This thesis primarily focuses on studying the impact of Distributed Generation (DG) on the electromechanical transients in the electric grid (distribution, transmission or combined transmission and distribution (TandD) systems) using a Three Phase Dynamics Analyzer (hereafter referred to as TPDA). TPDA includes dynamic models for electric machines, their controllers, and a three-phase model of the electric grid, and performs three-phase dynamic simulations without assuming a positive sequence network model. As a result, TPDA can be used for more accurate investigation of electromechanical transients in the electric grid in the presence of imbalances. At present, the Electromagnetic Transient Program (EMTP) software can be used to perform three-phase dynamic simulations. This software models the differential equations of the entire electric network along with those of the machines. This calls for solving differential equations with time constants in the order of milliseconds (representing the fast electric network) in tandem with differential equations with time constants in the order of seconds (representing the slower electromechanical machines). This results in a stiff set of differential equations, making such an analysis extremely time consuming. For the purpose of electromechanical transient analysis, TPDA exploits the difference in the order of time constants and adopts phasor analysis of the electric network, solving differential equations only for the equipment whose dynamics are much slower than those of the electric network. Power Flow equations are solved using a graph trace analysis based approach which, along with the explicit partitioned method adopted in TPDA, can eventually lead to the use of distributed computing that will further enhance the speed of TPDA and perhaps enable it to perform dynamic simulation in real time . In the work presented here, first an overview of the methodology behind TPDA is provided. A description of the object oriented implementation of TPDA in C++/C# is included. Subsequently, TPDA is shown to accurately simulate power system dynamics of balanced networks by comparing its results against those obtained using GE-PSLF®. This is followed by an analysis that demonstrates the advantages of using TPDA by highlighting the differences in results when the same problem is analyzed using a three-phase network model with unbalances and the positive sequence network model as used in GE-PSLF®. Finally, the impact of rapidly varying DG generation is analyzed, and it is shown that as the penetration level of DG increases, the current and voltage oscillations throughout the transmission network increase as well. Further, rotor speed deviations are shown to grow proportionally with increasing DG penetration. / Master of Science

Many distributed energy resource (DER) systems are remotely located and are often interfaced at low or medium voltage levels through power electronics converters such as voltage-sourced converters (VSC). Therefore, a weak-grid situation is encountered where the voltage and frequency at the point of DER coupling can experience fluctuations. A power converter designed to operate in normal and strong grid conditions may not perform satisfactorily during such weak and distorted grid conditions. Hence, considering the full dynamics of the system during weak-grid conditions in the design of converter control is indispensable to ensure the stability of the DER and the grid. For instance, the phase-locked loop (PLL) has been identified as a critical component of the VSC controller that can compromise the DER performance during weak-grid conditions. This dissertation investigates and enhances the performances of inverters connected to weak and polluted grids. It primarily presents a novel approach of enhancing the inverter current controller by including the PLL state variables among the entire system state and use them to optimally generate the control input for the VSC. This mitigates the loop interactions between the PLL and other control loops resulting in a mitigation of the oscillations that could cause system instabilities. The procedure is accomplished using the recently developed linear model of the enhanced PLL (EPLL) for single-phase applications and using a model of the three-phase PLL developed in this dissertation. Extensive simulation and experimental results are presented to evaluate and validate the proposed control approaches. Full practical models of all system components are considered for simulation studies. The experimental tests are done on a practical inverter connected to the utility grid. Significant improvement of the inverter performance in weak-grid conditions is confirmed. This dissertation offers a systematic way of integrating and designing the PLL and controller in a VSC to achieve a robust performance in weak-grid conditions.

