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Moghimi, Mojtaba. "Modelling and Optimization of Energy Management Systems in Microgrids and Multi-Microgrids". Thesis, Griffith University, 2018. http://hdl.handle.net/10072/385882.
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With the new challenges brought by the high penetration of Renewable Energy Resources (RESs) into the modern grid, developing new solutions and concepts are necessary. Microgrid (MG) is one of the new concepts introduced to overcome upcoming issues in the modern electricity grids. MGs and Multi-Microgrids (MMGs) are defined as the building blocks of smart grids. MGs are the small units, where power generation and consumption happen at the same location and MG makes the decisions by itself. MGs can operate grid-connected or island mode depending on the functionality of the MG. Energy Management System (EMS) is the decision making centre of the MG. The data from the devices is received by the EMS and after processing, the commands are sent to the controllable components. Management of voltage, active and reactive power, neutral current, unit commitment and economic dispatch are of the tasks of EMS.
In this PhD thesis, an optimal EMS for MGs and MMGs is developed. The main objective of this project by developing the EMS is to optimize the energy flow in the MGs and MMGs to obtain peak load shaving in a cost beneficial system. In order to achieve an efficient EMS, communication system, forecasting system, scheduling system, and optimization system are modelled and developed. Different types of EMS operation, centralized, decentralized and distributed, are investigated in this work to achieve the best combination for MMG EMS operation.
The communication system is mainly utilizing Modbus TCP/IP protocol for data transmission at local level and Internet of Things (IoT) protocols (MQTT) for the global communication level. A communication operation algorithm is proposed to manage the MMG EMS under different communication operation modes and communication failure conditions. Furthermore, a monitoring system is developed to collect the data from different devices in the MG. The data is processed in the MG EMS and the commands are sent to components through the communication infrastructure. The link between MGs and MMGs is through the proposed two-level communication system, where the expansion of MGs to a MMG is investigated. In the MMG, MGs are functioning as a unit while having different priorities and operating under different policies. Each MG has its own MG EMS and the EMSs transfer information through the communication system between each other in either centralized, decentralized, distributed, or no communication modes under the MMG EMS.
The forecasting system is required in the EMS to predict the future MG characteristics such as power generation and consumption. The forecasted data is the input to the optimization and scheduling system of EMS. Employing the forecasting system in the EMS would increase the accuracy of the optimization and scheduling systems. In this thesis, the timeseries-based forecasting algorithms are employed to predict next day’s active power using the load data, generation data, weather data and temperature data as the inputs.
The heart of EMS is the scheduling and optimization system. The purpose of the scheduling system is to define the amount and the time of energy flow in the MG for different generation sources and consumption loads. Furthermore, scheduling system is responsible for peak load shaving and valley filling. On the other hand, the optimization system has the task of minimizing the operation costs of the MGs. The role of market in the scheduling and optimization is important. Time of Use (ToU) tariff is the pricing system, which determines the peak and off peak hours for energy usage pricing. In order to apply the optimization system, a model of the system, an objective function and systems constraints are defined, where aging of battery energy storage system (BESS), operational cost of components and MG cost benefits are considered. To operate the EMS scheduling and optimization system, IBM CPLEX Optimization Studio solver conducts the optimization while for the scheduling system, objective function and constraints are defined in MATLAB. In this thesis, a rule-based, MILP and MIQP optimization system for commercial MGs including electric vehicles (EVs) are proposed to investigate performance of MG EMS for different case studies.
In this thesis, the literature for different scheduling and forecasting systems is investigated and different optimization algorithms are analysed. The communication protocols utilized in this research are described and compared to other protocols in the literature. In different chapters of this thesis, the modelling of MGs and MMG EMS, different modules of EMS, forecasting, optimization, scheduling and communication systems are described and analysed. A novel communication system for MMG EMS operation is proposed for commercial buildings. The performance of MG EMS and MMG EMS is examined for power and neutral current sharing, operation cost optimization, and demand peak shaving applications and results are compared to investigate the performance of proposed algorithms.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text
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Zhang, Fan. "Operation of Networked Microgrids in the Electrical Distribution System". Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1467974481.
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Awad, Bieshoy Awad Boutros. "Operation of Energy MicroGrids". Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54179/.
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Integrated Operation is a strategy to operate the Energy MicroGrid as an integrated system. In this strategy, a CHP plant, an electric water heater, and thermal storage were operated to support both electricity and heat networks of the Energy MicroGrid. An Integrated Optimal Power Flow was formulated and was used to investigate the advantages of this Integrated Operation. Simulations indicated that Integrated Operation minimised generation curtailment and load shedding. It also reduced electricity imported from the main grid and the operating cost.
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Hornik, Tomas. "Power quality in microgrids". Thesis, University of Liverpool, 2010. http://livrepository.liverpool.ac.uk/1456/.
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Rapidly increasing energy demand from the industrial and commercial sector, especially in the current climate of high oil prices, steadily reducing energy sources and at the same time increased concerns about environmental changes, have caused fast development of Distributed Power Generation Systems (DPGS) based on renewable energy. A recent concept is to group DPGS and the associated loads to a common local area forming a small power system called a microgrid. This small autonomous system formed by DPGS can offer increased reliability and effciency of future power system networks. Furthermore, the improvement of the control capabilities and operational features of microgrids brings environmental and economic benefits. The introduction of microgrids improves power quality, reduces transmission line congestion, decreases emission and energy losses, and effectively facilitates the utilisation of renewable energy resources. As a consequence of the fast expanding DPGS based on renewable energy sources, Transmission System Operators (TSO) have issued strict interconnection requirements (grid code compliance), e.g., on power quality control, reactive power control, fault ride-through etc. Among these different requirements issued by the grid operators, power quality have recently gained a lot of attention due to excessive non-linear and unbalanced loads over-stressing the power systems and causing system failure. As nonlinear and/or unbalanced loads can represent a high proportion of the total load in small-scale systems, the problem with power quality is a particular concern in microgrids. In this work, different control strategies are proposed and implemented for the grid and microgrid connected voltage-source inverters (VSI), based on H^inf and repetitive control techniques. The repetitive control, which is regarded as a simple learning control method, offers very good performance for voltage and current tracking as it can deal with a very large number of harmonics simultaneously. This leads to a very low Total Harmonic Distortion (THD) of the output voltage and/or the current even in the presence of nonlinear loads and/or grid distortions. Initially, a voltage controller proposed in the literature for microgrid applications is further developed and experimentally tested. The aim is to improve power quality and tracking performance, while considerably reducing the complexity of the controller design. The model of the plant is reduced for single-input-single-output (SISO) repetitive control design. As a consequence, the design becomes much simpler and the stability evaluation easier. Moreover, a frequency adaptive mechanism is proposed so that the controller can cope with grid frequency variations in the grid-connected mode. This mechanism allows the controller to maintain very good tracking performance over a wide range of grid frequencies. Then, a H^inf repetitive control strategy for the inverter current is proposed and validated with experiments. As a result, the power quality and tracking performance are considerably improved. In order to demonstrate the improvements, the proposed controller is compared with the traditional proportional-resonant (PR), proportional- integral (PI) and predictive deadbeat (DB) controllers. Finally, the advantages of the proposed voltage and current controllers based on H^inf and repetitive control techniques are put together for consideration in microgrid applications and experimentally tested. The proposed cascaded current-voltage control strategy is not a simple combination of the two control strategies, but a complete re-design after realising that the inverter LCL filter can be split into two separate partsfor the design of the controllers. As a consequence, the cascaded controller is able to maintain low THD in both the microgrid voltage and the current following into/from the grid at the same time. It also enables seamless transfer of the operation mode from standalone to grid-connected or vice versa. It turns out that the voltage controller can be reduced to a proportional gain cascaded with the internal model (in a re-arranged form), which can be easily implemented in real applications. Experiments under different scenarios (e.g. in the standalone mode or in the grid-connected mode, with linear, nonlinear or unbalanced loads etc.) are presented to demonstrate the excellent performance of the controllers.
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Levi, Patricia Janet. "Feasibility of grid compatible microgrids". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/108215.
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Thesis: S.M. in Technology and Policy, Massachusetts Institute of Technology, School of Engineering, Institute for Data, Systems, and Society, Technology and Policy Program, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 133-139).
There are 1.1 billion people in the world who lack access to electricity, mostly in rural areas. The expansion of the central grid has been slow in many developing countries, hampered by a lack of supply, poor finances, and politics. Distribution companies in these countries are often cash strapped, in a tremendous amount of debt and are unable to make adequate investments in infrastructure. Off-grid technologies can be the most cost-effective choice in remote areas, and they also can offer a solution for communities that will not receive reliable centralized electricity for many years. These solutions include solar home systems and microgrids. However, investment in microgrids has been discouraged by the risk of the central grid expanding into the service area of a microgrid. An attractive solution is to create technical standards for microgrids such that they are able to connect to the grid if or when it arrives, and to provide regulations for the integration of these systems into the operation of the main grid. This arrangement could reduce the risk to microgrid investors significantly. While existing literature speculates on the value of such a system, the costs and benefits have not been quantified. This analysis uses the Reference Electrification Model, a tool developed in collaboration by the Massachusetts Institute of Technology and IIT Comillas - Madrid, to assess the costs and benefits that might arise when using grid compatible microgrids. These results and an assessment of the regulatory context and forthcoming regulations show that grid compatible microgrids can provide significant social value, but only if supported by sufficient subsidies and a recognition of the costs imposed on society by depriving so many people of electricity.
by Patricia Janet Levi.
S.M. in Technology and Policy
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Blasi, Bronson Richard. "DC microgrids: review and applications". Kansas State University, 2013. http://hdl.handle.net/2097/16823.
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Master of ScienceDepartment of Architectural Engineering and Construction Science
Fred Hasler
This paper discusses a brief history of electricity, specifically alternating current (AC) and direct current (DC), and how the current standard of AC distribution has been reached. DC power was first produced in 1800, but the shift to AC occurred in the 1880’s with the advent of the transformer. Because the decisions for distribution were made over 100 years ago, it could be time to rethink the standards of power distribution. Compared to traditional AC distribution, DC microgrids are significantly more energy efficient when implemented with distributed generation. Distributed generation, or on-site generation from photovoltaic panels, wind turbines, fuel cells, or microturbines, is more efficient when the power is transmitted by DC. DC generation, paired with the growing DC load profile, increases energy savings by utilizing DC architecture and eliminating wasteful conversions. Energy savings would result from a lower grid strain and more efficient utilization of the utility grid. DC distribution results in a more reliable electrical service due to short transmission distances, high service reliability when paired with on-site generation, and efficient storage. Occupant safety is a perceived concern with DC microgrids due to the lack of knowledge and familiarity in regards to these systems. However, with proper regulation and design standards, building occupants never encounter voltage higher than 24VDC, which is significantly safer than existing 120VAC in the United States. DC Microgrids have several disadvantages such as higher initial cost due, in part, to unfamiliarity of the system as well as a general lack of code recognition and efficiency metric recognition leading to difficult certification and code compliance. Case studies are cited in this paper to demonstrate energy reduction possibilities due to the lack of modeling ability in current energy analysis programs and demonstrated energy savings of approximately 20%. It was concluded that continued advancement in code development will come from pressure to increase energy efficiency. This pressure, paired with the standardization of a 24VDC plug and socket, will cause substantial increases in DC microgrid usage in the next 10 years.
