologyfor vulnerability studies with the help of the followingthemes: The properties of the infrastructure systems, threatsand hazards, vulnerability and consequence analysis, andmeasures for creating robust and resilient systems.

In the second paper we discuss how to assess vulnerabilityof power delivery systems with the help of standard powersystem performance indices. In two case studies, Swedish powerdelivery disturbance data is analyzed with statistical methods.We demonstrate that the disturbance size of large disturbancesfollows a power law distribution, and that the time betweendisturbances is exponentially distributed.

In third paper, we model electrical power networks asgraphs, and conduct empirical studies of two power transmissiongrids. We calculate values of topological characteristics ofthe networks and compare their error and attack tolerance, i.e.their performance when vertices are disabled, with twofrequently used model networks. Further, we perform a graphinfluenced vulnerability analysis of a fictitious powernetwork, and evaluate di.erent strategies to decrease thevulnerability of the system.

Direct electrical heating (DEH) of pipelines is a flow assurance method that has proven to be a good and reliable solution for preventing the formation of hydrates and wax in multiphase flow lines. The technology is installed on several pipelines in the North Sea and has become StatoilHydros preferred method for flow assurance. Tyrihans is the newest installation with 10 MW DEH for a 43 km pipline. However, the pipeline represents a considerable single-phase load which makes the power system dependent on a balancing unit for providing symmetrical conditions. This limits the step out distance and is not suitable for subsea installation. Aker Solutions has proposed several specially connected transformers for subsea power supply of DEH systems, Scott-T being one of them. The Scott-T transformer is a three-to-two-phase transformer which provides balanced electrical power between the two systems when the two secondary one-phase loads are equal. By implementing this transformer, it can be possible to install the power supply subsea as there is no need for a balancing unit. In addition, the system may be applicable for long step out distances. This is because the pipeline is inductive and can use the reactive power produced by the long cable which also can increase the critical cable length. There are however some limitations on this system using the Scott-T transformer. There is a large variation in the magnetic permeability between individual joints of the pipeline. This can result in different load impedance of the two pipe sections connected to the Scott-T transformer. The result is unbalance in the power system. The method of symmetrical components is applied to investigate the behavior during unbalanced loading of the Scott-transformer. The relationship between the negative- and the positive sequence component of the current is used to express the degree of unsymmetry. For the simulations in SIMPOW, the Scott-T transformer is modelled by the use of Dynamic Simulation Language. The simulations on the DSL model give correct and reliable results for analysing the the degree of unsymmetry in the Scott-T transformer. When the load impedance of one pipe section is varied, simulation proves that it can change between 0.75 and 1.34 per unit of the other pipe impedance. The Scott-T transformer does still provide electrical power between the two systems which is below the limit for the degree of unsymmetry (15%). Case 1 and Case 2 introduce two possible configurations for a subsea DEH system with the Scott-T transformer implemented. The configurations include an onshore power supply which is connected to a subsea power system for direct electrical heating and a subsea load at the far end of the subsea cable. The pipeline in Case 1 is 100 km long and is divided into two pipe sections of 50 km which are connected to a Scott-T transformer. The pipeline in Case 2 is 200 km long and is divided into four pipe sections of 50 km each. There are two Scott-T transformers in Case 2. For normal operation of the subsea load (50 MW, cosfi=0.9) and heating the pipe content from the ambient sea emperature, the results indicate that tap changers are necessary to keep the Scott-T transformers secondary terminal voltage at 25 kV. This meets the requirement in both cases for heating the pipe content from 4 to 25 degrees celsius within 48 hours after a shutdown of the process. The degree of unsymmetry is zero for both cases when the system is operated as normal. However, all system simulations indicate that reactive power compensation has to be included for Case 1 as well as for Case 2 in order to have a power factor of unity at the onshore grid connection. The fault scenarios indicate that the degree of unsymmetry is dependent on both the type of fault and the power supply in the system. For Case 1, the relationship (I-/I+) is only of 3.3% in the subsea cable when there is a short-circuit at DEHBUS3, but as much as 87% at the grid connection. The degree of unsymmetry in the Scott-T transformer is then 67%. This is far beyond the limit for maximum negative sequence component of 15%. The significant unsymmetry in the line between the grid and BUS1 is most likely due to the large power delivered to the fault. During the fault, the reactive power delivered to the system increases from 10.6 Mvar to 131.9 Mvar after the fault, but the active power increases only from 75.2 MW to 87.1 MW. This means that it is most likely the reactive power that contributes to the consequent unsymmetry and negative sequence component of the current. There are two Scott-T transformers installed in Case 2. If the DEH system is only heating the pipe section closest to shore (at DEHBUS33), simulations show that the three-phase power system becomes unsymmetric which results in different phase currents. The degree of unsymmetry at the grid connection is 32% when only the pipe section at DEHBUS33 is heated. In addition, the unbalance in the three-phase system caused by SCOTT1 involves unbalance in the SCOTT2 transformer as well. The load voltages are not equal in magnitude and dephased of 90 degrees for this mode, but are 32 kV and 35 kV respectively and dephased of 88 degrees. This concludes a very important behavior of the Scott-T transformer. The simulations conclude that the Scott-T transformer provides symmetrical conditions for both configurations when the two load impedances are equal. However, Case 2 shows an important result when installing two Scott-T transformers in the same system. Unbalanced loading of one of the specially connected transformers gives unsymmetrical conditions in the three-phase system which results in unbalanced load voltages for the other Scott-T transformer. The analysis is limited to the configurations given for Case 1 and Case 2, but shows typical results when an alternative transformer connection is implemented in a DEH system.

