Dissertations / Theses: 'Grid reactive power support'

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Eiriksson, Eysteinn. "Distribution grid capacity for reactive power support." Thesis, KTH, Elkraftteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-221829.

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The modern power system is changing at a rate faster than would have been expected20 years ago. More and more conventional power plants will be shut down in favour ofdistribution generation (DG). This is happening now with the trend of introducing renewableenergy sources (RES) to the power system.The grids were designed to transfer power from generating units connected to the highvoltage grids towards the end consumers connected to the low voltage grids. With changedpower mix, power flows in the system will change resulting in possible grid problems. Oneof the main problems is keeping the voltage within operational limits of the system. Whenthe generation exceeds the consumption in a distribution network, the power will flow fromthe low voltage network towards the high voltage network (reverse power flow) which willcause the voltage to rise in the low voltage network. Reactive power support from DG canbe a valuable resource to mitigate the problem. Reactive power is necessary to operatethe power system. The main source of reactive power is synchronous generators. If thissource is shut down, the reactive power must come from another source.This thesis investigates if DG could be used to support reactive power to the highvoltage transmission network to control the voltage. For this purpose, a distributionsystem located close toWorms, Germany will be studied. This distribution system consistsof two MV feeders with high penetration of DG, mostly photovoltaic (PV) but also windturbines (WT). Consumption and generation measurement data was provided by the localdistribution system operator (DSO). A few reactive power control methods are introducedand tested on this system. From the results, it is concluded that it is possible to providereactive power support from distribution networks and a voltage dependent reactive powercontrol can be used to this purpose.
Det moderna kraftsystemet förandras snabbara än vad som hade förväntats för 20 årsedan. Fler och fler konventionella kraftverk kommer att stängas till fördel för distributionsgenering.Detta händer nu med trenden att introducera förnybara energikällor tillkraftsystemet.Nätverket utformades för att överföra kraft från generatorer som är anslutna till högspänningsnätetmot konsumenter anslutna till lågspänningsnätet. Med ändrad kraftblandningkommer strömflödena i systemet att förändras vilket resulterar i eventuella nätproblem.Ett av huvudproblemen är att hålla spänningen inom operativa gränser för systemet.När generationen överstiger förbrukningen i ett distributionsnät, kommer strömmen attströmma från lågspänningsnätet till högspänningsnätet vilket kommer att leda till attspänningen stiger i lågspänningsnätet. Reaktivt kraftstöd från distributionsgenering kanvara en värdefull resurs för att mildra problemet. Reaktiv effekt är nödvändig för att drivaelsystemet. Huvudkällan för reaktiv kraft är synkrona generatorer. Om den här källanstängs av måste den reaktiva effekten komma från en annan källa.Denna avhandling undersöker om distributionsgenering skulle kunna användas för attstödja reaktiv kraft till högspänningsöverföringsnätet för att styra spänningen. För dettaändamål studeras ett distributionssystem som ligger nära Worms, Tyskland. Detta distributionssystembestår av två MV-matare med med mycket distributionsgenerering, främstsolceller men även vindturbiner. Förbruknings- och generationsmätningsdata tillhandahöllsav den lokala distributionssystemoperatören. Några reaktiva effektstyrningsmetoderintroduceras och testas på detta system. Av resultaten dras slutsatsen att detär möjligt att tillhandahålla reaktivt kraftstöd från distributionsnät och en spänningsberoendereaktiv effektstyrning kan användas för detta ändamål.

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Johnson, Benjamin Anders. "Modeling and Analysis of a PV Grid-Tied Smart Inverter's Support Functions." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/994.

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The general trends in the past decade of increasing solar cell efficiency, decreasing PV system costs, increasing government incentive programs, and several other factors have all combined synergistically to reduce the barriers of entry for PV systems to enter the market and expand their contribution to the global energy portfolio. The shortcomings of current inverter functions which link PV systems to the utility network are becoming transparent as PV penetration levels continue to increase. The solution this thesis proposes is an approach to control the inverters real and reactive power output to help eliminate the problems associated with PV systems at their origin and in addition provide the grid with ancillary support services. The design, modeling, and analysis of a grid-tied PV system was performed in the PSCAD software simulation environment. Results indicate that in the presence of grid disturbances the smart inverter can react dynamically to help restore the power system back to its normal state. A harmonic analysis was also performed indicating the inverter under study met the applicable power quality standards for distributed energy resources.

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Samadi, Afshin. "Large Scale Solar Power Integration in Distribution Grids : PV Modelling, Voltage Support and Aggregation Studies." Doctoral thesis, KTH, Elektriska energisystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154602.

