Thesis (Ph.D.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (PhD (Electrical Engineering))--Cape Peninsula University of Technology, 2018. / Electrical energy can be easily used and converted to other forms of energy for various applications. Technological advancement increases the dependency on electricity to a great extent. Various internal and external factors are responsible for the bad quality of power in power systems. The performance of the system is greatly affected by the presence of harmonics, as well as voltage and frequency variations, which leads to the malfunctioning of the device and decline of power quality and supply at load side. The reactive power compensation is carried out for better power quality. The literature survey is done to find the best and efficient scheme for reactive power compensation and mitigation of various power quality problems. The devices which are used to measure various power quality factors are discussed. Various mitigating schemes are surveyed in order to compensate reactive power and to improve the power quality at the distribution end. The integration of the most widely used renewable energy, wind energy in the distribution system creates technical issues like stability of the grid, harmonic distortion, voltage regulation, active and reactive power compensation etc. which are restricted to IEC and IEEE standards. One of the topics this thesis addresses is regulation in the reactive power generated along with voltage regulation by using an effective power electronics device known as a STATCOM. The main power quality factors like overvoltage and voltage flickers are mitigated by establishing STATCOMs in small wind farms. The wind farms are equipped with three wind turbines. These three wind turbines found in the wind farm can be operated together or one after another with an introduced delay. A glitch in even a little piece of a power grid can result in loss of efficiency, income and at times even life. In this manner, it is basic to outline a system which can distinguish the faults of the power system and take a faster response to recover it back to required reactive power. Two devices STATCOM and D-STATCOM are used for this purpose in this thesis. The D-STATCOM circuit and operating principle are also discussed in thesis. Different topologies of D-STATCOM discussed with their benefits and shortcomings. The voltage, current and hybrid technologies of D-STATCOM are also discussed.

Orientador: Percival Bueno de Araujo / Banca: Anna Diva Plasencia Lotufo / Banca: George Lauro Ribeiro de Brito / Resumo: Este trabalho apresenta estudos referentes à estabilidade a pequenas perturbações do SEP, considerando a atuação de FACTS para o amortecimento das oscilações eletromecânicas de baixa frequência. São abordados os dispositivos FACTS TCSC (Thyristor Controlled Series Capacitor) e o SSSC (Static Synchronous Series Compensator). É realizada a representação e modelagem dos dispositivos FACTS no SEP inserindo no Modelo Sensibilidade de Potência. Para melhorar o desempenho do SEP no que se refere à estabilidade a pequenas perturbações, controladores suplementares são propostos para aumentar o desempenho dos dispositivos TCSC e SSSC, introduzindo o amortecimento necessário ao SEP. Adicionam-se os controladores suplementares POD no modelo modificado para os dispositivos TCSC e SSSC para verificar sua atuação. Para encontrar a melhor localização para instalação dos dispositivos é usado a teoria dos resíduos. Esta mesma teoria é usada também para o ajuste dos parâmetros dos controlares juntamente com outro ajuste feito através de Redes Neurais Artificiais (RNA), que é proposto como alternativa de comparação ao método dos resíduos. Simulações são efetuadas em um sistema teste simétrico para se verificar resultados e a eficácia do controlador POD (parâmetros ajustados pela RNA proposta), acoplados aos dispositivos FACTS, na manutenção da estabilidade a pequenas perturbações do SEP. Palavras-chave: Controladores POD. Estabilidade de sistema de potência. Redes neurais artificiais. TCSC e SSSC / Abstract: This work presents studies referred to short term Electric Power System (EPS) perturbations, considering the actuation of FACTS devices for low frequency electromechanical oscillation damping. The devices considered are: FACTS TCSC (Thyristor Controlled Series Capacitor) and the SSSC (Static Synchronous Series Compensator). It is representation and modeling FACTS devices in the EPS inserting in the Power Sensitivity Model. To improve the performance of the EPS considering the short term perturbations, additional controllers are proposed to increase the performance of the TCSC and SSSC devices, introducing the necessary damping to the EPS. The additional POD controller is added to the modified model for TCSC and SSSC devices to verify the acting. The residual theory is used to find the best location to install the devices. The same theory is used to adjust the parameters of the controllers and an adjustment with Artificial Neural Networks (ANN) is proposed as an alternative to the residual method. Simulations are effectuated for a symmetric test system to verify the efficiency of the POD controller (parameters adjusted by the ANN proposed), coupled with the FACTS devices, to maintain the stability considering the short term perturbations / Mestre