Disturbances in the supply of electric power can have serious implications for everyday life as well as for national (homeland) security. A power outage can be initiated by natural disasters, adverse weather, technical failures, human errors, sabotage, terrorism, and acts of war. The vulnerability of a system is described as a sensitivity to threats and hazards, and is measured by P (Q(t) > q), i.e. the probability of at least one disturbance with negative societal consequences Q larger than some critical value q, during a given period of time (0,t]. The aim of the thesis is to present methods for quantitative vulnerability analysis of electric power delivery networks to enable effective strategies for prevention, mitigation, response, and recovery to be developed. Paper I provides a framework for vulnerability assessment of infrastructure systems. The paper discusses concepts and perspectives for developing a methodology for vulnerability analysis, and gives examples related to power systems. Paper II analyzes the vulnerability of power delivery systems by means of statistical analysis of Swedish disturbance data. It is demonstrated that the size of large disturbances follows a power law, and that the occurrence of disturbances can be modeled as a Poisson process. Paper III models electric power delivery systems as graphs. Statistical measures for characterizing the structure of two empirical transmission systems are calculated, and a structural vulnerability analysis is performed, i.e. a study of the connectivity of the graph when vertices and edges are disabled. Paper IV discusses the origin of power laws in complex systems in terms of their structure and the dynamics of disturbance propagation. A branching process is used to model the structure of a power distribution system, and it is shown that the disturbance size in this analytical network model follows a power law. Paper V shows how the interaction between an antagonist and the defender of a power system can be modeled as a game. A numerical example is presented, and it is studied if there exists a dominant defense strategy, and if there is an optimal allocation of resources between protection of components, and recovery.
QC 20100831

In electric power distribution systems, the major determinant in electricity supply strategy is the quantity of demand. Customers need to be accurately represented using updated nodal load information as a requirement for efficient control and operation of the distribution network. In Distribution Load Estimation (DLE), two major categories of data are utilized: historical data and direct real-time measured data. In this thesis, a comprehensive survey on the state-of-the-art methods for estimating loads in distribution networks is presented. Then, a novel method for representing historical data in the form of Representative Load Curves (RLCs) for use in real-time DLE is also described. Adaptive Neuro-Fuzzy Inference Systems (ANFIS) is used in this regard to determine RLCs. An RLC is a curve that represents the behavior of the load during a specified time span; typically daily, weekly or monthly based on historical data. Although RLCs provide insight about the variation of load, it is not accurate enough for estimating real-time load. This therefore, should be used along with real-time measurements to estimate the load more accurately. It is notable that more accurate RLCs lead to better real-time load estimation in distribution networks. This thesis addresses the need to obtain accurate RLCs to assist in the decision-making process pertaining to Radial Distribution Networks (RDNs).This thesis proposes a method based on Adaptive Neuro-Fuzzy Inference Systems (ANFIS) architecture to estimate the RLCs for Distribution Networks. The performance of the method is demonstrated and simulated, on a test 11kV Radial Distribution Network using the MATLAB software. The Mean Absolute Percent Error (MAPE) criterion is used to justify the accuracy of the RLCs.
M.S.E.E.
Masters
Electrical Engineering and Computing
Engineering and Computer Science
Electrical Engineering

