Distributed Generation (DG) is one of the technologies approved by the South African government for the country's generation expansion to meet future load demand and to support economic growth. DGs change the conventional power flow (generation, transmission to distribution) by injecting real and reactive power at distribution voltage levels. The change in the conventional power flow creates complexity in the power system grid planning due to the conversion of the power system from a passive network to an active network. Introduction of bi-directional power flow on the power system can, among other benefits reduce local power demand which opens opportunities for capital investment deferrals on the transmission and distribution sectors. Consequently, DG impact on the transmission and distribution grid planning has been studied by other researchers. However, previous studies evaluated DG integration on a regulated market and assumed a certain level of generation availability during network peaking period. None of the studies have yet evaluated the benefits on an unregulated market using real measured data. Furthermore, SA distribution network expansion is also being planned without incorporating DGs on the network because of unreliability of wind and solar energy and the network operator's inability to influence the size, location and penetration level of DGs. This planning approach forces the network operator to do more to ensure high network strength. This approach can also result in network overdesign and unnecessary capital expenditure due to the potential benefits that can be deduced from DGs. This dissertation therefore aims to investigate whether incorporating future DG integration in distribution network planning can alleviate financial ramifications of grid code compliance requirements. The data used in the simulations was obtained from the distribution network operator and comprises of both real and reactive power values with a sampling time of 60 minutes for a period of a year. Simulations were conducted for both low and high load conditions to cover the extreme ends of the network and the parameters that were assessed are thermal rating, voltage regulation and network grid losses. Results showed that thermal constraints that are expected on the network when DGs are not considered are not evident when DGs are considered. Results further revealed that there are undervoltage improvements on the network when DGs are considered, and this reduces the capital expenditure that would have otherwise been incurred without DGs to result in a grid code compliant network. Furthermore, there is evidence of reduction in losses under high load conditions and increase in losses under low load conditions in the simulation results. Reduction in losses is caused by supplementary generation from wind and solar plants while increase in losses is due to excessive generation from wind plants which necessitate transportation over long distances to the nearest load centres. In addition to location, size and penetration levels as described in the literature, technology selection for a particular load type is also of utmost important to maximise the DG benefits on the network.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23158号 / 工博第4802号 / 新制||工||1751(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 引原 隆士, 教授 大村 善治, 特定講師 木村 真之 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Indiana University-Purdue University Indianapolis (IUPUI) / The interconnection of distributed resources requires specific voltage regulation, monitoring, protective relaying, power quality, and islanding detection. For this reason IEEE established standard IEEE 1547 that ensures the compliance with such requirements and it will help formulate technical specifications for grid interconnection with Distributed Generator (DG) resources. In search of meeting the IEEE 1547 standard requirement of detecting unintentional islanded operation, there has been ongoing research to develop anti-islanding methods that can detect the different changes that can occur when the grid is disconnected. A team of Electrical Engineering faculty at Indiana University Purdue University Indianapolis has worked previously on testing a DG unintentional Islanding Detection Scheme. This scheme uses an active anti-islanding method in which a small 1 Hz perturbation signal is added into the DG system and it helps detect when the grid is disconnected. The scheme uses the premise that a frequency deviation caused by perturbation to the system is smaller when the grid is connected than when it is in an island. In an initial dynamic simulation model for the islanding detection scheme, a two-machine microgrid system is used to explore frequency and voltage responses when the grid is disconnected. In this thesis, the two-machine microgrid is expanded to a ten-machine system so it can be shown that the frequency deviation caused by a perturbation signal is much smaller when the grid is connected even for a larger DG network. The 1 Hz component of the DG electrical frequency in a multiple machine microgrid system is also calculated in this thesis. This project was conducted in different stages. First, it was necessary to calculate the steady state power flow and electric power of a three-machine system and update the two-machine MATLAB program with the necessary changes. After making the changes, it was necessary to simulate the system and adjust the inertia of the machine that represents the grid to ensure that the simulation output was close in magnitude to previous testing results. When the three-machine system was successfully generated, a brand new program was created so a multiple machine system could be simulated. Then the multiple machine program was used to simulate and experiment with up to a ten-machine system. Finally a program to calculate the 1 Hz component of the DG electrical frequency was generated and used to show that the magnitude squared of the 1 Hz component is inversely proportional to the number of machines connected to the system. These last findings will later help set the threshold for islanding detection appropriately for different numbers of DG.

