Distributed Generators (DGs) are being increasingly utilized in power system distribution networks to provide electric power at or near load centers. These are generally based on technologies like solar, wind and biomass and range from 10 kW to 50 MW. Research work carried out in this thesis relates to the optimal siting and sizing of DGs in order to maximize the system voltage stability and improve voltage profile. This has been formulated as an optimization problem and solved using LINGO software. Power flow equations have been embedded in the LINGO formulation, along with other operating constraints. The solution provides optimal values of the bus voltage magnitudes and angles, which have been utilized to compute a stability index. Finally, a multi-objective formulation has been developed to simultaneously optimize the size and placement of the DGs. The impact of the DGs on voltage stability and voltage profile has been studied on I standard distribution test systems and verified using three-phase unbalanced power flow software developed at Mississippi State University (MSU). Results indicate that the sizing and siting of DGs are system dependent and should be optimally selected before installing the distributed generators in the system.

Reliability is a key aspect of power system design and planning. In this research we present a reliability analysis algorithm for large scale, radially operated (with respect to substation), reconfigurable, electrical distribution systems. The algorithm takes into account equipment power handling constraints and converges in a matter of seconds on systems containing thousands of components. Linked lists of segments are employed in obtaining the rapid convergence. A power flow calculation is used to check the power handling constraints. The application of distributed generators for electrical distribution systems is a new technology. The placement of distributed generation and its effects on reliability is investigated. Previous reliability calculations have been performed for static load models and inherently make the assumption that system reliability is independent of load. The study presented here evaluates improvement in reliability over a time varying load curve. Reliability indices for load points and the overall system have been developed. A new reliability index is proposed. The new index makes it easier to locate areas where reliability needs to be improved. The usefulness of this new index is demonstrated with numerical examples. / Master of Science

The integration of distributed generators (DGs) into the distribution grid has exacerbated voltage unbalance issues leading to greater risks of reducing equipment lifetime, equipment damages, and increased ohmic losses. Most approaches to regulating voltage in distribution systems only focus on voltage magnitude and neglect phasor discrepancies and do little to remedy voltage unbalance. To combat this, a novel Optimal Power Flow (OPF) is designed to help operate these resources in a manner that curtails voltage unbalance using the reactive power compensation capabilities of inverters. The OPF was run for a wide variety of loading conditions on a pair of systems using MATLAB and was shown to improve the voltage profile of the system in addition to minimizing losses in most cases. However, it is noted that the OPF loses exactness in highly stressed conditions and is unable to provide meaningful solutions / Master of Science / With the power grid getting greener and smarter by the day, a slew of new challenges arise to overcome. Distributed sources of energy like solar panels and batteries are being added to the grid right from the household level. While they are desirable for reducing our need for traditional sources of energy, the addition of these resources has been shown to cause issues in the quality of the power grid. This is particularly observed at the low-voltage domestic part of the grid where the resources cause issues with the voltage quality. The distribution grid is unbalanced by nature and adding these resources only amplifies this problem. To help mitigate voltage quality issues grid operators are starting to require voltage regulation capabilities from resources to be connected to the grid and a lot of work has been conducted to find the optimal strategies for operating these resources. However, existing paradigms for these sources only focus on fixing the voltage magnitude part of the power quality and neglect phasor relationships. This thesis aims to bridge this gap by developing a method to determine the optimal operation of these resources by using the voltage regulation capability to address both voltage magnitude and voltage unbalance issues in addition to optimal operation.

