Navegando por Assunto "Distributed generation"

Agora exibindo 1 - 11 de 11

Acesso aberto (Open Access)
Análise dinâmica da condição de runaway em reguladores de tensão devido á presença de geração fotovoltaica nas redes de distribuição
(Universidade Federal do Pará, 2016-08-19) COSTA, Juliana Portugal da; VIEIRA, João Paulo Abreu; http://lattes.cnpq.br/8188999223769913
Intelligent Transport Systems are several information and communication technologies applied to vehicular transportation. It is called intelligent due to its memory capacity, sensing, communication, information processing and adaptive behavior. Within this universe, the Vehicular Ad-hoc Networks (VANET) provide communication between vehicles, as well as the telecommunications infrastructure over the roads. In order to achieve connectivity continues with high data rate and low latency, the integration of vehicular networks with LTE system is pointed as a potential access technology solution. There are many challenges found to reach the QoS requirements characteristic of entertainment applications, road safety and traffic efficiency. Therefore, this dissertation proposes a methodology for the study of the impact of radio resource scheduling algorithms for vehicular networks using LTE as the access technology. This study uses a discrete simulation approach, carried out with NS-3 and SUMO tools, to evaluate five scheduling algorithms: RR, PF, TTA, CQA and PSS. The criteria used in the analysis are throughput, delay, packet loss, spectral efficiency, fairness and qualitative analysis of computational complexity. The results indicate for vehicular networks is more appropriate to apply strategies that guarantee high level of fairness between connected vehicles. The evaluation also confirm the need to use algorithms more specific, taking into account the data generation pattern of these kind of application, with the aim to ensure the best performance for the network.
Acesso aberto (Open Access)
Comparação entre métodos de fluxo de carga para redes de distribuição ativas
(Universidade Federal do Pará, 2018-12-04) AMARAL, Lucas Felipe; VIEIRA, João Paulo Abreu; http://lattes.cnpq.br/8188999223769913
This dissertation presents a comparative study of load flow methods for analysis of active distribution networks. The proposed study takes into account the changes already faced by distribution systems, such as a high penetration of distributed generation (DG), while considering the typical characteristics of distribution networks, as the high R/X ratios. These characteristics impose difficulties on the performance of both backward-forward sweep and decoupled-based power flow methods. On the other hand, modified algorithms based on the decoupled method, such axis rotation fast decoupled and fast decoupled via pu normalization, can be efficiently applied to distribution system analysis. Thereby, a comparison of performance in terms of number of iterations and computational effort is carry out between the following methods: Newton-Raphson, Current Summation, Axis Rotation Fast Decoupled and Fast Decoupled via Complex pu. Normalization. The performance of each method is analyzed for different DG penetration levels, DG modelled as PQ and PV buses, and different R/X ratios. In addition, the influence of the base angle of both decoupled methods on the number of iterations was analyzed. The methods were tested in four distribution systems: 2-bus system, IEEE 69-bus system, 476-bus system and 1080-bus system.
Acesso aberto (Open Access)
Desenvolvimento e modelagem de uma nanorrede de distribuição em corrente contínua em baixa tensão com sistemas de geração distribuída
(Universidade Federal do Pará, 2019-10-23) TORRES, Pedro Ferreira; MACÊDO, Wilson Negrão; http://lattes.cnpq.br/3386249951714088
The concept of direct current distribution minigrids has been gaining ground in academia and industry regarding the development of distribution grid applications with high penetration of distributed energy sources and storage systems. The adoption of a direct current distribution system facilitates the integration of sources such as photovoltaic and wind generation and storage systems such as batteries, as these technologies in general operate intrinsically in direct current. This work presents the development of a direct current distribution nanogrid (DCDN) installed in the laboratory of the Grupo de Estudos e Desenvolvimento de Alternativas Energéticas (GEDAE), of the Universidade Federal do Pará. The developed grid is composed of three photovoltaic generation and storage systems in battery banks and three load banks, distributed over the 200 m grid in a ring topology, with a 24 Vdc bus. Two simulation methodologies were developed and are capable of reproducing the nanogrid’s operational behavior under static and dynamic conditions, allowing the evaluation of the grid performance over a day of operation. Tests are also presented with measurements at strategic points of the grid to evaluate the system behavior under specific operating conditions, being normal or under contingency. The results attest the nanogrid's ability to reliably supply the loads, as long as it respects the limitations of the implemented power generation and storage capacities. In addition, it was found that the characteristics related to the topology of the commercial charge controller that is used to form the DC distribution nanogrid benefits the power quality for the developed grid size and topology.