abstract: Corrective transmission topology control schemes are an essential part of grid operations and are used to improve the reliability of the grid as well as the operational efficiency. However, topology control schemes are frequently established based on the operator's past knowledge of the system as well as other ad-hoc methods. This research presents robust corrective topology control, which is a transmission switching methodology used for system reliability as well as to facilitate renewable integration. This research presents three topology control (corrective transmission switching) methodologies along with the detailed formulation of robust corrective switching. The robust model can be solved off-line to suggest switching actions that can be used in a dynamic security assessment tool in real-time. The proposed robust topology control algorithm can also generate multiple corrective switching actions for a particular contingency. The solution obtained from the robust topology control algorithm is guaranteed to be feasible for the entire uncertainty set, i.e., a range of system operating states. Furthermore, this research extends the benefits of robust corrective topology control to renewable resource integration. In recent years, the penetration of renewable resources in electrical power systems has increased. These renewable resources add more complexities to power system operations, due to their intermittent nature. This research presents robust corrective topology control as a congestion management tool to manage power flows and the associated renewable uncertainty. The proposed day-ahead method determines the maximum uncertainty in renewable resources in terms of do-not-exceed limits combined with corrective topology control. The results obtained from the topology control algorithm are tested for system stability and AC feasibility. The scalability of do-not-exceed limits problem, from a smaller test case to a realistic test case, is also addressed in this research. The do-not-exceed limit problem is simplified by proposing a zonal do-not-exceed limit formulation over a detailed nodal do-not-exceed limit formulation. The simulation results show that the zonal approach is capable of addressing scalability of the do-not-exceed limit problem for a realistic test case. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2015

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2013 / The demand for electrical energy has kept on increasing, thus causing power systems to be more complex and bringing the challenging problems of electrical energy generation, transmission, stability, as well as storage to be examined more thoroughly. With the advent of high-speed computation and the desire to analyze increasingly complex behaviour in power systems, simulation techniques are gaining importance and prevalence. Nevertheless, while simulations of large, interconnected complex power systems are feasible, they remain time-consuming. Moreover, the models and parameters used in simulations are uncertain, due to measurement uncertainty, the need to represent a complex behaviour with low-order models, and the inherent changing nature of the power system. This research explores the use of a model reduction technique and the applications of a Real-Time Digital Simulator (RTDS) to reduce the uncertainty in large-scale complex power system models. The main goal of the research is to develop a reduced order model and to investigate the applications of the RTDS simulator in reduction of large, interconnected power systems models. The first stage of the study is to build and simulate the full model of the power system using the DigSILENT and RTDS simulators. The second phase is to apply model reduction technique to the full model and to determine the parameters in the reduced-order model as well as how the process of reduction increases this model uncertainty. In the third phase the results of the model reduction technique are compared based on the results of the original model - IEEE standard benchmark models has been used. The RTDS was used for comparative purposes. The thesis investigations use a particular model reduction technique as Coherency based Method. Though the method ideas are applicable more generally, a concrete demonstration of its principles is instructive and necessary. Further, while this particular technique is not relevant to every system, it does apply to a broad class of systems and illustrates the salient features of the proposed methodology. The results of the thesis can be used in the development of reduced models of complex power systems, simulation in real-time during power system operation, education at universities, and research. Keywords: IEEE benchmark models, reduced models, Coherency based Method, DigSILENT, RTDS, model uncertainty, power system stability