Distributed energy resources (DE) with power electronics interfaces and logic control using local measurements are capable of providing reactive power related to ancillary system services. In particular, local voltage regulation has drawn much attention in regards to power system reliability and voltage stability, especially from past major cascading outages. This dissertation addresses the challenges of controlling the DEs to regulate the local voltage in distribution systems. First, an adaptive voltage control method has been proposed to dynamically modify the control parameters of a single DE to respond to system changes such that the ideal response can be achieved. Theoretical analysis shows that a corresponding formulation of the dynamic control parameters exists; hence, the adaptive control method is theoretically solid. Also, the field experiment test results at the Distributed Energy Communications and Controls (DECC) Laboratory in single DE regulation case confirm the effectiveness of this method. Then, control methods have been discussed in the case of multiple DEs regulating voltages considering the availability of communications among all the DEs. When communications are readily available, a method is proposed to directly calculate the needed adaptive change of the DE control parameters in order to achieve the ideal response. When there is no communication available, an approach to adaptively and incrementally adjust the control parameters based on the local voltage changes is proposed. Since the impact from other DEs is implicitly considered in this approach, multiple DEs can collectively regulate voltages closely following the ideal response curve. Simulation results show that each method, with or without communications, can satisfy the fast response requirement for operational use without causing oscillation, inefficiency or system equipment interference, although the case with communication can perform even faster and more accurate. Since the proposed adaptive voltage regulation method in the case of multiple DEs without communication, has a high tolerance to real-time data shortage and can still provide good enough performance, it is more suitable for broad utility applications. The approach of multiple DEs with communication can be considered as a high-end solution, which gives faster and more precise results at a higher cost

The main topic of this research is the efficient operation of a modernized distribution grid from both the customer side and utility side. For the customer side, this dissertation discusses the planning and operation of a customer with multiple demand response programs, energy storage systems and distributed generators; for the utility side, this dissertation addresses the implementation and assessment of voltage/VAR control and conservation voltage reduction in a distribution grid with distributed generators. The objectives of this research are as follows: (1) to develop methods to assist customers to select appropriate demand response programs considering the integration of energy storage systems and DGs, and perform corresponding energy management including dispatches of loads, energy storage systems, and DGs; (2) to develop stochastic voltage/VAR control techniques for distribution grids with renewable DGs; (3) to develop optimization and validation methods for the planning of integration of renewable DGs to assist the implementation of voltage/VAR control; and (4) to develop techniques to assess load-reduction effects of voltage/VAR control and conservation voltage reduction. In this dissertation, a two-stage co-optimization method for the planning and energy management of a customer with demand response programs is proposed. The first level is to optimally select suitable demand response programs to join and integrate batteries, and the second level is to schedule the dispatches of loads, batteries and fossil-fired backup generators. The proposed method considers various demand response programs, demand scenarios and customer types. It can provide guidance to a customer to make the most beneficial decisions in an electricity market with multiple demand response programs. For the implementation of voltage/VAR control, this dissertation proposes a stochastic rolling horizon optimization-based method to conduct optimal dispatches of voltage/VAR control devices such as on-load tap changers and capacitor banks. The uncertainties of renewable DG output are taken into account by the stochastic formulation and the generated scenarios. The exponential load models are applied to capture the load behaviors of various types of customers. A new method to simultaneously consider the integration of DGs and the implementation of voltage/VAR control is also developed. The proposed method includes both solution and validation stages. The planning problem is formulated as a bi-level stochastic program. The solution stage is based on sample average approximation (SAA), and the validation stage is based on multiple replication procedure (MRP) to test the robustness of the sample average approximation solutions of the stochastic program. This research applies big data-driven analytics and load modeling techniques to propose two novel methodologies to assess the load-reduction effects of conservation voltage reduction. The proposed methods can be used to assist utilities to select preferable feeders to implement conservation voltage reduction.