Acesso aberto (Open Access)
Estimativa da capacidade de hospedagem de geração distribuída em redes de distribuíção via algoritmos genéticos
(Universidade Federal do Pará, 2019-03-29) SOUSA, Alana Lima de; VIEIRA, João Paulo Abreu; http://lattes.cnpq.br/8188999223769913
The use of distributed generation (DG) and distributed energy sources (DER) close to the consumer centers has been gaining prominence around the world. The high penetration level of DG will shift the operation paradigm of electric energy systems, affecting power quality delivered to consumers. The active power injection from DG can cause several consequences to distribution systems, being overvoltage issue the most impacting of them. The reverse power flow from the DG units can cause voltage rise issue on distribution networks and consequently the DG shutdown. During unity power factor (pf) operation of DG, the distribution operators control overvoltage by active power curtailment. In this scenario emerges the GD hosting capacity concept, which consists of estimating the maximum power injected by GD without compromising voltage quality of the distribution system. This dissertation estimates the DG hosting capacity on MV distribution systems using genetic algorithms, considering as main limiting factor the overvoltage issue. Performance tests were performed on IEEE 33-bus and IEEE 69-bus systems.
Acesso aberto (Open Access)
Uma estratégia ativa para detecção de ilhamento em geradores fotovoltaicos por meio de injeção de sinais de teste
(Universidade Federal do Pará, 2016-10-27) CARVALHO, Fransérgio Martins; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
In this paper, is made a study of a active technique for detection of islanding that is proper for application in Grid-Connected Photovoltaic System (GCPS). The technique is based on injection of testing signals which affect negative-sequence of voltage after islanding case. Definitions and explanations are presented about power distributing system and about the elements which belong to Distributed Generation (DG). Standards about inverter’s function and about model of photovoltaic cell are presented. Details of islanding concept and its Non-Detection Zone (NDZ) as well as main current techniques for its detection are exhibited. It is shown the sequence-negative technique. Some instrumental applications related to negative-sequence measurement, sinusoidal inverter and PLL are developed. Models are designed to accomplish the injection and measurement of negative-sequence through VSI: controller and filter. Simulations were made to detect islanding under ordinary conditions of GCPS: irradiance variation and shading of photovoltaic cell; and under ordinary conditions of a power distribution system: charging variation and unbalanced charge. At last, the applied method performance is validated and compared.
Acesso aberto (Open Access)
Formulação analítica para estudo de redes de distribuição ativas considerando a presença de reguladores de tensão
(Universidade Federal do Pará, 2019-09-26) BRITO, Hugo Rodrigues de; VIEIRA, João Paulo Abreu; http://lattes.cnpq.br/8188999223769913
Step voltage regulators (SVRs) located at medium-voltage radial feeders are often part of many strategies to mitigate interconnection impacts of distributed generation (DG) units. However, conventional methods for rapid analysis of characteristic parameters of active distribution networks do not usually factor the effect of SVR tap operations in their calculations. This dissertation proposes a novel analytical formulation for the assessment of the influence of such devices, based on mathematical modification of traditional expressions found in the literature. The developed theoretical framework concerns voltage variation along the feeder, requirement of reactive power, electrical losses and DG hosting capacity. The proposed approach is validated via comparative studies conducted in a simple test-system, as well as in a long 34.5 kV rural feeder that contains two cascaded SVRs along with a high penetration DG at its far end. The Open Distribution Simulator Software (OpenDSS) is used for modelling, traditional load flow simulations and quasi-static time series analyses. Results show the merits of the developed formulation in correctly estimating active distribution networks’ parameters in the presence of SVRs, which marks an improvement over conventional tools for DG integration preliminary studies.