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Yassuda, Yamashita Damiela. "Hierarchical Control for Building Microgrids". Thesis, Poitiers, 2021. http://www.theses.fr/2021POIT2267.
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Représentant plus d'un tiers de la consommation mondiale d'électricité, les bâtiments sont le secteur énergétique majeur pour promouvoir l’usage des énergies renouvelables. L'installation à la fois de sources d’énergie rénouvelable et d'un système de stockage d'énergie électrique dans les bâtiments peut favoriser la transition énergétique vers un système électrique à faible émission de carbone, tout en permettant aux consommateurs d'énergie finaux de bénéficier d'une énergie propre. Malgré tous ces avantages, cette topologie innovante et distribuée d’un Micro-réseau dédié au Bâtiment (MB)nécessite des changements importants dans le réseau actuel, qui dépend des politiques énergétiques et d’avancement technologiques.La conception d'un Système de Gestion de l'Energie (EMS) capable de gérer efficacement les composants électriques du micro-réseau sans menacer la stabilité du réseau principal est un obstacle au développement des MB. Pour atténuer les effets néfastes introduits par des acteurs d’énergie imprévisibles, le concept d'autoconsommation est de plus en plus adopté. Néanmoins, une analyse technico-économique plus approfondie est nécessaire pour piloter d’une manière optimaledes systèmes de stockage d'énergie afin d’atteindre des indices d'autoconsommation plus élevés.Face à ces enjeux, le but de ce doctorat est de proposer un EMS pour les micro-réseaux installés dans les bâtiments afin de maximiser leur taux d’autoconsommation à un coût d’exploitation minimum. Parmi les architectures de contrôle, la structure hiérarchique s'est avérée efficace pour gérer des objectifs contradictoires qui ne sont pas dans la même échelle de temps. Ainsi, une structure de contrôle Hiérarchique à Modèle Prédictif (HMPC) a été adoptée pour remédier aux incertitudes liées aux déséquilibres de puissance ainsi qu’établir un compromis entre la réduction du coût de fonctionnement et le respect du code de l’énergie français.Considérant que les bâtiments ne sont pas homogènes et nécessitent des solutions adaptées à leur besoin, le contrôleur proposé a été couplé à deux modules fonctionnant à base d’analyse de données. Le premier algorithme consiste à gérer les inexactitudes dans les modèles internes de l’HMPC. Sans avoir besoin de régler aucun paramètre, cet algorithme améliore la précision du modèle de batteries jusqu'à trois fois et augmente jusqu'à dix fois la précision du modèle de stockage d'hydrogène, réduisant ainsi la dépendance de l’EMS aux étapes de modélisation. Le deuxième algorithme détermine de manière autonome les paramètres de l’HMPC et facilite le compromis entre les aspects économiques et énergétiques. S'appuyant uniquement sur l'analyse des données de déséquilibre de puissance et des mesures, le contrôleur hiérarchique spécifie quel dispositif de stockage d'énergie doit fonctionner quotidiennement en fonction de l'estimation du taux d'autoconsommation et du coût de fonctionnement du micro-réseau. Ces estimations diminuent les dépenses annuelles du micro-réseau en évitant la pénalisation en ce qui concerne les exigences d'autoconsommation et en réduisant la dégradation et l'entretien des systèmes de stockage d'énergie.L’EMS proposé s'est également révélé capable de charger de préférence les batteries des véhicules électriques en période de surplus d’énergie et les décharger pendant les périodes de déficit pour réduire les échanges d’énergie avec le réseau principal. Les résultats ont aussi montré que la contribution des batteries de véhicules électriques dépend de la taille du parc de véhicules, de leur temps de connexion et du profil de déséquilibre de puissance. En conclusion, à travers les simulations utilisant le dimensionnement réel d'un bâtiment public et résidentiel, l’EMS hiérarchique s'est avéré efficace pour gérer de nombreux dispositifs de stockage d'énergie et contribuer à l’essor de micro-réseaux dédiés aux bâtiments à l’avenirRepresenting more than one-third of global electricity consumption, buildings undergo the most important sector capable of reducing greenhouse gas emissions and promote the share of Renewable Energy Sources (RES). The integrated RES and electric energy storage system in buildings can assist the energy transition toward a low-carbon electricity system while allowing end-energy consumers to benefit from clean energy. Despite its valuable advantages, this innovative distributed Building Microgrids (BM) topology requires significant changes in the current electric grid, which is highly dependent on grid energy policies and technology breakthroughs.The complexity of designing a robust Energy Management System (EMS) capable of managing all electric components inside the microgrid efficiently without harming the main grid stability is one of the greatest challenge in the development of BM. To mitigate the harmful effects of unpredictable grid actors, the concept of self-consumption has been increasingly adopted. Nonetheless, further technical-economic analysis is needed to optimally manage the energy storage systems to attain higher marks of self-consumption.Faceing these issues, the purpose of this doctoral thesis is to propose a complete framework for designing a building EMS for microgrids installed in buildings capable of maximising the self-consumption rate at minimum operating cost. Among all possible control architectures, the hierarchical structure has proved effective to handle conflicting goals that are not in the same timeframe. Hence, a Hierarchical Model Predictive (HMPC) control structure was adopted to address the uncertainties in the power imbalance as well as the trade-off between costs and compliance with the French grid code.Considering that buildings are not homogeneous and require solutions tailored to their specific conditions, the proposed controller was enhanced by two data-driven modules. The first data-driven algorithm is to handle inaccuracies in HMPC internal models. Without needing to tune any parameter, this algorithm can enhance the accuracy of the battery model up to three times and improve up to ten times the precision of the hydrogen storage model. This makes the building EMS more flexible and less dependent on pre-modelling steps.The second data-oriented algorithm determines autonomously adequate parameters to HMPC to relieve the trade-off between economic and energy aspects. Relying only on power imbalance data analysis and local measurements, the proposed hierarchical controller determines which energy storage device must run daily based on the estimation of the annual self-consumption rate and the annual microgrid operating cost. These estimations decrease microgrid expenditure because it avoids grid penalties regarding the requirements of annual self-consumption and reduces the degradation and maintenance of energy storage devices.The proposed EMS also demonstrated being capable of exploiting the potentials of shifting in time the charging of batteries of plug-in electric vehicles. The simulation confirmed that the proposed controller preferably charges electric vehicles’ batteries at periods of energy surplus and discharges them during periods of energy deficit, leading the building microgrid to reduce grid energy exchange. The results also showed that electric vehicle batteries' contribution depends on the size of the vehicle parking, their arrival and departure time, and the building’s net power imbalance profile. In conclusion, through simulations using the dataset of both public and residential buildings, the proposed hierarchical building EMS proved its effectiveness to handle different kinds of energy storage devices and foster the development of forthcoming building microgrids
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Guo, Yuanzhen. "ECONOMIC OPERATION OF TYPICAL MICROGRIDS". UKnowledge, 2018. https://uknowledge.uky.edu/ece_etds/131.
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A microgrid is a subnetwork of power system that consists of a group of distributed energy sources and loads. It is designed to integrate distributed generation, loads, energy storage devices, converters, and monitoring and protection devices. Generally, a successful microgrid could run both in island mode (off-grid) and in grid-connected mode (on-grid), being able to convert between two modes at any time. With continuous development of the power system, distributed renewable generation unit accounts for an increasing proportion, since microgrid could effectively connect these generation units to the main grid, thereby improving the energy efficiency and the energy structure. Microgrid is increasingly playing an important role in the power system.
This thesis focuses on reducing the cost of microgrids through economic operation, including both static and dynamic economic operations. Three cases are tested based on these two methods. Also, each case will include four situations including one without ESS and three situations with 2MWh ESS, 3MWh ESS, 4MWh ESS, respectively.
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TUCCI, MICHELE. "Scalable control of islanded microgrids". Doctoral thesis, Università degli studi di Pavia, 2018. http://hdl.handle.net/11571/1214890.
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In the recent years, the increasing penetration of renewable energy sources has motivated a growing interest for microgrids, energy networks composed of interconnected Distributed Generation Units (DGUs) and loads. Microgrids are self-sustained electric systems that can operate either connected to the main grid or detached from it. In this thesis, we focus on the latter case, thus dealing with the so-called Islanded microGrids (ImGs). We propose scalable control design methodologies for both AC and DC ImGs, allowing DGUs and loads to be connected in general topologies and enter/leave the network over time. In order to ensure safe and reliable operations, we mirror the flexibility of ImGs structures in their primary and secondary control layers. Notably, off-line control design hinges on Plug-and-Play (PnP) synthesis, meaning that the computation of individual regulators is complemented by local optimization-based tests for denying dangerous plug-in/out requests. The solutions presented in this work aim to address some of the key challenges arising in control of AC and DC ImGs, while overcoming the limitations of the existing approaches. More precisely, this thesis comprises the following main contributions: (i) the development of decentralized primary control schemes for load-connected networks (i.e. where local loads appear only at the output terminals of each DGU) ensuring voltage stability in DC ImGs, and voltage and frequency stability in AC ImGs. In contrast with the most commonly used control strategies available in the literature, our regulators guarantee offset-free tracking of reference signals. Moreover, the proposed primary local controllers can be designed or updated on-the-fly when DGUs are plugged in/out, and the closed-loop stability of the ImG is always preserved. (ii) Novel approximate network reduction methods for handling totally general interconnections of DGUs and loads in AC ImGs. We study and exploit Kron reduction in order to derive an equivalent load-connected model of the original ImG, and designing stabilizing voltage and frequency regulators, independently of the ImG topology. (iii) Distributed secondary control schemes, built on top of primary layers, for accurate reactive power sharing in AC ImGs, and current sharing and voltage balancing in DC ImGs. In the latter case, we prove that the desired coordinated behaviors are achieved in a stable fashion and we describe how to design secondary regulators in a PnP manner when DGUs are added/removed to/from the network. (iv) Theoretical results are validated through extensive simulations, and some of the proposed design algorithms have been successfully tested on real ImG platforms.In the recent years, the increasing penetration of renewable energy sources has motivated a growing interest for microgrids, energy networks composed of interconnected Distributed Generation Units (DGUs) and loads. Microgrids are self-sustained electric systems that can operate either connected to the main grid or detached from it. In this thesis, we focus on the latter case, thus dealing with the so-called Islanded microGrids (ImGs). We propose scalable control design methodologies for both AC and DC ImGs, allowing DGUs and loads to be connected in general topologies and enter/leave the network over time. In order to ensure safe and reliable operations, we mirror the flexibility of ImGs structures in their primary and secondary control layers. Notably, off-line control design hinges on Plug-and-Play (PnP) synthesis, meaning that the computation of individual regulators is complemented by local optimization-based tests for denying dangerous plug-in/out requests. The solutions presented in this work aim to address some of the key challenges arising in control of AC and DC ImGs, while overcoming the limitations of the existing approaches. More precisely, this thesis comprises the following main contributions: (i) the development of decentralized primary control schemes for load-connected networks (i.e. where local loads appear only at the output terminals of each DGU) ensuring voltage stability in DC ImGs, and voltage and frequency stability in AC ImGs. In contrast with the most commonly used control strategies available in the literature, our regulators guarantee offset-free tracking of reference signals. Moreover, the proposed primary local controllers can be designed or updated on-the-fly when DGUs are plugged in/out, and the closed-loop stability of the ImG is always preserved. (ii) Novel approximate network reduction methods for handling totally general interconnections of DGUs and loads in AC ImGs. We study and exploit Kron reduction in order to derive an equivalent load-connected model of the original ImG, and designing stabilizing voltage and frequency regulators, independently of the ImG topology. (iii) Distributed secondary control schemes, built on top of primary layers, for accurate reactive power sharing in AC ImGs, and current sharing and voltage balancing in DC ImGs. In the latter case, we prove that the desired coordinated behaviors are achieved in a stable fashion and we describe how to design secondary regulators in a PnP manner when DGUs are added/removed to/from the network. (iv) Theoretical results are validated through extensive simulations, and some of the proposed design algorithms have been successfully tested on real ImG platforms.
