Дисертації: "Hybrid AC/DC Grid"

1

Briggner, Viktor, Pontus Grahn, and Linus Johansson. "Centralized Versus Distributed State Estimation for Hybrid AC/DC Grid." Thesis, KTH, Industriell ekologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189112.

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State estimation enables for values throughout a power transmission grid to be known with a higher level of certainty. New technologies for bulk power transmission and power grid measuring enables for new possibilities in the energy sector and it is required that state estimation algorithms are developed to adapt to these new technologies. This project aims to develop a state estimator (SE) that is modified for hybrid AC/HVDC grids with voltage source converters (VSC) and phasor measurement units (PMU). Two different sets of architectures are tested. The centralized architecture where one common SE is implemented for both AC and DC grids or the distributed where a separate SE for every grid is used. The method used for the SE is the weighted least square (WLS) method. The SE will be developed based on the power grid model ’The CIGRE B4 DC Grid Test System’, designed by the International Council on Large Electric Systems (CIGRE) as a benchmark system. The SE is subject to four different scenarios in order to evaluate the quality of the SE, benefits of added phasor measurements and choice of architecture for the SE. The results of the tests show that the developed SE improves the accuracy of state values on the DC grid. However, regarding the AC state values of the converters the results of the test are ambiguous. Furthermore the distributed architecture offered slightly less accurate AC values than the centralized. The addition of PMU measurements improved the error of the estimated values.

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2

Briggner, Viktor, Pontus Granhn, and Linus Johansson. "Centralized Versus Distributed State Estimation for Hybrid AC/DC Grid." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-200635.

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3

Alsharif, Sameer. "MANAGEMENT OF HYBRID (AC-DC) MICRO-GRIDS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1355191663.

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4

Agbemuko, Adedotun Jeremiah. "Modelling and control strategies for hybrid AC/DC grids." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667950.

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The proposals for large-scale deployment of renewable energy sources is leading to the need for more cross-border interconnections creating a pan-European power system, at the EU level. Such interconnections may take advantage of existing AC systems, but also of the DC links or DC grids under development; hence, hybrid AC/DC grids. Although hybrid AC/DC transmission grids are far from being truly large-scale, they are beginning to evolve as key components of future transmission infrastructures. By hybrid AC/DC grids, power electronic interfaces are invariably implied. As a consequence, several challenges are beginning to emerge at the network level due to the increasing adoption of these devices. The dynamics and interactions that may appear in such integrated systems are relatively unknown since they will interconnect at least two subnetworks of AC and DC characteristics. Understanding how several classes of interaction could occur is key to proper design of controllers to mitigate them. Further, changes to how subnetworks should be securely operated in unison is required. Therefore, a rethought is necessary in the presence of these devices. Nevertheless, the answer to the question of how to detect detrimental behaviours? Is central to any proposed solution. Currently, traditional methods for modelling and analysis are showing inadequacies. Lack of consistent methods to model and analyse the phenomena often result to complicated solutions as existing literature suggests. Even more important are models that are tractable, flexible, and technology agnostic to allow abstraction of the underlying challenges. Hence, methods to better understand and assess the mechanism of interactions at system level, that may impact secure operation are required. In addition, methods that are intuitive and efficient to detect sources of interactions, and isolate them as rapidly as possible are preferred. This goes to the heart of flexibility and tractability. Therefore, this thesis presents methodologies and strategies for modelling and control of large-scale hybrid AC/DC transmission grids from a systematic perspective, with the consideration of the controllable devices. This thesis employs several potent high-level methodologies that possess physical connotation, are technology agnostic, and provide tractability for control. Subsequently, recommended control strategies are easy to adopt as their physical significance can be established. The principal findings of this thesis are that, system interactions between subnetworks are dependent on the broad characteristics of the each subnetwork. Thus, manipulating any of these characteristics subject to considerations, improves the overall behaviour. Within each subnetwork, interactions depend mainly on the dynamics of existing controllers, and the interconnection between several devices. Then, questions on how to detect and mitigate interactions as efficiently as possible, while incorporating the most relevant behaviour is answered. Furthermore, the conflict of control requirements of each subnetwork of the hybrid AC/DC network is highlighted. Thus, information about these requirements are leveraged to achieve overall compromises without jeopardizing minimum performance. To conclude, following the assessment of detrimental interactions and their corresponding mechanism, control strategies that take these into consideration are proposed and demonstrated.
Per complir amb l'objectiu del gran desplegament de les energies renovables cal ampliar les interconnexions entre diferents països creant una xarxa elèctrica de transmissió a nivell Europeu. Aquestes interconexions poden aprofitar els sistemes en corrent altern (CA) ja existents però també de Links en corrent continu (CC) or xarxes en CC. Tot i que les xarxes de transmissió hibrides CA i CC son encara lliuny de ser una realitat, s'estan començant a posicionar como una component principal de les infrastructures de transmissió del futur. A les xarxes CA i CC, electronica de potencia n'és part fortament implicada. Com a conseqüència de l'ús d'aquests elements, varis reptes comencen a emergir degut a la seva complexitat innerent i la seva gran utilització. Les dinàmiques i les interaccions que poden apareixer en aquest sistema integrat són desconegudes doncs, aquest interconnectarà com a minim dos sub xarxes amb diferents caracteristiques com son la CA i la CC. Entendre com diferents interaccions poden succeir es clau per a poder dissenyar de manera adequada els control·ladors i mitigar-les. A més a més, canvis en la operació coordinada de les subxarxes és requerit. Aleshores, repensar com resoldre el problema és necessari quan ens trovem en presencia d'aquestes components. Però, la responsta a la pregunta; Com detectem comportaments negatius? es rellevant per a qualsevol soluciió que es vulgui propossar. Els mètodes tradicionals de modelització i anàlisi mostren insuficiències. La manca de mètodes coherents per modelar i analitzar els fenòmens sovint es tradueix en solucions complicades com suggereix la literatura existent. Encara són més importants els models tractables, flexibles i agnòstics que permetin la abstracció dels reptes subjacents. Per tant, es requereixen mètodes per comprendre i valorar millor el mecanisme dinteraccions a nivell del sistema que puguin afectar un funcionament segur. A més, es prefereixen mètodes intuïtius i eficients per detectar fonts dinteraccions i aïllar-les el més ràpidament possible. Això arriba al cor de la flexibilitat i la traçabilitat. Per tant, aquesta tesi discuteix les estratègies de modelatge i control de les xarxes de transmissió híbrides CA / CC a gran escala des d'una perspectiva sistemàtica, tenint en compte els dispositius controlables. Aquesta tesi utilitza una potent metodologia dalt nivell que té una connotació física, és tecnologia agnòstica i tractable. Posteriorment, les estratègies de control recomanades són fàcils dadoptar ja que es pot establir la seva significació física. Els principals resultats d'aquesta tesi són que, les interaccions del sistema entre subxarxes depenen de les àmplies característiques de cada subxarxa. Per tant, la manipulació daquestes característiques subjectes a consideracions millora el comportament general. Dins de cada subxarxa, les interaccions depenen principalment de la dinàmica dels controladors existents en dispositius controlables i de la interconnexió entre diversos dispositius. A continuació, es responen preguntes sobre com detectar i mitigar les interaccions de la manera més eficaç possible, alhora que incorporar el comportament més rellevant. A més, es posa de manifest el conflicte de requisits de control de cada subxarxa de la xarxa híbrida CA / CC. Així, es pot aprofitar la informació sobre aquests requisits per aconseguir compromisos generals sense posar en perill el rendiment mínim. Validar i demostrar aquests models i estratègies de control ha estat una contribució clau en aquesta tesi.

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5

Salehi, Pour Mehr Vahid. "Development and Verification of Control and Protection Strategies in Hybrid AC/DC Power Systems for Smart Grid Applications." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/804.

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Modern power networks incorporate communications and information technology infrastructure into the electrical power system to create a smart grid in terms of control and operation. The smart grid enables real-time communication and control between consumers and utility companies allowing suppliers to optimize energy usage based on price preference and system technical issues. The smart grid design aims to provide overall power system monitoring, create protection and control strategies to maintain system performance, stability and security. This dissertation contributed to the development of a unique and novel smart grid test-bed laboratory with integrated monitoring, protection and control systems. This test-bed was used as a platform to test the smart grid operational ideas developed here. The implementation of this system in the real-time software creates an environment for studying, implementing and verifying novel control and protection schemes developed in this dissertation. Phasor measurement techniques were developed using the available Data Acquisition (DAQ) devices in order to monitor all points in the power system in real time. This provides a practical view of system parameter changes, system abnormal conditions and its stability and security information system. These developments provide valuable measurements for technical power system operators in the energy control centers. Phasor Measurement technology is an excellent solution for improving system planning, operation and energy trading in addition to enabling advanced applications in Wide Area Monitoring, Protection and Control (WAMPAC). Moreover, a virtual protection system was developed and implemented in the smart grid laboratory with integrated functionality for wide area applications. Experiments and procedures were developed in the system in order to detect the system abnormal conditions and apply proper remedies to heal the system. A design for DC microgrid was developed to integrate it to the AC system with appropriate control capability. This system represents realistic hybrid AC/DC microgrids connectivity to the AC side to study the use of such architecture in system operation to help remedy system abnormal conditions. In addition, this dissertation explored the challenges and feasibility of the implementation of real-time system analysis features in order to monitor the system security and stability measures. These indices are measured experimentally during the operation of the developed hybrid AC/DC microgrids. Furthermore, a real-time optimal power flow system was implemented to optimally manage the power sharing between AC generators and DC side resources. A study relating to real-time energy management algorithm in hybrid microgrids was performed to evaluate the effects of using energy storage resources and their use in mitigating heavy load impacts on system stability and operational security.

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6

Farias, de Barros Heitor. "Planification de réseaux de distribution mixtes AC/DC." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALT050.

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L'intégration croissante des ressources énergétiques natives en courant continu à l'échelle de réseaux électriques, telles que les systèmes photovoltaïques, les véhicules électriques, les systèmes de stockage et les centres de données, remet en question le choix conventionnel des systèmes de distribution en courant alternatif (AC) au niveau de la moyenne tension (MV). Cette recherche vise à évaluer la viabilité technique et économique des réseaux de distribution MV AC/DC en développant des outils de planification pour les réseaux hybrides.L'étude propose des modèles de planification optimale des systèmes de distribution pour traiter les connexions MVDC point à point et les topologies hybrides, qui incorporent des ressources DC connectées au système par le biais de convertisseurs DC/DC, en utilisant des formulations telles que la programmation linéaire en nombres entiers mixtes, quadratique et conique de second ordre. Parmi les principales contributions de cette recherche, une analyse documentaire approfondie des hypothèses de planification a été réalisée, la proposition d'un modèle linéaire de pertes pour les stations de conversion AC/DC et DC/DC tenant compte de l'efficacité variable en fonction de la charge, l'incorporation de contraintes topologiques pour tenir compte des topologies radiales par morceaux, et l'évaluation des avantages économiques pour un large ensemble de paramètres dans le cadre des marchés de l'électricité dérégulés.Les perspectives futures comprennent l'étude de l'scalabilité des modèles proposés à des réseaux de distribution à plus grande échelle, l'exploration des tendances émergentes dans la résolution de l'optimisation et l'inclusion de choix liés à la conception dans les outils de planification
The increasing integration of utility-scale DC-native energy resources, such as photovoltaic systems, electric vehicles, storage systems, and data centers, challenges the conventional choice of AC distribution systems at the Medium Voltage (MV) level. This research aims to evaluate the technical and economic viability of AC/DC MV distribution networks by developing planning tools for hybrid networks.The study proposes optimal distribution system planning models to address point-to-point MVDC connections and hybrid topologies, which incorporate DC resources connected to the system through DC/DC converters, using formulations such as Mixed Integer Linear, Quadratic and Second Order Conic Programming. Some of the key contributions of this research include an extensive literature review of planning hypotheses, the proposal of a linear model of losses for AC/DC and DC/DC conversion stations accounting for part-load efficiency, the incorporation of topological constraints to accommodate piece-wise radial topologies, and the assessment of economic benefits across a wide range of parameters within the framework of unbundled electricity markets.Future perspectives include investigating the scalability of the proposed models to larger-scale distribution networks, exploring emerging trends in the optimization solving and including design-related choices in the planning tools

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7

Lo, Franco Francesco. "Integrazione di sistemi di accumulo a batterie e impianti fotovoltaici di grande taglia per applicazioni grid-connected." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.

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In un impianto fotovoltaico connesso alla rete elettrica, l’ integrazione di un sistema di accumulo permette di raccogliere l’ energia dal solare nelle ore di minor richiesta di rete (di giorno), ed erogarla nei momenti di bassa produzione e di maggiore richiesta di rete (la sera). In collaborazione con ENGIE Eps, è sorta l’ esigenza di confrontare tre diverse tipologie di accoppiamento delle batterie in un impianto ibrido PV+Batteria connesso alla rete elettrica. La prima architettura è chiamata AC coupling poiché il BESS (Battery Energy Storage System) è connesso tramite opportuni convertitori, direttamente alla rete elettrica. La terza e la seconda architettura sono denominate DC Coupling poiché il BESS è collegato tramite un convertitore o senza, al lato DC dell’ impianto. Il confronto è stato realizzato analizzando i flussi di potenza dell’ impianto facendo riferimento a dati di produzione reali forniti da ENGIE Eps. Più in particolare, sono stati forniti i dati di produzione e di irraggiamento di un impianto reale di potenza massima pari a 285 MW, con storage di capacità pari a 275 MWh. La valutazione della potenza richiesta all’ impianto è stata ottenuta dall’analisi del segnale AGC relativo alla rete nella quale l’ impianto è inserito. Tale segnale `e stato generato a partire da dati di frequenza di rete forniti dall’ azienda. Dall’ analisi precedentemente descritta si è individuata l’ architettura migliore in termini di rendimento, che risulta essere la DC coupling con DC/DC sulla batteria. Nell’ ultima parte della tesi si è inoltre svolto su richiesta di ENGIE Eps, lo studio del controllo dei convertitori relativi all’ architettura in esame. La strategia di controllo individuata è descritta nel dettaglio in questo documento.

