Voltage stability is a major concern when planning and operating electrical power systems.As demand for electric power increases, power systems are stressed more and more. TheFACTS family of components were introduced to utilize the existing grid to a higherdegree, while still maintaining system stability.This thesis investigates if the addition of another SVC to the Swedish national gridcould increase the power transfer from north to south. Placement of the SVC was basedon two different indices used to indicate weak areas of the grid; the Q-V sensitivity indexand the V CPI index.Simulations were performed with both the added SVC and regular switched shuntcompensation and the results were compared against each other. Studies were alsoperformed to investigate the effect of an SVC installed at the grid connection of a large(1000 MW) wind farm. Simulations were performed where the wind farm was modeledby either doubly fed induction generators (DFIG) or single cage induction generators.This simulation study was performed using PSSTME, based on a detailed model ofthe Nordic power system as it existed in 2007.The studies showed that adding a ±200 MVAr SVC to the Swedish national gridcould increase the power transfer by 150 MW, where an equally rated switched shuntcapacitor/reactor would result in a 100 MW increase. In these studies, the transfercapacity was limited by voltage collapse situations.However, installing the same ±200 MVAr SVC at the connection of a large windfarm showed an increase in power transfer by 1000 MW, while the switched shuntcompensation only resulted in a 500 MW increase. In the simulations that showed thegreatest increase in transfer capacity, the added wind farm was modeled by single-cageinduction generators. In this case the transfer capacity was limited by transient stabilityproblems.

När tekniken utvecklas ställs krav på tillverkande företag för att behålla eller överta marknadsandelar, inte minst genom att vara kostnadseffektiva. För att med små förluster tillverka avancerade produkter i ett högteknologiskt klimat krävs att produktionssystemet är anpassat till de produkter som produceras genom ett ständigt förbättringsarbete. För att uppnå effektiv produktion måste företag eliminera begränsningar inom produktionssystemet ofta benämnda som flaskhalsar. Ett sätt att identifiera flaskhalsar är genom händelsestyrd simulering som tillsammans med flermålsoptimering är fördelaktiga verktyg för att bepröva systemen utan att fysiskt genomföra förändringar. Syftet med denna fallstudie är att genom en simuleringsstudie undersöka vilka förbättringar som bör implementeras på en monteringslina som leder till ett högre produktionstakt genom mindre balanseringsförluster och en högre utnyttjandegrad. Genom en tidsstudie insamlades data som vidare användes för att kartlägga monteringslinan i en nulägesanalys. Insamlade data utgjorde grunden för att skapa en simuleringsmodell som en virtuell avbild av produktionssystemet. Genom händelsestyrd simulering analyserades flaskhalsar i modellen med hjälp av flermålsoptimering som ett verktyg för att föreslå de mest lönsamma och genomförbara förändringarna. Sex olika experiment utformades för att undersöka hur stor påverkan olika processparametrar har i varierande produktionskoncept. Experimenten visade att takten till stor del begränsar produktionssystemet. Genom att endast sänka takten kunde produktionstakten öka med över 25 %. Vidare visade experimenten att fokus på reducering av processtid hos tre stationer tillsammans med kortare takt kunde öka produktionstakten med över 30 % från nuvarande prestanda. / As technology evolves, manufacturing companies are pushed with greater and greater requirements to maintain or gain market shares, not least through being cost-efficient. To manufacture advanced products whilst minimizing waste in a high-technology climate, production systems are required to be adapted for their respective products and a continuous work of improvement is highly necessary. To achieve efficient manufacturing, producers reach to minimize constraints in the production system. One way to identify bottlenecks is through discrete-event simulation, which in combination with multi-objective optimization is a powerful tool for testing and improving a system without any physical interaction with the production equipment. The purpose of this thesis is to, through a simulation study, analyze possible improvements of an advanced assembly line to increase utilization and minimize balancing losses. Data was collected through a time study and was later used to map the process and build a model of the production system to be used for simulation. Further, the model’s constraints were analyzed through discrete-event simulation and multiple-objective optimization to find profitable and manageable alternatives for improvement. Six experiments were conducted to investigate the effects of different changes in process parameters in varying production system concepts. The experiments indicated that the takt time was a significant limitation of the system. The sole reduction of takt time resulted in a theoretical improvement of throughput equivalent to over 25%. A further focused reduction of three process times could lead to a total of 30% increase.

In recent years, both a significant increase in electrical demand and a large influx of intermittent renewable energy sources have put a considerable stress on the nation’s electrical grid. Conventional power flow control techniques such as capacitor banks and tap-changing transformers are incapable of adequately handling the rapid fluctuations in power supply and demand that today’s grid experiences. Flexible AC Transmission System (FACTS) controllers are a practical way to compensate for such rapid power fluctuations. One type of shunt FACTS controller is the Static Synchronous Compensator (STATCOM), which uses fully controllable switches to source or sink reactive power to a point on the grid, thus reducing voltage fluctuations due to load changes. The purpose of this thesis is to model and simulate the operation of two Distribution STATCOMs (D-STATCOMs) operating on the same point on the grid. These D-STATCOMs also utilize parallel full-wave rectifiers that directly connect the ac grid to the dc capacitor of the D-STATCOMs. Parameters such as power loss, reaction time, stability, and THD are measured for several test scenarios. Results from this thesis show that two D-STATCOMs operating on the same point can be stable and effective under a wide range of conditions. This thesis also concludes that the inclusion of parallel rectifiers with the D-STATCOMs results in no performance improvement of the D-STATCOMs.