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Lilla, Stefano <1969>. "Energy Management Systems of Microgrids". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/8778/1/Lilla_Stefano_Tesi.pdf.
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The distributed operation of parts of the system, denoted as microgrids or, more generally, as local energy communities, could be an effective answer to the issues posed by the increasing complexity of the modern power distribution systems facing the increasing penetration of renewable energy sources and the electrification of urban transportation.
The results of the research activities described in the thesis can be divided into three main parts. The first one is the modeling and analysis of low voltage power distribution networks feeding residential, commercial and small-scale industrial consumers including distributed generation units and storage systems. It focuses on an optimization model that has been applied to the energy management system of an experimental microgrid. A mixed integer linear programming model is developed and presented, which takes into account the unbalanced operation of the LV network.
The second part focuses on the day-ahead operational planning of a local energy community, which is assumed able to implement transactive energy control actions with allocation of the network power loss. The problem has been addressed by means of two different optimization procedures, namely a centralized mathematical programming model and a specific distributed optimization procedure based on the adoption of the alternating direction method of multipliers (ADMM).
The third part is the day-ahead optimization of the operation of a local energy system consisting of photovoltaic units, energy storage systems and loads aimed at minimizing the electricity procurement cost, considering the uncertainties in the load and generation forecasts. Two mixed integer linear programming models are adopted, each for a different representation of the battery: a simple energy balance constraint and the Kinetic Battery Model. The chapter describes the generation of the scenarios, the construction of the scenario tree and the intraday decision-making procedure based on the solution of the multistage stochastic programming.
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Vogt, Thorsten [Verfasser]. "Multikriterielle Betriebsstrategien industrieller Microgrids / Thorsten Vogt". Paderborn : Universitätsbibliothek, 2019. http://d-nb.info/1203710771/34.
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Mei, Jie S. M. Massachusetts Institute of Technology. "Applications of game theory in microgrids". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118055.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 57-62).
A microgrid, which can be defined as a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid, has been studied extensively in recent years. This paper will explore the application of non-cooperative game and cooperative game in microgrids. For an individual microgrid that is connected with renewable energy sources through DC-DC converters, a non-cooperative game theory based PI controller tuning method is proposed to help make more stable output voltage. For microgrids that are connected in network, a cooperative game theory based local energy exchange scheme is proposed to help them meet their energy requirements while achieving higher individual utility.
by Jie Mei.
S.M.
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Sabhlok, Vikalp Pal. "Dynamics and challenges of microgrids implementation". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/80685.
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Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 64-69).
Microgrids have the capability of operating on an island mode as well as an integrated mode with the smart grid, depending on the requirement and objectives. Recently, microgrids projects have gained popularity both in developed world and developing world because of their ability to lower cost, increase resiliency and overall power quality. However, most of the studies on microgrids till now have focused on the technological challenges associated with design and implementation of microgrids. This study tries to develop an industry perspective on the recent development of microgrids. Several case studies from both developed world and developing world are explained to understand drivers, constraints and challenges of microgrid implementation. A generic model used by Weil and Utterback (2005) forms the basis for this study to develop a conceptual model, mapping different social, technological, market and regulatory factors which influence technology and industry evolution. The same model is used to develop a scenario analysis to predict future development of microgrids as a technology and as an industry.
by Vikalp Pal Sabhlok.
S.M.
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Sam, Al-Attiyah. "Nested Microgrids: Operation and Control Requirement". Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201088.
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Nested Microgrids refers to the interconnection of multiple microgrids into one network. Theyare connected through the Nested Microgrid Network which forms the electrical link betweenthem and facilitates power exchange.In this thesis the concept of Nested Microgrids is investigated. This resulted in theconceptualization of three different implementation methods. Inter-microgrid interaction in termsof controllers and required communication is also analyzed. The functions would differ from anormal microgrid and they are discussed thoroughly in this report. Real life projects are alsopresented.The efficacy and implementation of the proposed control functions are verified with time-domainsimulations. Four microgrid control functions, islanding, resynchronization, feeder load shed ongenerator overload and black start are investigated in Nested Microgrid scenarios. Differentcontrol strategies and exchange of information among the microgrid controllers are proposed forstable Nested Microgrids operation. This project provides the ground work for future work toexpand upon the theory provided and apply it into practical scenarios.Nested Microgrids (nästlade mikronät) hänvisar till sammankoppling av flera mikronät i ettnätverk. De är anslutna via ett Nested Microgrid Network som bildar den elektriska kopplingenmellan dem och underlättar effektutbytet.I denna avhandling undersöks begreppet Nested Microgrids. Detta har resulterat ikonceptualisering av tre olika integreringsmetoder. Interaktion mellan mikronät i form avstyrenheter samt nödvändig datakommunikation analyseras också. Kontrollfunktionerna kommeratt skilja sig från ett normalt mikronät, och dessa diskuteras grundligt i denna rapport. Verkligaprojekt presenteras också.Funktionaliteten och implementeringen av de föreslagna styrfunktionerna verifieras medtidsdomänsimuleringar. Fyra styrfunktioner för mikronät undersöks i scenarier med NestedMicrogrids; Islanding, Resynchronization, Feeder Load Shed on Generator Overload och BlackStart. Olika kontrollstrategier och utbyte av information mellan mikronätens styrenheter föreslåsför stabil kapslade microgrids drift. Projektet ligger till grund för det framtida arbetet att utökateorin och tillämpa den i praktiska situationer.
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Sampaio, Junior Adalberto Ribeiro. "Controle de microgrids dirigido por modelos". Universidade Federal de Goiás, 2014. http://repositorio.bc.ufg.br/tede/handle/tede/3859.
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Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG
The use of model driven engineering (MDE) and models at runtime represent an important tools for the development and management of complex systems. We show how a model driven approach can be used to create a manager able to control the various components of a microgrid, besides adding autonomic behavior in this kind of system. Applying an architecture that respects the hierarchy of controllers present in microgrids, we show how devices can be controlled through calls and events that are targeted to a manager and defined in its model. This model-driven approach facilitates the control of devices and allows customization of the bahavior of a microgrid by the end user in charge of managing it.
O uso de engenharia de software dirigida por modelos (MDE) e de modelos em tempo de execução constitui uma ferramenta importante para desenvolver e controlar sistemas complexos. Neste trabalho utilizamos uma abordagem dirigida por modelos para controlar sistemas de distribuição de energia elétrica conhecidos como microgrids. Mostramos como uma abordagem dirigida por modelos pode ser utilizada para criar um gerente capaz de controlar os diversos componentes de uma microgrid, além de adicionar comportamento autonômico neste tipo de sistema. Aplicando uma arquitetura que respeita a hierarquia dos controladores presentes em microgrids, mostramos como os dispositivos podem ser controlados por meio de chamadas e eventos direcionados ao gerente de recursos e definidos em seu modelo. Essa forma de controle dirigido por modelos facilita a definição do controle dos dispositivos de uma microgrid por parte do usuário, além de permitir uma personalização do comportamento global de uma microgrid.
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Hurtt, James William. "Residential Microgrids for Disaster Recovery Operations". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/19242.
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The need for a continuous supply of electric power is vital to providing the basic services of modern life. The energy infrastructure that the vast majority of the world depends on, while very reliable, is also very vulnerable. This infrastructure is particularly vulnerable to disruptions caused by natural disasters. Interruptions of electric service can bring an end to virtually all the basic services that people are dependent on. Recent natural disasters have highlighted the vulnerabilities of large, economically developed, regions to disruptions to their supply of electricity. The widespread devastation from the 2011 Japanese Tsunami and Hurricane Irene in North America, have demonstrated both the vulnerability of the contemporary power grids to long term interruption of service and also the potential of microgrids to ride through these interruptions. Microgrids can be used before, during, and after a major natural disaster to supply electricity, after the main grid source has been interrupted. This thesis researches the potential of clean energy microgrids for disaster recovery. Also a model of a proposed residential microgrid for transient analysis is developed. As the world demands more energy at increasingly higher levels of reliability, the role of microgrids is expected to grow aggressively to meet these new requirements. This thesis will look at one potential application for a microgrid in a residential community for the purpose of operating in an independent island mode operation.Master of Science
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Chang, Chin-Yao. "Hierarchical Control of Inverter-Based Microgrids". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471815065.
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Yuan, Chen. "RESILIENT DISTRIBUTION SYSTEMS WITH COMMUNITY MICROGRIDS". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480478081556766.
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Benahmed, Sif Eddine. "Distributed Cooperative Control for DC Microgrids". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0056.