Smart grid is more than just the smart meters. The future smart grids are expected to include a high penetration of distributed generations (DGs), most of which will consist of renewable energy sources, such as solar or wind energy. It is believed that the high penetration of DGs will result in the reduction of power losses, voltage profile improvement, meeting future load demand, and optimizing the use of non-conventional energy sources. However, more serious problems will arise if a decent control mechanism is not exploited. An improperly managed high PV penetration may cause voltage profile disturbance, conflict with conventional network protection devices, interfere with transformer tap changers, and as a result, cause network instability. Indeed, it is feasible to organize DGs in a microgrid structure which will be connected to the main grid through a point of common coupling (PCC). Microgrids are natural innovation zones for the smart grid because of their scalability and flexibility. A proper organization and control of the interaction between the microgrid and the smartgrid is a challenge. Cooperative control makes it possible to organize different agents in a networked system to act as a group and realize the designated objectives. Cooperative control has been already applied to the autonomous vehicles and this work investigates its application in controlling the DGs in a micro grid. The microgrid power objectives are set by a higher level control and the application of the cooperative control makes it possible for the DGs to utilize a low bandwidth communication network and realize the objectives. Initially, the basics of the application of the DGs cooperative control are formulated. This includes organizing all the DGs of a microgrid to satisfy an active and a reactive power objective. Then, the cooperative control is further developed by the introduction of clustering DGs into several groups to satisfy multiple power objectives. Then, the cooperative distribution optimization is introduced iii to optimally dispatch the reactive power of the DGs to realize a unified microgrid voltage profile and minimize the losses. This distributed optimization is a gradient based technique and it is shown that when the communication is down, it reduces to a form of droop. However, this gradient based droop exhibits a superior performance in the transient response, by eliminating the overshoots caused by the conventional droop. Meanwhile, the interaction between each microgrid and the main grid can be formulated as a Stackelberg game. The main grid as the leader, by offering proper energy price to the micro grid, minimizes its cost and secures the power. This not only optimizes the economical interests of both sides, the microgrids and the main grid, but also yields an improved power flow and shaves the peak power. As such, a smartgrid may treat microgrids as individually dispatchable loads or generators.

Yes / This paper proposes a novel method for planning active distribution networks (ADNs) with the integration of an active network management (ANM) scheme using coordinated voltage control (CVC) through on-load tap changer (OLTC) transformers. The method was formulated as a security-constrained optimal power flow (SCOPF) problem to minimize total operational costs, which maximizes the utilization of renewable distributed generators (DGs) over a planning horizon. The ANM scheme was applied using OLTC to ensure safe operation and reduce voltage violations in the network. To analyse the impact of ANM, the planning problem was examined both with and without the ANM scheme. Moreover, SCOPF, considering the N-1 line contingency analysis and multi-DG configuration, was implemented to analyse the feasibility of the proposed method and the advantages of ANM under contingency situations. The method was validated on a weakly-meshed 16-bus UK generic distribution system (UKGDS). The results showed that ANM can lower operational costs and maintain network voltage for operation in feasible conditions even in the case of a contingency. Moreover, the ANM scheme mitigated the voltage rise effect caused by DGs and maximized their utilization.