Cooling, Heating and Power (CHP) systems have been recognized as a key alternative for thermal energy and electricity generation at or near end-user sites. CHP systems can provide electricity while recovering waste heat to be used for space and water heating, and for space cooling. Although CHP technology seems to be economically feasible, because of the constant fluctuations in energy prices, CHP systems cannot always guarantee economic savings. However, a well-designed CHP system can guarantee energy savings, which makes necessary the quantification of non-conventional benefits from this technology in order to offset any economic weakness that can arise as consequence of energy prices. Some aspects that could be included in a non-conventional evaluation are: building energy rating, emission of pollutants, power reliability, power quality, fuel flexibility, brand and marketing benefits, protection from electric rate hikes, and benefits from promoting energy management practices. This study focuses on two aspects: building energy rating and emission reduction of pollutants, related to CHP system energy performance. Two methodologies have been developed in order to estimate the energy related benefits from CHP technology. To determine the energy performance, a model has been developed and implemented to simulate CHP systems in order to estimate the building-CHP system energy consumption. The developed model includes the relevant variables governing CHP systems such as: type and size of the components, individual component efficiencies, system operating mode, operational strategy, and building demand for power, heating, and cooling. The novelty of this model is the introduction of the Building Primary Energy Ratio (BPER) as a parameter to implement a primary energy operational strategy, which allows obtaining the best energy performance from the building-CHP system. Results show that the BPER operational strategy always guarantees energy savings. On the other hand, results from a cost-oriented operational strategy reveal that for critical design conditions, high economic savings can be obtained with unacceptable increment of energy consumption. For Energy Star Rating and Leadership in Energy and Environmental Design (LEED) Rating, results show that CHP systems have the ability to improve both ratings.

No description available.

Within recent years, interest in the installation of solar-based, wind-based, and various other renewable Distributed Energy Resources (DERs) and Energy Storage (ES) systems has risen; in part due to rising energy costs, demand for cleaner power generation, increased power quality demands, and the need for additional protection against brownouts and blackouts. A viable solution for these requirements consists of installation of small-scale DER and ES systems at the single-phase (1Φ) distribution level to provide ancillary services such as peak load shaving, Static-VAr Compensation (STATCOM), ES, and Uninterruptable Power Supply (UPS) capabilities through the creation of microgrid systems. To interconnect DER and ES systems, power electronic converters are needed with not only control systems that operate in multiple modes of operation, but with islanding detection and resynchronization capabilities for isolation from and reclosure to the grid. The proposed system includes control architecture capable of operating in multiple modes, and with the ability to smoothly transfer between modes. Phase-Locked Loops (PLLs), islanding detection schemes, and resynchronization protocols are developed to support the control functionality proposed. Stationary frame PLL developments proposed in this work improve upon existing methods by eliminating steady-state noise/ripple without using Low-Pass Filters (LPFs), increasing frequency/phase tracking speeds for a wide range of disturbances, and retaining robustness for weakly interconnected systems. An islanding detection scheme for the stationary frame control is achieved through the stability of the PLL system interaction with the converter control. The proposed detection method relies upon the conditional stability of the PLL controller which is sensitive to grid-disconnections. This method is advantageous over other methods of active islanding detection mainly due to the need for those methods to perturb the output to test for islanding conditions. The PLL stability method does not inject signal perturbations into the output of the converter, but instead is designed to be stable while grid-connected, but inherently unstable for grid-disconnections. Resynchronization and reclosure to the grid is an important control aspect for microgrid systems that have the ability to operate in stand-alone, backup modes while disconnected from the grid. The resynchronization method proposed utilizes a dual PLL tracking system which minimizes voltage transients during the resynchronization process; while a logic-based reclosure algorithm ensures minimal magnitude, frequency, and phase mismatches between the grid and an isolated microgrid system to prevent inrush currents between the grid and stand-alone microgrid system. / Ph. D.

Dramatic improvements in renewable energy and small-scale distributed generation (DG) technologies have been made in the last twenty years. Nevertheless, they remain underutilized in the American electric utility system. Despite the immense environmental, technical, and financial promise of renewable energy systems and DG technologies, such generators still constitute a very small percentage of electricity generation capacity in the United States. This relative neglect occurs despite remarkable gains in their technical performance and reductions in their cost of producing power—the result (in part) of dramatic government support for several decades. Moreover, the technologies often demonstrate great environmental benefits that appeal to policymakers and consumers. At the same time, they offer ways to enhance strained distribution and transmission networks. This project attempts to answer the apparently paradoxical question: why do new energy technologies that offer such impressive benefits also find the least use? The dissertation emphasizes how the history and culture of the community of electricity producers and users helps explain why the new technologies have seen little use. Going beyond technical explanations of alleged low capacity factors and high capital costs, it focuses on the social nature of decision making among participants in the electric utility system. The approach not only helps us understand the glossing over of renewable energy and distributed generation technologies, but also suggests ways of overcoming the barriers faced by their advocates. / Ph. D.

