A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in ful lment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / This research investigates the power sharing between distributed energy resources with voltage and frequency droop control. A case study based on voltage sources in an islanded microgrid is set up in the laboratory, referred to as: The Example Microgrid. The Example Microgrid consists of two synchronous generators, active and reactive power loads. A simulation model is constructed based on the laboratory set-up, where componentwise and system-wise testing are completed. The simulation results are validated with the experimental set-up, and it is concluded that the model accurately represents the physical system under steady-state conditions. Further simulation studies on conventional droop controllers are conducted based on the Example Microgrid model. The results indicate that the use of conventional droop control is inappropriate for small, low-voltage islanded microgrids. As a possible application of this work, three variations of adapted droop controllers are simulated and their performance evaluated. It is found that with the adapted droop controllers, the power sharing error can be minimised / M T 2016

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018. / As the electric energy demand grows, there is a significant increase in the penetration of renewable generation (RG) in the existing electrical grid network. Interconnecting of renewable generation technologies to an existing distribution system has proven to provide various benefits such as meeting the growing load demand and its contribution to energy system decarbonisation, long-term energy security and expansion of energy access to new energy consumers in the developing urban and rural areas. However, the aim of this thesis is to conduct a study on the impacts of renewable generation on the power quality of electrical grid. Therefore, this work aims at assessing the potential effects of Distributed Generation (DG) on the operation of electric power system by modelling of harmonics and voltage distortion. With different types of renewable generation available at present, it is believed that some designs contribute significantly to electrical network’s Power Quality (PQ). After the analysis of harmonic currents (chapter 6 and 7 of this thesis) introduced by renewable generation technologies, their negative impact on the power quality of the grid is seen to be apparent at point of connection (POC) but only within controlled limits. Analytical method for modeling of harmonic interactions between the grid and aggregated distributed generation technologies are investigated using DIgSILENT Power Factory software and the results obtained are discussed.

Smart grid has been described as the Energy Internet: Where Energy Technology meets Information Technology. The incorporation of such technology into vast existing utility infrastructures offers many advantages, including possibilities for new smart appliances, energy management systems, better integration of renewable energy, value added services, and new business models, both for supply- and demand-side management. Smart grid also replaces aging utility technologies that are becoming increasingly unreliable, as the average ages for many critical components in utility systems now exceed their original design lives. However, while smart grid offers the promise of revolutionizing utility delivery systems, many questions remain about how such systems can be rolled out at the state, regional, and national levels. Many unique regulatory and market structure challenges exist, which makes it critical to pick the right technology for the right situation and to employ it in the right manner. Technology Roadmapping may be a valuable approach for helping to understand factors that could affect smart grid technology and product development, as well as key business, policy and regulatory drivers. As emerging smart grid technologies are developed and the fledgling industry matures, a critical issue will be understanding how the combination of industry drivers impact one another, what barriers exist to achieving the benefits of smart grid technologies, and how to prioritize R&D and acquisition efforts. Since the planning of power grids often relies on regional factors, it will also be important investigate linkages between smart grid deployment and regional planning goals. This can be used to develop strategies for overcoming barriers and achieving the benefits of this promising new technology. This research builds upon existing roadmapping processes by considering an integrated set of factors, including policy issues, which are specifically tuned to the needs of smart grids and have not generally been considered in other types of roadmapping efforts. It will also incorporate expert judgment quantification to prioritize factors, show the pathways for overcoming barriers and achieving benefits, and discussing the most promising strategies for achieving these goals.

The increasing demand for and prevalence of distributed energy resources (DER) such as solar power, electric vehicles, and energy storage, present a unique set of challenges for integration into a legacy power grid, and accurate models of the low-voltage distribution systems are critical for accurate simulations of DER. Accurate labeling of the phase connections for each customer in a utility model is one area of grid topology that is known to have errors and has implications for the safety, efficiency, and hosting capacity of a distribution system. This research presents a methodology for the phase identification of customers solely using the advanced metering infrastructure (AMI) voltage timeseries. This thesis proposes to use Spectral Clustering, combined with a sliding window ensemble method for utilizing a long-term, time-series dataset that includes missing data, to group customers within a lateral by phase. These clustering phase predictions validate over 90% of the existing phase labels in the model and identify customers where the current phase labels are incorrect in this model. Within this dataset, this methodology produces consistent, high-quality results, verified by validating the clustering phase predictions with the underlying topology of the system, as well as selected examples verified using satellite and street view images publicly available in Google Earth. Further analysis of the results of the Spectral Clustering predictions are also shown to not only validate and improve the phase labels in the utility model, but also show potential in the detection of other types of errors in the topology of the model such as errors in the labeling of connections between customers and transformers, unlabeled residential solar power, unlabeled transformers, and locating customers with incomplete information in the model. These results indicate excellent potential for further development of this methodology as a tool for validating and improving existing utility models of the low-voltage side of the distribution system.

