Rozprawy doktorskie: „HYBRID AC DC MICROGRID”

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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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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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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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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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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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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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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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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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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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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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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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Sarker, Partha Sarathi. "DYNAMIC MODELING, STABILITY ANALYSIS AND CONTROL OF AC/DC INTERCONNECTED MICROGRID USING DQ-TRANSFORMATION". Master's thesis, Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/518146.

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Electrical and Computer Engineering
M.S.E.E.
In recent years, there have been significant changes in power systems due to the integration of renewables, distributed generation, switched power loads, and energy storage systems, etc. Locally these AC/DC microgrids include both DC generation (such as solar PV) and AC generation (such as wind generation), various DC and AC loads, converters and inverters, and energy storage systems, such as storage batteries and supercapacitors. DC systems are often characterized as low inertia systems whereas AC generation and systems are usually high inertia and high time constant systems. As such, various components of the microgrid will have different temporal characteristics in case of disturbances, such as short circuit, load switchings, etc. which may lead to instability of the microgrid. This research develops the first principle model for coupling the AC and the DC subsystem of an integrated AC/DC microgrid utilizing the dq-framework. The developed model is highly nonlinear and captures the dynamic interaction between the AC and DC subsystems of the microgrid. Lyapunov stability is used to evaluate the stability of the complete system. Simulation results show that the AC and DC subsystems are tightly dynamically coupled so that any disturbance in one subsystem induces transients in the other subsystem. Induced transients due to pulse loads on the AC and DC subsystems clearly show that generator damper winding alone may not be enough to mitigate transients in the microgrid. Addition of prime mover and excitation system controllers for the generator improves the transients primarily on the AC subsystem. Thus, a battery storage with a charge/discharge controller was also added to the DC subsystem. Simulations of the AC/DC microgrid with all three controllers validate the smooth operation of the system for all types of disturbances. The proposed method can be extended in modeling microgrid with multiple generators and various types of loads.
Temple University--Theses

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Briggner, Viktor, Pontus Grahn i 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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Briggner, Viktor, Pontus Granhn i 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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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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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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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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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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18

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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19

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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20

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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21

Musa, Aysar [Verfasser], Antonello [Akademischer Betreuer] Monti i 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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Tulpule, Pinak J. "Control and optimization of energy flow in hybrid large scale systems - A microgrid for photovoltaic based PEV charging station". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313522717.

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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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Hotz, Matthias [Verfasser], Wolfgang [Akademischer Betreuer] Utschick, Mario [Gutachter] Paolone i 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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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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26

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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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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Priyadarshanee, Lipsa. "Modeling and control of hybrid ac/dc microgrid". Thesis, 2012. http://ethesis.nitrkl.ac.in/3938/1/thesis_lipsa.pdf.

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Renewable energy based distributed generators (DGs) play a dominant role in electricity production, with the increase in the global warming. Distributed generation based on wind, solar energy, biomass, mini-hydro along with use of fuel cells and microturbines will give significant momentum in near future. Advantages like environmental friendliness, expandability and flexibility have made distributed generation, powered by various renewable and nonconventional microsources, an attractive option for configuring modern electrical grids. A microgrid consists of cluster of loads and distributed generators that operate as a single controllable system. As an integrated energy delivery system microgrid can operate in parallel with or isolated from the main power grid. The microgrid concept introduces the reduction of multiple reverse conversions in an individual AC or DC grid and also facilitates connections to variable renewable AC and DC sources and loads to power systems. The interconnection of DGs to the utility/grid through power electronic converters has risen concerned about safe operation and protection of equipment’s. To the customer the microgrid can be designed to meet their special requirements; such as, enhancement of local reliability, reduction of feeder losses, local voltages support, increased efficiency through use of waste heat, correction of voltage sag or uninterruptible power supply. In the present work the performance of hybrid AC/DC microgrid system is analyzed in the grid tied mode. Here photovoltaic system, wind turbine generator and battery are used for the development of microgrid. Also control mechanisms are implemented for the converters to properly co-ordinate the AC sub-grid to DC sub-grid. The results are obtained from the MATLAB/ SIMULINK environment.

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Tovar, Luís Gonçalo Cipreste Leal de Médicis. "Hybrid AC/DC Microgrids for Rural Electrification". Master's thesis, 2020. https://hdl.handle.net/10216/132845.