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Long term supporting schemes for photovoltaic (PV) system installation have led to accommodating large numbers of PV systems within load pockets in distribution grids. High penetrations of PV systems can cause new technical challenges, such as voltage rise due to reverse power flow during light load and high PV generation conditions. Therefore, new strategies are required to address the associated challenges. Moreover, due to these changes in distribution grids, a different response behavior of the distribution grid on the transmission side can be expected. Hence, a new equivalent model of distribution grids with high penetration of PV systems is needed to be addressed for future power system studies. The thesis contributions lie in three parts. The first part of the thesis copes with the PV modelling. A non-proprietary PV model of a three-phase, single stage PV system is developed in PSCAD/EMTDC and PowerFactory. Three different reactive power regulation strategies are incorporated into the models and their behavior are investigated in both simulation platforms using a distribution system with PV systems. In the second part of the thesis, the voltage rise problem is remedied by use of reactive power. On the other hand, considering large numbers of PV systems in grids, unnecessary reactive power consumption by PV systems first increases total line losses, and second it may also jeopardize the stability of the network in the case of contingencies in conventional power plants, which supply reactive power. Thus, this thesis investigates and develops the novel schemes to reduce reactive power flows while still keeping voltage within designated limits via three different approaches: decentralized voltage control to the pre-defined set-points developing a coordinated active power dependent (APD) voltage regulation Q(P)using local signals developing a multi-objective coordinated droop-based voltage (DBV) regulation Q(V) using local signals In the third part of the thesis, furthermore, a gray-box load modeling is used to develop a new static equivalent model of a complex distribution grid with large numbers of PV systems embedded with voltage support schemes. In the proposed model, variations of voltage at the connection point simulate variations of the model’s active and reactive power. This model can simply be integrated intoload-flow programs and replace the complex distribution grid, while still keepingthe overall accuracy high. The thesis results, in conclusion, demonstrate: i) using rms-based simulations in PowerFactory can provide us with quite similar results using the time domain instantaneous values in PSCAD platform; ii) decentralized voltage control to specific set-points through the PV systems in the distribution grid is fundamentally impossible dueto the high level voltage control interaction and directionality among the PV systems; iii) the proposed APD method can regulate the voltage under the steady-state voltagelimit and consume less total reactive power in contrast to the standard characteristicCosφ(P)proposed by German Grid Codes; iv) the proposed optimized DBV method can directly address voltage and successfully regulate it to the upper steady-state voltage limit by causing minimum reactive power consumption as well as line losses; v) it is beneficial to address PV systems as a separate entity in the equivalencing of distribution grids with high density of PV systems.

The Doctoral Degrees issued upon completion of the programme are issued by Comillas Pontifical University, Delft University of Technology and KTH Royal Institute of Technology. The invested degrees are official in Spain, the Netherlands and Sweden, respectively. QC 20141028

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Zhang, Weiyi. "Control of grid connected power converters with grid support functionalities." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/456312.

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The installation of power generation systems based on renewable energy sources has been increasing exponentially over the last decades. However, in spite of the well-known merits of such energy sources, the expansion of renewable-based generation (RG) plants, which interface the grid through power converters, can produce also negative impacts on the electrical grid, due to its power processing mechanism, which is different from traditional generation plants. In fact, the regulation capability of the grid can decrease as much as the share of the RG increases. To avoid this, power conversion systems belonging to RG plants are requested to be more grid-friendly, and responsive to the electrical network conditions. In this way, they can contribute to the electrical network stability as other generation does, instead of behaving as simply grid-feeding systems focused on injecting as much power as possible.This PhD dissertation is focused on the control of grid-connected power converters with grid support functionalities based on the Synchronous Power Controller (SPC) concept. The SPC is an established solution for controlling grid connected power converters and equipping them with emulated and improved synchronous machine characteristics. In addition to the general goal of improving the grid interaction of the RG plants, grid support functionality stands as a main property among the characteristics given by the SPC. In this dissertation the virtual admittance structure, contained in the electrical block of the SPC, which emulates the stator output impedance of the synchronous machines, is analyzed. Moreover, it is extended to a study case where the admittance value can be different for positive- and negative-sequence components. The designed virtual admittance block contains three branches, which are responsible for positive-sequence current injection, negative-sequence current injection and other harmonic components, respectively. The converter¿s performance under asymmetrical grid fault is especially considered in this case.The analysis and arrangements in the design of the SPC¿s power loop controller is another contribution of this research. Other methods that consider synchronous machine emulation normally construct the controller by reproducing the synchronous generation swing equation. Based on the virtual implementation, which is free from mechanical constraints, one can set a proper damping factor achieving thus better dynamics compared to the traditional synchronous machines. However, the increase of the damping factor changes the inherent power-frequency (P-f) droop characteristics, which may lead to undesired deviations in the active power generation. In the framework of this PhD, a method that modifies the conventional swing equation emulation and lets the inherent P-f droop characteristics be configurable, independently of the inertia and damping characteristics, is proposed.The work presented in this dissertation is supported by mathematical and simulation analysis. Moreover, in order to endorse the conclusions achieved, a complete experimental validation has been conducted. As it will be shown, the performance of the SPC has been validated in tests once the main parts, namely virtual admittance and power loop controller, and other parts are settled. The simulation and experimental test scenarios include events like changes in the power operation point, frequency sweeps, voltage magnitude changes, start-up and parallel converters operation, which are given under different control configurations like the different structures for the power loop controller and different control parameters. This PhD research also compares the transient performance of the SPC-based power converters with the ones achieved with conventional control methods.
Los convertidores de potencia conectados a la red actúan comúnmente como interfaz entre plantas de generación basadas en energía renovable y la red eléctrica, permitiendo así el procesado de energía eólica y fotovoltaica y su inyección a red. El control de estos convertidores conectados a la red ha sido objeto de estudio en las últimas décadas, ya que su comportamiento y prestaciones influye de forma determinante tanto en la calidad de la red eléctrica, así como en el cumplimiento de los requisitos de conexión a la red fijados por los códigos de red. Junto con la expansión de las plantas de generación de energía renovable, su impacto en el sistema eléctrico ha crecido también, lo cual ha hecho que se lleven a cabo muchos trabajos de investigación orientados a armonizar la penetración de renovables con la estabilidad de la red. Con los sistemas de control actuales la capacidad de regulación de la red disminuye tanto como la proporción de la generación renovable aumenta. En las redes eléctricas del futuro, se espera que los convertidores de potencia, que actúan como interfaz, exploten sus posibilidades de cómputo y control permitiendo mejorar la interacción de la generación renovable con la red. En este contexto los controles de tipo “droop control”, los cuales son ampliamente utilizados en sistemas de generación tradicionales, se pueden aplicar a los convertidores conectados a red para habilitar funciones de soporte de red, ya que estos contribuyen al control de tensión y frecuencia primaria ajustando el intercambio de potencia activo y reactiva de forma proporcional a la desviación de la frecuencia y magnitud de la tensión en el punto de conexión. En el caso de regulación de frecuencia, y para que este sea bidireccional, el convertidor puede interactuar con la red con la ayuda de sistemas de almacenamiento de energía. Sin embargo, la inclusión del “droop control” no conlleva una solución global. Incluso si se ajusta de forma óptima y se dispone de reserva de energía, aún hay cuestiones como la respuesta inercial que no se pueden dar con este tipo de control. La generación en los sistemas tradicionales se lleva a cabo principalmente por generadores síncronos. Comparados con estos, los convertidores conectados a la red difieren principalmente en la falta de la característica electromecánica. En consecuencia, la estática y la dinámica de las unidades de generación de energía renovable son diferentes en comparación con los generadores síncronos. La dinámica de estos convertidores es altamente dependiente de los sistemas de sincronización (PLL), cuyo comportamiento se degrada en condiciones de red adversas o distorsionadas. Además, el control de potencia normalmente depende control de potencia instantáneo. Debido a las diferentes dinámicas, la inercia total en la red no aumenta junto con la integración de las energías renovables. Sin embargo, los códigos de red han incluido requerimientos tales como “inercia sintética" en los requisitos. Otras deficiencias del control del convertidor convencional incluyen el rendimiento inferior bajo condiciones de avería de red, en conexión de red débil y conexión de red de relación X / R baja. Esta tesis doctoral estudia y valida el control de los convertidores conectados a la red con funcionalidades de soporte de red. El objetivo general del trabajo es mejorar las características de interacción de la red de las plantas de generación de energía renovable mediante la especificación de los convertidores conectados a la red con características de la máquina síncrona emulada y mejorada. La tesis ha aportado contribuciones o ha mostrado originalidades en los siguientes aspectos: Un enfoque de ajuste de bucle de control de corriente interno generalizado; Diseño detallado y validación de la admisión virtual para convertidores conectados a la red; Diseño detallado y validación del circuito de control de potencia para la emulación de inercia y amortiguación.