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Muitas das atuais técnicas de simulação de redes elétricas de potência são baseadas em plataformas computacionais do tipo EMTP. Basicamente, este método de simulação transforma os componentes elétricos a parâmetros concentrados e a topologia da rede em um procedimento matemático recursivo. Para cada nova iteração, a solução da rede é estimada como uma função de estados prévios e valores de entrada atuais. Passos de integração pequenos geram soluções precisas por estender a banda de freqüências representada. No entanto, isto também aumenta a carga computacional limitando o tamanho da rede, a faixa de freqüência ou afetando o tempo de resposta do processo. Esta situação conflitante tem sido atacada por vários pesquisadores, muitos procurando formas alternativas de aumentar o passo de integração. Este trabalho introduz um novo método para simulação de redes elétricas lineares. Mesmo baseando nas técnicas utilizadas no EMTP, o método leva a um conjunto diferente de equações convenientes para conjugar com técnicas de filtragem digital multitaxa. O resultado final é a decomposição de sinais e da rede em sub-bandas de freqüências. Cada uma das simulações em sub-bandas da rede elétrica é feita com um passo de integração máximo, sempre representando carga computacional mínima. Além disso, o procedimento permite uma estimativa on-line se uma saída de sub-banda tem contribuição irrelevante ao resultado final da simulação, suspendendo o correspondente módulo de operação e, consequentemente, reduzindo a carga computacional. Como resultado, tem-se um simulador capaz de adaptar a complexidade do modelo de acordo com os dados da simulação.Modelos de linhas de transmissão a parâmetros distribuídos são introduzidos, conectados ao modelo da rede a parâmetros concentrados. Um método de computação específica é desenvolvido para uma operação global do sistema.Casos ilustrativos são incluídos mostrando a eficiência do simulador proposto em comparação com técnicas tradicionais.
Most of present day electric power network simulation techniques are based on computational platforms of the EMTP type. Basically, following this approach, the simulation method transforms the electric lumped components and the network topology into a recursive mathematical procedure. For each new integration step the network solution is evaluated as a function of previous state and present input values. Small integration steps increase solution accuracy, by extending the frequency band. However, this also increases computational requirements, limiting network size, frequency bandwidth or affecting the procedure response time. This conflicting situation hes been attacked by many researchers, mostly looking for different forms of increasing the integration step.This work introduces a new approach to linear electric network simulation. Although closely following the EMTP basic techniques, the method leads to a different set of equations, more convenient to conjugate with multirate digital filtering techniques. The final result is the decomposition of signal and network models into subbands of frequencies. Each of the network subband simulations is performed with maximum integration time step, always representing minimum computational burden. Moreover, the procedure allows to on-line estimate if a particular subband model output has negligible contribution to the final simulation result. While this situation remains, the corresponding module operation is suspended, reducing the computational load. As a result, the simulator is able to adapt its model complexity, on line, according to the simulation requirements. Distributed transmission line models are introduced, connected to the lumped network parameter models. A specific computational procedure is shown to operate the overall system.Illustrative cases are included, supporting the simulator proposed efficiency when compared to conventional procedures.

Thesis: Ph. D., Massachusetts Institute of Technology, Engineering Systems Division, 2015.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 235-240).
Scarce pipeline capacity in regions that rely on natural gas technologies for electricity generation has created volatile prices and reliability concerns. Gas-fired generation firms uniquely operate as large consumers in the gas market and large producers in the electricity market. To explore the effects of this coupling, this dissertation investigates decisions for firms that own gas-fired power plants by proposing a mixed-integer linear programming model that explicitly represents multi-year pipeline capacity commit- ments and service agreements, annual forward capacity offers, annual maintenance schedules, and daily fuel purchases and electricity generation. This dissertation's primary contributions consist of a detailed representation of a gas-fired power-plant owner's planning problem; a hierarchical application of a state-based dimensionality reduction technique to solve the hourly unit commitment problem over different tem- poral scales; a technique to evaluate a firm's forward capacity market offer, including a probabilistic approach to evaluate the risk of forced outages; a case study of New England's gas-electricity system; and an exploration of the applicability of forward capacity markets to reliability problems for other basic goods.
by Tommy Leung.
Ph. D.