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O objetivo principal desta dissertação é construir um modelo de uma rede híbrida AC/DC no Software Simulink e estudar a maneira como funciona em diferentes condições e cenários. Esta tese divide-se em seis capítulos: o primeiro, a Introdução, explica os principais objetivos, as contribuições, a motivação e como a tese está organizada; o segundo capítulo, o Estado da Arte, reporta-se aos conceitos básicos da eletricidade em áreas rurais, como é que as micro redes e micro redes híbridas funcionam, as suas arquiteturas, modelos utilizados, aplicações, implementação elétrica e a sua importância nestes meios mais afastados das grandes cidades; no capítulo 3 e 4, apresenta-se uma explicação mais sucinta acerca da simulação e testes que se vão realizar; o terceiro capítulo foca-se mais na parametrização dos modelos, nos diferentes cenários para a rede, com o intuito de analisá-la, e na estrutura e implementação das redes AC e DC a ser estudadas; o quarto capítulo explica, de forma mais pormenorizada, como os modelos são construídos e como funcionam as funções de controlo dos mesmos; no capítulo 5, realiza-se uma simulação para cada um dos cenários definidos e é feita uma análise a cada um dos resultados obtidos; no último capítulo, são definidas todas as principais conclusões de todo este projeto.
The main objective of this dissertation is to build a hybrid AC/DC microgrid model in the Software Simulink and to study the way it works and performs in different scenarios. This thesis is divided into six chapters: the first one, the Introduction, explains the main objectives, the contributions, the motivation and how the thesis is organized; the second chapter, the State of Art, reports the basic concepts of electricity in rural areas, how the microgrids and hybrid microgrids work, its architecture, models, electrical implementations, applications and the importance of these grids in places that are located far away from the big cities and the main grids; in chapters 3 and 4, it is stated a more succinct explanation about the simulation and tests that will be performed; the third one focuses more on the parametrization of the models, the different scenarios to test and in the structure and implementation of the AC and DC microgrids that are being studied; the fourth chapter explains how models are designed, how they work and how their control functions operate; in chapter 5, the results of the simulation for each scenario are analysed and studied; in the last chapter, all the main conclusions taken from this thesis are defined.

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Tovar, Luís Gonçalo Cipreste Leal de Médicis. "Hybrid AC/DC Microgrids for Rural Electrification". Dissertação, 2020. https://hdl.handle.net/10216/132845.

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O objetivo principal desta dissertação é construir um modelo de uma rede híbrida AC/DC no Software Simulink e estudar a maneira como funciona em diferentes condições e cenários. Esta tese divide-se em seis capítulos: o primeiro, a Introdução, explica os principais objetivos, as contribuições, a motivação e como a tese está organizada; o segundo capítulo, o Estado da Arte, reporta-se aos conceitos básicos da eletricidade em áreas rurais, como é que as micro redes e micro redes híbridas funcionam, as suas arquiteturas, modelos utilizados, aplicações, implementação elétrica e a sua importância nestes meios mais afastados das grandes cidades; no capítulo 3 e 4, apresenta-se uma explicação mais sucinta acerca da simulação e testes que se vão realizar; o terceiro capítulo foca-se mais na parametrização dos modelos, nos diferentes cenários para a rede, com o intuito de analisá-la, e na estrutura e implementação das redes AC e DC a ser estudadas; o quarto capítulo explica, de forma mais pormenorizada, como os modelos são construídos e como funcionam as funções de controlo dos mesmos; no capítulo 5, realiza-se uma simulação para cada um dos cenários definidos e é feita uma análise a cada um dos resultados obtidos; no último capítulo, são definidas todas as principais conclusões de todo este projeto.
The main objective of this dissertation is to build a hybrid AC/DC microgrid model in the Software Simulink and to study the way it works and performs in different scenarios. This thesis is divided into six chapters: the first one, the Introduction, explains the main objectives, the contributions, the motivation and how the thesis is organized; the second chapter, the State of Art, reports the basic concepts of electricity in rural areas, how the microgrids and hybrid microgrids work, its architecture, models, electrical implementations, applications and the importance of these grids in places that are located far away from the big cities and the main grids; in chapters 3 and 4, it is stated a more succinct explanation about the simulation and tests that will be performed; the third one focuses more on the parametrization of the models, the different scenarios to test and in the structure and implementation of the AC and DC microgrids that are being studied; the fourth chapter explains how models are designed, how they work and how their control functions operate; in chapter 5, the results of the simulation for each scenario are analysed and studied; in the last chapter, all the main conclusions taken from this thesis are defined.