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Wang, Zhongkui. "Reactive Power Control and Optimization of Large Scale Grid Connected Photovoltaic Systems in the Smart Grid." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1388764166.

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Nylander, Gabriel. "Compensating the Changing Reactive Power in the Medium-Voltage Grid in Stockholm." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-286340.

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A decline in inductive reactive power has been noted by several DNOs around Europe for the last decade. Why this is happening is unknown. One of the DNOs is the Swedish DNO Ellevio AB that has seen large decreases in demand of inductive reactive power from their primary substations. The capacitor banks that are installed at the primary substations have historically been used to compensate the inductive load with capacitive reactive power. However, with a declining inductive load, the need for VAr compensation is diminishing. This thesis sets out to find out why Ellevio has been seeing a decrease in inductive reactive power and how the VAr compensation should be carried out in the future when the load is becoming more capacitive. The results from the thesis show that the decrease can be attributed to technological changes in lighting, motors and electronic loads as well as a change in consumer behavior. Lighting technology has gone from being a resistive and inductive load to a capacitive one. This is due to the phasing out of incadescent lightbulbs and fluorescent lighting with magnetic ballasts and being replaced by compact fluorescent light (CFL) with electronic ballasts and Light Emitting Diodes (LED). Furthermore, variable frequency drives are being used more frequently for controlling pumps and fans which results in the motor load being seen as capacitive from the grid side. The share of the electricity consumption going to power electronic loads, which tend to be capacitive, has also increased for the last decades. The phasing out of older technologies with newer ones results in the medium-voltage grid slowly becoming more capacitive. An optimal sizing of capacitor banks was found for all the primary substations in Stockholm for three scenarios: compensating just the primary-substation load reactive power, as currently done; compensating also the primary-substation transformers; and compensating load and transformers with one transformer out of service. Furthermore, a comparison between controlling the capacitor banks from the primary substations to controlling them from the bulk supply point substation. The results indicate that the compensation of capacitive reactive power can be controlled in a more efficient way from the bulk supply point with a fewer amount of switches from the capacitor banks.
En markant minskning i induktiv reaktiv effekt har noterats från mellanspänningsnätet för flera elnätsföretag i Europa det senaste decenniet. Vad denna minskning beror på är okänt. Ett av dessa elnätsföretag är Ellevio AB som har sätt en markant minskning i induktiv reaktiv effekt från sina fördelningsstationer i Stockholm. Denna minskning har lett till att de kondensatorbatterier som används för att kompensera den induktiva lasten med kapacitiv reaktiv effekt används i en allt lägre utsräckning. Det här examensarbetet har undersökt vad som kan ligga bakom minskning i induktiv reaktiv effekt samt hur VAr-kompensering ska utföras i framtiden när lasten blir allt mer kapacitiv. De resultat som erhållits från examensarbetet tyder på att minskningen i induktiv reaktiv effekt kan attribueras till ett flertal olika teknologiska förändringar som har skett genom åren. De kan delas upp i tre kategorier: belysning, motorer samt elektroniska laster. Belysningsteknologi har gått från att vara resistiv och induktiv till att idag vara kapacitiv. Detta beror på att glödlampor och belysningsarmaturer med induktiva driftdon har ersatts med belysningsarmaturer med elektroniska driftdon samt LED-lampor. Laster från motorer har även förändrats. Frekvensomriktare som bland annat används till pumpar och fläktar används i allt större utstäckning och leder till att den induktiva lasten från induktionsmotorer istället ses som en kapacitiv last från nätets sida. Det har även skett förändringar i vilka enfasmotorer som används i vardagen. Kylskåp har gått från att historiskt vara en stor induktiv last till att idag ha en effekfaktor nära 1. Samtidigt som de induktiva lasterna har försvunnit har andelen av elektriciteten som konsumeras av elektronik ökat markant vilket har lett till att dagens hushåll oftast generar reaktiv effekt. En optimal storlek på kondensatorbatterierna togs fram för alla fördelningsstationer i Stockholm för tre olika fall. Det första fallet är när kondensatorbatterierna enbart ska kompensera den induktiva lasten från lägre ner i nätet. Det andra fallet kompenserades även den induktiva lasten från transformatorerna som finns installerade i fördelningsstationerna. Till sist undersöktes även hur storleken på kondensatorbatteriena kan optimeras om det inträffar ett fel på en transformator som leder till att lasten från den transformator där det förekommit ett fel överföras till de andra transformatorerna som finns installerade i fördelningsstationen. Dessutom undersöktes om den reaktiva effektkompenseringen från kondensatorbatterierna kan optimeras genom att flytta kompenseringen från 11kV-sidan på fördelningsstationerna till 33kV-sidan på tryckpunktsstationerna. Resultaten visar att kompenseringen av kapacitiv reaktiv effekt kan kontrolleras på ett mer effektivt sätt från tryckpunktstationerna med färre antal till och från kopplingar från kondensatorbatterierna