Acesso aberto (Open Access)
Impacto da proteção do tipo crowbar dos aerogeradores de indução duplamente excitados nos sistemas de proteção de redes de distribuição
(Universidade Federal do Pará, 2016-04-07) ARIAS, Piedy Del Mar Agamez; NUNES, Marcus Vinícius Alves; http://lattes.cnpq.br/9533143193581447
The continued incorporation of distributed generation from renewable sources to electricity networks in the world, has contributed positively in the energy supply, energy efficiency and reduction of polluting gases. Nevertheless, new challenges related to the variations in power quality, system stability, short circuit levels, among others, continue to be research. The Brazil has added in recent years an important amount of gigawatts to networks through the connection of large wind farms. In addition, recent possibilities for consumers to make small generators and exchange energy in the distribution network aims to connect another quantity of gigawatts. In this context, this work presents the analysis of the impact of Crowbar protection of double feed induction generator (DFIG) on protection systems used in radial distribution networks to evaluate its influence on the coordination of overcurrent protection functions when there are faults in the network. To reach this goal, assessments of contributions to short-circuit currents of DFIG connected to the grid during disturbance, was simulated in DIGSILENT Power Factory 14.1 software where two cases where considered. The first includes the non-inclusion of crowbar protection and the second considers the inclusion of this protection during a network disturbance. The strategy implemented on crowbar protection proposed the series resistance insertion in the rotor circuit when thresholds velocity, current in the rotor and voltage at the connection point, are Exceeded. The results provide relevant short-circuit levels information that from now on must be considered during previous DFIG connection studies due to the importance they represent to coordinate overcurrent protection function under dynamic and steady state conditions.
Acesso aberto (Open Access)
Impacto de redes de distribuição com massiva conexão de geradores fotovoltaicos na estabilidade de tensão de longo-prazo em sistemas de potência
(Universidade Federal do Pará, 2017-03-31) BARATA, Heitor Alves; VIEIRA, João Paulo Abreu; http://lattes.cnpq.br/8188999223769913
This dissertation aims to show the impact of distributed photovoltaic generators connected to distribution networks on long term voltage stability using full time simulation. The effect of different penetration levels of photovoltaic generation is investigated. Different distribution network models considering distributed generation (DG) connections is also investigated: 1) Load and DG represented by ZIP model and negative active power loads, respectively, connected to the substation bus; 2) Load and DG represented by ZIP model and dynamic equivalent, respectively, connected to the substation bus; 3) Load and GD represented by ZIP model and dynamic model, respectively, distributed along a MV distribution network. Equipments such as On-Load Tap Changer (OLTC) transformers, Overexcitation Limiter (OEL), static loads and step voltage regulators are taken into account in the analyzes, since they significantly affect the long-term voltage stability. The investigations were conducted using both the power flow software ANAREDE and transient stability simulator ANATEM, developed by the Electrical Energy Research Center (CEPEL). For the purpose of power flow studies, photovoltaic generators are modeled as PQ buses with Q=0. The modelling of photovoltaic generators for dynamic studies is based on WECC (Western Electricity Coordinating Council) model, wich was inserted into file User Defined Controller (CDU) from ANATEM. The undervoltage protection of photovoltaic generator is also considered. The case studies were performed on a combined transmission and distribution model.