A recente abertura de mercado, a carência de recursos públicos para investimentos em geração de energia, a dificuldade de realização de empreendimentos de grande porte por razão ambiental, bem como o programa de universalização do atendimento têm criado novas oportunidades no Setor Elétrico brasileiro, dentre as quais está a exploração de geração distribuída. Nesse âmbito, as micro redes que associam vários geradores de pequeno porte, operados por centro regional, vêm se revelando como uma interessante solução tanto para o investidor como para o atendimento de áreas de concessão específicas. Esta pesquisa apresenta um modelo de análise econômica da participação de geradores distribuídos, operando de forma pseudo-cooperativa, fundamentado na teoria dos jogos. O modelo foca o cliente, com futuro potencial de ser livre, capaz de gerar a sua própria energia através de geradores distribuídos. Uma micro-rede de geradores distribuídos pode ser constituída de vários agentes que, não obstante tenham toda ou parte de sua produção contratualmente comprometida, resolvem atuar de forma cooperada para auferir o ganho decorrente dos diferentes custos marginais de operação das máquinas, para cada nível de despacho de suas unidades. O modelo proposto prevê que a otimização da participação dos despachos das unidades cooperadas, em cada situação de carga, é obtida pela minimização global dos custos marginais totais, determinando a produção de cada gerador. O compartilhamento doganho advindo da cooperação é dado pela aplicação da Função de Shapley, que se fundamenta nas características técnicas e econômicas de operação de cada unidade. ) O modelo desenvolvido neste trabalho formulou o conceito pseudo-cooperação, que prevê a disponibilidade parcial da capacidade de geração de um ou mais agentes para produção dedicada à demanda cooperada da micro rede, de forma que a capacidade restante permanece para o agente oferecer a oportunidades do mercado. A otimização dos ganhos, tanto da rede cooperada como do agente que disponibiliza parte de sua capacidade ao mercado, é realizada através do compartilhamento do ganho da cooperação, da receita obtida da venda de energia ao mercado e do prêmio que o(s) agente(s) que transgride(m) sua(s) cota(s) mínima(s) de cooperação paga(m) aos participantes da cooperação. Com essa abordagem de cooperação parcial e otimização dos ganhos tornou-se possível maximizar os benefícios para os agentes e obter uma capacidade adicional, chamada neste trabalho de \"Sobra\", disponível para venda ao mercado. Desta forma, e como conclusão principal, pôde-se verificar que é possível a obtenção de ganhos adicionais sempre que um ou mais geradores trabalham de forma cooperada e que a pseudo-cooperação apresenta uma forma de aumentar esse ganho / The recent market expansion, the lack of public resources for investments in power generation, the difficulty of deployment of large projects due to environmental reasons, and also the program \"Universalização do Atendimento\" (program that aims to attend all country) has provided new opportunities on the Brazilian Electric Sector. One of these opportunities is the exploration of distributed generation. Under this idea, an interesting solution for the investor and also for the service provider in specific concession areas is the micro-grids. The micro-grids associate several small load generators it selves and these micro-grids are operated by regional centers. This research presents a model of economical analysis of the participation of distributed generators, operating in a pseudo-cooperative way, based in the game theory. The model adresses non free consumers that further may have the capability to be able to generate its own energy through distributed generators, as free consumers. A micro-grid of distributed generators can be composed by several agents that decide to act in a cooperative way aiming to earn from each level of dispatched power, through the different operational cost of the machines in the micro-grid. This is possible even having all or part the production already contractually committed. For each load situation, the proposed model foresees that the dispatch of power in each cooperated units is optimized by the global reduction of the costs thataffect the production of each generator. The share of the gain from the cooperation is given by the application of the Shapley function that is based in the technical and economical characteristics of operation of each unit. ) The developed model in this work has formulated a pseudo-cooperation concept, which foresees the partial availability of the generation capacity of one or more agents for dedicated production to the cooperated demand of the micro grid, so that the remaining capacity is available to be offered to opportunities of the market. The optimization of the gain over the cooperated grid, and also over the agent that make available its partial capacity to the market, is accomplished through the share of the cooperated gain, through the revenue obtained from the energy sold to the market, and also through the prize that the agents pay to other participants of the cooperation when they reach their minimal commitment. With the partial cooperation and gain optimization approach, it was possible to maximize the benefits for the agents and to obtain a surplus, called in this work of \"Sobra\", available to sell to the market. The main conclusion is that it is possible to obtain additional benefits whenever one or more generator work in a cooperative basis and that the pseudo-cooperation is a way to grown this benefits.

