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Fault detection and classification are crucial procedures for electric power distribution systems because they can minimize the occurrence of faults. The methods for fault detection and classification have become more problematic because of the significant expansion of distributed energy resources in distribution systems and the change in their currents due to the action of short-circuiting. In this context, to fill this gap, this study presents a robust methodology for short-circuit fault detection and classification with the insertion of distributed generation units. The proposal methodology progresses in two stages: in the former stage, the detection is based on the continuous analysis of three-phase currents, whose characteristics are extracted through maximal overlap discrete wavelet transform. In the latter stage, the classification is based on three fuzzy inference systems to identify the phases with disturbance. The short-circuit type is identified by counting the shorted phases. The algorithm for short-circuit fault detection and classification is developed in MATLAB programming environment. The methodology is implemented in a modified IEEE 34-bus test system and modeled in ATPDraw with three scenarios with and without distributed generation units and considering the following parameters: fault type (single-phase, two-phase, and three-phase), angle of incidence, fault resistance (high impedance fault and low impedance fault), fault location bus, and distributed generation units (synchronous generators and photovoltaic panels). The accuracy is greater than 94.9% for the detection and classification of short-circuit faults for more than 20,000 simulated cases.

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Cassava is a staple food in many countries, and this food source differs from other crops in that its processing generates a highly polluting and toxic residue (manipueira) that requires further treatment. The present study analyzed the economic feasibility of anaerobic digestion of manipueira for producing clean electricity through distributed generation (DG) while simultaneously eliminating toxic compounds. This eliminates the toxic residues. For this, an approach for the sizing of DG plants from manipueira biogas was presented, a non-trivial task which is not widespread in the literature. For two plants with different capacities, a deterministic economic analysis was carried out based on the criteria of Net Present Value, Internal Rate of Return, and Discounted Payback. Finally, the project risk was assessed through a sensitivity and stochastic analysis using Monte Carlo Simulation. The empirical verification was done on Brazilian data. When considering the NPV criterion, the results indicate a feasibility probability of 9.25% and 81.21% for scenarios 01 and 02, respectively. The results show that scale gains were important in reducing the impact of the investment and, at the same time, the larger scale of the project makes the cost of capital more relevant to the result. These findings show the need for subsidies for the investment, in addition to the promotion of specific credit lines that enable small-scale generation, or that can improve results in greater capacity.

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This paper proposes a time-series stochastic socioeconomic model for analyzing the impact of the pandemic on the regulated distribution electricity market. The proposed methodology combines the optimized tariff model (socioeconomic market model) and the random walk concept (risk assessment technique) to ensure robustness/accuracy. The model enables both a past and future analysis of the impact of the pandemic, which is essential to prepare regulatory agencies beforehand and allow enough time for the development of efficient public policies. By applying it to six Brazilian concession areas, results demonstrate that consumers have been/will be heavily affected in general, mainly due to the high electricity tariffs that took place with the pandemic, overcoming the natural trend of the market. In contrast, the model demonstrates that the pandemic did not/will not significantly harm power distribution companies in general, mainly due to the loan granted by the regulator agency, named COVID-account. Socioeconomic welfare losses averaging 500 (MR$/month) are estimated for the equivalent concession area, i.e., the sum of the six analyzed concession areas. Furthermore, this paper proposes a stochastic optimization problem to mitigate the impact of the pandemic on the electricity market over time, considering the interests of consumers, power distribution companies, and the government. Results demonstrate that it is successful as the tariffs provided by the algorithm compensate for the reduction in demand while increasing the socioeconomic welfare of the market.

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Protection coordination of AC microgrids (MGs) is a challenging task since they can operate either in grid-connected or islanded mode which drastically modifies the fault currents. In this context, traditional approaches to protection coordination, that only consider the time multiplier setting (TMS) as a decision variable may no longer be able to guarantee network security. This paper presents a novel approach for protection coordination in AC MGs that incorporates non-standard characteristic features of directional over-current relays (OCRs). Three optimization variables are considered for each relay: TMS, maximum limit of the plug setting multiplier (PSM) and standard characteristic curve (SCC). The proposed model corresponds to a mixed integer non-linear programming problem. Four metaheuristic techniques were implemented for solving the optimal coordination problem, namely: particle swarm optimization (PSO), genetic algorithm (GA), teaching-learning based optimization (TLBO) algorithm and shuffled frog leaping algorithm (SFLA). Numerous tests were run on an IEC MG as well as with the distribution portion of the IEEE 30-bus test system. Both systems incorporate distributed generation (DG) and feature several modes of operation. A comparison was made with other MG protection coordination approaches proposed in the specialized literature. In all cases, the proposed approach found reduced coordination times, evidencing the applicability and efficacy of the proposed approach.