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ARAUJO, MARCELO DE MELO. "REACTIVE POWER SUPPORT COST ALLOCATION METHOD BASED ON CIRCUIT LAWS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=10511@1.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Com a implantação do novo modelo econômico nos sistemas de potência, a justa remuneração das empresas provedoras de serviços ancilares tem se tornado um assunto grande importância. O suporte de potência reativa, por se tratar também de um serviço ancilar, está inserido neste contexto. Desta forma, a factível identificação dos agentes beneficiários pelo suporte, bem como as proporções deste beneficiamento podem implicar em um mecanismo viável de remuneração para os custos de cada fonte provedora. Este trabalho apresenta um método de alocação de custos pelo suporte de potência reativa baseado nos princípios fundamentais da teoria de circuitos elétricos, buscando determinar a contribuição de potência reativa de cada fonte para cada barra de carga. Para isto, é sugerida uma modelagem de fontes de tensão, que permite levar em conta a natureza local da relação Q-V, proporcionando uma abordagem simples e clara do problema. Complementarmente é apresentado um método de alocação das perdas reativas em cada ramo de transmissão entre as fontes provedoras de potência reativa. Para validar o método proposto, são realizados testes em sistemas de potência de pequeno e médio porte, apresentado as parcelas de contribuição de cada fonte de potência reativa para cada carga, e adicionalmente para as perdas reativas em cada ramo de transmissão. Comparações são estabelecidas com um método existente, onde é constatado que o método proposto apresenta maior coerência com as propriedades elétricas dos sistemas de potência, destacando-se a verificação clara da natureza local do consumo de potência reativa. Em relação aos resultados da alocação de perdas reativas, verifica-se que o método serve como indicativo sobre o uso da rede de transmissão por parte de cada fonte de potência reativa.
After implantation of power systems` new economic model, a fair remuneration strategy of ancillary services suppliers had became an important issue. Reactive power support is also an ancillary service, thus, it belongs to this context. Then, identification of service beneficiaries as well as the benefit proportions may take a feasible remuneration mechanism for each source. This work presents a reactive power support cost allocation method based on fundamental principles of circuit theory, where reactive power contribution from each source to each load is calculated. This method suggests a modeling of voltage sources, which takes into account the Q-V relationship, providing a simple and clear treatment of the problem. Additionally, a reactive loss allocation method to each branch is presented. To validate the proposed method, tests with small and medium size systems are realized. So, there are presented results of reactive power demand and transmission losses allocation into systems` sources. Comparisons with an existent method are established, when we can verify that the proposed method brings more coherence with the electrical properties of power systems and the local nature of reactive power consumption. In the other hand, results of reactive losses allocation can indicate the transmission network usage by each reactive power source.

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Omole, Adedamola. "Voltage Stability Impact of Grid-Tied Photovoltaic Systems Utilizing Dynamic Reactive Power Control." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3615.

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Photovoltaic (PV) DGs can be optimized to provide reactive power support to the grid, although this feature is currently rarely utilized as most DG systems are designed to operate with unity power factor and supply real power only to the grid. In this work, the voltage stability of a power system embedded with PV DG is examined in the context of the high reactive power requirement after a voltage sag or fault. A real-time dynamic multi-function power controller that enables renewable source PV DGs to provide the reactive power support necessary to maintain the voltage stability of the microgrid, and consequently, the wider power system is proposed. The loadability limit necessary to maintain the voltage stability of an interconnected microgrid is determined by using bifurcation analysis to test for the singularity of the network Jacobian and load differential equations with and without the contribution of the DG. The maximum and minimum real and reactive power support permissible from the DG is obtained from the loadability limit and used as the limiting factors in controlling the real and reactive power contribution from the PV source. The designed controller regulates the voltage output based on instantaneous power theory at the point-of-common coupling (PCC) while the reactive power supply is controlled by means of the power factor and reactive current droop method. The control method is implemented in a modified IEEE 13-bus test feeder system using PSCAD® power system analysis software and is applied to the model of a Tampa Electric® PV installation at Lowry Park Zoo in Tampa, FL. This dissertation accomplishes the systematic analysis of the voltage impact of a PV DGembedded power distribution system. The method employed in this work bases the contribution of the PV resource on the voltage stability margins of the microgrid rather than the commonly used loss-of-load probability (LOLP) and effective load-carrying capability (ELCC) measures. The results of the proposed method show good improvement in the before-, during-, and post-start voltage levels at the motor terminals. The voltage stability margin approach provides the utility a more useful measure in sizing and locating PV resources to support the overall power system stability in an emerging smart grid.

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Pilgrim, J. D. "Genetic algorithms for optimal reactive power compensation planning on the national grid system." Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.631723.

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Tomaszewski, Michal. "Reactive power management capabilities of Swedish sub-transmission and medium voltage level grid." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240411.