A recente abertura de mercado, a carência de recursos públicos para investimentos em geração de energia, a dificuldade de realização de empreendimentos de grande porte por razão ambiental, bem como o programa de universalização do atendimento têm criado novas oportunidades no Setor Elétrico brasileiro, dentre as quais está a exploração de geração distribuída. Nesse âmbito, as micro redes que associam vários geradores de pequeno porte, operados por centro regional, vêm se revelando como uma interessante solução tanto para o investidor como para o atendimento de áreas de concessão específicas. Esta pesquisa apresenta um modelo de análise econômica da participação de geradores distribuídos, operando de forma pseudo-cooperativa, fundamentado na teoria dos jogos. O modelo foca o cliente, com futuro potencial de ser livre, capaz de gerar a sua própria energia através de geradores distribuídos. Uma micro-rede de geradores distribuídos pode ser constituída de vários agentes que, não obstante tenham toda ou parte de sua produção contratualmente comprometida, resolvem atuar de forma cooperada para auferir o ganho decorrente dos diferentes custos marginais de operação das máquinas, para cada nível de despacho de suas unidades. O modelo proposto prevê que a otimização da participação dos despachos das unidades cooperadas, em cada situação de carga, é obtida pela minimização global dos custos marginais totais, determinando a produção de cada gerador. O compartilhamento doganho advindo da cooperação é dado pela aplicação da Função de Shapley, que se fundamenta nas características técnicas e econômicas de operação de cada unidade. ) O modelo desenvolvido neste trabalho formulou o conceito pseudo-cooperação, que prevê a disponibilidade parcial da capacidade de geração de um ou mais agentes para produção dedicada à demanda cooperada da micro rede, de forma que a capacidade restante permanece para o agente oferecer a oportunidades do mercado. A otimização dos ganhos, tanto da rede cooperada como do agente que disponibiliza parte de sua capacidade ao mercado, é realizada através do compartilhamento do ganho da cooperação, da receita obtida da venda de energia ao mercado e do prêmio que o(s) agente(s) que transgride(m) sua(s) cota(s) mínima(s) de cooperação paga(m) aos participantes da cooperação. Com essa abordagem de cooperação parcial e otimização dos ganhos tornou-se possível maximizar os benefícios para os agentes e obter uma capacidade adicional, chamada neste trabalho de \"Sobra\", disponível para venda ao mercado. Desta forma, e como conclusão principal, pôde-se verificar que é possível a obtenção de ganhos adicionais sempre que um ou mais geradores trabalham de forma cooperada e que a pseudo-cooperação apresenta uma forma de aumentar esse ganho / The recent market expansion, the lack of public resources for investments in power generation, the difficulty of deployment of large projects due to environmental reasons, and also the program \"Universalização do Atendimento\" (program that aims to attend all country) has provided new opportunities on the Brazilian Electric Sector. One of these opportunities is the exploration of distributed generation. Under this idea, an interesting solution for the investor and also for the service provider in specific concession areas is the micro-grids. The micro-grids associate several small load generators it selves and these micro-grids are operated by regional centers. This research presents a model of economical analysis of the participation of distributed generators, operating in a pseudo-cooperative way, based in the game theory. The model adresses non free consumers that further may have the capability to be able to generate its own energy through distributed generators, as free consumers. A micro-grid of distributed generators can be composed by several agents that decide to act in a cooperative way aiming to earn from each level of dispatched power, through the different operational cost of the machines in the micro-grid. This is possible even having all or part the production already contractually committed. For each load situation, the proposed model foresees that the dispatch of power in each cooperated units is optimized by the global reduction of the costs thataffect the production of each generator. The share of the gain from the cooperation is given by the application of the Shapley function that is based in the technical and economical characteristics of operation of each unit. ) The developed model in this work has formulated a pseudo-cooperation concept, which foresees the partial availability of the generation capacity of one or more agents for dedicated production to the cooperated demand of the micro grid, so that the remaining capacity is available to be offered to opportunities of the market. The optimization of the gain over the cooperated grid, and also over the agent that make available its partial capacity to the market, is accomplished through the share of the cooperated gain, through the revenue obtained from the energy sold to the market, and also through the prize that the agents pay to other participants of the cooperation when they reach their minimal commitment. With the partial cooperation and gain optimization approach, it was possible to maximize the benefits for the agents and to obtain a surplus, called in this work of \"Sobra\", available to sell to the market. The main conclusion is that it is possible to obtain additional benefits whenever one or more generator work in a cooperative basis and that the pseudo-cooperation is a way to grown this benefits.