abstract: With growing complexity of power grid interconnections, power systems may become increasingly vulnerable to low frequency oscillations (especially inter-area oscillations) and dependent on stabilizing controls using either local signals or wide-area signals to provide adequate damping. In recent years, the ability and potential to use wide-area signals for control purposes has increased since a significant investment has been made in the U. S. in deploying synchrophasor measurement technology. Fast and reliable communication systems are essential to enable the use of wide-area signals in controls. If wide-area signals find increased applicability in controls the security and reliability of power systems could be vulnerable to disruptions in communication systems. Even though numerous modern techniques have been developed to lower the probability of communication errors, communication networks cannot be designed to be always reliable. Given this background the motivation of this work is to build resiliency in the power grid controls to respond to failures in the communication network when wide-area control signals are used. In addition, this work also deals with the delay uncertainty associated with the wide-area signal transmission. In order to counteract the negative impact of communication failures on control effectiveness, two approaches are proposed and both approaches are motivated by considering the use of a robustly designed supplementary damping control (SDC) framework associated with a static VAr compensator (SVC). When there is no communication failure, the designed controller guarantees enhanced improvement in damping performance. When the wide-area signal in use is lost due to a communication failure, however, the resilient control provides the required damping of the inter-area oscillations by either utilizing another wide-area measurement through a healthy communication route or by simply utilizing an appropriate local control signal. Simulation results prove that with either of the proposed controls included, the system is stabilized regardless of communication failures, and thereby the reliability and sustainability of power systems is improved. The proposed approaches can be extended without loss of generality to the design of any resilient controller in cyber-physical engineering systems. / Dissertation/Thesis / Ph.D. Electrical Engineering 2014

This paper investigates the various parameters that effect voltage stability in sub-transmission power networks. The paper first looks at contributions from equipment: generators, transmission lines, transformers, capacitors, SVCs and STATCOMs. The paper also looks at the effects of loads on voltage stability. Power flow solutions, PV and VQ curves are covered. The study models an existing voltage problem i.e., a long, radial, 115 kV sub-transmission network that serves a 65 MW load. The network model is simulated with the following voltage instability countermeasures: adding a capacitor, adding an SVC, adding a STATCOM, tying to a neighboring transmission system, adding generation and bringing in a new 230 kV source. Then, using the WECC heavy-winter 2012 power flow base case and Siemens PTI software, VQ and PV curves are created for each solution. Finally, the curves are analyzed to determine the best solution.