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Au cours des dernières années, le réseau électrique connait une transformation rapide avec la pénétration massive des unités de production renouvelables et distribuées. Le concept de microgrids (micro-réseau électrique) est un élément clés de cette transition énergétique. Ces micro-réseaux sont constitués par un ensemble de plusieurs unités de production distribuées (DGUs), d'unités de stockage (SUs) et de charges interconnectées par des lignes électriques. Un microgrid peut être installé dans plusieurs endroits, par exemple dans des maisons, des hôpitaux, des quartiers, etc. et fonctionne soit en mode connecté au réseau principale, soit en mode isolé (autonome). Les microgrids sont confrontés à plusieurs défis liés à la garantie de la stabilité, la cybersécurité, l'optimisation des coûts énergétiques, la gestion de l'énergie, la qualité de l'énergie, etc. Dans ce travail, nous concentrons notre attention sur le contrôle des microgrids à courant continu en mode de fonctionnement autonome. La principale contribution de cette thèse est l’établissement de lois de commande par retour d’état distribuées assurant un partage de courant proportionnel entre les unités de production, une régulation de la tension moyenne des lignes et un équilibrage simultané des états de charge des éléments de stockage. En partant de l'hypothèse que les agents (DGU ou SU) ont les mêmes paramètres physiques, la preuve de la convergence exponentielle et globale est donnée en l’absence d’une connaissance de la charge présente sur le réseau. La thèse est divisée en trois parties. La première partie présente le concept des microgrids, un état de l’art sur leurs stratégies de contrôle et les préliminaires mathématiques nécessaires tout au long du manuscrit. La deuxième partie constitue la contribution théorique de cette thèse et aborde la synthèse de lois de contrôle distribuées, garantissant les objectifs envisagés en l’absence d’une connaissance de la charge variable sur le réseau et même en cas de perturbation constantes au niveau de l’entrée de commande. Cette garantie est apportée en considérant trois actions intégrales distribuées de type consensus. Dans la troisième partie, les contrôleurs proposés sont évalués dans différents scénarios par le biais de simulation Matlab/Simulink et de tests Hardware-in-the-Loop (HIL) en temps réel. Les résultats montrent que les objectifs de contrôle sont atteints avec succès, ce qui illustre l'efficacité de la méthodologie de contrôle proposéeIn recent years, the power grid has undergone a rapid transformation with the massive penetration of renewable and distributed generation units. The concept of microgrids is a key element of this energy transition. Microgrids are made up of a set of several distributed generation units (DGUs), storage units (SUs) and loads interconnected by power lines. A microgrid can be installed in several locations, for example in houses, hospitals, a neighborhood or village, etc., and operates either in connected mode to the main grid or in isolated (autonomous) mode. Microgrids are facing several challenges related to stability assurance, cyber-security, energy cost optimization, energy management, power quality, etc. In this work, we focus our attention on the control of islanded direct current microgrids. The main contribution is the design of a new distributed control approach to provably achieve current sharing, average voltage regulation and state-of-charge balancing simultaneously with global exponential convergence. The main tools are consensus in multi-agent systems, passivity, Lyapunov stability, linear matrix inequalities, etc. The thesis is divided into three parts. The First part presents the concept of microgrids, a literature review of their control strategies and the mathematical preliminaries required throughout the manuscript. The second part deals with the design of the proposed distributed control approach to achieve the considered objectives. The system is augmented with three distributed consensus-like integral actions, and a distributed-based static state feedback control architecture is proposed. Starting from the assumption that the agents (DGUs or SUs) have the same physical parameters, we provide proof of global exponential convergence. Moreover, the proposed control approach is distributed, i.e., each agent exchange relative information with only its neighbors through sparse communication networks. The proposed controllers do not need any information about the parameters of the power lines neither the topology of the microgrid. The control objectives are reached despite the unknown load variation and constant disturbances. In the third part, the proposed distributed controllers are assessed in different scenarios through Matlab/Simulink simulation and real-time Hardware-in-the-Loop experiment. The results show that the control objectives are successfully achieved, illustrating the effectiveness of the proposed control methodology
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Ting, Sean. "Protection in Low Voltage DC Microgrids". Thesis, Ting, Sean (2017) Protection in Low Voltage DC Microgrids. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/38695/.
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Protection is an important aspect when designing a microgrid system, as it ensures the network is able to run safely. As the debate between AC vs. DC protection schemes continue, there appear to be distinct advantages and disadvantages on each side with respect to reliability, efficiency, security, environmental and economic concerns. In this thesis, a low voltage DC microgrid protection scheme used in a data center is proposed. The final goal of this project is to develop a network and perform a fault analysis study while investigating different aspects of power protection schemes. Research is done on different protection devices which will be used to protect their respective components.
Three types of faults will be tested on the system for fault current observation purposes. In order to calculate the theoretical fault current of the battery and converter, Microsoft Excel will be used. ICAPS by Intusoft will be used to simulate three different faults in the network. Fault 1 will be on the positive and negative pole of the converter/battery and the load. Fault 2 is a double line to ground fault located on one of the feeders near the load. Fault 3 is a single line to ground impedance located on one of the positive pole of the feeder with a high impedance.
Results show that there are commercial devices available to protect components in such a system. Ultra hybrid DC circuit breakers are used to protect the converter, Molded Case Circuit Breakers are used for feeder protection, and lastly fuses or circuit breakers can be used for battery protection.
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Melly, Nicholas Kipchirchir. "Short-term solar forecasting for microgrids". Thesis, Melly, Nicholas Kipchirchir (2019) Short-term solar forecasting for microgrids. Masters by Coursework thesis, Murdoch University, 2019. https://researchrepository.murdoch.edu.au/id/eprint/51339/.
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This thesis explores the need and application of short-term solar forecasting (STSF) in microgrids. Among several solar forecasting methods, a justification for the choice of sky imaging tools as a preferred method for STSF in microgrids is provided.
The rapid increase in the uptake of solar PV in the electricity grid has shown a convergence in research in the fields of solar forecasting and management of the electricity grid. This energy transition from fossil fuel powered generation to renewable energy generation characterised by consumer-controlled energy generation and the emergence of smart grid has created a surge in demand for real time solar PV forecast information. The relationship between short-term solar forecasting information and microgrid PV generation fluctuation is analysed together to identify areas for the application of STSF technique in microgrid management.
To achieve this, the various solar forecasting methods are discussed with a view of identifying suitable techniques for microgrid applications. Sky imaging is identified as a preferred method thus the operation principle of a sky imaging tool is explained followed by analysis of capabilities of several tools/products available in the market. A summary chart showing the capabilities of WobaS, Steady eye, Instacast and CloudCAM STSF tools is presented in a table.
Three case studies are selected to demonstrate the need and application of STSF under the following scenarios:
• Case 1: Uncontrollable distributed energy resource for this case solar PV, together with centrally located fossil fuel powered power plant with no STSF tool in use.
• Case 2: Centrally located and controllable solar PV plant, a central fossil fuel power plant and energy storage using STSF tool.
• Case 3: Virtual power plant using STSF tool.
Through this approach the need, application and associated benefits of STSF is clearly shown. The benefits in cost savings for the combination of STSF with battery storage is demonstrated. Overall this thesis connects STSF and microgrid management.
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Fonkwe, Fongang Edwin. "Towards resilient plug-and-play microgrids". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122685.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 159-164).
Microgrids have the potential to increase renewable energy penetration, reduce costs, and improve reliability of the electric grid. However, today's microgrids are unreliable, lack true modularity, and operate with rudimentary control systems. This thesis research makes contributions in the areas of microgrid modeling and simulation; microgrid testing and model validation; and advanced control design and tools in microgrids. These contributions are a step toward design, commissioning, and operation of resilient plug-and-play (pnp) microgrids, which will pave the way towards a more sustainable and electric energy abundant future for all.
"Facebook Inc. funded a portion of my PhD trajectory (2017 - 2019) by way of a Research Fellowship"
by Edwin Fonkwe Fongang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Weyrich, Morris Gregory. "On the benefits and costs of microgrids". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114561.
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This thesis examines the benefits that Microgrids can provide to a variety of stakeholders and considers their costs. A flexible framework is proposed in which to consider Microgrid stakeholders, benefits, and benefit allocation. A methodology is presented for evaluating several key benefits, namely: reliability improvement, ancillary service provision, investment deferral resulting from both peak load reduction and ancillary service provision, as well as emissions reduction. Finally, several Microgrid case studies are evaluated as business cases using the methodology presented in order to illustrate benefit estimation and allocation, and to better understand the interaction between the parameters that define a Microgrid project and the resultant benefits seen by each stakeholder.Cette thèse êtudie les avantages que peuvent fournir aux intéressées les micro-réseaux, et propose une approche à l'évaluation des couts et bénéfices. Un cadre flexible est proposé pour classer les intéressés, les avantages, et la répartition des avantages. Une méthodologie est présentée pour évaluer quelques avantages clés, incluant: amélioration de fiabilité, fourniture des services auxiliaires, possibilité de différer les investissements requis par l'augmentation de la charge par la réduction de la charge de pointe, et la réduction des émissions perturbatrices. Enfin, quelques études de cas micro-réseaux existants sont présentées, sous la forme de cas d'aaires à l'aide de la méthodologie présentée. Ceci est fait afin d'illustrer l'estimation et l'allocation des avantages, et pour une meilleure compréhension de l'interaction entreles paramètres qui définissent un projet de micro-réseau et les avantages dont bénéficient chacun des intéssés.
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Alibeik, Maryam. "Different configurations of microgrids and power converters". Thesis, Purdue University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1573479.
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This thesis proposes a two-phase microgrid system with voltages in quadrature. The two-phase microgrid system presents the following advantages: 1) constant power through the power line at balanced condition; 2) two voltages available by using a three-wire system; 3) optimized voltage utilization compared to a three-phase system; and 4) a direct connection of both symmetrical two-phase and single-phase machines. Power analysis and symmetrical components of this kind of microgrid have also been studied through this thesis. Besides the two-phase microgrid system, the hybrid DC/AC microgrid has been analyzed. Both hybrid DC/AC and two-phase microgrid need power interfaces such as power converters to be connected to the grid. Also two different types of power converters have been proposed and studied during this thesis.
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Zhang, D. "Optimal design and planning of energy microgrids". Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1418705/.
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Microgrids are local energy providers which reduce energy expense and gas emissions by utilising distributed energy resources (DERs) and are considered to be promising alternatives to existing centralised systems. However, currently, problems exist concerning their design and utilisation. This thesis investigates the optimal design and planning of microgrids using mathematical programming methods. First, a fair economic settlement scheme is considered for the participants of a microgrid. A mathematical programming formulation is proposed involving the fair electricity transfer price and unit capacity selection based on the Game-theory Nash bargaining approach. The problem is first formulated as a mixed integer non-linear programming (MINLP) model, and is then reformulated as a mixed integer linear programming (MILP) model. Second, an MILP model is formulated for the optimal scheduling of energy consumption of smart homes. DER operation and electricity consumption tasks are scheduled based on real-time electricity pricing, electricity task time windows and forecasted renewable energy output. A peak charge scheme is also adopted to reduce the peak demand from the grid. Next, an MILP model is proposed to optimise the respective costs among multiple customers in a smart building. It is based on the minimisation/maximisation optimisation approach for the lexicographic minimax/maximin method, which guarantees a Pareto-optimal solution. Consequently each customer will pay a fair energy cost based on their respective energy consumption. Finally, optimum electric vehicle (EV) battery operation scheduling and its related degradation are addressed within smart homes. EV batteries can be used as electricity storage for domestic appliances and provide vehicle to grid (V2G) services. However, they increase the battery degradation and decrease the battery performance. Therefore the objective is to minimise the total electricity cost and degradation cost while maintaining the demand under the agreed threshold by scheduling the operation of EV batteries.
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Liu, Jianzhe. "On Control and Optimization of DC Microgrids". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512049527948171.