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8

Anderson, Glenn Warwick Jan. "Hybrid simulation of AC-DC power systems." Thesis, University of Canterbury. Electrical and Computer Engineering, 1995. http://hdl.handle.net/10092/1176.

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Transient stability studies are primarily concerned with the generator response of ac power systems and use only steady state type equations to model HVdc converter terminals. These equations are adequate for small disturbances at the converter terminals but cannot accurately represent a converters behaviour during, and through its recovery of, a significant transient disturbance. A detailed three phase electromagnetic analysis is necessary to describe the converters correct behaviour. This thesis describes an accurate and effective hybrid method combining these two types of studies, for analyzing dynamically fast devices such as HVdc converters within ac power systems. Firstly, conventional techniques are reviewed for both a transient stability analysis of power systems and for an electromagnetic transient analysis of HVdc converters. This review deals in particular with the two programs that constitute the hybrid developed in this thesis. Various techniques are then examined to efficiently and accurately pass the dynamic effects of an HVdc link to an ac system stability study, and the dynamic effects of an ac system to a detailed HVdc link study. An optimal solution is derived to maximise the inherent advantages of a hybrid. Finally, the hybrid is applied to a test system and its effectiveness in performing its task is shown.

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9

Podes, Christopher. "AC/DC: Let There Be Hybrid Cooling." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3434.

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In today’s increasingly energy conscious society, the methods of providing thermal comfort to humans are constantly under scrutiny. Depending on the climate, and the comfort requirements of the occupants, buildings can be designed to heat and cool occupants with passive methods, as well as mechanical methods. In the subtropics, where buildings often need to be heated in the winter and cooled in the summer, a synthesis of these two methods would be ideal. However, there is a disconnect between the integration of passive cooling and mechanical air conditioning, in subtropical architecture. A study of user attitudes, based out of Australia, found that, “Central control of temperatures has been used to cut demand by preventing users from altering thermostats and other parts of the building for microclimate control. In particular, windows are sealed to prevent tampering.”1 Reliance on air conditioning has the everyday person convinced that if we save energy in the right places, we can use air conditioning as much as we like. The same study goes on to state, “Air-conditioning has been assumed to replace the need for climate design features in buildings creating poor thermal design and high energy use.”2 This can be most clearly seen in our public buildings. Fully conditioned buildings pump cool air into sealed envelopes, adjusting the thermostat to regulate thermal comfort year-round, often in a climate in which mechanical air conditioning is needed only four months of the year, and during the warmest hours of the day. Inversely, ventilated buildings provide passive cooling in a climate in which the temperature and humidity are often too high for thermal comfort during the same four months of the year. In his book Natural Ventilation in Buildings, Francis Allard points out that the global energy efficiency movement, begun in the early 1990s, has now emerged as a concept that incorporates active air conditioning and sitespecific climate design of buildings into one holistic approach.3 However, these buildings exist in more dry and temperate climates, and do not fully apply to the subtropics as cooling models. A model is needed for subtropical architecture allowing a building to reach both ends of the spectrum; from natural ventilation, through mechanical ventilation, to mechanical air conditioning. The goal of this thesis is to design a hybrid model for subtropical architecture which maximizes the use of natural and mechanical ventilation, and minimizes the use of mechanical air conditioning. The vehicle for this explanation is the design of an educational facility. Research of thermal comfort needs for occupants in the subtropics was accompanied with observation studies. This research was compared with case study, site and program analysis. The analysis was supplemented by a handbook of passive and mechanical cooling which was compiled to aid in establishing cooling strategies for the design process. The implementation of the research and analysis was brought to a conclusion that successfully achieved the goals of this thesis. By using passive methods to lower the temperature of the air surrounding the classroom buildings, the incoming air used to cool the occupants reached temperatures low enough to be considered comfortable inside the classrooms.

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10

Qiao, Feng. "Hybrid AC/DC distribution network voltage control." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/22978.

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A hybrid AC/DC distribution network can be formed after integration of increasing numbers of electronically interfaced distributed generators (DGs) and microgrids (MGs). Voltage/Var control (VVC) in this evolved system requires to control not only the traditional VVC resources such as transformer tap changer and shunt capacitor but also the newly emerged ones such as DGs and MGs. In addition, various stakeholders such as MG's operator and distribution network operator coexist in this evolved system. They usually represent distinct operational interests and make the VVC even more difficult. Therefore, VVC in hybrid AC/DC distribution networks expects to addresses not only the coordination among various voltage/var resources but also the conflicting interests of different stakeholders. In this thesis, various VVC schemes are developed to address above mentioned concerns, which provide promising solutions for system operators in future hybrid AC/DC distribution networks. Driven by advancements in power conversion and communication technologies, the dispersed MGs can be participated in VVC scheme and coordinated with other VVC resources. This thesis firstly proposes a VVC scheme to leverage the flexible power injections from grid-tied MGs. The tuning range of MGs' reactive power injections are widen by controlling local energy storage systems. Then, a two-layer VVC control scheme is developed. The upper layer is a multi-objective voltage/var optimisation model that schedules all the VVC resources including grid-tied MGs. The lower layer consists of various controllers in MGs, which aims to maintain the local power quality and to execute the setpoints sending from the upper layer. Although VVC performance can be enhanced by controlling MGs' reactive power injections, a lack of consideration for their active power control could result in deterioration on MG's local power supply. To this end, a coordinated VVC scheme is proposed to link MG's power management with VVC. The control of MG's local devices and control of voltage/var resources in distribution network are allocated into two different but interlinked optimisation models. Furthermore, the mechanically controlled OLTC and SC and electronically controlled DGs and MGs are scheduled in different timescales. Finally, a multi-objective VVC scheme is proposed to maximise the VVC contributions from various stakeholders such as MGs and distribution network operator. Since trade-off solutions are utilised in this scheme, it is promising to be used in multi-lateral cases where MGs are not unilaterally controlled by distribution network operators. The scheme is supported by an identification approach which fairly quantifies the VVC contributions from various stakeholders. Each stakeholder could be rewarded in proportion to its VVC contribution, so their participations are motivated without conflicts to satisfy voltage control requirements.

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11

Santiago-González, Juan Antonio. "Miniaturization of Ac-Dc power converters for grid interface." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120371.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.
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 185-189).
In this thesis we present a two-stage ac/dc grid-connected converter for computer applications. Also known as off-line power supplies, these converters have to meet various demanding specifications such as a wide input voltage range (typically 0-376 V), large voltage step down (typical output voltages range from 12-48 V), harmonic current limits and galvanic isolation. The focus of this work is in the reduction in volume of ac/dc converters while keeping efficiency constant or improving it, which is challenging to achieve while meeting all the specifications. The thesis breaks down the converter in subsystems and explores architectural and topological trade-offs, modeling, component selection and control methods. The performance of each individual subsystem is experimentally verified. The first stage of the converter is a step-down power factor correction (PFC) converter. This stage interacts with the grid and draws the necessary ac power from the line and rectifies it. Following the PFC is a capacitor bank, which is used to both buffer the ac power from the line and to provide hold-up energy to the output. The capacitor selection process is detailed in the thesis. The second stage of the converter provides isolation and regulation to the output. Two different approaches to the second stage converter are presented: using commercially available, "plug and play" converters and developing a custom converter. The full system is evaluated with both solutions and is compared to other state of the art converters. The final prototype achieves an efficiency of 95.33% at full power (250 W) and 230 Vac input, and a power density of 35 W/in3.
by Juan Antonio Santiago-González.
Ph. D.

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12

Mino, Kazuaki. "Novel hybrid unidirectional three-phase AC-DC converter systems /." [S.l.] : [s.n.], 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18185.

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13

Webb, Victor-Juan Eli. "Design of a 380 V/24 V DC Micro-Grid for Residential DC Distribution." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1355247158.

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14

Dong, Dong. "Ac-dc Bus-interface Bi-directional Converters in Renewable Energy Systems." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28495.

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This dissertation covers several issues related to the ac-dc bus-interface bi-directional converters in renewable energy systems. The dissertation explores a dc-electronic distribution system for residential and commercial applications with a focus on the design of an ac-dc bi-directional converter for such application. This converter is named as the â Energy Control Centerâ due to its unique role in the system. First, the impact of the unbalanced power from the ac grid, especially the single-phase grid, on the dc system operation is analyzed. Then, a simple ac-dc two-stage topology and an advanced digital control system is proposed with a detailed design procedure. The proposed converter system significantly reduces the dc-link capacitor volume and achieves a dynamics-decoupling operation between the interfaced systems. The total volume of the two-stage topology can be reduced by upto three times compared with the typical design of a full-bridge converter. In addition, film capacitors can be used instead of electrolytic capacitors in the system, and thus the whole system reliability is improved. A set of ac passive plus active filter solutions is proposed for the ac-dc bus-interface converter which significantly reduces the total power filter volume but still eliminate the total leakage current and the common-mode conducted EMI noises by more than 90%. The dc-side low-frequency CM voltage ripple generated by the unbalanced ac voltages can be eliminated as well. The proposed solution features a high reliability and fits three types of the prevalent low-voltage ac distribution systems. Grid synchronization, a critical interface control in ac-dc bus-interface converters, is discussed in detail. First, a novel single-phase grid synchronization solution is proposed to achieve the rejection of multiple noises as well as the capability to track the ac voltage amplitude. Then, a comprehensive modeling methodology of the grid synchronization for three-phase system is proposed to explain the output frequency behaviors of grid-interface power converters at the weak grid, at the islanded condition, and at the multi-converter condition. The proposed models provide a strong tool to predict the grid synchronization instabilities raised from industries under many operating conditions, which is critical in future more-distributed-generation power systems. Islanding detection issues in ac-dc bus-interface converters are discussed in detail. More than five frequency-based islanding detection algorithms are proposed. These solutions achieve different performances and are suitable for different applications, which are advantageous over existing solutions. More importantly, the detailed modeling, trade-off analysis, and design procedures are given to help completely understand the principles. In the end, the effectiveness of the proposed solutions in a multiple-converter system are analyzed. The results drawn from the discussion can help engineers to evaluate other existing solutions as well.
Ph. D.

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15

Santos, Heron Alves dos. "Design of a controlled single-phase ac-dc converter for interconnection of DC and AC buses of a microgrid." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=12977.

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Анотація:

The recent growth expectation of the participation of solar-photovoltaic energy sources in the power generation matrix has significantly increased the number of grid-connected systems. For connection to power grid, it is essential to use a dc-ac converter, which is able to suit the characteristics of the power provided by the photovoltaic modules to grid parameters. This dissertation presents a project proposal of a 2 kW single phase dc-ac converter for connecting a 311 V dc bus to a 220 Vrms ac bus of a microgrid. The proposed converter is bidirectional and allows, when necessary, the power flow from ac to dc bus. The study shows, through simulation and prototype implementation in the laboratory, that with the application of an appropriate control strategy it is possible to control the direction of power flow, as well as properly modulating the current flowing between two buses, dc, powered by photovoltaic panels and the battery bank, and the ac, at grid side. The prototype had a yield of about 91% and has injected electric current with low harmonic content (THDi less than 5%).
A recente expectativa de crescimento da participaÃÃo da energia solar-fotovoltaica na matriz de geraÃÃo de energia elÃtrica aumentou significativamente o nÃmero de conexÃes desses sistemas Ã rede elÃtrica. Para que a interligaÃÃo com a rede elÃtrica convencional seja possÃvel, Ã indispensÃvel a utilizaÃÃo de conversores CC/CA, capazes de adequar as caracterÃsticas da energia disponibilizada pelos mÃdulos fotovoltaicos aos padrÃes da rede. Esta dissertaÃÃo apresenta uma proposta de projeto de conversor CC/CA de 2 kW para conexÃo de dois barramentos de uma microrrede, um CC em 311 V e outro CA em 220 Vrms. O conversor proposto Ã bidirecional e permite, quando necessÃrio, o fluxo de energia elÃtrica do barramento CA para o CC. O estudo realizado mostra, atravÃs de simulaÃÃes e de implementaÃÃo de protÃtipo em laboratÃrio, que com a aplicaÃÃo de uma estratÃgia de controle adequada Ã possÃvel controlar o sentido do fluxo de potÃncia do conversor, assim como modular apropriadamente a corrente que flui entre dois barramentos, o CC, alimentado por painÃis fotovoltaicos e por banco de baterias, e o barramento CA, do lado da rede elÃtrica. O protÃtipo desenvolvido apresentou rendimento de cerca de 91% e forneceu corrente elÃtrica de baixo conteÃdo harmÃnico (THDi menor que 5%).

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16

McClure, Morgan Taylor. "A Modular Architecture for DC-AC Conversion." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1340812711.

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17

Verdolin, Rogerio. "Overvoltages and coupling effects on an ac-dc hybrid transmission system." Canadian Electric Association Conference, 1995. http://hdl.handle.net/1993/5147.

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Abstract Adding a dc circuit to an existing transmission line is one method of significantly increasing the power transfer capability of a transmission corridor. The resulting hybrid system has significant coupling between the ac and dc circuits, not only because of the proximity of the circuits, but also from the fact that they may share the same sending end or receiving end ac systems. The resultant interaction produces overvoltages on the dc system which can be somewhat higher than for a conventional dc scheme. This thesis investigates the overvoltages on a hybrid ac-dc transmission system and suggests some design considerations which could be taken into account to reduce stresses on certain critical components which result from such an arrangement. Blocking filters consisting of a parallel L-C combination in series with the dc converter were included to limit the flow of fundamental frequency current in the dc line. This thesis also investigates the proper blocking filter configuration to be used as an incorrectly chosen blocking filter can cause resonance overvoltages on the dc line at fundamental frequency. A method of eliminating dc components of the currents in the transformer windings of a dc converter is presented. The method uses the technique of firing angle modulation. It is shown that merely eliminating the fundamental frequency component on the dc side may not remove this dc component. The impact of such control action at one converter on the other converters in the dc transmission system is also presented. It is also shown that the undesirable side effects of such a scheme include increased generation of non-characteristic harmonies on both the ac and dc sides. The study is performed using an electromagnetic transients simulation program and theoretical calculations.