Power losses are always a cause of worry for any power grid. In India, the situation is even worse. Though recent reports by Ministry of Power shows that Aggregate Technical and Commercial losses (AT &C losses) have come down from 36.64% in 2002-03 to 27% in 2011-12, yet they are much higher than the losses seen in many of the developed nations. The reduction shown in power loss is because of the Electricity Act, 2003 and the amendments made to it in 2007 which controlled the commercial losses rather than the technical losses. According to Ministry of Power, technical losses (Transmission & Distribution losses or T&D losses) in India are reported to be 23.65% in 2011-12. However, according to the study done by EPRI, for systems deployed in developed countries, these losses are estimated to be in the range of 7-15.5%. T & D losses occur in four system components namely step-up transformers and high voltage transmission (0.5-1%), step down to in intermediate voltage, transmission and step down to sub transmission voltage level (1.5-3%), sub-transmission system and step down to low voltage for distribution (2-4.5%), and distribution lines (3-7%). 1% of power loss is approximately equivalent to annual loss of Rs 600 million for a single state. Hence, in a year, loss in distribution line alone causes approximate loss of Rs 1.8-4.2 billion per state. Understanding and reducing power losses in distribution lines which contribute nearly 50% of the total T&D losses assume significance and has formed the motivation for the work reported in the thesis. In recent years, the trend has been to encourage users to generate solar power predominantly at residential complexes and captive power plants at industrial complexes. It has been suggested in the literature that Distributed Generation (DG) can not only reduce the load demanded from the power grid but also the power loss. In this thesis, it has been shown that by the choice of proper size and location of DG, the power loss can be reduced substantially as compared to unplanned deployment of DGs. The objective of the thesis is to design strategy for location of distributed user generated power to maximize the reduction in power loss. The thesis begins with a study of distributed generation in primary distribution networks and proceeds to problem formulation, with the aim being to develop an algorithm that can find out the optimal locations for DG allocation in a network. A greedy approximation algorithm, named OPLODER (i.e. Optimal Locations for Distributed Energy Resources), is proposed for the same and its performance on a benchmark data set is observed, which is found to be satisfactory. The thesis then moves on to describe the actual data of 101,881 commercial, residential and industrial consumers of Bangalore metropolitan area. A loss model is discussed and is used to calculate the line losses in LV part of the grid and loss is estimated for the said actual data. The detailed analysis of the losses in the distribution network shows that in most cases the losses are correlated with the sanctioned load. However there are also some outliers indicating otherwise. The analysis concludes that the distributed generated sources need to be optimally located in order to benefit fully. Also presented thereafter is a study about the impact of electrical properties and the structure of the network on power loss. In the second part of the thesis, OPLODER was again used to process the BESCOM data of 101,881 consumers by modeling them to be connected in three topologies namely Bus (i.e. linear structure), Star (i.e. directly connected) and Hybrid (i.e. tree structure). In case of Bus topology, when DG capacity available is 5% of the demand in substation, OPLODER reduced the loss from 14.65% to 10.75%, from 11.63% to 7.71% and from 13.33% to 9.24% for IISc, Brindavan, and Gokula substations respectively. Similarly, for the same amount of DG in case of star topology, OPLODER reduced loss from 1.75% to 1.26%, from 3.39% to 2.59% and from 2.96% to 1.99% for IISc, Brindavan, and Gokula substations respectively. Thereafter, the available real world data is re-modeled as a tree-type structure which is closer to the real world distribution network and OPLODER is run on it. The results obtained are similar to those presented above and are highly encouraging. When applied to the three substations viz. IISc, Brindavan and Gokula, the power loss dips from 9.95% to 7.42%, from 6.01% to 4.44% and from 8.07% to 5.95%, in case of DG used is 5% of the demand in substation. For the optimal strategies worked out in the thesis, additional overheads will be present. These overheads are studied and it has been found that the present infrastructure and technologies will be sufficient to handle the smart distribution network and the optimal strategy for distributed sources.