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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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Abuhilaleh, Mohammad Mahmoud Jamil. "Power Management and Control Strategies in Hybrid AC/DC Microgrids". Thesis, 2020. http://hdl.handle.net/10453/143867.

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University of Technology Sydney. Faculty of Engineering and Information Technology.
The future trend of the power system is to ensure reliable, flexible, affordable and efficient power supply for customers with lower emissions. Conventional AC or DC microgrid suffers from increased losses and lower efficiency due to several AC-DC and DC-AC conversions. Therefore, hybrid microgrid (HMG) is getting popular to meet the growing penetration of modern DC loads and renewable energy sources with DC outputs into the existing AC power systems. The main objective of this dissertation is to develop and implement improved power management and control strategy to improve the performance of the hybrid microgrid. The first study proposes an improved power management and control coordination strategy for an autonomous HMG. The HMG considered in this part consists of multiple AC and DC sub-microgrids (SMGs) with different voltage levels. The hierarchical coordination of power management and control strategy for the autonomous HMG is introduced and analyzed. The designed system incorporates both the primary and secondary control levels to ensure a seamless and accurate transfer of power among the SMGs. A new technique for transferring power with a focus on the secondary control level is presented. The second study proposed in this thesis is a novel approach of distributed coordination control for multiple SMGs within the HMG. The traditional control method for power flow management among AC and DC SMGs is based on the proportional power-sharing principle. The proposed method suggests a distributed control system that ensures total controllability for the parallel interlinking converters (ILCs). It overcomes the total dependency on a specific variable for power exchange. The proposed method not only enables control of the power flow between SMGs but also ensures the continuity of power transfer in the event of a single SMG failure. The third study in this work focuses on coordinating the control and power management strategy for the multiple parallel ILCs that link the AC and DC SMGs together. The proposed new approach aims to manage the power flow across the HMG while regulating the voltage and frequency for the SMGs as part of the process. The main objective of the proposed method is to keep the HMG in autonomous operation with active power proportionally shared among its ILCs and distributed sources. The presented outer control loop is a modified arrangement that could not only ensure accurate power-sharing but also suppresses the circulating current at the DC side.

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DUONG, BUI MINH, i 斐明陌. "Simulation and Field Test of AC Microgrid and DC Microgrid Fault Protection Systems". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/31669675526650996614.