The purpose of this thesis is to explore the importance of Smart Grid and to conduct a full feasibility analysis of its implementation in Bangladesh. A smart grid is an electric power system that improves grid accuracy and effectiveness by reacting to systemic disruptions proactively. For a developing country like Bangladesh, it is important for both increased electricity generation and to prevent power outage. A basic necessity for individuals and economies is the efficient transmission and distribution of electricity alongside vital energy supplies. The thesis examines and describes the features and economic topology of Smart Grid, as well as potential solutions to Bangladesh's power issue. It also covers the sustainable transmission and distribution of electricity, as well as the integration of communication and smart monitoring technologies of smart grid.

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This dissertation presents the analysis and development of an innovative semiconductor device and topology for the high power current source converter (CSC). The CSC is very attractive in high power applications due to its lower output dv/dt, easy regeneration capability and implicit short-circuit protection. Traditionally, either a symmetrical gate turn-off (GTO) thyritor or an asymmetrical GTO in series with a diode is used as the power switch in the CSC. Since the GTO has a lower switching speed and requires a complicated gate driver, the symmetrical GTO based CSC usually has low dynamic response speed and low efficiency. To achieve high power rating, fast dynamic response speed and low harmonics, an advanced semiconductor device and topology are needed for the CSC. Based on symmetrical GTO and power MOSFET technologies, a symmetrical emitter turn-off (ETO) thyristor is developed that shows superior switching performance, high power rating and reverse voltage blocking capability. The on-state characteristics, forced turn-on characteristics, forced turn-off characteristics and the load-commutated characteristics are studied. Test results show that although the load-commutation loss is high, the developed symmetrical ETO is suitable for use in high power CSC due to its low conduction loss, fast switching speed and reverse voltage blocking capability. The snubberless turn-on capability is preferred for a semiconductor device in a power conversion system, and can be achieved for devices with forward biased safe operation area (FBSOA). The FBSOA of the ETO is investigated and experimentally demonstrated. The ETO device has excellent FBSOA due to the negative feedback provided by the emitter switch. However, the FBSOA for a large area ETO is poor. A new ETO concept is therefore proposed for future development in order to demonstrate the FBSOA over a large area device. To improve the turn-on performance of the large area ETO, a novel concept, named the transistor-mode turn-on, is proposed and studied. During the transistor-mode turn-on process, the ETO behaves like a transistor instead of a thyristor. Without a snubber, the transistor-mode turn-on for the ETO is hard to achieve. Through the selection of a proper gate drive and di/dt snubber, the transistor-mode turn-on can be implemented, and the turn-on performance for the ETO can be dramatically improved. To increase the power rating of the CSC without degrading the utilization of power semiconductor devices, a novel multilevel CSC, named the parallel-cell multilevel CSC, is proposed. Based on a six-switch CSC cell, the parallel-cell multilevel CSC has the advantages of high power rating, low harmonics, fast dynamic response and modularity. Therefore, it is very suitable for high power applications. The power stage design, modeling, control and switching modulation scheme for a parallel-cell multilevel CSC based static var compensator (STATCOM) are analyzed and verified through simulation. / Ph. D.

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Este trabalho trata do UPFC (Unified Power Flow Controller), que corresponde a um dos mais promissores dispositivos FACTS de última geração, pois apresenta a capacidade de controle independente de todos os parâmetros básicos do sistema elétrico de potência (tensão, impedância e ângulo de fase). Com base nos modelos já propostos para representação deste equipamento em regime permanente, é realizada análise e proposta de um modelo que permite uma abordagem prática, para simulação do UPFC em softwares de fluxo de potência comerciais que não possuem modelos dedicados para este dispositivo. São revisitados os conceitos associados ao UPFC, com apresentação dos modelos analisados e seus respectivos parâmetros, assim como os equipamentos instalados e estimativa de custos para implantação. Através de simulações utilizando o modelo de transformador ideal associado à impedância do transformador série e compensador estático, são obtidos os parâmetros para o modelo de injeção de potências e realizadas simulações que demonstram a equivalência entre estes modelos. Finalmente, é realizada a análise de aplicação do UPFC em um sistema de distribuição de alta tensão, onde há forte presença de geração distribuída com sua sazonalidade característica e linhas que realizam a interligação entre diferentes fontes do sistema, havendo a necessidade de controle do fluxo de potência e melhoria dos níveis de tensão em função dos critérios técnicos e aspectos regulatórios. / This work is about UPFC which corresponds to one of the most promising last generation FACTS device, for it presents independent control in all basic parameters of the electrical power system (voltage, impedance and phase angle). Based on models that have already been proposed to represent this equipment in steady state, an analysis has been made and a model that permits practical approach is proposed to simulate the UPFC in commercial power flow softwares that do not yet support this device. The associated UPFC concepts are revisited with the presentation of analyzed models and their respective parameters as well as the installed equipments and cost estimate for implementation. Through simulations using ideal transformer associated to the series transformer impedance and static Var compensator model, parameters are obtained for the power injection model and simulations were run that showed a similarity between these models. Finally, a UPFC application analysis was done for a region of high voltage distribution system, where there is a strong presence of distributed generation typically seasonal and lines which connect different sources of the system, having the necessity of controlling the power flow and improvement of the voltage levels due to the technical criteria and regulatory aspects.