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18

White, Terence H. "A three-phase hybrid dc-ac inverter system utilizing hysteresis control." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FWhite%5FTerence.pdf.

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19

Fox, Ian Micah. "Design and Applications of Hybrid Switches in DC-AC Power Converter Topologies." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543157006458193.

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20

Rotsios, Christopher. "Analysis and Design of An Off-Grid Residential Power System." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2214.

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This thesis aims to provide a recommended power system design for optimal efficiency, reliability, and cost in off-grid applications. The power system examined in this project is a residence in an off-grid community called Quail Springs that generates its energy from roof mounted solar panels. The existing system was analyzed to see what equipment can remain, what needs to be upsized, and what needs to be added to the system. Two power systems are considered for the residence: a fully AC power system and a hybrid AC/DC power system. Simulations were run in PSCAD to compare the efficiencies of the two proposed systems at varying load. The results of the simulations showed the hybrid power system to be generally less efficient when supplying AC and DC loads, but greater than 5% more efficient when only supplying DC load. Although the hybrid AC/DC system is approximately 70% more expensive, it is still the final recommended design due to potential efficiency gains and in an effort to provide educational opportunities that may lead to further efficiency gains in future hybrid AC/DC power systems.

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21

Odnegård, Joakim. "Fault Impact Mitigation in Grid Connected Converters." Thesis, KTH, Elektrisk energiomvandling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-107494.

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The present thesis deals with fault impact mitigation in grid connected converters used for High Voltage Direct Current transmission. Certain critical fault cases require additional obstructing protection actions to ease the impact on the converter valves. DC sided faults drives high fault currents through the converters. Single phase to ground faults at the converter AC bus results in overvoltages across the converter valve arms. The phenomenon of these faults are described both for symmetric and asymmetric configurations. Different available solutions are explained and evaluated. Simulations in PSCAD/EMTDC show the impact of the protection measures. A three phase short circuit introduced on the tertiary winding of the transformer is an effective temporary measure against the destructive fault cases. It is shown in this report that a tertiary shortcircuit will greatly reduce the overvoltages after converter bus faults and redirect a large part of the fault currents after DC faults. With the lower voltage on the tertiary winding, it is a suitable connection point for short circuit devices.

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22

Robinson, Jonathan. "Efficiency and performance analysis of AC and DC grid based wind farms connected to a high voltage DC transmission line." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86959.

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A trans-Canadian grid could lead to increased ability to integrate wind energy by increasing capacity, improving reliability, and reducing effects of non-dispatchable generation by integrating renewable energy sources over a wide geographical area. Use of HVDC technology in the trans-Canadian grid would result in lower losses for the long transmission lines required and also would provide other benefits, such as lower right-of-way requirements, high reliability, and fault isolation. However, there are no current installations connecting a tapped connection to an HVDC line; all HVDC lines are operated using two terminals. This thesis proposes two methods of connecting a wind farm to an HVDC line. Techniques using an AC grid based wind farm and a DC grid based wind farm are analyzed based on their efficiency and component requirements, as well as their ability to operate during normal and fault conditions. The advantages and disadvantages of both solutions are compared, and while the best overall efficiency can be obtained using an AC system, high efficiencies can also be obtained for the DC system when combined with wind turbines with a MV output voltage. Preliminary simulation analysis shows that the DC grid design provides superior isolation of the HVDC line from faults on the wind farm grid, but both the AC and DC grids have potential issues implementing fault ride through, depending on the location of the fault.
Un réseau trans-canadien peut aider à intégrer l'énergie éolienne, qui s'étend sur une vaste zone géographique, en augmentant la capacité de transfert de puissance des lignes de transport et en réduisant les effets non-contrôlables des sources d'énergie renouvelable. L'utilisation de la technologie 'HVDC' peut réduire les coûts des longues lignes de transmission et aussi offrir d'autres avantages comme la réduction de l'empreinte géographique, une meilleure fiabilité, et la localisation des défauts. Toutefois, il n'y a pas de raccordements multi-terminaux HVDC en opération. Cette thèse propose deux méthodes de connexion d'un parc éolien à une ligne HVDC, utilisant des réseaux c.a. et c.c. Le rendement, les composantes requises et la performance transitoire des deux méthodes de connexion sont présentés. Une meilleure efficacité peut être obtenue avec le réseau c.a., mais en intégrant les éoliennes MT, l'efficacité du réseau c.c. est améliorée. Des études préliminaires démontrent que le réseau c.c. aide à une meilleure isolation d'un court-circuit dans le parc éolien qui pourrait se transmettre aux lignes HVDC. Les deux réseaux sont capables de réduire les effets d'un court-circuit, mais peuvent avoir des problèmes à demeurer en service sans déclenchement pour un défaut transitoire.

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23

Chen, Fang. "Control of DC Power Distribution Systems and Low-Voltage Grid-Interface Converter Design." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77532.

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DC power distribution has gained popularity in sustainable buildings, renewable energy utilization, transportation electrification and high-efficiency data centers. This dissertation focuses on two aspects of facilitating the application of dc systems: (a) system-level control to improve load sharing, voltage regulation and efficiency; (b) design of a high-efficiency interface converter to connect dc microgrids with the existing low-voltage ac distributions, with a special focus on common-mode (CM) voltage attenuation. Droop control has been used in dc microgrids to share loads among multiple sources. However, line resistance and sensor discrepancy deteriorate the performance. The quantitative relation between the droop voltage range and the load sharing accuracy is derived to help create droop design guidelines. DC system designers can use the guidelines to choose the minimum droop voltage range and guarantee that the sharing error is within a defined range even under the worst cases. A nonlinear droop method is proposed to improve the performance of droop control. The droop resistance is a function of the output current and increases when the output current increases. Experiments demonstrate that the nonlinear droop achieves better load sharing under heavy load and tighter bus voltage regulation. The control needs only local information, so the advantages of droop control are preserved. The output impedances of the droop-controlled power converters are also modeled and measured for the system stability analysis. Communication-based control is developed to further improve the performance of dc microgrids. A generic dc microgrid is modeled and the static power flow is solved. A secondary control system is presented to achieve the benefits of restored bus voltage, enhanced load sharing and high system efficiency. The considered method only needs the information from its adjacent node; hence system expendability is guaranteed. A high-efficiency two-stage single-phase ac-dc converter is designed to connect a 380 V bipolar dc microgrid with a 240 V split-phase single-phase ac system. The converter efficiencies using different two-level and three-level topologies with state-of-the-art semiconductor devices are compared, based on which a two-level interleaved topology using silicon carbide (SiC) MOSFETs is chosen. The volt-second applied on each inductive component is analyzed and the interleaving angles are optimized. A 10 kW converter prototype is built and achieves an efficiency higher than 97% for the first time. An active CM duty cycle injection method is proposed to control the dc and low-frequency CM voltage for grounded systems interconnected with power converters. Experiments with resistive and constant power loads in rectification and regeneration modes validate the performance and stability of the control method. The dc bus voltages are rendered symmetric with respect to ground, and the leakage current is reduced. The control method is generalized to three-phase ac-dc converters for larger power systems.
Ph. D.

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24

Aquino, Joshua Jonn O. "Microcontroller Design of a Bidirectional Three-Level Pulse Width Modulation AC/DC Converter for Vehicle-to-Grid Application." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/850.

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Bidirectional chargers provide plug-in electric vehicles (EV) the ability to not only transfer energy from the grid to the vehicle, but also transfer energy from the vehicle to the grid (V2G). The V2G mode allows power utility companies to offset peak power consumption thus allowing household consumers and industry corporations to save money on their electricity bills. This paper describes the design choices of bidirectional chargers and provides the implementation details for a Three-Level PWM AC-DC based charger. Although the three-level PWM AC-DC design requires a more complex controller than its counterparts, Matlab Simulink simulations show the design provides lower total harmonic distortion (THD) and reduced stress to the charger’s components making it a viable charger design for the electric vehicle industry.

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25

Farhadi, Mustafa. "Hybrid Energy Storage Implementation in DC and AC Power System for Efficiency, Power Quality and Reliability Improvements." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2471.

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Battery storage devices have been widely utilized for different applications. However, for high power applications, battery storage systems come with several challenges, such as the thermal issue, low power density, low life span and high cost. Compared with batteries, supercapacitors have a lower energy density but their power density is very high, and they offer higher cyclic life and efficiency even during fast charge and discharge processes. In this dissertation, new techniques for the control and energy management of the hybrid battery-supercapacitor storage system are developed to improve the performance of the system in terms of efficiency, power quality and reliability. To evaluate the findings of this dissertation, a laboratory-scale DC microgrid system is designed and implemented. The developed microgrid utilizes a hybrid lead-acid battery and supercapacitor energy storage system and is loaded under various grid conditions. The developed microgrid has also real-time monitoring, control and energy management capabilities. A new control scheme and real-time energy management algorithm for an actively controlled hybrid DC microgrid is developed to reduce the adverse impacts of pulsed power loads. The developed control scheme is an adaptive current-voltage controller that is based on the moving average measurement technique and an adaptive proportional compensator. Unlike conventional energy control methods, the developed controller has the advantages of controlling both current and voltage of the system. This development is experimentally tested and verified. The results show significant improvements achieved in terms of enhancing the system efficiency, reducing the AC grid voltage drop and mitigating frequency fluctuation. Moreover, a novel event-based protection scheme for a multi-terminal DC power system has been developed and evaluated. In this technique, fault identification and classifications are performed based on the current derivative method and employing an artificial inductive line impedance. The developed scheme does not require high speed communication and synchronization and it transfers much less data when compared with the traditional method such as the differential protection approach. Moreover, this scheme utilizes less measurement equipment since only the DC bus data is required.

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26

LaBella, Thomas Matthew. "A High-Efficiency Hybrid Resonant Microconverter for Photovoltaic Generation Systems." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50526.

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The demand for increased renewable energy production has led to increased photovoltaic (PV) installations worldwide. As this demand continues to grow, it is important that the costs of PV installations decrease while the power output capability increases. One of the components in PV installations that has lots of room for improvement is the power conditioning system. The power conditioning system is responsible for converting the power output of PV modules into power useable by the utility grid while insuring the PV array is outputting the maximum available power. Modular power conditioning systems, where each PV module has its own power converter, have been proven to yield higher output power due to their superior maximum power point tracking capabilities. However, this comes with the disadvantages of higher costs and lower power conversion efficiencies due to the increased number of power electronics converters. The primary objective of this dissertation is to develop a high-efficiency, low cost microconverter in an effort to increase the output power capability and decrease the cost of modular power conditioning systems. First, existing isolated dc-dc converter topologies are explored and a new topology is proposed based on the highly-efficient series resonant converter operating near the series resonant frequency. Two different hybrid modes of operation are introduced in order to add wide input-voltage regulation capability to the series resonant converter while achieving high efficiency through low circulating currents, zero-current switching (ZCS) of the output diodes, zero-voltage switching (ZVS) and/or ZCS of the primary side active switches, and direct power transfer from the source to the load for the majority of the switching cycle. Each operating mode is analyzed in detail using state-plane trajectory plots. A systematic design approach that is unique to the newly proposed converter is presented along with a detailed loss analysis and loss model. A 300-W microconverter prototype is designed to experimentally validate the analysis and loss model. The converter featured a 97.7% weighted California Energy Commission (CEC) efficiency with a nominal input voltage of 30 V. This is higher than any other reported CEC efficiency for PV microconverters in literature to date. Each operating mode of the proposed converter can be controlled using simple fixed-frequency pulse-width modulation (PWM) based techniques, which makes implementation of control straightforward. Simplified models of each operating mode are derived as well as control-to-input voltage transfer functions. A smooth transition method is then introduced using a two-carrier PWM modulator, which allows the converter to transition between operating modes quickly and smoothly. The performance of the voltage controllers and transition method were verified experimentally. To ensure the proposed converter is compatible with different types of modular power conditioning system architectures, system-level interaction issues associated with different modular applications are explored. The first issue is soft start, which is necessary when the converter is beginning operation with a large capacitive load. A novel soft start method is introduced that allows the converter to start up safely and quickly, even with a short-circuited output. Maximum power point tracking and double line frequency ripple rejection are also explored, both of which are very important to ensuring the PV module is outputting the maximum amount of available power. Lastly, this work deals with efficiency optimization of the proposed converter. It is possible to use magnetic integration so that the resonant inductor can be incorporated into the isolation transformer by way of the transformer leakage inductance in order to reduce parts count and associated costs. This chapter, however, analyzes the disadvantages to this technique, which are increased proximity effect losses resulting in higher conduction losses. A new prototype is designed and tested that utilizes an external resonant inductor and the CEC efficiency was increased from 97.7% to 98.0% with a marginal 1.8% total cost increase. Additionally, a variable frequency efficiency optimization algorithm is proposed which increases the system efficiency under the high-line and low-line input voltage conditions. This algorithm is used for efficiency optimization only and not control, so the previously presented simple fixed-frequency modeling and control techniques can still be utilized.
Ph. D.

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27

Elsayed, Ahmed T. "Optimum Distribution System Architectures for Efficient Operation of Hybrid AC/DC Power Systems Involving Energy Storage and Pulsed Loads." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/3005.