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Ren, Wei. "The feasibility of microgrids for large facilities". Kansas State University, 2017. http://hdl.handle.net/2097/35482.
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Master of ScienceDepartment of Architectural Engineering and Construction Science
Fred L. Hasler
Typical building power supplied from power plants has significantly evolved over the last century. After power is generated and transferred from the power plant, it is distributed to the customer. The concept of Microgrid was introduced to address increasing concerns with power reliability requirements for some facilities. The Microgrid is a localized electric grid that can operate autonomously from the traditional electric grid (Macrogrid). Compared with generator sets, a Microgrid provides a faster system response and recovery to either whole or part of the electric load for a facility. The Microgrid can operate under two operation conditions: grid-tied mode and island mode. When it is working individually like an “island”, the system is not providing or receiving disturbance to or from the Macrogrid. The purpose of this paper is to give a detailed introduction of Microgrid and present research and conclusion about its feasibility. This report references previously published research to explain what a Microgrid is. Also, two detailed case studies provide a discussion about the feasibility of the Microgrid in terms of its reliability, economics and environmental impact - air quality. Although there are many challenges that Microgrids are facing, there are quite a number of reasons to consider them. The goal is to balance the benefits and challenges of Microgrids depend on each case. No doubt, the existing power grid will still provide the majority of power supply for global population. However, many companies and government-funded laboratories are investing time and money into research and development of Microgrids. With the advancement of the Microgrids, it is likely that Microgrids will be playing a larger role in providing secure, reliable energy to the building industry.
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Vijayaragavan, Krishna Prasad. "Feasibility of DC microgrids for rural electrification". Thesis, Högskolan Dalarna, Energiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:du-25850.
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DC system and DC microgrids are gaining popularity in recent times. This thesis suggests a method to state the workability of a DC based PV system using the softwares Simulink, PVsyst and HOMER. The aims of this project include suggesting a DC based architecture, finding out the performance ratio and a cost analysis. The advantages of the DC based system, the cost benefits associated with it and its performance will determine its feasibility. Not many softwares have the functionality to simulate DC based PV systems. PVsyst is considered as one of the most sought-out softwares for the simulation of PV systems. It can simulate a DC based PV system but has a lot of limitations when it comes to the architecture and voltage levels. Due to these factors, the results from softwares Simulink, Homer and PVsyst are used to calculate the performance ratio of the suggested DC system. The simulation of the DC system involves modelling of a DC-DC converter. DC-DC converters are used in HVDC transmission and are being considered for small scale and medium scale microgrids. The DC-DC boost converter is coupled with a MPPT model in Simulink. P and O algorithm is chosen as the MPPT algorithm as it is simple and widely used. The Simulink model of PV array and MPPT based boost converter provides the power output at the needed voltage level of 350V. The input for the Simulink model is obtained from the results of HOMER. The inputs include solar irradiation data and cell temperature. The same input data is used for the simulations in HOMER and PVsyst. The performance ratio is obtained by combining the power output from Simulink with the other aspects of the system from PVsyst. The performance ratio is done only for the month of January due to the limitations in Simulink. The performance ratio is found out to be 65.5 %. The cost estimation is done for the distribution and power electronics aspects of the system. It is found out that the cost associated with the conductors will have an impact on the total cost only if the conductors used for distribution is more in length. The cost associated with the power converters will make a difference in total cost only if the system is within the range of 100kW. The study shows the workability of the PV based DC system based on the above mentioned aspects
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Huang, Po-Hsu. "Systematic control strategy for inverter-based microgrids". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121612.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 121-125).
Small-scale power systems, microgrids (MGs), are becoming economically and technically feasible due to cost-effective battery storage with high-bandwidth inverter interfaces, thus facilitating efficient energy utilization from renewable sources to maintain autonomous operation without a grid connection. Therefore, control of inverter-based or inverter-dominant systems is gaining a lot of attention while posing different challenges compared to traditional power systems. Conventional droop-based control architectures can provide power-sharing capability, and are considered to be a cost-effective and reliable solution for microgrids. However, experimental studies have revealed that for small-scale microgrids, stability is significantly compromised by the droop control due to low X/R ratios and short lines. Therefore, a proper modeling framework for obtaining concise and accurate models becomes important to understand the physical nature of the instability. Such a framework can further facilitate a systematic control design for stability enhancement, allowing the development of power-sharing strategies and plug-and-play functionality for efficient microgrid operation. In this thesis, high-fidelity reduced-order models for microgrids are first developed and investigated. Then, based on the proposed models, concise and simple stability certificates are derived along with virtual impedance methods for local and global stability enhancement. Detailed discussions are carried out on the control design that aims at achieving both droop stability and controller robustness. Finally, a power and energy management scheme based on secondary compensation is developed to enhance operational efficiency. The integrated solution provides a comprehensive reference for the development of stable, reliable, and flexible inverter-based microgrids. All results are validated through both simulation and experimental studies.
by Po-Hsu Huang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Benamane, Siad Sabah. "DC Microgrids Control for renewable energies integration". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLE006.
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La forte proportion des sources d'énergie intermittentes présente de nouveaux défis pour la stabilité et la fiabilité des réseaux électriques. Dans ce travail nous considérons la connexion de ces sources avec et un système de stockage hybride via un MicroGrid à courant continu (DC) afin de satisfaire les contraintes de connexion au réseau (les Grid-Codes). L'objectif principal ici est de concevoir un système pouvant répondre à ces exigences et nous permettant d'obtenir un comportement Plug and Play; cette approche est basée sur la "philosophie System of Systems ". utilisant des méthodologies de contrôle distribué.Cette thèse constitue une contribution au contrôle DC MicroGrid et introduit une analyse rigoureuse de la dynamique du system. La stabilisation du système repose sur des dispositifs de stockage: les batteries pour l'équilibre énergétique et la réponse à long terme des variations des flux d'énergie tandis que les supercondensateurs traitent l'équilibre des puissances et des variations rapide du system.Nous présenterons d’abord l’analyse du MicroGrid DC dont le contrôle est conçu à partir des modèles détaillés des sources d’énergie et des systèmes de stockage. Ce réseau peut présenter un comportement instable créé par intermittence de la source, les commutation des convertisseurs et leurs électroniques puissance et les courants oscillatoires produits par certains types de charges. Par conséquent, le système est sujet à des variations rapides et lentes. . La stabilisation de tels systèmes reposera sur le fonctionnement de différentes technologies de stockage, telles que la batterie et les supercondensateurs, qui opèrent dans différentes échelles de temps.Nous proposons un schéma de contrôle hiérarchique, basé sur la théorie du contrôle non linéaire, en particulier de Lyapunov, le backstraping et d’entrée / sortie de feedback linéarisation. Le DC MicroGrid proposé et son contrôle sont vérifiés à la fois par simulations et par expérimentation Les résultats montrent la bonne performance du système sous des variations de production et de consommationThe large penetration intermittent energy sources, presents a new challenges to power systems' stability and reliability; we consider in this work their connection through a Direct Current (DC) MicroGrid and a hybrid storage system, in order to satisfy constraints of connection to the network (the so-called Grid-Codes). The main objective here is to design a system that can fulfil these requirements and allow us to attain a Plug and Play behaviour; this approach is based on the “System of Systems philosophy'' using distributed control methodologies.This thesis constitutes a contribution for DC MicroGrid control and introduces a rigorous dynamics' analysis.. The stabilization of the system is based on storage devices: batteries for energy balance and long term response of power flow, while supercapacitors deal with power balance and fast response.First it will be presented the analysis of the DC MicroGrid which control is designed based on detailed models of energy sources and storage systems. This grid may present an unstable behaviour created by the source’s intermittent output power, switching ripples from the power converters and their power electronic and oscillatory currents produced by some types of loads. Therefore the system is subject to both fast and slow variations. The stabilization of such systems will be based on the operation of different technologies of storage, such as battery and supercapacitor, in different time scales.We propose a hierarchical control scheme, based on nonlinear control theory, in particular Lyapunov, backstepping and input/output feedback linearization. The proposed DC MicroGrid and its control are then verified both by computer simulations and by experiments. The results show the good performance of the system under variations on production and on consumption
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Волчан, Дмитро Вячеславович. "Система управління мережею MicroGrid". Bachelor's thesis, КПІ ім. Ігоря Сікорського, 2020. https://ela.kpi.ua/handle/123456789/39369.
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Мета роботи: підвищити ефективність управління мережею Microgrid за рахунок вдосконалення системи управління електроенергією сонячних батарей для роботи в режимі реального часу.
В даній роботі наведено огляд розумних електромереж, їх роль та взаємодія з існуючими електромережами. Розглядаються різні методи та системи управління мережами MicroGrid, проводиться їх аналіз, характеристика та порівняння, надається характеристика основних рівнів керування мережею MicroGrid.
Надається аналіз основних переваг управління сонячною енергією відносно інших джерел енергії в мережі MicroGrid. Досліджується алгоритм визначення положення сонця та враховується вплив погодних умов в реальному часі. Показано, що даний метод підвищує ефективність системи накопичення енергії порівняно з традиційними системами управління енергією.Goal: improve the efficiency of Microgrid network management by improving the solar power management system for real time operation. This paper provides an overview of smart grids, their role and interaction with existing grids. It discusses the various methods and systems for managing the MicroGrid network, analyzes, characterizes, and compares them, and describes the main layers of MicroGrid network management. The main advantages of solar energy management over other sources of energy in the MicroGrid network are analyzed. The algorithm for determining the position of the sun is investigated and the influence of real-time weather conditions is taken into account. It is shown that this method increases the efficiency of the energy storage system in comparison with traditional energy management systems.
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Yii, See Mee. "Microgrid with distributed generators". Thesis, Yii, See Mee (2009) Microgrid with distributed generators. Other thesis, Murdoch University, 2009. https://researchrepository.murdoch.edu.au/id/eprint/3250/.
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The principal aim of this project is to study the energy production by solar energy system in close to the consumers and integrated into a microgrid. Microgrids are small-scale versions of today’s huge centralized electricity system, where it can generate, distribute and regulate the flow of electricity to consumers. Microgrids are able to feature the latest smart technology that increases efficiency and reliability and to create islands of sustainable energy within the larger grid. The main benefits of microgrids are:
•Microgrids increase power supply reliability.
•Microgrids make it easier to efficiently meet growing consumer demand.
•Microgrids make it possible to deploy clean, renewable energy.
The report gives an overview of the generator technologies, and discusses the characteristics of a microgrid and the barriers that have to be overcome if microgrids are to be deployed in Australia. A focus of the study is a microgrid of domestic users (housing estate) powered by photovoltaics (PV). In addition, this project will propose a method to evaluate the reliability of customers contracted with microgrid including distributed generators (DG) and power storage devices.
A model of the energy consumption is used to produce typical profiles for the electricity consumption. Focusing on the balance between generation and load, a methodology has been developed to determine the optimum combination of generators and energy storage in the microgrid. It is found that a microgrid consisting of around 3kW (max peak) per household and 50% reduction of the electricity consumption will maintain energy balance on a yearly basis if supplemented by energy storage. The principle conclusion is that microgrids do have real potential to make a major contribution to reducing Green house Gas Emissions from building.