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Abstract This paper aims to evaluate the perception of residents of a rural quilombola community, about the impacts of distributed energy generation (DG) on the social, economic and environmental dimensions. The main challenge of the proposed model was to quantify the main perceptions of the target population of the research, as well as maintain the coherence of the specifications of the sustainability parameters. Diffuse modeling allows the transformation of linguistic variables into numerical values, the disadvantage is the dependence of the specialist to construct the rules. The methodology used was the application of a semi-structured questionnaire, and the results were used as a reference to build the discourse domain of the input variables of the Fuzzy inference system, which generated an index of 54.1% classified in the category partially sustainable. Specifically, the economic and social dimensions obtained an index of 46.7% and the environmental dimension of 69%. From the perspective of the perception of the respondents, the variables with the greatest impact were: landscape change (LCH) 92%, environmental awareness (EA) and reduction of global warming (GW) with values of both 69%. The variable of the most prominent economic dimension was: cost of the system with a value of 69%. In the social dimension, the variables with the greatest impact were: Community Acceptability (AC), Expansion of the support network (ESN) with values of 69%. The proposed model allowed us to interpret the respondents' perception, and can be used to generate effective actions that solve the identified demands.

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Abstract The electrical system is becoming more robust with the insertion of distributed energy resources (DERs) and the need for energy autonomy by consumers, given that the current scenario is a growth in demand for electric energy. This paper aims to apply a computational model capable of determining the optimal hourly allocation of controllable loads in residence, as well as studying the optimal dispatch of residential microgrids considering management on the demand side. In addition, this paper presents an economic feasibility analysis of residential microgrids considering distributed generation from wind and solar sources, distributed storage, electric vehicles, and residential controllable loads. Thus, it was possible to conclude that in residence, the insertion of distributed energy generation and storage elements can present a significant reduction in electric energy costs, which can be even greater if these elements are associated with optimized controllable load management.

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Microgrids (MG) treat local energy supply issues effectively and from a point of view of the distribution grid, may be a power supply or virtual load. Despite holding a myriad of benefits, MGs also bear a set of challenges, including a higher fault rate. Currently, many articles focus on control techniques; however, little has been written about the techniques of control, hierarchical control, and fault-tolerant control (FTC) applied to MGs, which is the motive of this bibliographic revision on control systems. A brief comparison of the different approaches in the field of present-day research is carried out primarily addressing hierarchical control and fault tolerance. The objective of this investigation is to attract the interest of researchers to the field of control and fault tolerance applied to MGs, such as: modeling, testbed, benchmark systems, control and hierarchical control strategies, fault diagnosis and FTC.

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The objective of this study is to evaluate the potential for electricity generation in the State of São Paulo (SP) from the sewage treatment. A sewage treatment plant (STP) with domain in the production of biogas from wastewater treatment plant (WWTP) is the basis for this case study. The basic premise is that the very generation of electricity in STPs is advantageous for companies in the sanitation sector in Brazil, resulting in cost reductions of the treatment process. Gains at the end of the process are found in two levels, namely: (i) economic, by generating 165% of electricity from biogas burning in relation to the expend; (ii) energy, by adding a new sustainable and storable energy source equivalent to 4% of natural gas offered in the State of SP and 0,5% of electricity produced from biogas burning in relation to electricity consumption. In conclusion, the potential of electricity production linked to the biogas at STPs is capable of supply its domestic demand and export the surplus to other segments of the state and national economy.

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Abstract The demand for electricity is growing worldwide. At the same time, the non-renewable natural resources that account for a large proportion of the global energy matrix are rapidly depleting, which will pose a major challenge in the near future. Therefore, micro-grid models that use renewable energy sources, such as solar and wind, are rapidly developing and are becoming economically viable alternatives. The objective of this study was to evaluate the economic viability of installing solar and wind power generation systems in the NOVVALIGHT electrical components factory located in Campo Largo, Paraná, Brazil. The most viable model was the combination of solar and wind energy, which would generate approximately 260 MWh of energy per year. Using financing provided by the Brazilian Bank for Economic and Social Development (BNDES), this proposal has an eight-year payback period, net present value of BRL 149,097.42, and internal rate of return of 18%, demonstrating its economic viability.

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Abstract In Brazil, the demand for the acquisition and installation of photovoltaic systems has grown exponentially and, with that, the importance of studies considering their effects on the distribution grids power flow also grows. Due to the intermittent nature of photovoltaic generation, it is important to approach the analysis in a discrete way, taking into account the changes in the power injections during the studied period. Thus, this article presents the daily analysis of the effects of photovoltaic generation on the distribution system through the computational implementation of a discretized power flow routine. The implemented routine can also analyze the effects of other distributed generations on distribution grids, whether those grids are radial or not. The study results show positive impacts on the voltage quality obtained by the photovoltaic systems insertion, for a well-known distribution test system.