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After more than a century of the ultimate dominance of AC in distribution systems, DC distribution is being re-considered. However, the advantages of AC systems cannot be omitted. This is mainly due to the cheap and efficient means of generation provided by the synchronous AC machines and voltage stepping up/down allowed by the AC transformers. As an intermediate solution, hybrid AC/DC distribution systems or microgrids are proposed. This hybridization of distribution systems, incorporation of heterogeneous mix of energy sources, and introducing Pulsed Power Loads (PPL) together add more complications and challenges to the design problem of distribution systems. In this dissertation, a comprehensive multi-objective optimization approach is presented to determine the optimal design of the AC/DC distribution system architecture. The mathematical formulation of a multi-objective optimal power flow problem based on the sequential power flow method and the Pareto concept is developed and discussed. The outcome of this approach is to answer the following questions: 1) the optimal size and location of energy storage (ES) in the AC/DC distribution system, 2) optimal location of the PPLs, 3) optimal point of common coupling (PCC) between the AC and DC sides of the network, and 4) optimal network connectivity. These parameters are to be optimized to design a distribution architecture that supplies the PPLs, while fulfilling the safe operation constraints and the related standard limitations. The optimization problem is NP-hard, mixed integer and combinatorial with nonlinear constraints. Four objectives are involved in the problem: minimizing the voltage deviation (ΔV), minimizing frequency deviation (Δf), minimizing the active power losses in the distribution system and minimizing the energy storage weight. The last objective is considered in the context of ship power systems, where the equipment’s weight and size are restricted. The utilization of Hybrid Energy Storage Systems (HESS) in PPL applications is investigated. The design, hardware implementation and performance evaluation of an advanced – low cost Modular Energy Storage regulator (MESR) to efficiently integrate ES to the DC bus are depicted. MESR provides a set of unique features: 1) It is capable of controlling each individual unit within a series/parallel array (i.e. each single unit can be treated, controlled and monitored separately from the others), 2) It is able to charge some units within an ES array while other units continue to serve the load, 3) Balance the SoC without the need for power electronic converters, and 4) It is able to electrically disconnect a unit and allow the operator to perform the required maintenance or replacement without affecting the performance of the whole array. A low speed flywheel Energy Storage System (FESS) is designed and implemented to be used as an energy reservoir in PPL applications. The system was based on a separately excited DC machine and a bi-directional Buck-Boost converter as the driver to control the charging/discharging of the flywheel. Stable control loops were designed to charge the FESS off the pulse and discharge on the pulse. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.

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28

Qian, Hao. "A High-Efficiency Grid-Tie Battery Energy Storage System." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/29008.

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Lithium-ion based battery energy storage system has become one of the most popular forms of energy storage system for its high charge and discharge efficiency and high energy density. This dissertation proposes a high-efficiency grid-tie lithium-ion battery based energy storage system, which consists of a LiFePO4 battery based energy storage and associated battery management system (BMS), a high-efficiency bidirectional ac-dc converter and the central control unit which controls the operation mode and grid interface of the energy storage system. The BMS estimates the state of charge (SOC) and state of health (SOH) of each battery cell in the pack and applies active charge equalization to balance the charge of all the cells in the pack. The bidirectional ac-dc converter works as the interface between the battery pack and the ac grid, which needs to meet the requirements of bidirectional power flow capability and to ensure high power factor and low THD as well as to regulate the dc side power regulation. A highly efficient dual-buck converter based bidirectional ac-dc converter is proposed. The implemented converter efficiency peaks at 97.8% at 50-kHz switching frequency for both rectifier and inverter modes. To better utilize the dc bus voltage and eliminate the two dc bus bulk capacitors in the conventional dual-buck converter, a novel bidirectional ac-dc converter is proposed by replacing the capacitor leg of the dual-buck converter based single-phase bidirectional ac-dc converter with a half-bridge switch leg. Based on the single-phase bidirectional ac-dc converter topology, three novel three-phase bidirectional ac-dc converter topologies are proposed. In order to control the bidirectional power flow and at the same time stabilize the system in mode transition, an admittance compensator along with a quasi-proportional-resonant (QPR) controller is adopted to allow smooth startup and elimination of the steady-state error over the entire load range. The proposed QPR controller is designed and implemented with a digital controller. The entire system has been simulated in both PSIM and Simulink and verified with hardware experiments. Small transient currents are observed with the power transferred from rectifier mode to inverter mode at peak current point and also from inverter mode to rectifier mode at peak current point. The designed BMS monitors and reports all battery cells parameters in the pack and estimates the SOC of each battery cell by using the Coulomb counting plus an accurate open-circuit voltage model. The SOC information is then used to control the isolated bidirectional dc-dc converter based active cell balancing circuits to mitigate the mismatch among the series connected cells. Using the proposed SOC balancing technique, the entire battery storage system has demonstrated more capacity than the system without SOC balancing.
Ph. D.

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29

Caballero, Diaz Luis. "Contributions to the design and operation of a multilevel-active-clamped Dc-Ac grid- connected power converter for wind energy conversion systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/454979.

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Анотація:

The demand of wind energy has considerably increased during the last decades. In order to fulfil this great energy demand, wind energy conversion systems (WECS) are designed to manage higher power ratings. Currently, the most attractive power converter topology in commercial WECS is the conventional two-level back-to-back voltage-source converter (2L-B2B). However, the 2L-B2B topology could have difficulties to achieve an acceptable performance with the available switching devices for the largest WECS, even though having the cost advantage. Instead, multilevel converters increase the power without increasing neither current nor blocking voltage of the power semiconductors, enabling a cost-effective design for the largest WECS using the available switching devices. Within the multilevel converters, the 3L-NPC topology offers high penetration in the market of large WECS. However, one of its major drawbacks is that the power loss is unevenly distributed among the switching devices. Therefore, the 3L-NPC output power capability is limited by the thermal performance of the most stressed switching device, which depends on the operating point. The 3L-ANPC topology was proposed in order to improve the power loss distribution among the power semiconductors. The 3L-ANPC provides a controllable path for the neutral current. Hence, the 3L-ANPC is able to offer certain freedom to distribute the power loss among the power semiconductors. As a consequence, and compared to the 3L-NPC, the thermal performance is more uniform and the output power capability increases. However, there is still room for improvement. In light of the previous discussion, the proposed thesis defines enhanced design guidelines for the dc-ac grid-connected 3L-ANPC power converter, focused on improving its reliability and electrical performance, and following the trend of the current state of the art to define a feasible solution for the next generation of WECS. The thesis contributions are based on defining an enhanced power device configuration and a novel commutation sequence, avoiding concentrating both significant conduction and switching losses on a single power semiconductor device. This allows then selecting the most appropriate device for each converter position, which leads to a better converter efficiency and to a more uniform power loss distribution and thermal performance. This also leads to a higher converter power rating, and it is expected to improve the converter reliability.
La demanda de energía eólica ha incrementado considerablemente durante las últimas décadas. Con el objetivo de satisfacer esta gran demanda, los sistemas de conversión de energía eólica (WECS) son diseñados para operar con mayores niveles de potencia. Actualmente, la topología de convertidor de potencia más atractiva en los WECS comerciales es el convertidor de dos niveles operando en fuente de tensión y configuración back to back (2L-B2B). Sin embargo, esta topología podría tener dificultades para ofrecer un comportamiento aceptable en los WECS de mayor potencia con los dispositivos actuales, incluso aunque su coste sea reducido. En cambio, los convertidores multinivel pueden incrementar la potencia sin necesidad de incrementar la corriente ni el voltaje de bloqueo de los dispositivos, permitiendo conseguir un diseño adecuado para los WECS de mayor potencia usando los dispositivos actuales. Dentro de los convertidores multinivel, la topología 3L-NPC tiene una gran aceptación en el mercado eólico, siendo una solución común en los WECS de mayor potencia. Sin embargo, su gran inconveniente es que la potencia pérdida es distribuida de una manera desequilibrada entre los dispositivos. De este modo, la potencia de salida se ve limitada por el comportamiento térmico del dispositivo más estresado a nivel térmico, el cual depende del punto de operación. De esta manera, la topología 3L-ANPC fue propuesta con el objetivo de mejorar la distribución de las pérdidas del convertidor entre los dispositivos. El convertidor 3L-ANPC proporciona un camino totalmente controlable para la conexión del punto neutro. Por lo tanto, el convertidor 3LANPC es capaz de ofrecer cierto grado de libertad para distribuir la potencia pérdida entre los dispositivos. Como consecuencia, y comparado con el convertidor 3L-NPC, el comportamiento térmico es mucho más equilibrado y la potencia de salida puede ser incrementada. Sin embargo, todavía hay margen de mejora para alcanzar mejores prestaciones en el comportamiento del convertidor 3L-ANPC. A raíz de la argumentación anterior, la tesis propuesta define nuevas guías de diseño para el convertidor 3L-ANPC cc-ca conectado a la red. Las guías de diseño están focalizadas en mejorar la fiabilidad y el comportamiento eléctrico del convertidor, respetando la tendencia del estado del arte actual para definir una solución factible para la próxima generación de WECS. Las contribuciones de la tesis están basadas en definir una configuración de dispositivos mejorada y una secuencia de conmutación novedosa, evitando concentrar grandes pérdidas de conducción y de conmutación en un mismo dispositivo. Las contribuciones permiten seleccionar el dispositivo más adecuado para cada posición del convertidor, consiguiendo una mejor eficiencia y una distribución de pérdidas y comportamiento térmico más equilibrado. Además, también permiten operar con potencias más elevadas, y mejorar la fiabilidad del convertidor.

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30

Hadjikypris, Melios. "Supervisory control scheme for FACTS and HVDC based damping of inter-area power oscillations in hybrid AC-DC power systems." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/supervisory-control-scheme-for-facts-and-hvdc-based-damping-of-interarea-power-oscillations-in-hybrid-acdc-power-systems(cc03b44a-97f9-44ec-839f-5dcbcf2801f1).html.

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Modern interconnected power systems are becoming highly complex and sophisticated, while increasing energy penetrations through congested inter-tie lines causing the operating point approaching stability margins. This as a result, exposes the overall system to potential low frequency power oscillation phenomena following disturbances. This in turn can lead to cascading events and blackouts. Recent approaches to counteract this phenomenon are based on utilization of wide area monitoring systems (WAMS) and power electronics based devices, such as flexible AC transmission systems (FACTS) and HVDC links for advanced power oscillation damping provision. The rise of hybrid AC-DC power systems is therefore sought as a viable solution in overcoming this challenge and securing wide-area stability. If multiple FACTS devices and HVDC links are integrated in a scheme with no supervising control actions considered amongst them, the overall system response might not be optimal. Each device might attempt to individually damp power oscillations ignoring the control status of the rest. This introduces an increasing chance of destabilizing interactions taking place between them, leading to under-utilized performance, increased costs and system wide-area stability deterioration. This research investigates the development of a novel supervisory control scheme that optimally coordinates a parallel operation of multiple FACTS devices and an HVDC link distributed across a power system. The control system is based on Linear Quadratic Gaussian (LQG) modern optimal control theory. The proposed new control scheme provides coordinating control signals to WAMS based FACTS devices and HVDC link, to optimally and coherently counteract inter-area modes of low frequency power oscillations inherent in the system. The thesis makes a thorough review of the existing and well-established improved stability practises a power system benefits from through the implementation of a single FACTS device or HVDC link, and compares the case –and hence raises the issue–when all active components are integrated simultaneously and uncoordinatedly. System identification approaches are also in the core of this research, serving as means of reaching a linear state space model representative of the non-linear power system, which is a pre-requisite for LQG control design methodology.

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Musa, Aysar [Verfasser], Antonello [Akademischer Betreuer] Monti, and Albert [Akademischer Betreuer] Moser. "Advanced control strategies for stability enhancement of future hybrid AC/DC networks / Aysar A. Aydan Musa ; Antonello Monti, Albert Moser." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1210929228/34.

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32

Badawy, Mohamed O. "Grid Tied PV/Battery System Architecture and Power Management for Fast Electric Vehicles Charging." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468858915.

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Lopez, Santos Oswaldo. "Contribution to the DC-AC conversion in photovoltaic systems : Module oriented converters." Thesis, Toulouse, INSA, 2015. http://www.theses.fr/2015ISAT0001/document.