Submitted by Miriam Lucas (miriam.lucas@unioeste.br) on 2017-09-04T13:07:47Z No. of bitstreams: 2 Marcos_Tragueta_2017.pdf: 1953593 bytes, checksum: c89f1ba57bb6b1ba944410013aebbde7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-09-04T13:07:47Z (GMT). No. of bitstreams: 2 Marcos_Tragueta_2017.pdf: 1953593 bytes, checksum: c89f1ba57bb6b1ba944410013aebbde7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-05-05 / The insertion of distributed power sources of low power presents new challenges in the planning and operation of distribution systems. The coordination of the protection system is a challenge which modifies as the insertion of the distributed generation grows at any point in any system. In order to verify how the coordination is altered different indicators have been proposed in literature, seeking to express numerically the effect of this insertion on the pair of relays of a coordinated protection system. The Protection Coordination Index (PCI) and the Protection Miscoordination Index (PMI) are shown as valid indicators for this analysis. The purpose of this paper is to apply these quantifiers in the protection schemes of distribution lines of radial and grid systems that use Inverse Time Overcurrent Relays. By applying these indicators, it will be possible to judge if they will provide enough information to analyze the impact of GD insertion in the SDEE, otherwise, identify if there will be limitations which can be remedied by proposing new indicators. The new indicators proposed in this paper seek to cover the limitations observed, without necessarily using the same information. To achieve this goal, distributed generators will be connected at different points in the network, and its generation capacity will be changed in an increasing way; where for each insertion value and at each point of the system, the Coordination Time Intervals (CTI) between consecutive pairs of relays will be verified, and from these values, the quantitative indicators of the impact of the GD will be calculated. For this, a distribution grid system was modeled with a purpose of obtain the required quantities in the scaling of CT1s and relays, thus obtaining a selective coordinate operation, where for each primary relay there will be an extra relay, forming a protective pair. Next two protective systems were adjusted: one considering one-way relays and another, twoway relays. Finally, for the protection systems dimensioned and coordinated, the indexes found in the literature and the proposed indexes were calculated and compared to the same pair of relays, considering the same GD insertion value at different points of the system. Every indicator were valid to the quantification of the GD insertion impact in the protection schemes applied to SDEE, where IDP indicates a percentage of faults that will cause miscoordination, IDPP indicates the percentage of pairs of relays that will be miscoordinate for each fault, ICP shows wether the ITC variation will occur slowly or rapidly, where the faster variation will result in miscoordination rather than the slower one and ITC (%) imposes a restriction on ITC reduction indicating whether the insertion value will miscoordinate the pairs of relays analyzed through numerical values. / A inserção de fontes de energia distribuídas de baixa potência apresenta novos retos no planejamento e operação de sistemas de distribuição. Um reto é a coordenação do sistema de proteção que se altera a medida que a inserção de Geração Distribuída (GD) cresce em qualquer ponto de qualquer sistema. Para verificar como a coordenação é alterada, tem sido proposto, na literatura, diferentes indicadores que visam expressar numericamente qual é o efeito desta inserção nos pares de relés de um sistema de proteção coordenado. O Protection Coordination Index (PCI) e o Protection Miscoordination Index (PMI), se mostram como indicativos válidos para esta análise. O objetivo deste trabalho é aplicar estes quantificadores nos esquemas de proteção de linhas de distribuição de sistemas radiais e malhados que utilizem Relés de Sobrecorrente Direcionais de Tempo Inverso. Pela aplicação destes indicadores foi possível julgar se as informações obtidas são suficientes para a análise do impacto da inserção de GD nos SDEE, identificando o surgimento de limitações, sanadas pela proposição de novos indicadores. Para alcançar este objetivo, geradores distribuídos foram conectados em diferentes pontos da rede, e sua capacidade de geração foi alterada de forma crescente; onde para cada valor de inserção e em cada ponto do sistema, foram verificados os Intervalos de Tempo de Coordenação (ITC) entre pares de relés consecutivos, e a partir destes valores, os indicadores quantitativos do impacto da inserção de GD, calculados. Para isso, foi modelado um sistema de distribuição malhado, visando a obtenção das grandezas requeridas no dimensionamento dos TC's e relés, obtendo assim uma operação coordenada seletiva, onde para cada relé primário há pelo menos um de retaguarda, formando pares protetores. Em seguida dois sistemas de proteção foram ajustados: um considerando relés unidirecionais e outro, relés bidirecionais. Finalmente, para os sistemas de proteção dimensionados e coordenados, os índices encontrados na literatura e os índices propostos foram calculados e comparados para um mesmo par de relés, considerando um mesmo valor de inserção de GD em diferentes pontos do sistema. Todos os indicadores se mostraram válidos para a quantificação do impacto da inserção de GD nos esquemas de proteção aplicados a SDEE, onde IDP indica a porcentagem de faltas que irá ocasionar descoordenação, IDPP indica a porcentagem de pares de relés que irá se descoordenar para cada falta, ICP mostra se a variação de ITC ocorrerá de forma lenta ou rápida, onde a variação mais veloz resultará antes em descoordenação em relação à mais lenta e ITC (%) impõe uma restrição à redução de ITC indicando se o valor de inserção irá descoordenar os pares de relés analisados, através de valores numéricos.