Thesis (DTech (Engineering))--Cape Peninsula University of Technology, 2017.
The world has been experiencing energy-related problems following pressuring energy demands which go along with the global economy growth. These problems can be phrased in three paradoxical statements: Firstly, in spite of a massive and costless solar energy, global unprecedented energy crisis has prevailed, resulting in skyrocketing costs. Secondly, though the sun releases a clean energy, yet conventional plants are mainly being run on unclean energy sources despite their part in the climate changes and global warming. Thirdly, while a negligible percentage of the solar energy is used for power generation purposes, it is not optimally exploited since more than its half is wasted in the form of heat which contributes to lowering efficiency of solar cells and causes their premature degradation and anticipated ageing. The research is geared at addressing the issue related to unsatisfactory efficiencies and anticipated ageing of solar modules. The methodology adopted to achieve the research aim consisted of a literature survey which in turn inspired the devising of a high-efficiency novel thermal electric solar power panel. Through an in-depth overview, the literature survey outlined the rationale of the research interest, factors affecting the performance of PVs as well as existing strategies towards addressing spotted shortcomings. While photovoltaic (PV) panels could be identified as the most reliable platform for sunlight-to-electricity conversion, they exhibit a shortcoming in terms of following the sun so as to maximize exposure to sunlight which negatively affects PVs’ efficiencies in one hand. On the other hand, the inability of solar cells to reflect the unusable heat energy present in the sunlight poses as a lifespan threat. Strategies and techniques in place to track the sun and keep PVs in nominal operational temperatures were therefore reviewed.

1. National accounting standard 16 “Costs”. URL: https://zakon.rada.gov.ua; 2. Rymar T.M. Cost management strategy of energy companies in the process of technical re-equipment. Bulletin of the National University “Lviv Polytechnic”. Problems of economics and management. № 484. 2003. P. 361 – 366; 3. Azhnakin S.H. The problems of energy saving and energy efficiency of electric power companies’ operations. Economic innovations. № 55. 2013. P.9 – 22; 4. Germany’s onshore wind expansion continues to struggle. URL: https://www.euractiv.com; 5. Fomina O.V. Managerial accounting principles. Current economic problems. № 9. 2015. P. 392 – 397; 6. “Energy saving”: Ukrainian Law of the 1 st of July 1994 № 30. URL: https://zakon.rada.gov; 7. The share of “green” energy in Ukraine has doubled in a year - the Ministry of Energy. URL: https://www.ukrinform.ua.
This article evolves the problem of complexity of Ukrainian electricity field in terms of the electric power companies’ cost managing. The aspect of costs for environmental protection is pointed out. The importance of the managerial accounting principles in a costs management process is mentioned.
Дана стаття розкриває проблему уураїнської електроенергетики в умовах управління витратами підприємства. Висвітлено аспект витрат на охорону навколишнього середовища. Розкрито питання важливості принципів управлінського обліку у процесі управління витрат.

Decreasing gas prices and the pressing need for fast-responding electric power generators are currently transforming natural gas networks. The intermittent operation of gas-fired plants to balance wind generation introduces spatiotemporal fluctuations of increasing gas demand. At the heart of modeling, monitoring, and control of gas networks is a set of nonlinear equations relating nodal gas injections and pressures to flows over pipelines. Given gas demands at all points of the network, the gas flow task aims at finding the rest of the physical quantities. For a tree network, the problem enjoys a closed-form solution; yet solving the equations for practical meshed networks is non-trivial. This problem is posed here as a feasibility problem involving quadratic equalities and inequalities, and is further relaxed to a convex semidefinite program (SDP) minimization. Drawing parallels to the power flow problem, the relaxation is shown to be exact if the cost function is judiciously designed using a representative set of network states. Numerical tests on a Belgian gas network corroborate the superiority of the novel method in recovering the actual gas network state over a Newton-Raphson solver. This thesis also considers the coupled infrastructures of natural gas and electric power systems. The gas and electric networks are coupled through gas-fired generators, which serve as shoulder and peaking plants for the electric power system. The optimal dispatch of coupled natural gas and electric power systems is posed as a relaxed convex minimization problem, which is solved using the feasible point pursuit (FPP) algorithm. For a decentralized solution, the alternating direction method of multipliers (ADMM) is used in collaboration with the FPP. Numerical experiments conducted on a Belgian gas network connected to the IEEE 14 bus benchmark system corroborate significant enhancements on computational efficiency compared with the centralized FPP-based approach.
Master of Science