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博士
中原大學
電機工程研究所
104
Microgrid (MG) is an emerging configuration of power distribution systems, which mainly consists of distributed energy resources (DERs) such as renewable energy sources and distributed generators (DGs), energy storage systems (ESS), loads, energy management system (EMS), and protective devices. Main advantages of the microgrid are: (i) facilitating high penetration of renewable energy sources; (ii) improving reliability of the power system, and (iii) having high efficiency and low environment impacts. The microgrid, however, meets with certain challenges in (i) fault protection and coordination, (ii) power-flow control of distributed energy resources, (iii) seamless operation transitions of the microgrid between grid-connected and islanded operation modes, and (iv) power quality issues. This dissertation focuses on the development of fault protection systems for both the AC and DC microgrids. A fast and adaptable (FA) fault protection system is developed to protect multi-grounded AC microgrids. The proposed fault protection system can solve protection problems caused by the mixed combination of inverter-based DGs and rotating-based DGs in the microgrid, limitation of fault currents by DGs’ inverters under an islanded operation mode of the microgrid, and bi-directional fault currents/power flows. In other words, the novel fault protection system should be self-adaptive, aiming to deal with plug-and-play and peer-to-peer characteristics of the AC microgrid. Based on a Chi-square distribution statistic method, a simplified fault current analysis approach, and the support of communication system, tripping thresholds in the FA fault protection system can be automatically adjusted corresponding with the variational AC-microgrid DG and load combinations (e.g., connection and disconnection of source and load branches to and from the AC-microgrid). Additionally, the fast and adaptable AC-microgrid protection system can accurately detect, identify, and locate the faults within one and half cycles with the future combined with use of solid-state switches, aiming to prevent the fast tripping of inverter-based DGs during the fault period of the AC-microgrid. Simulation and experiment results of a multi-grounded 380V AC-MG test-bed at Institute of Nuclear Energy Research - Taiwan are available to validate the fast and adaptable AC-MG fault protection system proposed. As regards a novel DC-microgrid fault protection system, fast-acting fuses (FAFs) are combined with power electronic switches and digital relays to protect low-voltage DC microgrids. In particular, a DC-microgrid digital relay contains various fault protection modules such as differential current protection module, directional overcurrent/overcurrent protection modules, under-/over-voltage protection modules, and protection modules based on time derivatives of DC current and voltage to protect DC microgrids against pole-to-pole and pole-to-ground faults. Protection coordination strategies among different fault protection modules in a DC-microgrid digital relay, among the digital relays, and between the fuses and the digital relays are analysed to ensure high selectivity of the protection system. Aims of the novel DC-microgrid protection coordination system are to shorten critical fault clearing time and get cost-effectiveness while still ensuring high selectivity for the protection system. As a result, it is proposed that DC power sources such as PV arrays, battery and fuel-cell systems, and power converters should be protected by fast-acting fuses to get the cost-effectiveness of the protection system. DC-microgrid digital relays are required to protect source/load feeders, trunk lines, and common DC buses to get the high selectivity of the protection system. Leakage-current protection solutions are proposed for high-impedance grounded/ungrounded DC-microgrid configurations (e.g., symmetric DC mono-polar microgrids or DC bi-polar microgrids). Simulation and experiment results from a low-voltage DC microgrid test-bed are available with the effectiveness of the proposed DC-microgrid fault protection system as well as the protection coordination strategies being also evaluated.

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"Modeling and Large Signal Stability Analysis of A DC/AC Microgrid". Master's thesis, 2018. http://hdl.handle.net/2286/R.I.50493.

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abstract: The concept of the microgrid is widely studied and explored in both academic and industrial societies. The microgrid is a power system with distributed generations and loads, which is intentionally planned and can be disconnected from the main utility grid. Nowadays, various distributed power generations (wind resource, photovoltaic resource, etc.) are emerging to be significant power sources of the microgrid. This thesis focuses on the system structure of Photovoltaics (PV)-dominated microgrid, precisely modeling and stability analysis of the specific system. The grid-connected mode microgrid is considered, and system control objectives are: PV panel is working at the maximum power point (MPP), the DC link voltage is regulated at a desired value, and the grid side current is also controlled in phase with grid voltage. To simulate the real circuits of the whole system with high fidelity instead of doing real experiments, PLECS software is applied to construct the detailed model in chapter 2. Meanwhile, a Simulink mathematical model of the microgrid system is developed in chapter 3 for faster simulation and energy management analysis. Simulation results of both the PLECS model and Simulink model are matched with the expectations. Next chapter talks about state space models of different power stages for stability analysis utilization. Finally, the large signal stability analysis of a grid-connected inverter, which is based on cascaded control of both DC link voltage and grid side current is discussed. The large signal stability analysis presented in this thesis is mainly focused on the impact of the inductor and capacitor capacity and the controller parameters on the DC link stability region. A dynamic model with the cascaded control logic is proposed. One Lyapunov large-signal stability analysis tool is applied to derive the domain of attraction, which is the asymptotic stability region. Results show that both the DC side capacitor and the inductor of grid side filter can significantly influence the stability region of the DC link voltage. PLECS simulation models developed for the microgrid system are applied to verify the stability regions estimated from the Lyapunov large signal analysis method.
Dissertation/Thesis
Masters Thesis Engineering 2018

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Salgado, César Eduardo Marques. "Desenvolvimento dos conversores de potência para o sistema de alimentação de uma microrrede isolada baseada em energias renováveis". Master's thesis, 2018. http://hdl.handle.net/1822/60000.