Master of Science / Department of Electrical and Computer Engineering / Anil Pahwa / A time may soon come where prices of electricity vary by time of day or season. Time of Day (TOD) pricing is considered by many to be a key part of creating a more energy-efficient and renewable-energy friendly grid. TOD pricing is also an integral part of Smart Grid and is already available to some customers. With TOD pricing becoming a reality, intelligent dispatching systems that utilize Energy Storage Devices (ESDs) to maximize the use of renewable resources, such as energy produced by small, customer owned wind generators and roof-top solar generators, and grid energy while determining the most economical dispatch schedule could play an important role for both the customer and the utility. This purpose of this work is to create an algorithm upon which these dispatching systems can be based. The details of one proposed algorithm are presented. The full development of the algorithm from its most simplistic form into a much more complex system that takes into account all of the major nonidealities of a real system is given. Additionally, several case studies are presented to show the effectiveness of the algorithm from both a technical standpoint and an economic standpoint. The case studies simulated both wind and solar powered devices using data taken in the state of Kansas, but case studies to emulate electric rates and renewable resources in other areas of the country are presented as well. For each of these case studies, 20 year net present value calculations are presented to determine the economic viability of both the renewable energy production and the dispatching systems.

A participação da fonte solar fotovoltaica na matriz elétrica cresce de forma exponencial ao redor de todo o globo, tanto na modalidade centralizada quanto de forma distribuída. Essa inserção massiva tem relação direta com inúmeras políticas de incentivo aplicadas às fontes renováveis, motivadas pelas discussões sobre mudança do clima e pelos acordos para redução da emissão de gases de efeito estufa.Tais políticas são suportadas por subsídios governamentais, que dependem dos impostos e tributos pagos pela população, ou por encargos nas tarifas de energia elétrica, com impacto direto para o consumidor e para a competitividade econômica do país. Apesar de ainda incipiente no Brasil, a fonte solar fotovoltaica tem apresentado queda expressiva nos preços praticados em leilões, além de ter ultrapassado seus primeiros 700 MW instalados de forma distribuída no início de 2019, principalmente em residências e comércios. Este trabalho busca avaliar qual o impacto, para a receita das distribuidoras e para a tarifa dos consumidores, da inserção da fonte solar fotovoltaica na geração distribuída, impulsionada pelo sistema de compensação net metering. As projeções feitas neste estudo apontam para uma capacidade instalada próxima de 15 GW, no ano de 2030, em pouco mais de 2,2 milhões de residências, comércios e indústrias. Esse nível de inserção poderá causar perda de receita acumulada para as distribuidoras em torno de R$ 5 bilhões, até 2030. Para os consumidores, o efeito acumulado dos reajustes tarifários pode superar 10%, dependendo da área de concessão avaliada. Isso demonstra que o sistema de compensação net metering deve ser continuamente revisto, a fim de dar os estímulos corretos para a inserção da geração distribuída, sem, contudo, penalizar as empresas do setor e os demais consumidores. / The participation of the solar photovoltaic source in the electric matrix grows exponentially around the globe, both centrally and in distributed form. This massive insertion is directly related to numerous incentive policies applied to renewable sources, motivated by the discussions on climate change and agreements to reduce greenhouse gas emissions. Such policies are supported by government subsidies, which depend on the taxes paid by the population, or by charges on electricity tariffs, with a direct impact on the consumer and on the economic competitiveness of the country. Although still incipient in Brazil, the solar photovoltaic source has shown a significant drop in prices at auctions, in addition to having exceeded its first 700 MW installed in a distributed form at the beginning of 2019, mainly in residences and trade. This work aims to evaluate the impact of the utilities revenue and the consumers\' tariff due to the insertion of solar photovoltaic power in distributed generation, driven by the net metering compensation system. The projections made in this study point to an installed capacity of about 15 GW in 2030 in just over 2.2 million houses, businesses and industries. This level of insertion could cause accumulated revenue losses to utilities around R$ 5 billion by 2030. For consumers, the accumulated effect of tariff adjustments may exceed 10%, depending on the concession area evaluated. This demonstrates that the net metering compensation system must be continually revised in order to give the correct incentives for the insertion of distributed generation, without, however, penalizing the companies of the sector and other consumers.