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Alotibe, Mohammad. "Microgrid: modelling and control". Thesis, Alotibe, Mohammad (2010) Microgrid: modelling and control. Other thesis, Murdoch University, 2010. https://researchrepository.murdoch.edu.au/id/eprint/4065/.
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This thesis presents a complete model of a typical microgrid, together with identification of the required control strategies in order to operate this new type of power system. More specifically, it involves the modelling of PV systems, inverters, Phase Locked Loops (PLLs), loads and utility distribution networks, which can be then combined together to form a microgrid. The proposed microgrid control strategies in this thesis consider different operation conditions of a microgrid. For islanded operation, control techniques similar to those in conventional power systems are adopted and modified to regulate the microgrid operation. For grid-connected operation, constant current control and P-Q control schemes are used to control output powers of the sources within a microgrid. After examining the simulation results, it has been concluded that the designed microgrid model is adequate in its representation and it behaved in a way similar to real integrated power systems. Furthermore, proposed control strategies have proven their robustness and effectiveness in controlling the operation of microgrid while maintaining system stability.
The contents of this thesis lay a groundwork that allows for further investigation and development in the areas of microgrid control and microgrid modelling. In this report detailed descriptions on the modelling of typical microgrid components are provided, followed by control techniques demonstrations, and then simulation results for discussion and investigation.
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Paniagua, Sánchez-Mateos Jesús. "Reliability-Constrained Microgrid Design". Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-187715.
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Microgrids are new challenging power systems under development. This report presents a feasibility study of microgrid development. This is an essential task before implementing microgrid systems. It is extremely important to know the number and size of distributed energy resources (DERs) needed and it is necessary to compare investment costs with benefits in order to evaluate the profitability of microgrids. Under the assumption that a large number of DERs improves the reliability of microgrids an optimization problem is formulated to get the accurate mix of distributed energy resources. Uncertainty in physical and financial parameters is taken into account to model the problem considering different scenarios. Uncertainty takes place in load demanded, renewable energy generation and electricity market price forecasts, availability of distributed energy resources and the microgrid islanding. It is modeled in a stochastic way. The optimization problem is formulated firstly as a mixed-integer programming solved via branch and bound and then it is improved formulating a two stage problem using Benders’ Decomposition which shortens the problem resolution. This optimization problem is divided in a long-term investment master problem and a short-term operation subproblem and it is solved iteratively until it reaches convergence. Bender’s Decomposition optimization problem is applied to real data from the Illinois Institute of Technology (IIT) and it gives the ideal mix of distributed energy resources for different uncertainty scenarios. These distributed energy resources are selected from an initial set. It proves the usefulness of this optimization technique which can be also applied to different microgrids and data. The different solutions obtained for different scenarios are explained and analyzed. They show the possibility of microgrid implementation and determine the most favorable scenarios to reach the microgrid implementation successfully. Reliability is a term highly linked to the microgrid concept and one of the most important reasons of microgrid development. Thus an analysis of reliability importance is implemented using the importance index of interruption cost ( ) in order to measure the reliability improvement of developing microgrids. It shows and quantifies the reliability improvement in the system.
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Ross, Michael. "Energy storage system scheduling in wind-diesel microgrids". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95237.
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This thesis proposes a knowledge based expert system tool that can be used as an on- line controller for the charging/discharging of an energy storage system in a wind-diesel microgrid. The wind-diesel microgrid is modelled, and a typical energy storage system is implemented to test the functionality of the controller using hourly-discrete power val- ues. The results are compared against an offline optimization that was provided 24-hour lookahead wind values, as well as a controller that was implemented using artificial neural networks. The knowledge based expert system is then used to analyze the cost of energy, by means of a parametric analysis, consisting of varying the wind penetration, energy stor- age system power rating and energy rating to determine for which wind penetration values a storage system implementation would be technically and economically viable. Differ- ent storage technologies are tested in a one-year time frame to determine which would be best suited for this particular application. The energy storage systems are implemented as single-layer and dual-layer, in which the knowledge based expert system is modified for the latter analysis, in order to determine whether or not there are advantages to having a dual-layer storage system. Throughout these analyses, the flexibility of the knowledge based expert system controller to various energy storage systems and microgrid models is verified. It also demonstrates that, in a context of high base generation costs, energy storage can be a viable solution to managing wind power variations.Cette thèse propose un système expert avec une base de connaissance qui peut être utilisé comme un contrôleur lors de la charge et de la décharge d'un système de stockage d'énergie dans un micro-réseau éolien-diesel. Un micro-réseau éolien-diesel modèle est établi, et un stockage est installé pour tester les fonctionnalités du contrôleur en utilisant des valeurs de la puissance horaire. Les résultats sont comparés avec une optimisation utilisant 24 heures de valeurs en avance pour la vitesse du vent, et aussi avec un contrôleur basé sur un réseau de neurones artificiels. Le contrôleur système expert est ensuite utilisé pour analyser les coûts d'énergie d'une analyse paramétrique, en variant la pénétration du vent, la puissance nominale du stockage, et la capacité nominale du stockage. Cette analyse indique pour quelles valeurs de pénétration éolienne une mise en vre d'un stockage serait viable économiquement et techniquement. Différentes technologies de stockage sont testées afin de déterminer laquelle serait le mieux adapté pour cette application particulière. Les systèmes de stockage sont réalisés à l'aide d'un ou de plusieurs types de systèmes, et le contrôleur système expert est modifié en conséquence, afin de déterminer s'il y a des avantages à avoir ce type de stockage. Ces analyses montrent aussi que le contrôleur système expert a la capacité et la flexibilité de s'adapter à des technologies ainsi qu'à des micro-réseaux de différents types.
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Paquette, Andrew Donald. "Power quality and inverter-generator interactions in microgrids". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51803.
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This research addresses some of the difficulties faced when operating voltage controlled inverters with synchronous generators in microgrids. First, an overview of microgrid value propositions is provided, and the problems faced when attempting to use microgrids to provide improved power quality are discussed. Design considerations for different types of microgrids are provided to enable microgrids to deliver the desired functionality without adding unnecessary cost. The main body of this research investigates the poor transient load sharing encountered between voltage controlled inverters and synchronous generators in islanded operation. Poor transient load sharing results in high peak inverter rating requirements and high cost. The tradeoff between power quality and power sharing is highlighted, and methods to improve transient load sharing are proposed. The use of current limiting to protect inverters during faults and overloads is also investigated. Stability problems are identified when using simple inverter current limiting methods when operating in parallel with synchronous generators. Virtual impedance current limiting is proposed to improve transient stability during current limiting. The methods proposed in this thesis for mitigating inverter overloads and faults will allow for more reliable and cost effective application of inverter based distributed energy resources with synchronous generators in microgrids.
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Ojeda, Alejandro P. "A load shedding scheme for inverter based microgrids". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66450.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 71-72).
Over the last decade, penetration of microgrids containing distributed generation (DG) sources has increased in grid distribution systems. This requires the stable operation of microgrids when connected to the distribution system as well as during islanding. Islanding that is fault provoked is more likely to cause unstable microgrid operation than planned islanding. During fault provoked islanding, unstable operation is exacerbated when induction motor (IM) loads are present. Using the MATLAB simulation tool SimPowerSystems, an inverter-based microgrid model connected to the IEEE-13 distribution system was created. A load shedding scheme was developed in order to improve microgrid stability during fault provoked islanding conditions.
by Alejandro P. Ojeda.
M.Eng.
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Fero, Allison. "A scalable architecture for the interconnection of microgrids". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/115007.
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Thesis: S.M. in Technology and Policy, Massachusetts Institute of Technology, School of Engineering, Institute for Data, Systems, and Society, Technology and Policy Program, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 789-84).
Electrification is a global challenge that is especially acute in India, where about one fifth of the population has no access to electricity. Solar powered microgrid technology is a viable central grid alternative in the electrification of India, especially in remote areas where grid extension is cost prohibitive. However, the upfront costs of microgrid development, coupled with inadequate financing, have led to the implementation of small scale, stand alone systems. Thus, the costs of local generation and storage are a substantial barrier to acquisition of the technology. Furthermore, the issues of uncertainty, intermittency, and variability of renewable generation are daunting in small microgrids due to lack of aggregation. In this work, a methodology is provided that maximizes system-wide reliability through the design of a computationally scalable communication and control architecture for the interconnection of microgrids. An optimization based control system is proposed that finds optimal load scheduling and energy sharing decisions subject to system dynamics, power balance constraints, and congestion constraints, while maximizing network-wide reliability. The model is first formulated as a centralized optimization problem, and the value of interconnection is assessed using supply and demand data gathered in India. The model is then formulated as a layered decomposition, in which local scheduling optimization occurs at each microgrid, requiring only nearest neighbor communication to ensure feasibility of the solutions. Finally, a methodology is proposed to generate distributed optimal policies for a network of Linear Quadratic Regulators that are each making decisions coupled by network flow constraints. The LQR solution is combined with network flow dual decomposition to generate a fully decomposed algorithm for finding the dynamic programming solution of the LQR subject to network flow constraints.
by Allison Fero.
S.M. in Technology and Policy
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Cavanagh, Kathleen Alison. "Stability-constrained design for low voltage DC microgrids". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120235.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 91-93).
Microgrids are a promising solution to reducing the energy access gap. However, microgrids are inherently fragile systems as they are not globally stable. This thesis considers two voltage instabilities that can arise in DC microgrids as a result of tightly controlled loads in the presence of inductive delays. First, we examine the instability that arises when a constant power load is added to or removed from a network where the topology is unknown. While removing the dependence of the stability certificate on the interconnection structure creates a major technical challenge, it is beneficial as it allows for ease in network modification as the needs of a community vary. We thus develop conditions on individual power sources and loads such that a network comprised of many arbitrarily-connected units will be stable. We use Brayton-Moser potential theory to develop design constraints on individual microgrid components that certify transient stability-guaranteeing that the system will return to a suitable equilibrium after a change to the overall network loading. We find that stability can be guaranteed by installing a parallel capacitor at each constant power load, and we derive an expression for the required capacitance. Second, we analyze the small-signal instabilities in microgrids containing arbitrary, rather than constant power, loads. This network representation allows for a more accurate representation of DC loads controlled by power converters which have a destabilizing negative incremental impedance over a finite frequency band in contrast to constant power loads which have a negative incremental impedance over all frequencies. While there are many established methods for the small-signal stability certification of DC networks, these methods do not explicitly account for the influence of network. In contrast, we develop a method for stability assessment of arbitrary DC grids by introducing the Augmented Power Dissipation and showing that it's positive definiteness is a sufficient condition for stability. We present an explicit expression for this quantity through load and network impedances and show how it could be directly used for stability certification of complex networks.
by Kathleen Alison Cavanagh.
S.M.