For many years some people have dismissed the idea that small generators placed close to loads could replace large central generation plants. In the near future, this idea will probably hold true. However, many companies today are producing small generators that will have a great impact on the power grid. These generators can be used to improve the overall service to a particular area. Also, these generators can also be used to save an electric utility or end-use customer a significant amount of money. However, there are a lot of concerns in using distributed generation. As a result, there are many different issues that need to be investigated when distributed generation is used. In this thesis, a guidebook is developed for an engineer to use when distributed generation is being considered. By following this guidebook an engineer should be able to investigate proper engineering and economic issues. The engineering issues the engineer should consider are coordination, application of protective devices, voltage control, transformer winding configuration, reduction of losses and islanding. By following this guidebook, the engineer should also consider certain economic issues that include the impact of distributed generation on generation, transmission and distribution companies, the impact of distributed generation on wholesale and retail rates, and the costs associated with installation, operation and maintenance of distributed generation. As an example application, the requirements found in the guidebook are applied to a particular scenario for an existing facility that is served by a distribution company.

Electric power systems are a key infrastructure today. Power systems can be divided into three major parts: generation, transmission, and distribution. Out of these the distribution system is the most complex part and least studied system. In order to have continuous and reliable power to all customers it is necessary to have a good protection system. Major disturbances that are caused and last for a very short duration are called faults. With the advent of distributed generation (DG), the understanding of fault response has become more difficult. This thesis presents the study of the fault response and the factors that influence the fault response with and without DG. As a part of the fault analysis line to ground faults are placed at various locations on the I 13 node feeder test case. Simulations are conducted in PSCAD and the results are analyzed. At each node the voltage and the current changes at the time of the fault are recorded. A DG is added to the system and is located at various nodes for each fault and the impact of the DG on the fault voltage and current quantities is recorded. A comparison of the impact of faults at various locations is presented. The impact of faults without DG and with DG is also analyzed

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Yes / Distributed generators (DGs) are a reliable solution to supply economic and reliable electricity to customers. It is the last stage in delivery of electric power which can be defined as an electric power source connected directly to the distribution network or on the customer site. It is necessary to allocate DGs optimally (size, placement and the type) to obtain commercial, technical, environmental and regulatory advantages of power systems. In this context, a comprehensive literature review of uncertainty modeling methods used for modeling uncertain parameters related to renewable DGs as well as methodologies used for the planning and operation of DGs integration into distribution network. / This work was supported in part by the SITARA project funded by the British Council and the Department for Business, Innovation and Skills, UK and in part by the University of Bradford, UK under the CCIP grant 66052/000000.

This study presents a methodology and the necessary analytical tools to evaluate the alternatives to provide Internet access with embedded power generation in remote areas. The objective is to provide a screening tool for policy makers to analyze possible telecom and power alternatives. Results from the study demonstrate the technical alternatives to providing sustainable Internet and power access. The dissertation investigates innovative telecom technologies currently available on the market, and develops a model that generates a Telecom-and-Internet access map of a region or a small country. The map illustrates the combination of technologies and their locations that can provide wide-area Internet access to cover a majority of the population at the least cost. The model then looks at the design of a small-scale power system for a remote location where grid power is unavailable or unreliable. The methodology takes into account locally available energy resources, technical and economic parameters of each power generating technology, and the trade-off among investment costs, environmental costs and system robustness. Lastly, a computer simulation is conducted to verify that the power system design has the ability to meet the demand at the level of required reliability. A remote area of a developing country (Chittagong and Chittagong Hill Tracts - Bangladesh) is selected as a case study. Several scenarios are simulated in order to explore the possibility of extending the reach of the Internet and electric power to the remote area, and to conceptualize pilot projects as building blocks to build a countrywide infrastructure. Since the selected area is one of the least developed and most difficult to access in Bangladesh, demonstrating that the Internet and local power access can be provided to this area can serve as a model for similar places around the world. / Ph. D.

As the world's energy use continues to grow, the development of clean distributed generation becomes increasingly important. Fuel cells are an environmentally friendly renewable energy source that can be used in a wide range of applications and are ideal for distributed power applications. In this study, the power conversion element of a dual single-phase, 10 kW stand-alone fuel cell system is analyzed. The modular converter consists of a DC-DC front-end cascaded with a half-bridge inverter. The entire system is accurately modeled, to help determine any interactions that may arise. Control strategies based on simplicity, performance, and cost are evaluated. A simple voltage loop, with careful consideration to avoid transformer saturation, is employed for the phase-shifted DC-DC converter. Several experimental transfer functions were measured to confirm the modeling assumptions and verify the control design of the DC-DC converter. Two control options for the inverter are explored in detail, and experimental results confirm that the modulation index must be controlled to regulate the output voltage during various load conditions. The final system is implemented without the use of current sensors, thus keeping the inverter cost down. Experimental results using a power supply are given for resistive, inductive, and nonlinear loads and the performance is acceptable. Fuel cell test results, including transient response, are also displayed and analyzed. / Master of Science