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Dissertação de mestrado em Engenharia Eletrónica e de Computadores
A energia elétrica tem um papel extremamente importante no desenvolvimento de uma região, bem como na melhoria da qualidade de vida do ser humano. É assim fundamental eletrificar regiões isoladas e com elevadas taxas de subdesenvolvimento. A eletrificação da grande maioria destas regiões isoladas, passa pela produção local de energia recorrendo a fontes de energia renovável, quer por razões logísticas quer ambientais. Nesta dissertação são apresentados e descritos, os sistemas de eletrónica de potência que permitem implementar uma microrrede isolada com produção a partir de fontes renováveis e capacidade de armazenamento local de energia. O foco principal deste trabalho é o desenvolvimento e validação do sistema responsável pela implementação de uma microrrede isolada monofásica com tensão alternada sinusoidal de 230 V/50 Hz. O desenvolvimento do sistema responsável pela produção e armazenamento de energia encontra-se descrito numa dissertação com o tema complementar, realizada pelo colega de laboratório João Silva. Para a realização da presente dissertação foi necessário o estudo, dimensionamento e implementação do conversor CC-CA de três estágios. Este conversor pode ser dividido num conversor CC-CC em ponte completa isolado de alta frequência do tipo buck e num conversor CC-CA em ponte completa. Para ambos os conversores foi desenvolvido um controlador digital, sendo utilizado um controlador Proporcional Integral no conversor CC-CC e um controlador Preditivo no conversor CC-CA monofásico. Depois de desenvolvido o protótipo do sistema de alimentação da mirorrede isolada, foram realizados alguns ensaios laboratoriais de modo a validar a solução apresentada. Os ensaios realizados, permitiram analisar o comportamento do sistema para três tipos de carga diferentes: carga linear puramente resistiva; carga linear predominantemente indutiva; e carga não linear do tipo retificador com filtro capacitivo. Por último, foram ainda realizados alguns ensaios ao sistema desenvolvido na presente dissertação, interligado com o sistema complementar desenvolvido pelo colega João Silva. Perante os resultados obtidos, foi possível comprovar o conceito e validar o funcionamento do sistema de alimentação da microrrede isolada.
Electric power plays an essential role in the development of an isolated rural region, as well as in improving the overall human well-being. Therefore, the electrification of isolated and underdeveloped zones is a matter of extreme importance. Due to either logistic or environmental reasons, in most of these isolated regions, the required electrification involves the local energy production through renewable energy sources. In this dissertation, the power electronics system that allows the implementation of an islanded microgrid with local production and storage of energy is presented and described in detail. The main focus of this work is the development and validation of the power electronics system to implement a single-phase islanded microgrid with 230 V/50 Hz sinusoidal voltage. The electronic system responsible for energy production and storage is being developed within the dissertation work of the classmate João Silva. In order to complete this dissertation, it was required to study, sizing and implement a three-stage DC-AC converter. This converter is composed of a high-frequency isolated buck type full-bridge DC-DC converter and of a single-phase full-bridge DC-AC converter. A digital controller was developed for both converters, namely a Proportional Integral in the case of the DC-DC converter and a Predictive Deadbeat in the case of the DC-AC converter. After the development of the islanded microgrid power system prototype, some laboratorial tests were carried out to analyze the response of the presented solution. The elaborated tests allowed the analysis of the converters toward three different loads: a purely resistive linear load; a predominantly inductive linear load; and a rectifier with capacitive filter nonlinear load. Finally, a few tests were done on the system developed in the presented dissertation combined with the complementary system developed by João Silva. Concerning the final results, it was possible to prove the concept and to validate the operation of the islanded microgrid power system.

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36

Wang, Hui. "Shielding effect of AC conductors in AC/DC hybrid power transmission". 1990. http://hdl.handle.net/1993/17271.

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Fernandes, Fábio André. "Desenvolvimento dos conversores de potência para o sistema de alimentação de um centro social sustentável isolado". Master's thesis, 2015. http://hdl.handle.net/1822/54584.