Les travaux de recherche présentés dans ce mémoire ont pour objet d’apporter une vision stratégique d’intégration des productions distribuées (PD) dans les réseaux électriques. Ces travaux concernent la localisation optimale du point de raccordement, le dimensionnement et le type de production dans l’objectif de maximiser les bénéfices de la PD et de minimiser les pertes dans les réseaux. Les travaux de cette thèse concernent également la prise en compte de la variabilité de la charge et de la production dans la planification et la gestion opérationnelle des réseaux électriques. Tout d’abord, des algorithmes ont été développés pour les études des flux de puissance dans les systèmes d'alimentation en utilisant la méthode du complément Schur et la méthode « Run Length Encoding ». Ensuite, les pertes ont été estimées dans le calcul de la production réelle en développant un modèle linéaire simple, efficace et flexible. Par la suite, des productions décentralisées connectées aux réseaux électriques ont été modélisées en utilisant une méthode qui fusionne les filtres de Kalman et la théorie des graphes dans le but d'estimer la taille optimale de la production décentralisée. Une méthode qui comporte deux étapes est proposée. Dans la première étape, la méthode graphique est utilisée pour générer la matrice incidente pour construire le modèle linéaire et dans la deuxième étape, un algorithme Kalman est appliqué pour obtenir la taille optimale de production décentralisée à chaque jeu de barres. Les défis de l'utilisation de productions décentralisées ont été abordés pour minimiser la fonction objective (pertes de puissance réelle) en tenant compte de la capacité des productions décentralisées, de la capacité de la ligne de transmission et des contraintes de profil de tension. L’algorithme génétique et de techniques d'optimisations comme la méthode de points intérieurs ont été proposés pour déterminer localement et globalement le dimensionnement optimal et l'emplacement optimal des productions décentralisées dans les réseaux électriques. Enfin, un modèle de charge active a été conçu pour étudier différents types de courbe de charge (résidentielle, commerciale et industrielle). Nous avons développé également des algorithmes de simulation pour étudier l'intégration des parcs éoliens dans les réseaux électriques. Nous avons conçu des méthodes analytiques pour sélectionner la taille et l’emplacement d’une ferme éolienne, basé sur la réduction des pertes de puissance active. Nous avons montré que les variations de la vitesse moyenne annuelle du vent pourraient avoir un effet important sur les calculs de pertes de puissance active. Les méthodes analytiques et les algorithmes de simulation ont été développés sous Matlab/Simulink. / The research presented in this thesis aims at providing a strategic vision for the integration of distributed generators (DGs) into grid networks. This work focuses the optimal location of the connection point, dimensioning and type of production in order to maximize the benefits of DGs and minimize power losses in the networks. The work also concerns the impact of the variability of the load and the production in the planning and the operational management of the networks. First, algorithms have been developed for power flow studies in power systems using the Schur complement method and the "Run Length Encoding" method. Then, losses were estimated in the calculation of power output by developing a simple, efficient and flexible linear model. Subsequently, decentralized outputs connected to the electrical networks were modeled using a method that merges Kalman filters and graph theory in order to estimate the optimal size of decentralized production. A method which consists of two steps is proposed. In the first step, the graphical method is used to generate the incident matrix to construct the linear model and in the second step a Kalman algorithm is applied to obtain the optimal decentralized production size for each busbar. The challenges of using decentralized production have been addressed to minimize the objective function (real power losses) by taking into account the capacity of the decentralized productions, transmission line capacity and voltage profile constraints. The genetic algorithms and optimization techniques such as the method of interior points have been proposed to determine locally and globally the optimal dimensioning and the optimal location of the decentralized productions in the electrical networks. Finally, an active load model was designed to study different types of load curves (residential, commercial and industrial). We have also developed simulation algorithms to study the integration of wind farms in power grids. We have designed analytical methods to select the size and location of a wind farm, based on the reduction of active power losses. We have shown that variations in the mean annual wind speed could have a significant effect on the calculations of active power losses. Analytical methods and simulation algorithms were developed under Matlab / Simulink.