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Abstract The acceptance and deployment of electric power from sustainable sources, which are less polluting than fossils, have been a consensus throughout society. Specially, the growth of the installed capacity in photovoltaic energy has been considerable in distributed generation. In order to properly take advantage of this growing demand, it is necessary to adopt appropriate measures and procedures to improve the operation and performance of photovoltaic systems. The purpose of this work is to present such measures and procedures, under quantitative and qualitative analysis, using scientific methodologies and tools. In the end, a set of procedures was obtained that analyzes functional and structural aspects of small grid-connected photovoltaic systems. Its validation was carried out in a case study of photovoltaic system of the Department of Electrical Engineering (DELT) of the Federal University of Paraná (UFPR, Brazil).

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Abstract With the insertion of distributed generation in distribution networks, security analysis becomes crucial, in islanded operation or when the system is connected to the grid. Dynamic stability analyses are necessary in order to achieve minimum levels of security and reliability. Such analyses are obtained through the solution of the algebraic-differential set of equations that model the distribution grid and their generators, which requires numerical solution methods. Therefore, this paper presents a computational tool for transient stability and large disturbance frequency stability analysis, considering distribution systems with the insertion of biomass-fed distributed generation, which may, or may not, have speed regulation systems. The presented tool may be employed to assess assorted system indexes, such as the severity of disturbances, the quality of a given operating condition, in terms of voltage and frequency operating limits, and the response of both the system and the generators in face of the action of speed regulators.

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Abstract In a world where technology is even more essential, quality and reliability of electrical system are fundamental. In Brazil, country where most of the energy is produced thought power plants, the existing distribution network is overwhelmed and the needs for the consolidation of distributed generation is growing. Wind and Solar power generation from biomass and another renewable sources are one alternative to power plants, which requires large areas and massive investment. The renewable energy sources mentioned may be assembled in a way to generate reliable energy to properties far from the cities, such as rural zones, where often energy from power plants doesn't gets to. Distributed generation allows quick development of Brazilian farming and guarantees to the farmer independence from the energy dealerships. Microgrids assembled with renewable sources are one sustainable option and benefits Brazilian economy and society.

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Abstract Electricity is undoubtedly one of the most important resources in the modern world. As the demand for electric energy increases, conventional resources that are transformed into electric energy are being exhausted, generating a need to search for alternative sources, resulting in a significant increase in energy costs. This study presents an integrated project of an intelligent microgrid and energy management aimed at reducing energy costs. At the Federal University of Paraná (UFPR), electricity represents an annual cost of over BRL 13 million, which is the third largest operating expense of the university. In addition, the public education budget in Brazil has been decreased in recent years. Therefore, this study was conducted within the scope of UFPR and aimed to analyze three alternatives to reduce electric energy costs: i) demand management through an analysis of energy bills, ii) migration to the free energy market, and iii) the development of an in-house photovoltaic generation facility. A computational tool to optimize the contracted demand and simulate the annual savings with the free market and distributed generation projects was developed using Microsoft Excel. Payback, the net present value, and the internal rate of return were calculated. Finally, the economic viability of all alternatives was proven, with demand management demonstrating an economic potential of greater than BRL 500,000 per year, use of the free market saving more than BRL 300,000, and the developed in-house photovoltaic generation system achieving an economic impact of more than BRL 600,000 per year.

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ABSTRACT In the search for new options for the establishment of the energy matrix of Brazil, the Grid-Connected Photovoltaic Systems (GCPVS) are configured as an alternative to urban centers, because they allow the power generation at distributed mode, that is, generate energy at the place where it will be consumed and inject the surplus energy into the network. Faced with the prospect of installing Grid-Connected Photovoltaic System, the objective of this research is to characterize this type of photovoltaic system installed in Curitiba, State of Paraná, Brazil. This paper highlights that up to July 2017 the State of Paraná has 1031 GCPVS in operation, which corresponds to 6,6MW, while Curitiba has 204 GCPVS that represents 997.4 kW in operation, 82% of which are installed in residences. In addition, the study of a sample of 41 GCPVSs installed in Curitiba shows that 98% of these systems use multicrystalline modules, 75% use single phase inverters and 95% of these use inverters transformerless. This shows that the losses in the conversion process are reduced and the equipment is more compact using better technology than the inverters with transformer. Therefore, the main trend of photovoltaic energy market is to use transformerless inverters.