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Rising penetration of renewable energy sources in electric power grids isboth a challenge and an opportunity to optimally utilize the potential of eitherwind or PV energy sources, to stabilize operation of future power systems.Bi-directional ows between distribution and transmission system operatorscause signicant problems with keeping the voltages in the grid within admissiblelimits. This paper contains description of Oland's island mediumandlow-voltage electric power grid, ranging from 0.4 kV to 130 kV in thepurpose of quasi-static analysis of active and reactive power ows in the system.Goal of the analysis is to optimize reactive power exchange at the pointof connection with the mainland grid. In the analyzed grid system, thereis an enormous, 190 % penetration of wind sources. Capacity of the windparks connected to dedicated buses totals to 136.1 MW, that supply up to90.5 MW of load. With industry-wise reactive power capability limits, totalcontribution of wind parks reaches almost 66 MVAr, enabling to compensatedecits and extra surpluses of the reactive power in the grid. Presentedsystem is connected to the mainland's grid through one point of connection,which is simulated as Thevenin equivalent circuit. Main objective of thethesis is to test and analyze viable solutions to minimize reactive power exchangeat the point of connection at Stavlo substation connecting Oland'sand Sweden's electric grid keeping valid all necessary contingencies enforcedby current grid codes applied in Sweden as well as thermal limits of the linesand voltage limits of the system. Furthermore, state of the art of currentreactive power compensation methodologies and most promising techniquesto eciently and eectively control reactive power ow are outlined. Droopcontrol methodologies, with focus on global and local objectives, and smartgrid solutions opportunities are being tested and modeled by the authors andare comprehensively presented in this paper. Moreover, economic costs ofcontrol methods are compared. Analysis of active power losses in the systemas well as cost of implementation of alternative solutions is presented, wheremost nancially viable solutions are outlined, giving brief outlook into futureperspectives and challenges of electric power systems. It is shown that controllabilityof reactive power support by wind turbine generators can enhanceoperation of electric power grids, by keeping the reactive power ow minimizedat the boundary between grids of distribution and transmission systemoperators. Furthermore, results indicate that extra reactive power supportby wind turbine generators can lead to diminishment of active power losses inthe system. Presented system is being modeled in the PSS/E software dedicatedfor power system engineers with use of Python programming languages.Analysis of data was done either in Python or R related environments. Thesiswas written with cooperation between KTH and E.On Energidistribution AB.
Hogre genomslagskraft av förnyelsebara energikällor i elnäteten är bådeen utmaning och möjlighet för att optimalt kunna utnyttja potentialen av vindkraft och PV källor, med avseende på att stabilisera driften av framtida elkraftsystem. Tvåvägsflöden mellan distributionoch transmissionsoperatörer orsakar betydande problem att hålla spänningen i nätet inom tillåtna gränsvärden.Denna uppsats innehåller en beskrivning av Ö lands mellanoch lågspänningsnät,på 0.4 kV till 130 kV i syftet att utföra en kvasistatisk analys av aktiva och reaktiva effektflöden i systemet. Målet med analysen är att optimera det reaktiva effektutbytet i kopplingspunkten med fastlandets nät. I det analyserade systemet, finns det en enorm potential på 190% genomslagskraft av vindkraft. Kapaciteten på vindkraftsparker kopplade till medtagna samlingsskenor i systemet uppgår till 136,1 MW, som tillgodoser upp till 90.5 MW last. Med industrimässigt begränsad reaktiv effektkapabilitet, uppgår vindkraftsparkernas bidrag till nästan 66 MVAr, vilken möjliggör kompensation för underskott och överskott av reaktiv effekt i nätet. Det presenterade systemet är kopplat till fastlandet genom en kopplingspunkt, där fastlandet är simulerat som en Thevenin ekvivalent. Huvudsakliga målet med denna uppsats är att testa och analysera gångbara lösningar för att minimera det reaktiva effektutbytet vid kopplingspunkten i Stävlö, som kopplar ihop Ö land med resterande nät i Sverige, samtidigt som alla nödvändiga villkor enligt nuvarande nätkoder i Sverige bibehålls, liksom termiska gränser för ledningarna och spanningsgränser för systemet. Ytterligare beskrivs den bästa tillgängliga tekniken som finns idag för reaktiv effektkompensation, och de mest lovande teknikerna för att effektivt och verkningsfullt kontrollera reaktiva effektflöden. Droop-kontroll-metodologier, med fokus på globala och lokala tillämpningar, och smarta nät-möjligheter testas och modelleras av författarna och presenterar djupgående i detta arbete. Dessutom jämförs ekonomiska kostnader för olika kontrollmetoder. Analyser av aktiva effektförluster i systemet samt kostnader för implementation av alternativa lösningar presenteras, där de flesta gångbara losningar behandlas, och ger en överskådlig bild av framtida perspektiv och utmaningar i elkraftsystemet. Det visas att vindturbiners kontroll av reaktiv effekt, kan förbättra driften av elnäten, genom att minimera det reaktiva effektflödesutbytet i gränsen mellan distributionoch transmissionsoperatörers nät. Ytterligare pekar resultat på att extra understöd av reaktiv effekt från vindturbiner kan leda till förminskning av aktiva förluster i systemet. Det presenterade systemet modelleras i mjukvaruprogrammet PSS/E dedikerat för elkraftsingenjörer med hjälp av Python. Analys av data gjordes antingen i Pythoneller R-relaterade miljöer. Detta arbete har gjorts tillsam-mans med KTH och E.ON Energidistribution AB.

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Fonkwe, Fongang Edwin. "Reactive power support capability of flyback microinverter with pseudo-dc link." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101794.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 101-102).
The flyback micro-inverter with a pseudo-dc link has traditionally been used for injecting only active power in to the power distribution network. In this thesis, a new approach will be proposed to control the micro-inverter to supply reactive power to the grid which is important for grid voltage support. Circuit models and mathematical analyses are developed to explain underlying issues such as harmonic distortion, and power losses, which can limit the reactive power support capability. A novel current decoupling circuit is proposed to effectively mitigate zero crossing distortion. Simulations and experimental results are provided to support the theoretical propositions.
by Edwin Fonkwe Fongang.
S.M.