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Ces dernières années, un intérêt croissant pour les systèmes électroniques de puissance a été motivé par l'émergence de sources d'énergie distribuées et renouvelables raccordées aux réseaux électriques. Dans ce contexte, la nécessité de topologies de faibles puissances alimentées par quelques modules photovoltaïques, en évitant l'utilisation de transformateurs, a ouvert l'étude de convertisseurs spéciaux et l’étude des stratégies de commande associées afin d’assurer la stabilité, la fiabilité et un rendement élevé du dispositif. Une possible solution est d’utiliser un dispositif générique connu dans la littérature scientifique et commerciale comme « micro-onduleur » ou «convertisseur intégré au module » qui avec le module photovoltaïque définit un produit « plug and play » appelé "module AC".Ce travail est consacré à l'étude d'un micro-onduleur monophasé avec deux étapes sans transformateur raccordée au réseau. La topologie proposée est composé d’un convertisseur DC-DC non isolé élévateur avec un gain quadratique et un onduleur réducteur lié au réseau connectés en cascade. Le convertisseur DC-DC extrait en permanence la puissance maximale du module photovoltaïque malgré les changements dans les conditions environnementales. L'étape DC-AC injecte la puissance extraite par l'étape DC-DC dans le réseau et assure un niveau élevé de qualité de l’énergie. Les efforts de recherche de ce travail sont concentrés sur la mise au point de commandes utilisant comment base, la théorie de contrôle par mode de glissement, qui conduit à une mise en œuvre simple avec une description théorique complète validée á partir de simulations et expérimentations.Après avoir décrit l'état de l’art dans le premier chapitre, le manuscrit est divisé en quatre chapitres, qui sont dédiés respectivement à l’algorithme de recherche du point de puissance maximale (MPPT), á l’étape de conversion DC-DC, á l'étape de conversion DC-AC et finalement au micro-onduleur complet. Un nouvel algorithme de recherche extrémal du point de puissance maximale est développé (SM-ESC). Pour la étape DC-DC, le convertisseur élévateur quadratique avec seulement un interrupteur contrôlé est étudié utilisant le concept de résistance sans perte par mode de glissement (de l’acronyme anglais : Sliding-Mode Loss-Free-Resistor – SM-LFR) afin d’obtenir un gain de tension élevé avec un fonctionnement sûr et compatible avec l’algorithme MPPT. Pour la étape DC-AC, le convertisseur de pont complet est contrôlé comme un onduleur de source de puissance (de l’acronyme anglais : Power Source Inverter - PSI) en utilisant une commande par mode de glissement qui poursuit une référence sinusoïdale de courant de sortie. Cette commande est complétée par une boucle de régulation de la tension du bus DC qui assure une haute qualité d’énergie injectée dans le réseau. Enfin, les trois étapes constitutives sont fusionnées pour obtenir un micro-onduleur complètement contrôlé par la technique de mode de glissement, ce qui constitue le principal résultat et contribution de cette thèse
These last years, a growing interest in power electronic systems has been motivated by the emergence of distributed renewable energy resources and their interconnection with the grid. In this context, the need of low power topologies fed by a few photovoltaic modules avoiding the use of transformers opens the study of special converters and the associated control strategies ensuring stability, reliability and high efficiency. A resulted generic device known in the commercial and scientific literature as “microinverter” or “module integrated converter” performs a plug and play product together with the PV module called an “AC module”.This work is devoted to the study of a transformer-less single-phase double-stage grid-connected microinverter. The proposed topology has a non-isolated high-gain boost type DC-DC converter and a non-isolated buck type DC-AC converter connected in cascade through a DC bus. The DC-DC converter permanently extracts the maximum power of the PV module ensuring at the same time a good performance coping with power changes introduced by the change in the environmental conditions. The DC-AC stage injects the power extracted by the DC-DC stage into the grid ensuring a high level of power quality. The research efforts focus on the involved control functions based on the sliding mode control theory, which leads to a simple implementation with a comprehensive theoretical description validated through simulation and experimental results.After giving the state-of-the-art in the first chapter, the manuscript is divided into four chapters, which are dedicated to the Maximum Power Point Tracking (MPPT), the DC-DC stage and its control, the DC-AC stage and its control and the complete microinverter. A new Extremum Seeking Control (ESC) MPPT algorithm is proposed. The single-switch quadratic boost converter is studied operating as a Loss-Free-Resistor (LFR) obtaining a high DC output voltage level with a safe operation. The full-bridge converter is controlled as a Power Source Inverter (PSI) using a simple sliding-mode based tracking law, regulating the voltage of the DC bus and then ensuring a high power quality level in the grid connection. Finally, the three building blocks are merged to obtain a sliding mode controlled microinverter constituting the main result and contribution of the work

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Alves, Montanari Allan. "Enhanced instantaneous power theory for control of grid connected voltage sourced converters under unbalanced conditions." IEEE Transactions on Power Electronics, 2017. http://hdl.handle.net/1993/32184.

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This thesis introduces a new method especially designed to control the instantaneous power in voltage sourced converters operating under unbalanced conditions, including positive, negative and zero sequence content. A transformation technique, labelled mno transformation, was developed to enable the decomposition of the total instantaneous power flowing on three-phase transmission topologies into constant and oscillating terms. It is applied to three-wire and four-wire schemes, especially accommodating zero sequence unlike previous approaches. Classical and modern electric power theories are presented, particularly focusing on their definitions for adverse AC scenarios. The main mathematical transformations conceived to analyze such situations are summarized, showing their respective advantages and disadvantages. An enhanced instantaneous power theory is introduced. The novel proposed power equations, named mno instantaneous power components, expands the application of the p-q theory, which is attached to the αβ0 transformation. The mno instantaneous power theory is applied to develop an innovative power control method for grid connected voltage sourced converters in order to minimize power oscillations during adverse AC scenarios, particularly with zero sequence content. The method permits to sustain constant instantaneous three-phase power during unbalanced conditions by controlling independently the constant and the oscillating terms related to the instantaneous power. The effectiveness of the proposed control approach and the proposed power conditioning scheme was demonstrated using electromagnetic transient simulation of a VSC connected to an AC system.
May 2017

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Groen, Benjamin Carson. "Investigation of DC Motors for Electric and Hybrid Electric Motor Vehicle Applications Using an Infinitely Variable Transmission." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2696.

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Since the early 1900's demand for fuel efficient vehicles has motivated the development of electric and hybrid electric vehicles. Unfortunately, some components used in these vehicles are expensive and complex. AC motors, complex electronic controllers and complex battery management systems are currently used in electric (EV) and hybrid vehicles. This research examines various motors and speed control methods in an attempt to help designers identify which motors would be best suited for an EV powertrain application. The feasibility of using DC motors coupled with an Infinitely Variable Transmission (IVT), to obtain an innovative new electric or hybrid electric powertrain is also presented. The results of this research include an extensive review of the many motor types including a comparison chart and motor hierarchy. An experiment was designed and built to test motorspeed control methods. Testing with two DC separately-excited motors and a differential as an IVT was also conducted. These tests revealed that field weakening appears to be a viable low-costspeed-control method. Testing of these motors, coupled with an IVT revealed that the output of a differential or planetary gear set can be controlled by varying the speed of the inputs. Combining this information in a product development mentality led to the concept of using one DC motor as a power or traction motor while another motor acts as a speed controller, with the method of speedcontrol on the speed control motor being field weakening. This concept allows most of the power to be delivered at an efficient rate with a simple form of speed control. This concept may also eliminate the need for expensive, complex electronic motor controllers. This approach could be used to improve the safety and reduce battery management requirements by lowering the operating voltage of the entire system.

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Sahoo, Smrutirekha. "Impact Study: Photo-voltaic Distributed Generation on Power System." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-32369.

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The grid-connected photo-voltaic (PV) system is one of the most promising renewable energy solutions which offers many benefits to both the end user and the utility network and thus it has gained the popularity over the last few decades. However, due to the very nature of its invariability and weather dependencies, the large scale integration of this type of distributed generation has created challenges for the network operator while maintaining the quality of the power supply and also for reliable and safe operations of the grids. In this study, the behavioral impact of large scale PV system integration which are both steady and dynamic in nature was studied. An aggregate PV model suited to study the impacts was built using MATLAB/Simulink. The integration impacts of PV power to existing grids were studied with focus on the low voltage residential distribution grids of Mälarenergi Elnät AB (10/0.4 kV). The steady state impacts were related to voltage profile, network loss. It was found that the PV generation at the load end undisputedly improves the voltage profile of the grid especially for the load buses which are situated at farther end of the grid. Further, with regard to the overvoltage issue, which is generally a concern during the low load demand period it was concluded that, at a 50% PV penetration level, the voltage level for the load buses is within the limit of 103% as prescribed by the regulator excepting for few load buses. The voltage level for load buses which deviate from the regulatory requirement are located at distance of 1200 meter or further away from the substation. The dynamic impact studied were for voltage unbalancing in the grid, which was found to have greater impact at the load buses which is located farther compared to a bus located nearer to the substation. With respect to impact study related to introduction of harmonics to the grid due to PV system integration, it was found that amount of harmonic content which was measured as total harmonic distortion (THD) multiplies with integration of more number of PV system. For a 50 % penetration level of PV, the introduced harmonics into the representative network is very minimal. Also, it was observed from the simulation study that THD content are be less when the grid operates at low load condition with high solar irradiance compared to lower irradiance and high load condition.

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Hotz, Matthias [Verfasser], Wolfgang [Akademischer Betreuer] Utschick, Mario [Gutachter] Paolone, and Wolfgang [Gutachter] Utschick. "Optimal Power Flow in Hybrid AC/DC Power Systems : Modeling, Methods, and Design Implications / Matthias Hotz ; Gutachter: Mario Paolone, Wolfgang Utschick ; Betreuer: Wolfgang Utschick." München : Universitätsbibliothek der TU München, 2021. http://d-nb.info/123143452X/34.

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Moosavi, Anchehpoli Seyed Saeid. "Analysis and diagnosis of faults in the PMSM drivetrains for series hybrid electrical vehicles (SHEVs)." Thesis, Belfort-Montbéliard, 2013. http://www.theses.fr/2013BELF0224/document.

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L'intérêt pour les véhicules électriques ne cesse de croitre au sein de la société contemporaine compte tenu de ses nombreuses interrogations sur l’environnement et la dépendance énergétique. Dans ce travail de thèse, nous essayons d’améliorer l’acceptabtabilité sociétale du véhicule électrique en essayant de faire avancer la recherche sur le diagnostique des défauts d’une chaine de traction électrique. Les résultats escomptés devraient permettre à terme d’améliorer la fiabilité et la durabilité de ces systèmes.Nous commençons par une revue des problèmes des défauts déjà apparus dans les véhicules hybrides séries qui disposent de l’architecture la plus proche du véhicule électrique. Une étude approfondie sur le diagnostic des défauts d’un convertisseur de puissance statique (AC-DC) ainsi que celle du moteur synchrone à aimants permanents est menée. Quatre types de défauts majeurs ont été répertoriés concernant le moteur (court-circuit au stator, démagnétisation, excentricité du rotor et défaut des roulements). Au niveau du convertisseur, nous avons considéré le défaut d’ouverture des interrupteurs. Afin d’être dans les mêmes conditions d’utilisation réelle, nous avons effectué des tests expérimentaux à vitesse et charge variables. Ce travail est basé aussi bien sur l’expérimentation que sur la modélisation. Comme par exemple, la méthode des éléments finis pour l’étude de la démagnétisation de la machine. De même, l’essai en court-circuit du stator du moteur en présence d’un contrôle vectoriel.Afin de réaliser un diagnostic en ligne des défauts, nous avons développé un modèle basé sur les réseaux de neurones. L’apprentissage de ce réseau de neurone a été effectué sur la base des résultats expérimentaux et de simulations, que nous avons réalisées. Le réseau de neurones est capable d'assimiler beaucoup de données. Ceci nous permet de classifier les défauts en termes de sévérité et de les localiser. Il permet ainsi d'évaluer le degré de performance de la chaine de traction électrique en ligne en présence des défauts et nous renseigner ainsi sur l'état de santé du système. Ces résultats devraient aboutir à l’élaboration d’une stratégie de contrôle tolérant aux défauts auto-reconfigurable pour prendre en compte les modes dégradés permettant une continuité de service du véhicule ce qui améliorera sa disponibilité
The interest in the electric vehicles rose recently due both to environmental questions and to energetic dependence of the contemporary society. Accordingly, it is necessary to study and implement in these vehicle fault diagnosis systems which enable them to be more reliable and safe enhancing its sustainability. In this work after a review on problem of faults in the drivetrain of series hybrid electric vehicles (SHEV), a deep investigation on fault diagnosis of AC-DC power converter and permanent magnet synchronous motor (PMSM) have been done as two important parts of traction chains in SHEVs. In other major part of this work, four types of faults (stator winding inter turn short circuit, demagnetization, eccentricity ant bearing faults) of a PMSM have been studied. Inter turn short circuit of stator winding of PMSM in different speeds and loads has been considered to identify fault feature in all operation aspects, as it is expected by electric vehicle application. Experimental results aiming short circuits, bearing and eccentricity fault detection has been presented. Analytical and finite element method (FEM) aiming demagnetization fault investigation has been developed. The AC-DC converter switches are generally exposed to the possibility of outbreak open phase faults because of troubles of the switching devices. This work proposes a robust and efficient identification method for data acquisition selection aiming fault analysis and detection. Two new patterns under AC-DC converter failure are identified and presented. To achieve this goal, four different level of switches fault are considered on the basis of both simulation and experimental results. For accuracy needs of the identified pattern for SHEV application, several parameters have been considered namely: capacitor size changes, load and speed variations. On the basis of the developed fault sensitive models above, an ANN based fault detection, diagnosis strategy and the related algorithm have been developed to show the way of using the identified patterns in the supervision and the diagnosis of the PMSM drivetrain of SHEVs. ANN method have been used to develop three diagnosis based models for : the vector controlled PMSM under inter turn short circuit, the AC/DC power converter under an open phase fault and also the PMSM under unbalanced voltage caused by open phase DC/AC inverter. These models allow supervising the main components of the PMSM drivetrains used to propel the SHEV. The ANN advantages of ability to include a lot of data mad possible to classify the faults in terms of their type and severity. This allows estimating the performance degree of that drivetrains during faulty conditions through the parameter state of health (SOH). The latter can be used in a global control strategy of PMSM control in degraded mode in which the control is auto-adjusted when a defect occurs on the system. The goal is to ensure a continuity of service of the SHEV in faulty conditions to improve its reliability

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Karania, Nabil. "Contrôle du Compensateur Actif Parallèle à Génération Photovoltaïque pour les Réseaux Intelligents." Electronic Thesis or Diss., CY Cergy Paris Université, 2024. http://www.theses.fr/2024CYUN1288.