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Dissertação de mestrado integrado em Engenharia Eletrónica e de Computadores
A crescente motivação para a utilização de fontes de energias renováveis prende-se essencialmente com a redução das emissões de CO2 e com a melhoria da qualidade de vida da humanidade. Isto é especialmente verdade em comunidades pequenas, isoladas e autónomas, onde o acesso a fontes de energia renováveis é a única solução para satisfazer as suas necessidades energéticas. Nesta dissertação são estudados os sistemas de eletrónica de potência e os restantes constituintes de uma microrrede que permitem o funcionamento de um Centro Social Sustentável numa aldeia rural isolada, sem ligação a uma rede de energia elétrica. Estes incluem a produção de energia elétrica por fontes renováveis e por um motor-gerador (a biodiesel), um sistema de armazenamento de energia, e um conjunto de cargas locais. Especificamente, nesta dissertação é desenvolvido o sistema de alimentação da microrrede isolada. Este sistema é constituído por um conversor de potência CC-CA de três estágios que pode ser dividido num conversor CC-CC em ponte completa isolado de alta-frequência do tipo buck, controlado a MOSFETs e por um conversor CC-CA em ponte completa controlado a IGBTs. O sistema de controlo dos conversores é completamente digital e tem por base o DSC TMS320F28335 da Texas Instruments. Para validar a solução apresentada, foi desenvolvido um protótipo do sistema que engloba os dois conversores mencionados. Posteriormente, foram realizados diversos testes experimentais em ambiente laboratorial ao protótipo implementado. Este foi testado com uma tensão de entrada de 30 V que foi elevada para uma tensão constante de 160 V por intermédio do conversor CC-CC. Esta tensão retificada é posteriormente convertida para uma tensão sinusoidal de 132 V de pico a uma frequência de 50 Hz, através do inversor monofásico. Nestas condições, foi comprovado o conceito e validado o funcionamento do sistema de alimentação da microrrede isolada. Ao mesmo tempo, os resultados obtidos permitiram validar tanto o bom funcionamento do controlador proporcional-integral aplicado ao conversor CC-CC, como o controlador preditivo deadbeat aplicado ao conversor CC-CA.
The increasing motivation for the use of renewable energy sources is mainly due to the reduction of CO2 emissions and to the improvement of mankind life quality. This is particularly true in small, isolated and standalone communities, where the access to renewable energy sources may be the only solution to meet their energy needs. This master thesis aims to study the power electronic systems that allow the operation of a sustainable Social Centre in an islanded rural village without connection to a main power grid. These include the production of electricity from renewable sources and a motorgenerator set (biodiesel), an energy storage system, and a local power supply. Specifically in this work, the developed power converter needed for the microgrid power system is a three stage DC-AC converter. This power converter can be separated into a DC-DC full-bridge high-frequency isolated MOSFET-based converter and a DC-AC full-bridge IGBT-based converter. The control system is fully digital and implemented using the Texas Instruments microcontroller DSC TMS320F28335. In order to validate the presented solution was developed a prototype of the microgrid power system constituted by the converters mentioned and several experimental tests were carried out in laboratory environment. The developed prototype was tested with a 30 V DC input voltage which resulted in a constant 160 V DC voltage controlled by the DC-DC MOSFET-based converter. This rectified voltage is then converted to a sinusoidal wave with 132 V of peak at 50 Hz frequency by the single-phase inverter. Under these conditions, the concept has been proven and the proper functioning of the island microgrid power system was validated. At the same time, the obtained results allowed to validate not only the proper functioning of the proportional integral controller applied to the DC-DC converter but also the deadbeat predictive controller applied to the DC-AC converter.

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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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(10730034), Jonathan Ore. "The DC Nanogrid House: Converting a Residential Building from AC to DC Power to Improve Energy Efficiency". Thesis, 2021.

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The modern U.S. power grid is susceptible to a variety of vulnerabilities, ranging from aging infrastructure, increasing demand, and unprecedented interactions (e.g., distributed energy resources (DERs) generating energy back to the grid, etc.). In addition, the rapid growth of new technologies such as the Internet of Things (IoT) affords promising new capabilities, but also accompanies a simultaneous risk of cybersecurity deficiencies. Coupled with an electrical network referred to as one of the most complex systems of all time, and an overall D+ rating from the American Society of Civil Engineers (ASCE), these caveats necessitate revaluation of the electrical grid for future sustainability. Several solutions have been proposed, which can operate in varying levels of coordination. A microgrid topology provides a means of enhancing the power grid, but does not fundamentally solve a critical issue surrounding energy consumption at the endpoint of use. This results from the necessary conversion of Alternating Current (AC) power to Direct Current (DC) power in the vast majority of devices and appliances, which leads to a loss in usable energy. This situation is further exacerbated when considering energy production from renewable resources, which naturally output DC power. To transport this energy to the point of application, an initial conversion from DC to AC is necessary (resulting in loss), followed by another conversion back to DC from AC (resulting in loss).