As the share of weather-dependent renewable electricity production increases, the demand for power system flexibility grows. In the Swedish power system, gas turbines have historically been utilised for back-up power generation. However, these gas turbines traditionally use fossil fuels, which limits their applications given Sweden’s target of net zero emissions of greenhouse gases. With recent technological advancements, fossil-free fuels, such as hydrogen and eMethanol have emerged as promising green alternatives, expanding the potential benefits of gas turbines in a power system. Possible applications include local bottleneck relief, providing grid inertia, voltage regulation, black start capability, and island operation capability. Market-based benefits include generating revenue by participating in both ancillary service markets and electricity markets. The benefits of a fossil-free gas turbine can be particularly valuable for distribution grids in need of strengthening, and where feed-in from the overlying grid is nearing maximum capacity. Therefore, gas turbine manufacturer Siemens Energy, and distribution network owner Mälarenergi, are interested in assessing the benefits that a fossil-free gas turbine can provide to the distribution network in Västerås, Sweden. Grid resilience benefits were evaluated through a literature study, while the market-based revenue potential were estimated using a quantitative bidding model. Included markets are the day-ahead electricity market and the ancillary service markets FCR-D, aFRR and mFRR. The model simulates the markets in 2022-2023 and uses forecasts based on historical data to determine the optimal bidding strategy. The study found that there is a large revenue potential with current fuel and market prices. The most promising configuration is a combination of eMethanol and hydrogen, with a profit potential of 72.6 MSEK/year, or a net present value of 463.2 MSEK. Operating on only hydrogen is also identified as a promising pathway. HVO100 and biomethane are, with current prices, less attractive alternatives. The results are highly sensitive to changes in costs, emphasising the importance of a diverse portfolio of fuels and potential markets for profitability. However, grid resilience benefits provide an incentive to invest in a fossil-free gas turbine, regardless of market-based revenue potential. As a suggested course of action, HVO100 or biomethane can be utilised during a transition period while the technology and infrastructure for hydrogen and eMethanol are being developed. Lastly, other technologies may offer certain services at a competitive cost, but the strength of the gas turbine lies in its extensive range of capabilities. / I samband med att andelen väderberoende förnybar elproduktion ökar, ökar även behovet av flexibilitet i elnätet. I det Svenska elsystemet har gasturbiner länge använts för att bidra med reservkraft. Dessa gasturbiner drivs vanligtvis med fossila bränslen, och således begränsas deras användningsområde av Sveriges ambitioner om nettonollutsläpp av växthusgaser. Närtida teknologiska framsteg har dock öppnat upp för möjligheten att, i allt större utsträckning, använda fossilfria bränslen i gasturbiner. Bland annat har e-Metanol och vätgas identifierats som två lovande alternativ, och med dessa bränslen får gasturbinen ett mycket bredare användningsområde. Möjliga nyttor inkluderar eliminering av lokala flaskhalsar i nätet, tillförsel av rotationsenergi, spänningsreglering, samt tillhandahållande av förmåga till dödnätsstart och ödrift. Därtill finns det en marknadsmässig nytta i att delta på stödtjänst- och elmarknaderna. Tjänsterna som en fossilfri gasturbin kan bidra med är troligtvis av särskilt intresse för distributionsnätsägare vars nät är i behov av förstärkning och där inmatningen från det överliggande nätet allt oftare närmar sig maxgränsen. Således vill gasturbintillverkaren Siemens Energy, tillsammans med distributionsnätsägaren Mälarenergi, utreda vilka nyttor som en fossilfri gasturbin kan bidra med i den svenska staden Västerås distributionsnät. Nyttor kopplade till elnätets motståndskraft utvärderades kvalitativt genom en literaturstudie, medan den marknadsmässiga intäktspotentialen utvärderades med hjälp av en kvantitativ budgivningsmodell. De marknader som inkluderas i studien är spotmarknaden (dagen-före-marknaden) samt stödtjänstmarknaderna FCR-D, aFRR och mFRR. Modellen simulerar marknaderna under perioden 2022-2023, och använder prognoser för att identifiera en optimal budgivningsstrategi, som avgör hur gasturbinen deltar på marknaderna. Studien kom fram till att det finns goda marknadsmässiga intäktsmöjligheter med dagens marknadspriser och bränslepriser. Den mest lovande bränslekonfigurationen är en kombination av e-Metanol och vätgas, med en uppskattad vinstpotential på 72.6 MSEK/år, motsvarande ett nettonuvärde på 463.2 MSEK. Drift på enbart vätgas identifierades också som ett lovande alternativ. Bränslena HVO100 och biometan är med dagens priser mindre lovande alternativ, dock enbart med avseende på den marknadsmässiga potentialen. Resultaten är mycket känsliga för kostnadsförändringar, varför vikten av gasturbinens bränsleflexibilitet och förmåga att delta på ett stort antal marknader bör understrykas. Nyttor kopplade till elnätets motståndskraft skapar dock incitament för en investering oberoende av den marknadsmässiga intäktspotentialen. Ett rekommenderat tillvägagångssätt vid en investering är att använda HVO100 eller biometan som bränsle under en övergångsperiod, i väntan på att teknologin och infrastrukturen för e-Metanol och vätgas utvecklas. I studien konstaterades det att andra teknologier kan erbjuda vissa tjänster till ett konkurrenskraftigt pris. Detta leder till slutsatsen att den fossilfria gasturbinens främsta styrka är en dess stora mångsidighet, snarare än dess enskilda förmågor.

As the load on the power system grows and new transmission facilities become increasingly difficult to build, the utilities must look to ways to make the most of the current transmission system. Adaptive relaying is one way to enhance the ability of the power system. On the Florida - Georgia interface an adaptive out-of-step relay is being installed. This relay determines if swings on the power system will remain stable by performing a better then real-time transient stability study. Because of the computing capacity required for a transient stability study, the study cannot be performed on the full power system. A reduced model must be used. In this thesis, various methods of obtaining reduced models for use in the relay will be explored. The models will be verified with a full system model using Electric Power Research Institute's (EPRI) Extended Transient-Midterm Stability Package (ETMSP). / Master of Science