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Dans les réseaux de distribution électrique et les réseaux intelligents, l'adoption généralisée des composants électroniques de puissance pose divers défis en matière de qualité de l'énergie. L'intégration des sources d'énergie renouvelable aggrave ces défis en raison des fluctuations de tension, des écarts de fréquence et de la distorsion des formes d'onde inhérents à ces sources, dont les performances dépendent des conditions météorologiques. Cette thèse aborde ces défis à travers trois solutions visant à améliorer la qualité de l'énergie électrique dans les réseaux de distribution, en se focalisant sur l'intégration des systèmes photovoltaïques (PV) dans la troisième solution.La première solution introduit une Structure Multi-Niveaux Développée du Convertisseur AC/DC/AC. Elle vise à réguler l'amplitude de tension, à garantir une tension de sortie en escalier approchant une sinusoïde et à éliminer un large rang d'harmoniques, y compris les harmoniques prédominantes affectant les charges sensibles telles que les entraînements de moteurs asynchrones. Ce travail développe une nouvelle technique de modulation pour contrôler la partie DC/AC du convertisseur, configurée via un onduleur en pont en H asymétrique en cascade.La deuxième solution implique un Système Avancé de Contrôle Hybride pour le Filtre Actif Parallèle (SAF) basé sur un Onduleur Multi-Niveaux (MLI). Cette solution améliore les performances du filtre actif parallèle, augmente sa fréquence de commutation apparente et réduit la taille de son filtre de couplage de sortie. Le contrôleur hybride, mis en œuvre à l'aide de réseaux de Petri (PN), assure un suivi de haute performance du courant de compensation, en plus de stabiliser, contrôler et équilibrer les tensions DC sur les entrées d'onduleur multi-niveaux. Une stabilité pratique des erreurs de tension continue est prouvée via le théorème de Lyapunov. Cette solution est explorée pour n modules en pont en H par phase, et les validations de mesure réelle et de simulation sont testées pour 2 et 3 modules dans un milieu industriel réel pour prouver son efficacité.La troisième solution présente une Structure PV connectée au réseau avec Filtre Actif Parallèle (SAF) basé sur un Onduleur Multi-Niveaux (MLI). Cette configuration améliore la qualité de l'énergie électrique et fournit de l'énergie renouvelable pour les charges et le réseau. Les entrées DC de l'onduleur multi-niveaux sont connectées directement aux sous-systèmes PV ou via des convertisseurs DC-DC. Des contrôleurs linéaires établissent la stratégie de contrôle du filtre actif parallèle basée sur (n) modules en pont H, comprenant l'injection de courant de compensation, la maximisation de la puissance produite par le système PV et la régulation des tensions DC sur les condensateurs. La modulation par largeur d'impulsion multi-porteuses assure une distribution équilibrée de l'énergie entre les modules. Des algorithmes de suivi du point de puissance maximale (MPPT), tels que Perturber et Observer (P&O), avec trois stratégies de contrôle comprenant le contrôleur proportionnel intégral, le rapport cyclique, et la commande prédictive (MPC), maximisent la génération d'énergie du sous-système PV. Le convertisseur DC-DC utilise des techniques de modulation PWM pour maintenir une fréquence de commutation constante.Les performances des trois solutions sont validées dans une usine textile souffrant d'impacts harmoniques sur la principale machine textile, représentant une charge sensible de 50 kVA, fournie par un entraînement de moteur asynchrone. Cet entraînement de moteur est sensible aux rangs prédominants du couple et des harmoniques de tension, nécessitant un contrôle approprié. Pour garantir des résultats fiables, des mesures sur site à l'aide d'appareils d'analyse de la qualité de l'énergie électrique sont collectées pour modéliser numériquement le réseau de l'usine. Les performances de chaque solution sont étudiées sur la charge sensible de cette usine textile
In the electrical distribution networks and smart grids, the widespread adoption of power electronics components among customer loads poses diverse challenges to power quality. The integration of renewable energy sources further exacerbates these challenges due to voltage fluctuations, frequency deviations, and waveform distortion inherent in these sources, significantly dependent on weather conditions. This thesis addresses these challenges through three distinct solutions for power quality improvement in distribution networks, focusing on integrating renewable energy sources, particularly photovoltaic (PV) systems, in the third solution.The first solution introduces a developed multi-level structure of an AC/DC/AC Converter. This solution aims to regulate voltage amplitude, ensure sinusoidal-like output stepping voltage, and mitigate a wide range of harmonics, including the predominant harmonics affecting sensitive loads such as asynchronous motor drives. To address these aspects, this work develops a novel modulation technique to control the DC/AC part of the converter, configured via an Asymmetrical Cascaded H-Bridge Inverter.The second solution involves an Advanced Hybrid Control System Developed for Shunt Active Filter Based on a Multi-Level Inverter. This solution improves the performance of the shunt active filter, raises its apparent switching frequency, and reduces the size of its output coupling filter. The hybrid controller, implemented using Petri Nets (PNs), ensures high-performance tracking of the compensating current, in addition to stabilizing, controlling, and balancing the DC voltages across the MLI inputs. The practical stability of the DC voltage errors is analytically proved via the Lyapunov theorem. This solution is explored in detail for n H-Bridge modules per phase, with real measurement and simulation validations evaluated for 2 and 3 H-Bridge modules per phase within a real industrial environment to prove the structure's effectiveness.The third solution presents a Grid-Connected PV Structure Incorporated with a Shunt Active Filter Based on a Multi-Level Inverter. This configuration enhances power quality and provides renewable energy for both loads and the grid. The DC inputs of the multi-level inverter are connected directly to PV subsystems or via DC-DC converters. Linear controllers are employed to establish the control strategy for the shunt active filter based on (n) H-bridge modules, including injecting compensating current, maximizing the produced power of the PV system, and regulating DC voltages across capacitors. Multi-carrier PWM modulation ensures balanced power distribution among the modules. Maximum Power Point Tracking (MPPT) algorithms, such as Perturb & Observe (P&O), with three control strategies including Proportional Integral, Duty-cycle, and Model Predictive Controller, are employed to maximize PV subsystem power generation. Additionally, the DC-DC converter utilizes PWM modulation techniques across all three control strategies to maintain a consistent switching frequency.The performance of the three aforementioned solutions is validated, for finite HB modules, within a textile factory suffering from harmonic impact on the main textile machine, which represents a sensitive load of 50 kVA, driven by an asynchronous motor. This motor drive is highly sensitive to predominant torque and voltage harmonics, requiring appropriate control of the fundamental output voltage amplitude and the phase and amplitude of the harmonic voltage components. This control system is particularly designed to regulate motor speed variation and mitigate undesired fluctuations caused by harmonic torques. To ensure reliable results, on-site measurements using power quality analyzer devices are collected to create a numerical model of the entire factory's network. Finally, the performance of each solution is investigated on the sensitive load operating within this textile factory

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de, Groot Martijn. "Development of a Plug and Play Solution for Commercial Off-grid Solar Refrigeration : Presenting a Battery Supported System Providing the AC Power Required to run a Coolfinity 300L Commercial Refrigerator." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302991.

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Анотація:

In this report the design and testing of a plug and play system to run Coolfinity’s Icevolt 300 refrigerator on solar panels is discussed. Such a system will be able to provide adequate cooling for food & beverages in area’s with unreliable or no electricity available. Currently such systems are only available for small chest refrigerators, while the Icevolt 300 is a large standing commercial refrigerator with a glass door. This is ideal for shops, cafés restaurants and smaller distribution centres. The system contains a solar charge controller, a battery and an inverter. First the component specifications and required solar panels are calculated. From those calculations system components are evaluated. A custom casing is designed to fit the components. An OEM is chosen and the chosen Inverter is tested extensively. The tests show that the inverter does not have any problems starting the Icevolt 300 compressor at a reduced voltage. Many battery manufacturers are evaluated and samples from three different manufacturers are obtained and tested. Samples of one of the manufacturers match specifications and have no issues with the high start up power of the compressor. A full system test proofs that the system works, but also indicates that the original refrigerator consumption estimate was too low. This means more PV panels are needed than originally estimated. With the information from the tests a new model is build that estimates the performance more accurate. A program is written to estimate the performance and decide the PV panels required. The pilot series of the case showed a lot of improvements are needed in the case design, especially on cost. A test is prepared in Mali but no test data is obtained yet. Based on the work done it would be recommend to investigate DC direct refrigerators instead of continuing the path of PV to AC systems.
I denna rapport diskuteras design och testning av ett plug and play - system för att köra Coolfinity’s Icevolt 300 -kylskåp på solpaneler. Ett sådant system kommer att kunna tillhandahålla tillräcklig kylning för mat och dryck i områden med opålitlig eller ingen tillgänglig el. För närvarande är sådana system endast tillgängliga för små kylboxar, medan Icevolt 300 är ett stort stående kommersiellt kylskåp med en glasdörr. Detta är idealiskt för butiker, kaféer och mindre distributionscentra. Systemet innehåller en laddningsregulator för solpaneler, ett batteri och en växelriktare. Först beräknas komponentspecifikationerna och nödvändiga solpaneler. Utifrån dessa beräkningar utvärderas systemkomponenter. Ett anpassat hölje är utformat för att passa komponenterna. En OEM väljs och den valda växelriktaren testas utförligt. Testerna visar att växelriktaren inte har några problem att starta Icevolt 300 -kompressorn med reducerad spänning. Många batteritillverkare utvärderas och prover från tre olika tillverkare erhålls och testas. Prover från en av tillverkarna matchar specifikationerna och har inga problem med kompressorns höga starteffekt. Ett fullständigt systemtest bevisar att systemet fungerar, men indikerar också att den ursprungliga uppskattningen av kylförbrukningen var för låg. Det betyder att fler PV -paneler behövs än vad som ursprungligen beräknades. Med informationen från testerna byggs en ny modell som uppskattar prestandan mer exakt. Ett program skrivs för att uppskatta prestanda och bestämma vilka PV -paneler som krävs. Pilotserien för höljet visade att många förbättringar behöver göras vad beträffar höljets design, särskilt vad gäller kostnaden. Ett test förbereds i Mali men inga testdata har erhållits ännu. Baserat på det utförda arbetet skulle det rekommenderas att undersöka direkta DC -kylskåp istället för att fortsätta vägen för PV till AC-system.

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41

Ali, Sadaqat. "Energy management of multi-source DC microgrid systems for residential applications." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0159.

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Comparé au réseau électrique alternatif (AC), le réseau électrique en courant continu (DC) a démontré de nombreux avantages tels que son interface naturelle avec les RES, les systèmes de stockage d'énergie et les charges en courant continu, une efficacité supérieure avec moins d'étapes de conversion, et un contrôle plus simple sans effet de peau et sans considérations sur le flux de puissance réactive. Le micro-réseaux DC reste une technologie relativement nouvelle, et ses architectures de réseau, stratégies de contrôle, techniques de stabilisation méritent d'énormes efforts de recherche. Dans ce contexte, cette thèse porte sur les problèmes de gestion de l'énergie d'un réseau électrique en courant continu (DC) multi-source dédié aux applications résidentielles. Le réseau électrique en courant continu (DC) est composé de générateurs distribués (panneaux solaires), d'un système de stockage d'énergie hybride (HESS) avec des batteries et un supercondensateur (SC), et de charges en courant continu, interconnectées via des convertisseurs de puissance DC/DC. L'objectif principal de cette recherche est de développer une stratégie avancée de gestion de l'énergie (EMS) d'améliorer l'efficacité opérationnelle du système tout en renforçant sa fiabilité et sa durabilité. Une plateforme de simulation hiérarchique de réseau électrique DC a été développée sous MATLAB/Simulink. Elle est composée de deux couches avec des échelles de temps différentes : une couche de contrôle de niveau local (échelle de temps de quelques secondes à quelques minutes en raison des comportements de commutation des convertisseurs) pour les contrôles des composants locaux, et une couche de contrôle de niveau système (avec une échelle de temps de quelques jours à quelques mois avec un test accéléré) pour la validation à long terme de l'EMS et son évaluation de performance. Dans la couche de contrôle de niveau local, les panneaux solaires, les batteries et le supercondensateur ont été modélisés et contrôlés séparément. Différents modes de contrôle tels que le contrôle de courant, le contrôle de tension et le contrôle du point de puissance maximale (MPPT) ont été mis en œuvre. Un filtre passe-bas (LPF) a été appliqué pour diviser la puissance totale du HESS : basse et haute fréquence pour les batteries et le supercondensateur. Différentes fréquences de coupure du LPF pour le partage de puissance a également été étudiée. Un EMS hybride bi-niveau combiné et un dimensionnement automatique ont été proposés et validés. Il couvre principalement cinq scénarios d'exploitation, notamment la réduction de la production des panneaux solaires, la réduction de la charge et trois scénarios via le contrôle du HESS associé à la rétention du contrôle de l'état de charge (SOC) du supercondensateur. Une fonction objective prenant en compte à la fois le coût en capital (CAPEX) et les coûts d'exploitation (OPEX) a été conçue pour l'évaluation des performances de l'EMS. L'interaction entre l'HESS et l'EMS a été étudiée conjointement sur la base d'un ensemble de données ouvertes de profils de consommation électrique résidentielle couvrant à la fois l'été et l'hiver. Finalement, une plateforme expérimentale de réseau électrique à courant continu (DC) multi-source a été développée pour valider en temps réel l'EMS. Elle est composée de quatre batteries lithium-ion, d'un supercondensateur, d'une alimentation électrique à courant continu programmable, d'une charge à courant continu programmable, de convertisseurs DC/DC correspondants et d'un contrôleur en temps réel (dSPACE/Microlabbox). Des tests accélérés ont été réalisés pour vérifier l'EMS proposé dans différents scénarios d'exploitation en intégrant des panneaux solaires réels et les profils de consommation de charge. Les plateformes de simulation hiérarchique de réseau électrique en courant continu (DC) et expérimentale, peuvent être utilisées de manière générale pour vérifier et évaluer divers EMS
Compared to the alternating current (AC) electrical grid, the direct current (DC) electrical grid has demonstrated numerous advantages, such as its natural interface with renewable energy sources (RES), energy storage systems, and DC loads. It offers superior efficiency with fewer conversion steps, simpler control without skin effect or reactive power considerations. DC microgrids remain a relatively new technology, and their network architectures, control strategies, and stabilization techniques require significant research efforts. In this context, this thesis focuses on energy management issues in a multi-source DC electrical grid dedicated to residential applications. The DC electrical grid consists of distributed generators (solar panels), a hybrid energy storage system (HESS) with batteries and a supercapacitor (SC), and DC loads interconnected via DC/DC power converters. The primary objective of this research is to develop an advanced energy management strategy (EMS) to enhance the operational efficiency of the system while improving its reliability and sustainability. A hierarchical simulation platform of the DC electrical grid has been developed using MATLAB/Simulink. It comprises two layers with different time scales: a local control layer (time scale of a few seconds to minutes due to converter switching behavior) for controlling local components, and a system-level control layer (time scale of a few days to months with accelerated testing) for long-term validation and performance evaluation of the EMS. In the local control layer, solar panels, batteries, and the supercapacitor have been modeled and controlled separately. Various control modes, such as current control, voltage control, and maximum power point tracking (MPPT), have been implemented. A low-pass filter (LPF) has been applied to divide the total HESS power into low and high frequencies for the batteries and supercapacitor. Different LPF cutoff frequencies for power sharing have also been studied. A combined hybrid bi-level EMS and automatic sizing have been proposed and validated. It mainly covers five operational scenarios, including solar panel production reduction, load reduction, and three scenarios involving HESS control combined with supercapacitor state of charge (SOC) control retention. An objective function that considers both capital expenditure (CAPEX) and operating costs (OPEX) has been designed for EMS performance evaluation. The interaction between the HESS and EMS has been jointly studied based on an open dataset of residential electrical consumption profiles covering both summer and winter seasons. Finally, an experimental platform of a multi-source DC electrical grid has been developed to validate the EMS in real-time. It comprises four lithium-ion batteries, a supercapacitor, a programmable DC power supply, a programmable DC load, corresponding DC/DC converters, and a real-time controller (dSPACE/Microlabbox). Accelerated tests have been conducted to verify the proposed EMS in different operational scenarios by integrating real solar panels and load consumption profiles. The hierarchical simulation and experimental DC electrical grid platforms can be generally used to verify and evaluate various EMS

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MIGLIAZZA, Giovanni. "Studio di nuove soluzioni di Inverter a corrente impressa per sorgenti energetiche rinnovabili e per azionamenti elettrici in ambito aerospaziale." Doctoral thesis, Università degli studi di Modena e Reggio Emilia, 2020. http://hdl.handle.net/11380/1200383.