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ABSTRACT The increase in energy demand in Brazil encourages the country to increasingly invest in generation of electric energy, where the demand for other renewable sources increases gradually because they have a lower impact on the environment. The use of Grid-Connected Photovoltaic Systems (GCPVS) is a viable solution for the country, since it presents favorable natural conditions for the use of solar energy. This study approaches the current scenario of three photovoltaic systems installed in Curitiba in 2016 and part of 2017: Green Office (GO) located in Curitiba Campus Downtown, Curitiba Campus Neoville, both of the Federal Technological University of Paraná (UTFPR), as well as a residence. By means of performance parameters, performance analysis of these systems were carried out and, in order to measure the length of time of the return of the initial investment in its installation, a study of the economic viability of these systems according to the current rate model in Brazil through economic engineering tools was carried out: Simple Payback and Discounted Payback, Net Present Value and Internal Rate of Return. Finally, the application of the saved value of electric energy bills was simulated in a bank account during the system´s lifespan.

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ABSTRACT Concerns about the environment and a growing demand for electricity have led to the intensive search for renewable energy sources. Photovoltaic solar energy, in the form of distributed generation, has shown a very high growth rate to an extent that in some regions it will be adopted on a large scale, thus being responsible for the supply of a significant portion of the load of this region. Some factors have favored the adoption of distributed generation: the drop in the price of solar panels and inverters, as well as its easy installation and maintenance. However, the large-scale adoption of solar distributed generation brings new challenges to the power distribution system. Network voltage control is an example. In conventional systems, voltage control is a properly addressed problem, but in networks with the presence of distributed generation, where at certain times of the day reverse energy flows can be observed, more detailed studies on voltage behavior are necessary concerning the power quality. This article makes an analysis of relevant studies on the effects that the insertion of photovoltaic distributed generation can cause in the voltage of the electric power distribution system under the optics of two phenomena: the fluctuation and the voltage ripple.

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ABSTRACT The Market share of electrical vehicles has been rising in the past few years and tends to rise even more. According to the International Energy Agency, an increase of 50% in the number of electrical vehicles is expected. Whilst that increase is beneficial from a greenhouse gases emissions drop point of view, that rise could, on the other hand, represent a major increase in the electrical power consumption. Besides, other problems such as harmonics and overloads could emerge from the massive connection of electrical vehicles to the electrical grid. Therefore, it is necessary to perform studies and simulations in order to estimate those problems and to mitigate the problems related to the inevitable expansion of the electric vehicle fleet in the near future. The present work intends to run simulations so as to identify the main effects of the electrification of the vehicular fleet in the city of Curitiba, as well as understand how the provision of ancillary services through the electrical vehicles can help in the process.

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ABSTRACT Distributed photovoltaic (PV) generation is characterized by the application of several small power plants in urban centers. This form of energy deserves special mention due to the possibility of installation in existing areas such as roofs and facades. Thus, the implementation of these systems represents positive modifications of the urban scenario, with the adhesion of PV modules, presenting much smaller social and environmental impacts than that of large conventional plants. In this sense, this study aims at analyzing the demand and consumption curves of the Center headquarters buildings of Federal University of Technology - Paraná (UTFPR) in Curitiba, by applying the COPEL's CAS Hemera platform, in order to determine the potential for implementation of grid-connected photovoltaic systems in this premise, because they allow the cost reductions in electric power. The first UTFPR's grid-connected photovoltaic system was introduced in December 2011, at the Center's headquarters, in one of the blocks of the university, which by the end of 2016 generated a total of 11.67 MWh of electricity. This paper proposes an expansion scenario for the existing grid-connected photovoltaic system, using the available coverage showing the shifting or reduction of energy demand peaks and the energy contribution to UTFPR's Center headquarters.

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Abstract The electrical sector is under constant evolution. One of the areas refers to the consumers that come to be generators, implementing distributed generation, interconnected to a smart grid. This article discusses the improvement of an algorithm, already presented in the literature, to make the best temporal allocation of loads, electric vehicle, storage and many sources of generation, aiming at the maximum financial performance, that is, the lowest value for the energy invoice The modeling consists of a Mixed Integer Linear Programming (MILP) algorithm, which considers each component of the system and weighs the maintenance and shelf life of storage devices, basically batteries, loads that can be reallocated and the concept of Vehicle-to-grid, performing a daily analysis. The simulation has considered the hypothetical case of a residence, in which are included storage, electric vehicle and redistribution of loads, as well as wind and solar generation. Several scenarios are simulated, with or without the presence of some of the components. The results indicate that the simplest model, only redistributing the loads, can provide a sensible monetary savings of approximately 60%, while with the application of all the components modeled, there can be a reduction in the invoice of 90%.

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