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12

Kraiczy, Markus [Verfasser]. "Reactive power grid adequacy studies for distribution grids with high distributed generation / Markus Kraiczy." Kassel : kassel university press c/o Universität Kassel - Universitätsbibliothek, 2021. http://d-nb.info/1232212032/34.

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13

Hinz, Fabian. "Voltage Stability and Reactive Power Provision in a Decentralizing Energy System." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-229585.

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Electricity grids require the ancillary services frequency control, grid operation, re-establishment of supply and voltage stability for a proper operation. Historically, conventional power plants in the transmission grid were the main source providing these services. An increasing share of decentralized renewable energy in the electricity mix causes decreasing dispatch times for conventional power plants and may consequently lead to a partial replacement of these technologies. Decentralized energy sources are technically capable of providing ancillary services. This work focuses on the provision of reactive power for voltage stability from decentralized sources. The aim is to answer the question of how voltage stability and reactive power management can be achieved in a future electricity system with increasing shares of decentralized renewable energy sources in an economical and efficient way. A methodology that takes reactive power and voltage stability in an electricity system into account is developed. It allows for the evaluation of the economic benefits of different reactive power supply options. A non-linear and a linearized techno-economic grid model are formulated for this purpose. The analysis reveals an increasing importance of reactive power from the distribution grid in future development scenarios, in particular if delays in grid extension are taken into account. The bottom-up assessment indicates a savings potential of up to 40 mio. EUR per year if reactive power sources in the distribution grid provide reactive power in a controlled manner. Although these savings constitute only a small portion of the total cost of the electricity system, reactive power from decentralized energy sources contributes to the change towards a system based on renewable energy sources. A comparison of different reactive power remuneration mechanisms shows that a variety of approaches exist that could replace the inflexible mechanisms of obligatory provision and penalized consumption of reactive power that are mostly in place nowadays.

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Siniscalchi, Minna Sara. "Advanced wind farm control strategies for enhancing grid support." Doctoral thesis, TDX (Tesis Doctorals en Xarxa), 2019. http://hdl.handle.net/10803/669244.

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Nowadays, there is rising concern among Transmission System Operators about the declining of system inertia due to the increasing penetration of wind energy, and other renewable energy systems, and the retirements of conventional power plants. On the other hand, by properly operating wind farms, wind generation may be capable of enhancing grid stability and ensuring continued security of power supply. In this doctoral thesis, new control approaches for designing wind farm optimization-based control strategies are proposed to improve the participation of wind farms in grid support, specially in primary frequency support.
Hoy en día, existe una significativa preocupación entre los Operadores de Sistemas de Transmisión sobre la cresciente penetración de le energía eólica y la tendiente eliminación de las centrales eléctricas convencionales que implica la disminución de la inercia del sistema eléctrico. Operando adecuadamente los parques eólicos, la generación eólica puede mejorar la estabilidad de la red eléctrica y garantizar la seguridad y un continuo suministro de energía. Esta tesis doctoral propone nuevas estrategias para diseñar controladores basados en optimización dinámica para parques eólicos y mejorar la participación de los parques eólicos en el soporte de la red eléctrica. En primer lugar, esta tesis doctoral presenta los enfoques clásicos para el control de parques y turbinas eólicas y cómo los conceptos de control existentes pueden ser explotados para hacer frente a los nuevos desafíos que se esperan de los parques eólicos. Esta tesis doctoral asigna un interés especial a cómo formular la función objetivo de que la reserva de potencia sea maximizada, para ayudar por el suporte de frequencia, y al mismo tiempo seguir la potencia demandada por la red. Sin embargo, el impacto de la estela de viento generada por una turbina sobre otras turbinas necesita ser minimizado para mejorar la reserva de potencia. Por lo tanto, a lo largo de esta tesis se proponen estrategias de control centralizado para parques eólicos enfocadas en distribuir óptimamente la energía entre las turbinas para que el impacto negativo de la estela en la reserva de potencia total se reduzca. Se discuten dos técnicas de control para proporcionar los objetivos de control mencionados anteriormente. Un algoritmo de control óptimo para encontrar la mejor distribución de potencia entre las turbinas en el parque mientras se resuelve un problema iterativo de programación lineal. En segundo lugar, se utiliza la técnica de control predictivo basada en modelo para resolver un problema de control multi-objetivo que también podría incluir, junto con la maximización de reserva de potencia, otros objetivos de control, tales como la minimización de las perdidas eléctricas en los cables de la red de interconexión entre turbinas y un controlador/supervisor. Además, la investigación realizada resalta la capacidad de las estrategias de control propuestas en esta tesis para proporcionar mayor reserva de potencia respecto a los conceptos comúnmente usados para distribuir la potencia total del parque eólico. La idea principal detrás del diseño de una estrategia de control de parques eólico es de encontrar una solución óptima dentro de un cálculo computacional relativamente bajo. Aunque los controladores centralizados propuestos en esta tesis reaccionan rápidamente a los cambios en la potencia de referencia enviada desde el controlador, algunos problemas pueden ocurrir cuando se consideran parques eólicos de gran escala debido a los retrasos existentes por el viento entre turbinas. Bajo estas circunstancias, la producción de energía de cada turbina está altamente acoplada con la propagación de la estela y, por ende, con las condiciones de funcionamiento de las otras turbinas. Esta tesis doctoral propone un esquema de control de parques eólicos no centralizados basado en una estrategia de partición para dividir el parque eólico en sub-conjuntos independientes de turbinas. Con la estrategia de control propuesta, el tiempo de cálculo se reduce adecuadamente en comparación con la estrategia de control centralizado mientras que el rendimiento en la distribución óptima de potencia es ligeramente afectado. El rendimiento de todas las estrategias de control propuestas en esta tesis se prueba con un simulador de parque eólico que modela el comportamiento dinámico del efecto de estela mediante el uso de un conocido y consolidado modelo dinámico de estela y, para un análisis más realista, algunas simulaciones se realizan con software avanzado basado en la técnica de Large Eddy Simulation.