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In questo lavoro di tesi è stata analizzata una particolare architettura di convertitore elettronico di potenza DC/AC denominata CSI (“Current Source inverter”). Storicamente, questa topologia è stata largamente impiegata per l’azionamento di macchine elettriche in media tensione. Il CSI, rispetto ai più diffusi Voltage Source Inverter (VSI) è caratterizzato da maggiori perdite di conduzione dei propri transistor ma è in grado di garantire un’affidabilità più elevata, siccome il corto-circuito di un qualunque mezzo-ponte (gamba dell’inverter) non determina una rottura (come nelle comuni architetture VSI), ma bensì è una normale condizione operativa all’interno di un periodo di commutazione della modulazione PWM. Una peculiarità importante di questa topologia è il suo funzionamento intrinseco come step-up nel caso la sorgente in ingresso al convertitore sia costituita da una sorgente di tensione continua seguita da un induttore. In questo lavoro si sono investigate modifiche topologiche rispetto all’architettura classica del CSI, nuove strategie di controllo e modulazioni PWM al fine di incrementare l’efficienza di conversione, ridurre il contenuto armonico indesiderato delle proprie correnti di uscita e limitare le correnti di modo comune. Cercando cosi, di rendere la topologia competitiva in applicazioni Industriali. Differenti soluzioni topologiche e di controllo del CSI sono state studiate per due differenti applicazioni: convertitori DC/AC grid-connected senza isolamento galvanico per sistemi fotovoltaici e per azionamenti elettrici per applicazioni aerospaziali. Nell’ambito dei convertitori DC/AC grid-connected sono state proposte soluzioni sia per sistemi trifase, sia per sistemi monofase. In particolare grazie all’aggiunta di uno o più transistor e a modulazioni PWM dedicate è stato possibile ridurre le perdite di conduzione, il contenuto armonico delle correnti iniettate in rete e la corrente di dispersione verso terra. Nella seconda applicazione come azionamento elettrico, si è investigato l’impatto della topologia nel mondo aerospaziale, proponendo una nuova strategia di controllo che permette di controllare la macchina elettrica unicamente attraverso un’architettura tradizionale CSI con sorgente di tensione continua e induttore serie, senza l’ausilio di un ulteriore convertitore DC-DC che regola la corrente in ingresso al CSI. Sfruttando la caratteristica intrinseca di innalzamento della tensione d’uscita dell’azionamento, sono stati progettati dei motori elettrici che potendo lavorare a tensioni più elevate e con basso contenuto armonico grazie al filtro d’uscita intrinseco del CSI, è possibile realizzare delle macchine con densità di potenza elevata, aspetto molto interessante in ambito aerospaziale.
In this thesis work, a particular DC / AC power converter architecture called CSI ("Current Source inverter") was analyzed. Historically, this topology has been widely used for driving medium voltage electrical machines. The CSI, compared to the more widespread Voltage Source Inverter (VSI) is characterized by higher semiconductor conduction losses but is able to guarantee a higher reliability as the short-circuit of any half-bridge (inverter leg) does not cause a break (as in VSI architectures), but rather it is a normal operating condition within the pattern of PWM modulation. An important peculiarity of this topology is its intrinsic operation as voltage step-up when the input source of the converter consists of a DC voltage with an inductor in series. In this work, some topological variations respect to the classical CSI architecture were investigated along with new control strategies and Space Vector Modulation(SVM) in order to increase the conversion efficiency, to reduce the undesired harmonic component of output currents, and to mitigate the common mode current. Different CSI topologies and control strategies have been designed for two different applications: DC / AC grid-connected converters without galvanic isolation for photovoltaic applications and electric drives for aerospace applications. In Grid-connected applications, DC / AC converter solutions have been proposed for three-phase and single-phase systems. In particular, thanks to the addition of one or more transistors and dedicated SVM, it was possible to reduce conduction losses, the harmonic component in the injected currents into the grid and the ground leakage current. In the second application, the impact of the CSI topology in the aerospace environment was investigated. The proposed control strategy allows to control the electric machine using only the traditional CSI architecture with a DC Voltage source and with an inductor in series, without the aid of an additional DC-DC converter that regulates the input current of the CSI. Taking advantage of the intrinsic step-up voltage characteristic and very low high frequency harmonic content of the output phase voltages (thanks to the intrinsic CSI output filter), electric motors can be designed for higher voltages allowing higher power density, very interesting aspect in the aerospace field.

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43

Rokrok, Ebrahim. "Controle en grid forming pour les convertisseurs d'électronique de puissance : application aux liaisons courant continus de Haute Tension (HVDC)." Electronic Thesis or Diss., Centrale Lille Institut, 2022. http://www.theses.fr/2022CLIL0012.

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Анотація:

Le développement rapide d’équipements raccordés sur les réseaux électriques avec des convertisseurs électroniques de puissance tels que les générateurs à base d‘énergie renouvelable et les liaisons de transmission sous haute tension continue entraîne un changement profond dans la physique même du système électrique. Aujourd'hui, les convertisseurs de puissance ont pour fonction principale d'injecter de l'énergie dans le réseau électrique, ce dernier s'appuyant sur des machines synchrones pour assurer tous les besoins nécessaires au fonctionnement et à la conduite du système électrique (par exemple, les services auxiliaires, la fourniture de réserve inertielle énergétique et de réserves dynamiques et fiables de puissance). Ce mode de fonctionnement des convertisseurs de puissance est appelé "grid-following" car suivant la tension alternative imposée au point de raccordement. Il présente plusieurs limitations, telles que : l'incapacité de fonctionner en mode autonome, des problèmes de stabilité dans des réseaux faibles et des fonctionnements défectueux, ainsi que des effets secondaires négatifs sur l'inertie du système. Pour relever ces défis, une alternative est de contrôler le convertisseur électronique de puissance pour générer et contrôler lui-même cette tension alternative. Dans cette thèse, une description fondamentale de cette commande en grid-forming est présentée avec une approche de modélisation quasi-statique simplifiée permettant de concevoir une régulation de la puissance active échangée avec le réseau AC. Plusieurs variantes de cette stratégie de contrôle sont mises en évidence et présentent des différences en termes de comportement dynamique sur la puissance active, de capacité d'émulation d'une réserve énergétique inertielle et de prise en charge de la fréquence du système. Les variantes sont ensuite classées en fonction de leurs capacités et fonctionnalités. Ces stratégies de commande ont été implémentées pour un convertisseur à 2 niveaux. Suivant une analyse de stabilité dite « petits signaux », la robustesse et leur capacité à fonctionner sur un réseau faible sont démontrées. De plus, les services auxiliaires tels que la réponse inertielle et le support au contrôle de la fréquence sont fournis de manière appropriée au réseau AC. Les questions de la protection contre les surintensités et de la synchronisation après défaut (tout en tenant compte de la limitation de courant) sont étudiées et une nouvelle méthode est proposée pour améliorer la stabilité transitoire du système électrique. Les résultats obtenus sont ensuite généralisés à une topologie de convertisseur multi-niveaux modulaire (MMC) avec succès. Avec cette commande, la fourniture d’une réserve inertielle est particulièrement intéressante pour gérer les transferts de puissance à l’interconnexion d’un réseau continu haute tension avec le réseau alternatif de transport d’électricité. La dernière partie de cette thèse évalue les performances dynamiques d'une liaison HVDC interconnectant deux réseaux AC et met en évidence la stratégie et les exigences appropriées pour la fourniture de réserve inertielle
The rapid development of converter-based devices such as converter-interfaced renewable generations and high-voltage direct-current (HVDC) transmission links is causing a profound change into the very physics of the power system. In this scenario, the power generation is shifted from the pollutant synchronous generators based on nuclear or fossil fuels to converter-based renewable resources. The modeling, control, and stability of the power converters are now one of the focuses of attention for researchers. Today, power converters have the main function of injecting power into the utility grid, while relying on synchronous machines that ensure all system needs (e.g., ancillary services, provision of inertia and reliable power reserves). This operation mode of power converters is called "Grid-following". Grid-following converters have several limitations, such as: inability to operate in a standalone mode, stability issues under weak grids and faulty conditions and also, negative side effect on the system inertia. To tackle these challenges, the grid-forming control as an alternative has shown its appropriate performance that could make this kind of control a promising solution to respond to the system needs and to allow a stable and safe operation of power system with high penetration rate of power electronic converters. In this thesis, a fundamental description of grid-forming control with a simplified quasi-static modeling approach aiming to regulate the converter active power by a voltage source behavior is presented. From the description, several variants of grid-forming strategies are identified that represent some differences in terms of active power dynamic behavior, inertia emulation capability and system frequency support. Hence, the presented grid-forming variants are then classified according to their capabilities/functionalities. From the small-signal stability and robustness point of view, the studied grid-forming controls, which are implemented to a 2-level VSC at first, show their ability to operate under very weak grid conditions. Moreover, the ancillary services such as inertial response and frequency support are appropriately provided to the AC grid. The questions of the grid-forming converters protection against overcurrent and their post-fault synchronization while considering the current limitation are investigated and a new method is proposed to enhance the transient stability of the system. All the obtained results are then extended to a modular multi-level converter (MMC) topology successfully. The use of a grid forming control in an HVDC converter is interesting for the grid to which it is connected due to the inertial effect that can be induced. Therefore, the final part of this thesis evaluates the dynamic performance of an HVDC link interconnecting two AC grids and highlights the proper strategy and requirements for inertia provision

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Qoria, Taoufik. "Nouvelles lois de contrôle pour former des réseaux de transport avec 100% d’électronique de puissance." Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAE041.

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Le développement rapide de la production d'énergie renouvelable intermittente et des liaisons HVDC entraîne une augmentation importante du taux de pénétration des convertisseurs statiques dans les réseaux de transport. Aujourd'hui, les convertisseurs statiques ont pour fonction principale d'injecter une puissance dans le réseau tout en s'appuyant sur des machines synchrones qui garantissent tous les besoins du système électrique. Ce mode de fonctionnement est appelé «Grid-following». Les convertisseurs contrôlés en Grid-following ont plusieurs limitations: leur incapacité à fonctionner en mode autonome, leurs problèmes de stabilité dans des réseaux faibles et en cas de défaut ainsi que leur effet négatif sur l'inertie équivalent du système. Pour relever ces défis, le contrôle en Grid-forming est une bonne solution pour répondre aux besoins du système électrique et permettre un fonctionnement stable et sûr du système même avec un taux de pénétration des convertisseurs statique de 100%. Tout d'abord, trois stratégies de contrôle en Grid-forming sont proposées pour garantir quatre fonctionnalités principales: contrôle de tension, contrôle de puissance, émulation d'inertie et le support de la fréquence. La dynamique et la robustesse du système basées sur chaque contrôle ont été analysées et discutées. Ensuite, selon la topologie du convertisseur, la connexion avec le réseau AC peut nécessiter des filtres et des boucles de contrôle supplémentaires. Dans le cadre de cette thèse, deux topologies de convertisseur ont été envisagées (VSC à 2-niveaux et VSC-MMC) et l'implémentation associée à chacune a été discutée. Enfin, les questions de la protection des convertisseurs Grid-forming contre les surintensités et leur synchronisation post-défaut ont été étudiées, puis, des algorithmes de limitation de courant et de resynchronisation ont été proposés pour améliorer la stabilité transitoire du système. Un banc d'essai a été développé pour confirmer les approches théoriques proposées
The rapid development of intermittent renewable generation and HVDC links yields an important increase of the penetration rate of power electronic converters in the transmission systems. Today, power converters have the main function of injecting power into the main grid, while relying on synchronous machines that guaranty all system needs. This operation mode of power converters is called "Grid-following". Grid-following converters have several limitations: their inability to operate in a standalone mode, their stability issues under weak-grids and faulty conditions and their negative side effect on the system inertia.To meet these challenges, the grid-forming control is a good solution to respond to the system needs and allow a stable and safe operation of power system with high penetration rate of power electronic converters, up to a 100%. Firstly, three grid-forming control strategies are proposed to guarantee four main features: voltage control, power control, inertia emulation and frequency support. The system dynamics and robustness based on each control have been analyzed and discussed. Then, depending on the converter topology, the connection with the AC grid may require additional filters and control loops. In this thesis, two converter topologies have been considered (2-Level VSC and VSC-MMC) and the implementation associated with each one has been discussed. Finally, the questions of the grid-forming converters protection against overcurrent and their post-fault synchronization have been investigated, and then a hybrid current limitation and resynchronization algorithms have been proposed to enhance the transient stability of the system. At the end, an experimental test bench has been developed to confirm the theoretical approach

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Al-Bayaty, Hussein Kamal Anwer. "Novel methods of utilization, elimination, and description of the distortion power in electrical circuits." Thesis, University of Plymouth, 2018. http://hdl.handle.net/10026.1/10646.