Power transmission grid infrastructures deliver electricity across large distance and are vital to the functioning of modern society. Increasingly these setups embody highly-coupled cyber-physical systems where advanced telecommunications networks are used to send status and control information to operate power transmission grid components, i.e., "smart grids". However, due to the high inter-dependency between the communication and power grid network layers, failure events can lead to further loss of control of key grid components, i.e., even if they are undamaged. In turn, such dependencies can exacerbate cascading failures and lead to larger electricity blackouts, particularly under disaster conditions. As a result, a range of studies have looked at modelling failures in interdependent smart grids. However most of these designs have not considered the use of proactive network-level survivability schemes. Indeed, these strategies can help maintain vital control connectivity during failures and potentially lead to reduced outages. Hence this thesis addresses this critical area and applies connection protection methodologies to reduce communication/control disruption in transmission grids. The performance of these schemes is then analyzed using detailed simulation for a sample IEEE transmission grid. Overall findings show a good reduction in the number of overloaded transmission lines when applying network-level recovery schemes.

Favorable price trends and increasing demand for renewable energy sources portend accelerating integration of solar photovoltaic (PV) generation into traditional electric power system networks. Managing the variable output of massive PV resources makes system frequency regulation more complex and expensive. ISOs must procure additional regulation and load following capacity, while power plants must supply more regulation work. In contrast to costly physical storage solutions, this thesis proposes to address the issue by reconfiguring the electricity market pricing structure to translate all power imbalances into real-time market price signals. More accurately determining the instantaneous value of energy, electric power markets could reward participants who can quickly respond to frequency fluctuations. By utilizing short term forward markets to monetize the risk associated with intermittency, the true cost of reliability is determined and could reduce wasteful capacity payments. This market redesign is an ideal open platform for disparate smart grid technologies which could encourage all suppliers, loads and generator, to offer supply or reduce consumption when it is needed most and could vastly improve frequency performance metrics.

An optimally designed thermosiphon for power electronics cooling is developed. There exists a need for augmented grid assets to facilitate power routing and decrease line losses. Power converter augmented transformers (PCATs) are critically limited thermally. Conventional active cooling system pumps and fans will not meet the 30 year life and 99.9% reliability required for grid scale implementation. This approach seeks to develop a single-phase closed-loop thermosiphon to remove heat from power electronics at fluxes on the order of 10 - 15 W/cm2. The passive thermosiphon is inherently a coupled thermal-fluid system. A parametric model and multi-physics design optimization code will be constructed to simulate thermosiphon steady state performance. The model will utilize heat transfer and fluid dynamic correlations from literature. A particle swarm optimization technique will be implemented for its performance with discrete domain problems. Several thermosiphons will be constructed, instrumented, and tested to verify the model and reach an optimal design.

The objective of the research is to develop a cost-effective, dynamic grid controller called the controllable network transformer (CNT) that can be implemented by augmenting existing load tap changing (LTC) transformers with an AC-AC converter. The concept is based on using a fractionally rated direct AC-AC converter to control the power through an existing passive LTC. By using a modulation strategy based on virtual quadrature sources (VQS), it is possible to control both the magnitude and the phase angle of the output voltage of the CNT without having any inter-phase connections. The CNT architecture has many advantages over existing power flow controllers, like absence of low frequency storage, fractional converter rating, retro-fitting existing assets and independent per-phase operation making it potentially attractive for utility applications. The independent control of the magnitude and the phase angle of the output voltage allow independent real and reactive power flow control through the CNT-controlled line. In a meshed network with asymmetric network stresses this functionality can be used to redirect power from critically loaded assets to other relatively under-utilized parallel paths. The power flow controllability of CNT can thus be used to lower the overall cost of generation of power. The solid state switches in the CNT with fast response capability enable incorporation of various additional critical functionalities like grid fault ride through, bypassing internal faults and dynamic damping. This bouquet of features makes the CNT useful under both steady state and transient conditions without compromising the grid reliability.