Acesso aberto (Open Access)
Impacto técnico e econômico da integração de uma geração distribuída de alta capacidade em um sistema de distribuição com reguladores de tensão em cascata
(Universidade Federal do Pará, 2019-11-14) COSTA, Marcelo Sousa; VIEIRA, João Paulo Abreu; http://lattes.cnpq.br/8188999223769913
This dissertation analyzes the technical and economical impact of the integration of a high capacity distributed generation (DG) in a distribution system composed of two feeders, both with two cascaded step voltage regulators (SVRs). Distribution networks with the presence of high capacity DG may subject SVR to reverse active power flow scenarios, which, depending on the control modes “Active Bidirectional Flow up to Opposite Limit” and “Reverse Flow by Cogeneration”, result in abnormal situations that lead the SVR to lose its regulating capacity. As a consequence, consumers may be subjected to severe undervoltage or overvoltage. This phenomenon, in which the SVR loses its ability to control the desired bus voltage, is known in technical literature as the reverse power tap changer runaway condition. In addition, high capacity GDs, depending on their location in the distribution system, can cause critical overvoltages. Some actions can be taken to reduce or mitigate this effect, such as distribution system reconfiguration, adjusting the SVR setpoint, and modifying DG control mode. The economic assessment was accomplished for all studied operating scenarios, highlighting technical and financial impacts on the utility and customers.
Acesso aberto (Open Access)
Modelagem e simulação da operação de sistemas de geração com fontes renováveis de energia suprindo minirrede de distribuição
(Universidade Federal do Pará, 2018-01-19) FERREIRA, Andreza Cardoso; GALHARDO, Marcos André Barros; http://lattes.cnpq.br/6672470707462259; PINHO, João Tavares; http://lattes.cnpq.br/0847897516772421
This work is about the development of computational models in Simulink/Matlab workspace, that simulate the operation in islanded or grid connected mode of electrical energy distribution microgrid with hybrid resources, belonging to the Group of Studies and Development of Energy Alternatives (Grupo de Estudos e Desenvolvimento de Alternativas Energéticas - GEDAE) of Universidade Federal do Pará (UFPA), in the Campus of Belém. This paper also describes the hybrid systems and its components (generation systems, power conditioners, microgrid and proposed loads), also the mathematical models, presenting the equations of components applied to dynamic studies. Then the component models that compose the system are validated and analyzed based on the experimental data. It also presents the integration of the proposed models of the hybrid system, simulating three different strategies or modes of operation as a case study. The developed model has the function of helping these studies, simplifying the analysis and providing different possibilities of simulations in short processing time. The principal aim of the work is to make available a computational model able to simulate in detail the behavior of a hybrid system in connected or isolated of conventional power grid operation conditions.
Acesso aberto (Open Access)
Pré-despacho ótimo da geração distribuída para melhoria da operação de redes de distribuição com presença de reguladores de tensão no modo bidirecional
(Universidade Federal do Pará, 2019-09-25) SOUZA, Valéria Monteiro de; VIEIRA, João Paulo Abreu; http://lattes.cnpq.br/8188999223769913
Electric power systems have been significantly altered over the last few years due to the increased integration of Distributed Generation (DG) into their networks. However, despite the proven advantages associated with the growing penetration of DGs, the modification of the traditional passive nature of such networks incurs several impacts. In order for these systems to have their security, reliability and robustness characteristics ensured, many studies have been developed to mitigate the verified problems caused by this sort of generation and to maximize its benefits. Within this context, it is conducted in this dissertation the integration study of an Independent Power Producer (IPP) in a long rural feeder located in the state of Pará, which contains cascaded step voltage regulators (SVRs) and presents the possibility of switching operations with a neighboring feeder. Upon connection of the IPP, the feeder’s SVRs might be subjected to reverse active power flow by the DG’s injected power as well as by topology reconfiguration of the network, leading them to lose their voltage control capability and indicating the occurrence of runaway condition. Thus, the possible operating scenarios, comprising different SVR configurations and real load profiles, were analyzed via simulations conducted in OpenDSS (Open Distribution Simulator Software). From the assessment of these results, a pre-dispatch optimization strategy for the IPP’s DG control was proposed, aiming not only to prevent the occurrence of runaway condition, but also to help ensure adequate voltage levels and preservation of reliability of the network into which it will be integrated. Perfomance tests of the developed strategy confirmed its feasibility as a tool to mitigate the impacts of high penetration DGs on reconfigurable distribution grids that contain SVR banks.