Tackling these losses requires a much finer level of resolution, namely that at the component level. If the network one level below the microgrid, i.e. the nanogrid, operated completely on DC power, these losses could be significantly reduced or nearly eliminated altogether. This network can be composed of appliances and equipment within a single building, coupled with an energy storage device and localized DERs to produce power when feasible. In addition, a grid-tie to the outside AC network can be utilized when necessary to power devices, or satisfy storage needs.

This research demonstrates the novel implementation of a DC nanogrid within a residential setting known as The DC Nanogrid House, encompassing a complete household conversion from AC to DC power. The DC House functions as a veritable living laboratory, housing three graduate students living and working normally in the home. Within the house, a nanogrid design is developed in partnership with renewable energy generation, and controlled through an Energy Management System (EMS). The EMS developed in this project manages energy distribution throughout the house and the bi-directional inverter tied to the outside power grid. Alongside the nanogrid, household appliances possessing a significant yearly energy consumption are retrofitted to accept DC inputs. These modified appliances are tested in a laboratory setting under baseline conditions, and compared against AC equivalent original equipment manufacturer (OEM) models for power and performance analysis. Finally, the retrofitted devices are then installed in the DC Nanogrid House and operated under normal living conditions for continued evaluation.

To complement the DC nanogrid, a comprehensive sensing network of IoT devices are deployed to provide room-by-room fidelity of building metrics, including proximity, air quality, temperature and humidity, illuminance, and many others. The IoT system employs Power over Ethernet (PoE) technology operating directly on DC voltages, enabling simultaneous communication and energy supply within the nanogrid. Using the aggregation of data collected from this network, machine learning models are constructed to identify additional energy saving opportunities, enhance overall building comfort, and support the safety of all occupants.

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Penner, Albert F. "Finite element computation of the DC corona currents injected into the AC conductors of a hybrid AC/DC transmission line". 1989. http://hdl.handle.net/1993/16935.

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Pan, Hsuan-Hung, i 潘宣宏. "An Implementation of Hybrid Three-Phase AC-DC Converter for Small-Scale Wind Turbines". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/42948283974183422720.

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碩士
國立成功大學
電機工程學系碩博士班
94
Due to the influence of the energy crisis and promotion of green power, many countries invest huge funds to conduct research on the renewable energy. Among the various energy source candidates, the most potential one is the wind-power generation. It is also the policy and developmental road map direction in our nation. However, the wind-power is not an unstable energy source. The output voltage and power of the wind-power generator may vary with the change of the wind speed. Therefore, promoting a stable and efficient wind-power generation has become a very important issue. The thesis shows hybrid AC to DC converter which combines the advantages of two types of switching converter scheme. The converter not only provides stable voltage output, but also improves the power factor and the whole efficiency of the system. The simulated wind-power generation platform adopts the NI company’s D&Q data acquiring card with the MATLAB/Simulink software to simulate the wind power condition. It also uses the MC33262 controlling IC to control the switching mechanism of the power module. The testing results reveal that the output voltage was well maintained at 400V level with variable generator rotating speed, ranging from 200 rpm to 700 rpm. The power factor and total harmonic distortion (THD) were all effectively improved, which have verified the feasibility of the proposed converter.

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Kjellander, Matilda, i Anders Tengvall. "Design of a small scale hybrid photovoltaic and wind energy system". Thesis, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-25710.

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Approaching problems with global warming due to the use of fossil fuels, means that new system solutions have to be investigated. This report investigates the possibility to expand an existing photovoltaic system with a wind turbine generator to simplify the expansion of renewable energy sources. Through an extensive literature study and simulation in SIMULINK the result has been developed and tested. It shows that it is possible to connect a wind turbine generator to the same inverter as the PV-modules if no MPPT algorithm for the PV-modules is integrated. To protect the inverter a dump load has to be connected. Because of the complexity a DC-coupled system brings, AC-coupling is advised when expanding PV-modules with a WTG. The optimal wind turbine is considered to be a permanent magnet synchronous generator connected to the AC-bus through a full-effect inverter. The turbine should be chosen according to the intended location based on wind conditions and desired energy production.

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