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Li, Xinyao. "Enhanced control and protection for inverter dominated microgrids". Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23510.
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Implementation of distributed energy resources (DER) has the potential to lower the carbon oxygen emissions, reduce the power distribution losses and improve the overall system operation. Despite the numerous advantages brought by these small-scale DERs, effective protection and control of such systems are still unsolved challenges. The distribution system is increasingly being confronted with congestion and voltage problems, which limits further penetration of DERs. Numerous studies have been conducted to analyse these challenges and provide recommendations or guidance for protection and control in the past few years. There is also a lot of effort to develop an advanced regime for integration of large amounts of DERs, such as the "microgrid". Microgrids are designed to provide control and protection of a cluster of DERs, storage units and loads in a way that can coordinate with the conventional utility grid operation with little conflict. As flexible as it is, a microgrid is connec ted to the utility grid behaving as a controllable entity in normal operation, and can be disconnected from the grid to present itself as a power island in emergency, e.g. system black-out. Since most of the DERs are interfaced with inverters, this thesis is dedicated to provide in-depth investigation of protection and control within inverter dominated microgrids. The thesis provides two main valuable contributions. Firstly, an enhanced control scheme for a microgrid consisting of multi inverter interfaced generators (IIG) is developed and compared to the conventional droop based decentralized control. The proposed control scheme is particularly designed for systems with IIGs interconnected via relatively long cable lengths (several kilo metres). It also allows switchless mode transition between islanded operation and grid-connected operation, which reduces the transient voltage and current oscillations, and enhances the transient behaviour of the IIGs. Compared to the conventional droop based decentralized control, the proposed control scheme has better operational stability and is immune to different lengths and R/X ratios of connecting cables. The proposed control also brings better voltage regulation and has a larger power output capacity. Secondly, a new travelling wave based protection scheme is developed which involves modification of an application friendly signal processing technique - Mathematical Morphology. The impact of distance to fault, fault inception angle and fault impedance is analysed and quantified. The thesis proposes a systematic protection solution which is proved to be immune to the changes of system topology, modes of operation and load conditions.
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Feroze, Hassan. "Multi-Agent Systems in Microgrids: Design and Implementation". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34687.
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The security and resiliency of electric power supply to serve critical facilities are of high importance in todayâ s world. Instead of building large electric power grids and high capacity transmission lines, an intelligent microgrid (or smart grid) can be considered as a promising power supply alternative. In recent years, multi-agent systems have been proposed to provide intelligent energy control and management systems in microgrids. Multi-agent systems offer their inherent benefits of flexibility, extensibility, autonomy, reduced maintenance and more. The implementation of a control network based on multi-agent systems that is capable of making intelligent decisions on behalf of the user has become an area of intense research.
Many previous works have proposed multi-agent system architectures that deal with buying and selling of energy within a microgrid and algorithms for auction systems. The others proposed frameworks for multi-agent systems that could be further developed for real life control of microgrid systems. However, most proposed methods ignore the process of sharing energy resources among multiple distinct sets of prioritized loads. It is important to study a scenario that emphasizes on supporting critical loads during outages based on the userâ s preferences and limited capacity. The situation becomes further appealing when an excess DER capacity after supplying critical loads is allocated to support non-critical loads that belong to multiple users. The previous works also ignore the study of dynamic interactions between the agents and the physical systems. It is important to study the interaction and time delay when an agent issues a control signal to control a physical device in a microgrid and when the command is executed. Agents must be able to respond to the information sensed from the external environment quickly enough to manage the microgrid in a timely fashion. The ability of agents to disconnect the microgrid during emergencies should also be studied. These issues are identified as knowledge gaps that are of focus in this thesis.
The objective of this research is to design, develop and implement a multi-agent system that enables real-time management of a microgrid. These include securing critical loads and supporting non-critical loads belonging to various owners with the distributed energy resource that has limited capacity during outages.
The system under study consists of physical (microgrid) and cyber elements (multi-agent system). The cyber part or the multi-agent system is of primary focus of this work. The microgrid simulation has been implemented in Matlab/Simulink. It is a simplified distribution circuit that consists of one distributed energy resources (DER), loads and the main grid power supply. For the multi-agent system implementation, various open source agent building toolkits are compared to identify the most suitable agent toolkit for implementation in the proposed multi-agent system. The agent architecture is then designed by dividing overall goal of the system into several smaller tasks and assigning them to each agent. The implementation of multi-agent system was completed by identifying Roles (Role Modeling) and Responsibilities (Social and Domain Responsibilities) of agents in the system, and modeling the Knowledge (Facts), rules and ontology for the agents. Finally, both microgrid simulation and multi-agent system are connected together via TCP/IP using external java programming and a third party TCP server in the Matlab/Simulink environment.
In summary, the multi-agent system is designed, developed and implemented in several simulation test cases. It is expected that this work will provide an insight into the design and development of a multi-agent system, as well as serving as a basis for practical implementation of an agent-based technology in a microgrid environment. Furthermore, the work also contributes to new design schemes to increase multi-agent systemâ s intelligence. In particular, these include control algorithms for intelligently managing the limited supply from a DER during emergencies to secure critical loads, and at the same time supporting non-critical loads when the users need the most.Master of Science
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Alqahtani, Ayedh H. A. S. "Modeling and Control of Photovoltaic Systems for Microgrids". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1381786869.
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Cingoz, Fatih. "EFFECTIVE POWER MANAGEMENT FOR AUTONOMOUS OPERATIONS OF MICROGRIDS". University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1469038927.
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Forel, Alexandre. "Distributed Model Predictive Operation Control of Interconnected Microgrids". Thesis, KTH, Reglerteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-206145.
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The upward trends in renewable energy deployment in recent years brings new challengesto the development of electrical networks. Interconnected microgrids appear as a novelbottom-up approach to the production and integration of renewable energy.Using model predictive control (MPC), the energy management of several interconnectedmicrogrids is investigated. An optimisation problem is formulated and distributed ontothe individual units using the alternating direction method of multipliers (ADMM). Themicrogrids cooperate to reach a global optimum using neighbour-to-neighbour communications.The benefits of using distributed operation control for microgrids are analysed and a controlarchitecture is proposed. Two algorithms are implemented to solve the optimisationproblem and their advantages or differences are confronted.Förnybara energikällor har ökat under senaste åren. Det innebär nya utmaningar förevolutionen av elektriska nät. Microgrids är en bottom-up ansats för produktion ochintegrering av förnybar energi.Energiförsörjning av flera sammankoppladeMicrogrids studeras in detta arbete genommodellbaserad prediktiv kontroll (MPC). Ett optimeringsproblem formuleras på de enskildaenheterna med Alternating DirectionMethod ofMultipliers (ADMM) och parallellberäkningar härledas.Microgrids samarbetar för att nå en global lösning av neighbourto-neighbour kommunikation.Distribuerad energiförsörjning av microgrids analyseras och två kontroll algorithmerutformas.
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Zhang, Xiaotian. "Modelling and control of power inverters in microgrids". Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/8073/.
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Power electronic converter systems play an important role in the interconnection of renewable energy sources in microgrids and utility grid. The interface between energy sources and microgrids is usually implemented by digitally controlled power inverters. This thesis provides a discrete modelling and design method for the digitally controlled inverters in microgrids. The fundamentals and background of digital control of power inverters are introduced. The small-signal models for digital pulse-width-modulations (PWMs) with delay effects are derived. Based on the models, the controllers can be designed using several methods according to the block diagrams. The simulation software and experimental environment for the digitally controlled inverters are described. For inverters operating in parallel, a linear voltage control scheme with duty-ratio feedforward is proposed. The control parameters are chosen according to the stable operating condition derived in z-domain. The closed-loop transfer function and output impedance for both the classical controller and the proposed controller are derived theoretically. A comparison reveals the advantages of the proposed control scheme: a unity closed-loop gain, no phase shift, good current sharing and low total harmonic distortion (THD) of the output voltage. The theoretical results are verified by the experimental setup of a system with two digitally controlled inverters connected in parallel. For digitally controlled grid-connected inverters with LCL filters, new small-signal z-domain models are deduced. The proposed methods model the inverters including different delay effects under most possible circumstances, which allows a direct design for controllers in z-domain. The stability boundaries obtained from the root loci of the classic models and the proposed models are compared to the simulation results, showing that the proposed z-domain models are more accurate in predicting instabilities. Experimental results are presented, showing the proposed models are also capable of predicting the values of control variables at the true sampling instants. The phase-shifted modulated multisampled multilevel inverter is studied. The filter current ripple frequency of the multilevel inverters is increased by the phase-shifted PWM. The small-signal z-domain model is derived. Compared to the bipolar switched inverter, the multisampled multilevel inverter is characterized by the capability of achieving higher feedback control gains, which improves the control performance. An experimental prototype based on a 10 kHz switching frequency, 80 kHz sampling frequency five-level single-phase H bridge inverter is tested to demonstrate the validity of the analysis.
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Ambia, Mir Nahidul. "Advanced control of multi-microgrids for grid integration". Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25722.
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Thanks to tremendous growing interest, the significant number of microgrids form a system called Multi-Microgrid, where multiple microgrids are interconnected to support local loads and exchange power to or from grid. Industry demands for advanced control and optimal coordination among microgrids with consideration of high penetration of renewable energy and complex system architectures. This thesis focuses on different key aspects of power systems and microgrids to develop novel approaches targeting the problem.
Firstly, different topologies of microgrids are studied from the literature review and most popular system architectures are considered in the study for proposing advanced control techniques. Distributed control systems with nested formation in the microgrids are proposed for improved power sharing strategy. The distributed control is designed to achieve self-healing capability of multi-microgrids during any contingency event. Local controllers of the inverters in each microgrid are interconnected through the nested formation. A nested optimization algorithm is designed to achieve power exchange between different microgrids. Multi-terminal HVDC network based multi-microgrids have been proposed for advanced control strategy due to its widespread application in power system. Adaptive droop control has been proposed based on consensus algorithm and matrix-based solutions to provide frequency support and power sharing between AC microgrids through the HVDC network. The proposed adaptive droop algorithm is featured to maintain frequency and voltage during contingency events and ensure efficient power sharing. Distributed hierarchical control system is proposed as well for multi-microgrids with nested formation-based optimization techniques to ensure proper power sharing in four-level based multi-microgrid topologies. The algorithm features energy management within the multi-microgrid through virtual controllers of primary and secondary frequency control. In addition, to the energy management issue, low system strength of grid has been considered to offer a wide range of areas under the advanced control of multi-microgrid. In that regard, single machine infinity bus model has been considered to implement control of grid forming inverters for integration with weak grid. Novel grid resynchronization and virtual synchronous generator control has been proposed to achieve multi-microgrids integration with weak grids.