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Boulanger, Isabelle. "Lillgrund Wind Farm Modelling and Reactive Power Control." Thesis, KTH, Elektriska energisystem, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119256.

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The installation of wind power plant has significantly increased since several years due to the recent necessity of creating renewable and clean energy sources. Before the accomplishment of a wind power project many pre-studies are required in order to verify the possibility of integrating a wind power plant in the electrical network. The creation of models in different software and their simulation can bring the insurance of a secure operation that meets the numerous requirements imposed by the electrical system. Hence, this Master thesis work consists in the creation of a wind turbine model. This model represents the turbines installed at Lillgrund wind farm, the biggest wind power plant in Sweden. The objectives of this project are to first develop an accurate model of the wind turbines installed at Lillgrund wind farm and further to use it in different kinds of simulations. Those simulations test the wind turbine operating according to different control modes. Also, a power quality analysis is carried out studying in particular two power quality phenomena, namely, the response to voltage sags and the harmonic distortion. The model is created in the software PSCAD that enables the dynamic and static simulations of electromagnetic and electromechanical systems. The model of the wind turbine contains the electrical machine, the power electronics (converters), and the controls of the wind turbine. Especially, three different control modes, e.g., voltage control, reactive power control and power factor control, are implemented, tested and compared. The model is tested according to different cases of voltage sag and the study verifies the fault-ride through capability of the turbine. Moreover, a harmonics analysis is done. Eventually the work concludes about two power quality parameters.

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Andersson, Robin. "Electric power quality in low voltage grid : Office buildings and rural substation." Thesis, Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-28441.

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The modern society uses more and more electronic devices needed to being able to function together. This put higher demands on the electrical grid together with that the typical load have changed from the past. Therefore utility companies are obliged to keep the voltage within certain limits for this to function. What exact these limits have been have not always been clear since they have not been gathered in one single document. This thesis is a cooperation with Kraftringen who also has been the initiator. Kraftringen would like to become more proactive in their work regarding electric power quality. For becoming more proactive continuously measurements have to be done but the locations have to be carefully selected in the beginning to get a wider perspective of the grid. Energy markets inspectorate (EI) is supervisory of the electric power quality in Sweden and since 2011 they have published a code of statutes (EIFS 2011:2 later 2013:1) intended to summarize limits on voltage. Some of the electrical power quality aspects are not mentioned in EIFS 2013:1 and standards have to be used to find limited values. Flicker and interharmonics are not mentioned in EIFS 2013:1 and for values on flicker the standard SS-EN 50160 has to be used and for interharmonics the standard SS-EN 61000-2-2 state limit values. Besides all this there are standards with stricter limits than EIFS 2013:1 e.g. for total harmonic distortion on voltage were SS-EN 61000-2-2 suggest 6 % instead of 8 %. Three different field studies have been conducted in order to get some perception of the present situation regarding electric power quality. Two measurements were conducted on a typical office building because they represents a large part of the typical load in Lund. The third measurement was conducted on a substation in a rural area to get a perception of the situation outside urban areas. These measurements shown that the overall electric power quality was within given limits according to EIFS 2013:1 and different standards. However, conducted measurements shown some interesting results. Both the typical office buildings have a slightly capacitive power factor which results in that the voltage inside the building is going to be slightly higher than at the substation. Since the voltage level at the measured urban substation was above nominal voltage level with about 2-5 % this could be problematic. Another eventual problem with a load with a capacitive power factor is resonance with the inductive parts of the grid like transformers leading to magnified harmonic levels. It is suggested that Kraftringen expand their number of permanent electric power quality measurement locations to get a better overview of the present situation. The best suited locations to start with are such that have received complaints earlier, preferably measured on the low voltage side of the transformer for also register the amount of zero sequence harmonics. Next step in the measurement expansion would be substations known to be under higher load than others or substations with a PEN-conductor in a smaller area than the phase conductors, supplying a typical office load with high amounts of third harmonics and unbalance. From this it would be appropriate to spread out the measurement locations geographically to better get to know the grids behaviour.

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Chen, Linwei. "Distribution network supports for transmission system reactive power management." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/distribution-network-supports-for-transmission-system-reactive-power-management(abcc8197-fd85-478b-b91a-fd3d0b3220db).html.

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To mitigate high voltages in transmission systems with low demands, traditional solutions often consider the installation of reactive power compensators. The deployment and tuning of numbers of VAr compensators at various locations may not be cost-effective. This thesis presents an alternative method that utilises existing parallel transformers in distribution networks to provide reactive power supports for transmission systems under low demands. The operation of parallel transformers in small different tap positions, i.e. with staggered taps, can provide a means of absorbing reactive power. The aggregated reactive power absorption from many pairs of parallel transformers could be sufficient to provide voltage support to the upstream transmission network. Network capability studies have been carried out to investigate the reactive power absorption capability through the use of tap stagger. The studies are based on a real UK High Voltage distribution network, and the tap staggering technique has been applied to primary substation transformers. The results confirm that the tap staggering method has the potential to increase the reactive power demand drawn from the transmission grid. This thesis also presents an optimal control method for tap stagger to minimise the introduced network loss as well as the number of tap switching operations involved. A genetic algorithm (GA) based procedure has been developed to solve the optimisation problem. The GA method has been compared with two alternative solution approaches, i.e. the rule-based control scheme and the branch-and-bound algorithm. The results indicate that the GA method is superior to the other two approaches. The economic and technical impacts of the tap staggering technique on the transmission system has been studied. In the economic analysis, the associated costs of applying the tap staggering method have been investigated from the perspective of transmission system operator. The IEEE Reliability Test System has been used to carry out the studies, and the results have been compared with the installation of shunt reactors. In the technical studies, the dynamic impacts of tap staggering or reactor switching on transmission system voltages have been analysed. From the results, the tap staggering technique has more economic advantages than reactors and can reduce voltage damping as well as overshoots during the transient states.