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Firstly, this thesis investigates the electrical power harmonics in an attempt to utilize harmonic current and its distortion power in a novel idea to reconvert the distortion power into useful power. This is done, in order to feed different DC or AC loads in single and three-phase power system by using passive or active filters and accordingly, develop a new topology of hybrid active power filter (HAPF). In addition, this circuit can be considered as a power factor corrector (PFC) because it reduces the total harmonic distortion (THD) and improves the power factor (PF). Secondly, this thesis works on a new design of active power factor correction (APFC) circuit presenting two circuits with the same design principle: the first design consists of two active switches without an external complex control circuit, while the second design contains a single active switch with an additional control circuit. The main contribution of this circuit is 98% reduction of the inductor's value used in the newly proposed PFC circuit in comparison with the conventional boost converter which may lead to a huge reduction in size, weight and the cost of the new PFC circuit. Also, the active switches depend on a carefully designed switching pattern that results in an elimination of the third order harmonic from the input source current which decreases the value of total current harmonic distortion (THDI) to (14%) and improves the input PF to (0.99). Consequently, the simplicity of the design without requiring a complex control circuit and without a snubber circuit plus the minimum size of inductor, gives the newly proposed circuit the superiority on other PFC circuits. Thirdly, this research aims to describe the distortion power through submitting two novel power terms called effective active power (Pef ) & reactive power (Qef ) terms with a new power diagram called Right-Angled Power Triangle (RAPT) Diagram. In addition, a novel de nition of total apparent power (St) has been submitted in order to illustrate the physical meaning of (St) in non-sinusoidal systems. The new RAPT Diagram is based on the orthogonality law and depends on geometrical summation to describe the relationship between different aspects (apparent-active-reactive) of power, and different components (total-fundamental distortion), drawing a bridge to connect the time domain with the frequency domain in a two-dimensional diagram.

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46

Houari, Azeddine. "Contribution à l'étude de micro-réseaux autonomes alimentés par des sources photovoltaïques." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0293/document.

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L'orientation énergétique actuelle vers le développement de systèmes électriques isolés, s'est traduit par l'établissement de nouvelles directives sur les performances et la fiabilité des structures de puissance mises en oeuvre, en particulier ceux à base d'énergies renouvelables. C'est dans ce contexte que s'inscrivent ces travaux de thèse, qui aboutissent à l'élaboration de nouveaux outils destinés à l'amélioration de la qualité d'énergie et de la stabilité d'un micro-réseau autonome. Concernant l'optimisation énergétique des interfaces de conversion pour un réseau autonome, nous avons développé de nouveaux algorithmes de commande basés sur le concept de platitude des systèmes différentiels. L'avantage de cette technique réside dans la possibilité d'implémentation de régulateurs à une boucle. Cela garantit des propriétés dynamiques élevées en asservissement et en régulation. De plus, une prédiction exacte de l'évolution des variables d'états du système est possible. Concernant la stabilité des micro-réseaux autonomes, nous avons proposé des outils pour traiter les phénomènes d'instabilités, causés notamment par la perte d'informations de charges et par le phénomène de résonance des filtres d'interconnexion
The actual electrical energy demand focuses on the development of stand-alone electrical systems which leads to the definition of new directives on performances and reliability of the electrical structures, especially those based on renewable energy. The main objective of this work concerns the development of new tools to improve the power quality and the stability of autonomous micro-grid systems. In this aim, new control algorithms based on the concept of differential flatness have been developed. The main advantage of the proposed technique is the possibility of implementing one loop controllers ensuring high dynamic properties. In the same time, it allows accurate prediction of the evolution of all state variables of the system. Concerning the stability of the autonomous micro-grid systems, we proposed tools to deal with instability phenomena either caused by the loss of load information and the resonance phenomenon of the passive filters

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Vidales, Luna Benjamin. "Architecture de convertisseur intégrant une détection de défauts d'arcs électriques appliquée au sources d'énergie continues d'origine photovoltaïques." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0040.

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Détection de défaut d'arcs intégrée dans un convertisseur intelligent contrôlé par FPGA pour les panneaux photovoltaïques. La mise au point de convertisseur intelligents intégrant des dispositifs de protection est une thématique que cherche à développer l'Institut Technologique de Morelia (Mexique) avec laquelle nous collaborons sur ce projet. L'objectif plus spécifique de ce travail repose sur la détection de défauts d'arc électrique en se basant sur le contrôle intelligent des onduleurs utilisés dans la gestion de l'énergie produite par des panneaux photovoltaïques. Depuis plusieurs années, le développement croissant des panneaux solaires photovoltaïques comme source d’énergie s’est imposé et la sécurité de ces dispositifs liée à la détection de défauts d’arcs électriques est devenu un enjeu majeur. L'approche que nous proposons dans ce travail est le développement d'une stratégie novatrice pour la surveillance et la prédiction de défaillance du réseau électrique constitué de panneaux solaires en présence de défauts d’arcs. Actuellement, la majorité des systèmes de détection comprennent des modules détecteurs disposés dans le circuit électrique à protéger dont la robustesse est loin d'être optimale. L'approche que nous proposons consiste à développer un dispositif de surveillance et de détection de défaut directement intégré dans l'onduleur intelligent. Le contrôle optimal de l'onduleur intelligent assurera une détection fiable de défaut d'arc sans déclenchement intempestif. Le dispositif comprendra également un système de coupure. La méthode de détection que nous privilégions sera basée sur l'analyse du courant et de la tension de ligne. Les algorithmes seront basés sur une analyse temps/fréquence des signatures courant et de tension suivie par une logique pertinente de décision de telle manière à minimiser le taux de fausses détections.Le noyau du convertisseur intelligent est constitué par un FPGA. Le parallélisme des traitements de données assurera le respect des contraintes temps réel. Dans le cadre du projet de thèse, la mise en œuvre, le test des algorithmes de détection et l’implémentation optimale afin de respecter les contraintes temps réel dans le FPGA sera mené dans le cadre d’une cotutelle de thèse entre l’institut technologique de Morelia et l’Université de Lorraine
In this research work, the development of a multilevel inverter for PV applications is presented. The PV inverter, has two stages one DC/DC converter and one DC/AC inverter, and is capable of generating an AC multilevel output of nine levels, it's a transformerless inverter and uses a reduced number of components compared to other topologies. The conception of a novel DC/DC converter is capable of generating two isolated DC voltage levels needed to feed the DC/AC stage. This DC/DC stage is developed in two variants, buck and boost, the _rst to perform the reduction of voltage when the DC bus is too high, and second to increase the voltage when the DC bus is too low to perform interconnection with the grid through the DC/AC inverter. This is achieved thanks to the parallel functioning of the developed topology, which make use of moderated duty cycles, that reduces the stress in the passive and switching components, reducing potential losses. The validation of the PV inverter is performed in simulation and experimental scenarios. In the other hand, the response of the inverter facing an arc fault in the DC bus is studied by performing a series of tests where the fault is generated in strategic points of the DC side, this is possible thanks to the design and construction of an arc fault generator based in the specifications of the UL1699B norm. During the tests is observed that with the apparition of an arc fault, there is a lost in the half-wave symmetry of the AC multilevel output voltage waveform, generating even harmonics which aren't present during normal operation, only when an arc fault is present in the DC system. The monitoring of even harmonics set the direction for developing the detection technique. Since the magnitude of even harmonics in the inverter is very low, the total even harmonic distortion is employed as a base for the detection technique presented in this thesis. The effectiveness of this method is verified with a series of tests performed with different loads

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Houari, Azeddine. "Contribution à l'étude de micro-réseaux autonomes alimentés par des sources photovoltaïques." Electronic Thesis or Diss., Université de Lorraine, 2012. http://www.theses.fr/2012LORR0293.

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L'orientation énergétique actuelle vers le développement de systèmes électriques isolés, s'est traduit par l'établissement de nouvelles directives sur les performances et la fiabilité des structures de puissance mises en oeuvre, en particulier ceux à base d'énergies renouvelables. C'est dans ce contexte que s'inscrivent ces travaux de thèse, qui aboutissent à l'élaboration de nouveaux outils destinés à l'amélioration de la qualité d'énergie et de la stabilité d'un micro-réseau autonome. Concernant l'optimisation énergétique des interfaces de conversion pour un réseau autonome, nous avons développé de nouveaux algorithmes de commande basés sur le concept de platitude des systèmes différentiels. L'avantage de cette technique réside dans la possibilité d'implémentation de régulateurs à une boucle. Cela garantit des propriétés dynamiques élevées en asservissement et en régulation. De plus, une prédiction exacte de l'évolution des variables d'états du système est possible. Concernant la stabilité des micro-réseaux autonomes, nous avons proposé des outils pour traiter les phénomènes d'instabilités, causés notamment par la perte d'informations de charges et par le phénomène de résonance des filtres d'interconnexion
The actual electrical energy demand focuses on the development of stand-alone electrical systems which leads to the definition of new directives on performances and reliability of the electrical structures, especially those based on renewable energy. The main objective of this work concerns the development of new tools to improve the power quality and the stability of autonomous micro-grid systems. In this aim, new control algorithms based on the concept of differential flatness have been developed. The main advantage of the proposed technique is the possibility of implementing one loop controllers ensuring high dynamic properties. In the same time, it allows accurate prediction of the evolution of all state variables of the system. Concerning the stability of the autonomous micro-grid systems, we proposed tools to deal with instability phenomena either caused by the loss of load information and the resonance phenomenon of the passive filters

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"Hybrid AC-High Voltage DC Grid Stability and Controls." Doctoral diss., 2017. http://hdl.handle.net/2286/R.I.46197.

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abstract: The growth of energy demands in recent years has been increasing faster than the expansion of transmission facility construction. This tendency cooperating with the continuous investing on the renewable energy resources drives the research, development, and construction of HVDC projects to create a more reliable, affordable, and environmentally friendly power grid. Constructing the hybrid AC-HVDC grid is a significant move in the development of the HVDC techniques; the form of dc system is evolving from the point-to-point stand-alone dc links to the embedded HVDC system and the multi-terminal HVDC (MTDC) system. The MTDC is a solution for the renewable energy interconnections, and the MTDC grids can improve the power system reliability, flexibility in economic dispatches, and converter/cable utilizing efficiencies. The dissertation reviews the HVDC technologies, discusses the stability issues regarding the ac and HVDC connections, proposes a novel power oscillation control strategy to improve system stability, and develops a nonlinear voltage droop control strategy for the MTDC grid. To verify the effectiveness the proposed power oscillation control strategy, a long distance paralleled AC-HVDC transmission test system is employed. Based on the PSCAD/EMTDC platform simulation results, the proposed power oscillation control strategy can improve the system dynamic performance and attenuate the power oscillations effectively. To validate the nonlinear voltage droop control strategy, three droop controls schemes are designed according to the proposed nonlinear voltage droop control design procedures. These control schemes are tested in a hybrid AC-MTDC system. The hybrid AC-MTDC system, which is first proposed in this dissertation, consists of two ac grids, two wind farms and a five-terminal HVDC grid connecting them. Simulation studies are performed in the PSCAD/EMTDC platform. According to the simulation results, all the three design schemes have their unique salient features.
Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2017

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JENA, RAVI KANTA. "POWER MANAGEMENT AND CO-ORDINATION CONTROL OF HYBRID AC DC MICROGRID IN GRID CONNECTED AND ISLANDED CONDITIONS." Thesis, 2019. http://dspace.dtu.ac.in:8080/jspui/handle/repository/17064.

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In remote rural areas, which are far from the primary grid network, mostly renewable power generators are introduced and there is the chance of a fragile transmission line connection. The rapidly growing demand and grid integration of renewable energies has laid the foundation for ac / dc microgrid. DGs ' interconnection with the utility / grid through interlinking converters has raised concerns about secure operation and equipment surveillance. The microgrid can be meant for the client to satisfy their needs and requirements; for example, improving local reliability, minimizing feeder losses, supporting local voltages, enhancing utilization by using waste heat, tension decrease or continuous power supply. The work's objective is to reconstitute control switching to suffer minimal transients in the microgrid. MATLAB / SIMULINK simulates the project. This report introduces a decentralized mechanism of power management for the hybrid microgrid to coordinate and promote the interacted sub-grids. First, considering the features of the popular bus setup, a Pdc − v2 dc droop control approach is suggested to sustain the common bus voltage and obtain energy sharing among storage sub grids. Secondly, as the interaction between numerous sub-grids is more problematic than the standard hybrid, a coordinated energy control strategy based on common bus voltage, ac sub-grid frequency, and dc sub- grid voltage is intended for the BADCs and BDDCs to grasp the power interaction between varying sub-grids. In addition, the proposed strategy reflects the capacities and load types of each sub grid; consequently, it is still necessary when sub grid capacities are not matched, and it can ensure the power quality of the sub grids with a high proportion of critical loads. This work suggests a revised topology of a hybrid ac / dc microgrid, where bidirectional ac / dc converters (BADCs) and bidirectional dc / dc converters (BDDCs) connect numerous sub- grids in the framework to the common bus.

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