Then, various simulation studies are performed to test the effectiveness of the proposed controls. The time domain simulations are performed on EMT power system tool PSCAD under different operating conditions, such as loading variations, N-1 contingency events, grid frequency change disturbance, islanding conditions etc. In addition to the time domain simulation studies, stability analysis of the proposed control has been carried out. In the stability analysis, pole-zero map, Nyquist plots and Bode plots have been demonstrated to analyse the stable conditions of the proposed control. The optimization algorithms results are also included in the simulation studies to reflect the performance of the control.
Finally, the advanced control solutions outcomes through time domain and stability results are compared with conventional control. It has been demonstrated that all proposed solutions perform better than conventional approaches and reflect significant improvement on the multi-microgrids. Furthermore, industry standards have been considered in the weak grid integration study and case studies are carried out based on power industry practices, including industry regulatory grid codes according to the power industry in Australia. The results indicate that the proposed controls are able to satisfy industry grid codes.
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Shoeb, Md Asaduzzaman. "Optimal operation and control of remote area microgrids". Thesis, Shoeb, Md Asaduzzaman ORCID: 0000-0002-6653-107X (2019) Optimal operation and control of remote area microgrids. PhD thesis, Murdoch University, 2019. https://researchrepository.murdoch.edu.au/id/eprint/54118/.
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Microgrid (MG) is a promising approach to proliferate distributed energy resources for electrification in remote areas. Remote area MGs usually operate as standalone systems and are supplied by a combination of conventional fossil fuel-based generators, renewable energy resources and energy storage systems. Irrespective of all considerations at the planning and design stage, such MGs are always prone to the uncertainties of their demand variation and the generation of their non-dispatchable renewable sources. Such events can cause voltage or frequency violation in the MG. This thesis has focused on developing proper operational and control techniques for such MGs. First, an effective management technique has been proposed and developed that can retain the voltage and frequency of the MGs within a predefined desired region, at least cost, using a multilayer scheme. If a violation is detected, the proposed technique will aim to define the most optimal generation level of dispatchable sources, MG’s best network configuration and engagement level of the supportive actions such as exchanging power with neighbouring MGs, utilising energy storages, demand response and renewable energy curtailment (if and when available). The technical, reliability and environmental aspects of the MG are considered within the proposed technique along with the operational cost. The determined optimal control variables will then be sent to the local controllers to apply proper arrangements in the system to retain the voltage or frequency within the desired range. On the other hand, some techniques are available in the literature that can predict the uncertainties of demand and renewable energy sources a few minutes ahead. Using such techniques, the voltage or frequency violation can also be predicted in short-horizon and prevented with the introduction of a suitable preventive controller. Hence, this thesis has then proposed and developed a look-ahead controller that uses the short-horizon prediction data of demand and renewable generation to determine any prospective voltage or frequency violation. Another alternative is temporarily coupling the adjacent MGs to support each other and form a system of coupled MGs. Thus, the thesis has then proposed and developed a suitable technique to form systems of coupled MGs while preserving the voltage and frequency of each MG and reassuring the optimal performance of all MGs. The proposed optimisation approach tries to solve the voltage or frequency problem by coupling the MGs when the local actions, such as energy storages, are inadequate or cost-ineffective. Another technique has also been proposed and developed that can readjust the dispatch of the suitable generation units, between the optimisations, to support small changes in load. To this end, the potential field concept is used by the loads to select suitable generation units to make the decision very quickly. The decision is made based on different criteria, such as cost, reliability, emission, and power loss. This process requires low computational efforts and can be done instantly. Besides, a periodic optimisation is performed by the MG’s central controller to retune the whole system and reconfirm the optimal operation. The performance of the developed techniques has been demonstrated and validated through extensive numerical analyses in MATLAB®.
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Wang, J. "The control of grid-connected inverters in microgrids". Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3001702/.
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Microgrids based on renewable power generation are under increasing develop-ment all over the world. Grid-connected inverters form an indispensable interface between the microgrids and power grid, to deliver the renewable energy into the grid by controlling the injected current. Inductor-capacitor-inductor (LCL) filters have been widely adopted to attenuate the high-frequency harmonics generated by the in-verters. However resonance of the LCL filters significantly affects the system control performance in terms of stability, transient response, grid synchronization, and power quality. This thesis carries out comprehensive stability analyses and proposes novel current control methods for studying and improving the performance of LCL-filtered grid-connected inverters. Firstly, a systematic study is carried out on the relationship between the time de-lay and stability of single-loop controlled grid-connected inverters that employ in-verter current feedback (ICF) or grid current feedback (GCF). The ranges of time delay for system stability are analyzed and deduced in the continuous s-domain and discrete z-domain. It is found that in the optimal range to achieve the maximum bandwidth and ensure adequate stability margins, the existence of a time delay weakens the stability of the ICF loop, whereas a proper time delay is required to maintain the stability of the GCF loop. The present work explains, for the first time, why different conclusions on the stability of ICF loop and GCF loop have been drawn in previous studies. To improve system stability, a linear predictor based time delay reduction method is proposed for ICF, while a time delay addition method is used for GCF. A controller design method is then presented that guarantees adequate stability margins. The study of the delay-dependent stability is validated by simula-tion and experiment. Secondly, three current control methods (the single-loop control based on ICF, that based on GCF, and a dual-loop control with capacitor current feedback (CCF) active damping) are compared by investigating their LCL resonance damping mech-anism. The virtual impedance introduced by each method is identified, which com-prises frequency-dependent resistance (positive or negative) and reactance (inductive or capacitive). The reactance shifts the LCL resonance frequency while a positive resistance provides damping to the resonance and hence stabilizes the system. Using the virtual impedance, the system stability is analyzed. The stable range of sampling frequency for the above methods is deduced, as well as the gain boundaries of the controllers. The simple and intuitive stability analysis approach by means of virtual impedance can be extended to other single- or dual-loop control methods. The study facilitates the analysis and design of control loops for grid-connected inverters with LCL filters, and it has been verified by experiment. Thirdly, a pseudo-derivative-feedback (PDF) current control is, for the first time, applied to three-phase LCL-filtered grid-connected inverters, which significantly im-proves the transient response of the system to a step change in the reference input through the elimination of overshoot and oscillation. A complex vector method is ap-plied to the modeling of three-phase LCL-filtered inverters in a synchronous rotating frame (SRF) by taking cross-couplings into consideration. Two PDF controllers with different terms in an inner feedback path are developed for an ICF system and a GCF system, respectively. For the ICF system, a simple PDF controller with a proportional term is used. Compared with a proportional-integral (PI) controller, which can only reduce the transient overshoot by decreasing controller gains, the PDF controller is able to eliminate the transient overshoot and oscillation over a wide range of controller parameters. For the GCF system, a PDF controller with a proportional term and a second-order derivative is developed. Active damping is achieved with only one feedback variable of the grid current, and simultaneously the system transient response is improved. Both theoretical analysis and experimental results verify the advantages of the PDF control over PI control methods. Fourthly and finally, a direct grid current control method without phase-locked loop (PLL) is proposed to attenuate low-order current harmonics in three-phase LCL-filtered grid-connected inverters. In comparison with conventional indirect or direct controllers which need PLL and are difficult to achieve satisfactory harmonic attenuation performance, the proposed method is able to satisfactorily mitigate the harmonic distortion, and at the same time reduce control complexity and computation burden because PLL is avoided. It is found that the direct grid current control is necessary to effectively suppress the current harmonics caused by the distortion in grid voltage. Active damping is achieved with an inner ICF loop, which is found to be superior to the widely used CCF damping in improving system stability. A sys-tematic controller design procedure is proposed to optimize the system performance. Experimental results confirm the improved harmonic attenuation ability of the pro-posed method in comparison to that of conventional control methods.
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Pashajavid, Ehsan. "Stable Overload Management Schemes for Isolated Coupled Microgrids". Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/59064.
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Enhancing the self-healing capability of the isolated AC microgrids (MGs) through mutual support of neighbouring MGs is the main objective of this thesis. Instead of a back-to-back converter, an instantaneous static switch (ISS) is employed to form a coupled-MG system to avoid the power loss incurred by the converters. The stable schemes for both interconnections of the MGs during overloading and isolation of the coupled MGs when overloading is removed are accurately developed.
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Abdelrazek, Ahmed Abdelhakim Moustafa. "Transformerless Grid-Tied Impedance Source Inverters for Microgrids". Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3427190.
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Renewable energy source (RESs) diffusion into the power system is continuously increasing, where the world cumulative installed capacity of solar and wind energy sources increased from around 63.2 GW in 2005 to around 903.1 GW in 2017 according to International Renewable Energy Agency (IRENA). The energy utilization from these RESs implies the use of what is called power conditioning stage (PCS). Such PCS acts as an interfacing layer between the RES side and the customer side, i. e. the load or the grid. These PCSs can utilize many different configurations depending on the employed RES, where the two-stage architecture is commonly used with solar photovoltaic (PV) systems due to the low or variable output voltage. Such two-stage architecture is usually implemented using a boost converter in order to regulate the PV source output voltage and maximize the output power, and a voltage source inverter (VSI) in order to achieve the inversion operation. On the other hand, impedance source inverters represent a different family of the existing PCSs, which are called single-stage power converters as they embraces the boosting capability within the inversion operation. This family of PCSs is seen as an interesting and competitive alternative to the twostage configuration, which are mandatory for low or variable voltage energy sources, such as PV and fuel cell energy sources. Therefore, these impedance source inverters have been utilized in many different applications, such as distributed generation and electric vehicles.
This family of PCSs, i. e. impedance source inverters, has experienced a fast evolution during the last few years in order to replace the conventional two-stage architecture since the first release of the three-phase Zsource inverter (ZSI) in 2003. Consequently, many research activities have been established in order to improve the ZSIs performance from different perspectives, such as overall voltage gain, voltage stresses across the different devices, continuity of the input current, and conversion efficiency.
Among these different topological improvements, the conventional ZSI and the quasi-ZSI (qZSI), are the most commonly used structures. Accordingly, the objective of this thesis is to study and reinforce the performance of this family of PCSs. Hence, the work in this thesis starts first by addressing the challenges behind eliminating the low frequency transformer in grid-tied PV systems in order to improve the conversion system efficiency, where a new measurement technique for the dc current component is proposed in order to effectively mitigate this dc current component. Then, the performance of the classical impedance source inverters has been assessed by studying all the possible modulation schemes and proposing a new one, under which the efficiency of these classical impedance source inverters have been improved. Furthermore, the partial-load operation of these impedance source inverters, considering the three-phase qZSI, has been studied and the possible ways of achieving a wide range of operation have been investigated.
Due to the seen demerits behind the classical impedance source inverters, an alternative new topology, which is called split-source inverter (SSI), is proposed, under which these demerits have effectively been mitigated or eliminated. Then, the challenges behind grid-tied operation of this single-stage dc-ac power converters has been investigated considering the SSI topology. It is worth to note that all the prior mentioned contributions have been validated experimentally.
Finally, this thesis is divided into two chapters, where the first chapter introduces an extended summary of the work done concerning the thesis topic, while the second part includes some selected papers from the publications that have been developed during the doctoral study. These selected papers give all the details of the work done in each section in the extended summary.