The Energy Independence and Security Act of 2007 established that the current electric grid was inadequate to serve the United States needs. Congress mandated that the U.S. transition to a more intelligent grid for the future. The Department of Energy was tasked with making this goal a reality. Six years later in 2013, only marginal progress has been made. Outside of smart meter rollouts and pilots programs funded through the American Recovery and Reinvestment Act of 2009 (ARRA), many issues still need to be addressed in order to realize the U.S. Smart Grid vision. Most of the barriers to progress are not technological; the research and business community are rising to the occasion and meeting the challenge through innovation. However, policy issues present a large barrier to overcome. With issues ranging from vague Smart Grids goals issued by the Department of Energy to a general lack of consumer knowledge about the Smart Grid. This paper seeks to identify the gaps in the current electric grid and policy schema are inadequate and suggest recommendations to encourage and expedite the growth of the U.S. Smart Grid.

Orientador: Aílton Akira Shinoda / Co-orientador: Ruy de Oliveira / Banca: Christiane Marie Schweitzer / Banca: Élvio João Leonardo / Resumo: Nas últimas décadas, os desafios no setor de energia elétrica têm aumentado significativamente, quer seja por questões referentes à forma como a energia é gerada e distribuída, ou pela postura do consumidor perante a rede elétrica. Diante da necessidade de uma reestruturação no negócio de energia elétrica, países investem em um conceito conhecido como Smart Grid, que tem como alvo a otimização e automação da rede de energia elétrica, utilizando tecnologias de informação e comunicação avançadas. Entre os principais objetivos propostos pela implementação das Smart Grids estão: aumento na confiabilidade da rede; redução de falhas no fornecimento de energia; redução de tempo e custo com manutenção na rede; registros mais precisos do consumo de energia; inserção de fontes renováveis de energia na rede, a fim de proporcionar um ambiente mais limpo. Investimentos em tecnologias de comunicação, componente fundamental para o bom desempenho das Smart Grids, merecem atenção especial. Diminuir o tempo de recuperação a falhas, inserir fontes de energias alternativas, entre outras funcionalidades, requerem uma rede eficiente e rápida. Os domínios de uma Smart Grid, possuem demandas de comunicação diversificadas, o que exige o emprego de diferentes tecnologias de comunicação, tornando sua implementação complexa. Dentre os protocolos de comunicação existentes, o Distributed Network Protocol 3.0 (DNP3) é um protocolo de comunicação baseado nas especificações do IEC (International Eletrotechnical Commission) e adaptado para ser utilizado em aplicações altamente seguras com taxa de transmissão de dados moderada. Vários trabalhos apontam para possíveis utilizações do protocolo DNP3 em conjunto com outros padrões de comunicação (IEEE 802.3, IEEE 802.11, IEEE 802.15.4). O IEEE 802.15.4 é um padrão de baixo consumo e seu uso tem sido difundido como solução adequada para redes de sensores sem fio em... / Abstract: Over the last decades, the challenges in the electricity sector have significantly increased, either by the issues regarding the way energy is generated and distributed by the consumer's attitude towards the electrical grid. In order to restructure the business model in the electricity sector, countries around the world have decided to invest in a concept known as Smart Grid. This system includes technologies such as digital, information and communication Technology (ICT). This concept aims to optimize and automate the electricity sector. The major changes proposed by the implementation of the Smart Grid are: higher network reliability, less failures in the power supply, lower time and costs of maintenance in the network, more accurate records of energy use by the consumer; and insertion of new energy sources in the network, contributing to reducing carbon dioxide emissions. Thus, investments in communication technologies is considered a key component for the performance of Smart Grids, as this technology demands diversified communication protocols that have to be fast and might involve a complex communication network. Among the existing communication protocols, the Distributed Network Protocol 3.0 (DNP3) is a protocol based on the specifications of the IEC (International Electrotechnical Commission) and adapted for use on highly secure applications with moderate data transmission rates. Several studies have pointed to possible use of the DNP3 protocol in conjunction with other communication standards such as IEEE 802.3, IEEE 802.11 and IEEE 802.15.4. The IEEE 802.15.4 is a standard for low power consumption and it has been disseminated as an appropriate solution for wireless sensor networks in several areas, such as industrial, commercial, residential and academic. The implementation of a heterogeneous communication network - to study and evaluate the behavior of a particular technology - is a highly costly process. However, computer ... / Mestre