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Park, Sung Yeul. "A Wide Range and Precise Active and Reactive Power Flow Controller for Fuel Cell Power Conditioning Systems." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28645.

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This dissertation aims to present a detailed analysis of the grid voltage disturbance in frequency domain for the current control design in the grid-tie inverter applications and to propose current control techniques in order to minimize its impact and maximize feasibility of the power conditioning system in distributed generations. Because the grid voltage is constantly changing, the inverter must be able to response to it. If the inverter is unable to respond properly, then the grid voltage power comes back to the system and damages the fuel cell power conditioning systems. A closed-loop dynamic model for the current control loop of the grid-tie inverter has been developed. The model explains the structure of the inverter admittance terms. The disturbance of the grid voltages has been analyzed in frequency domain. The admittance compensator has been proposed to prevent the grid voltage effect. The proposed lead-lag current control with admittance compensator transfers current properly without system failure. In order to get rid of the steady-state error of the feedback current, a proportional-resonant controller (PR) has been adopted. A PR control with admittance compensation provides great performance from zero power to full power operation. In addition, active and reactive power flow controller has been proposed based on the PR controller with admittance compensation. The proposed active and reactive power flow control scheme shows a wide range power flow control from pure leading power to pure lagging power. Finally, the proposed controller scheme has been verified its feasibility in three phase grid-tie inverter applications. First of all, a half-bridge grid-tie inverter has been designed with PR controller and admittance compensation. Then three individual grid-tie inverters has been combined and produced three phase current to the three phase grid in either balanced condition or unbalanced condition. The proposed control scheme can be applied not only single phase grid-tie inverter application, but also three phase grid-tie inverter application. This research can be applicable to the photovoltaic PCS as well. This technology makes renewable energy source more plausible for distributed generations.
Ph. D.

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Martin, Almenta Macarena. "Domestic refrigeration load participation for grid support in power systems with high wind penetrations." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707826.

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The thesis investigates the application of domestic fridge freezer loads for demand side participation (DSP), with the aim of quantifying the benefits of its implementation in the Irish Single Electricity Market (SEM). The thermal and electrical consumption characteristics of a domestic fridge freezer appliance were analysed experimentally, and used to inform the development of a numerical model for a single appliance. Various control strategies were investigated using the model, which vary the temperature limits of the appliance thermostat. The price control strategy based on the day ahead system marginal price was shown to be the most effective. An aggregate numerical model was subsequently developed in order to assess the DSP potential in Ireland considering different appliance characteristics. Staggering the start time at which the control strategy is activated for the individual appliances was shown to be important for avoiding undesired secondary consumption peaks. For a typical winter week in 2020, a peak reduction of at least 68% of the average winter refrigeration load and average overall refrigeration running cost reduction of 8.2% are achieved. The DSP potential was further analysed in the context of integrating domestic refrigeration as a virtual power plant in the SEM for a winter week in December 2020 with significant events of wind curtailment. An equivalent power network of Northern Ireland was implemented in a realistic unit commitment and economic dispatch model of the SEM. The integration of DSP leads to a reduction of the total generation cost in Northern Ireland approximately by €13,000 and an additional 200 MWh of wind generation is introduced into the power system, reducing the wind curtailment by 0.2% for a system non-synchronous penetration of 75%. The work shows that this DSP scheme can provide significant benefits to the system operator and thus is a viable candidate for implementation in the SEM.

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Badran, Ahmad. "Integrating Wind Power into The Electric Grid : Predictive Current Control Implementation." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-99640.

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The increasing penetration of wind power into the power system dominated by variable-speed wind turbines among the installed wind turbines will require further development of control methods. Power electronic converters are widely used to improve power quality in conjunction with the integration of variable speed wind turbines into the grid. In this thesis, a detailed model of the Predictive Current Control (PCC) method will be descripts for the purpose of control of the grid-connected converter. The injected active and reactive power to the grid will be controlled to track their reference value. The PCC model predicts the future grid current by using a discrete-time model of the system for all possible voltage vectors generated by the inverter. The voltage vector that minimizes the current error at the next sampling time will be selected and the corresponding switching state will be the optimal one. The PCC is implemented in Matlab/Simulink and simulation results are presented.

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Garg, Aditie. "Designing Reactive Power Control Rules for Smart Inverters using Machine Learning." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83558.

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Due to increasing penetration of solar power generation, distribution grids are facing a number of challenges. Frequent reverse active power flows can result in rapid fluctuations in voltage magnitudes. However, with the revised IEEE 1547 standard, smart inverters can actively control their reactive power injection to minimize voltage deviations and power losses in the grid. Reactive power control and globally optimal inverter coordination in real-time is computationally and communication-wise demanding, whereas the local Volt-VAR or Watt-VAR control rules are subpar for enhanced grid services. This thesis uses machine learning tools and poses reactive power control as a kernel-based regression task to learn policies and evaluate the reactive power injections in real-time. This novel approach performs inverter coordination through non-linear control policies centrally designed by the operator on a slower timescale using anticipated scenarios for load and generation. In real-time, the inverters feed locally and/or globally collected grid data to the customized control rules. The developed models are highly adjustable to the available computation and communication resources. The developed control scheme is tested on the IEEE 123-bus system and is seen to efficiently minimize losses and regulate voltage within the permissible limits.
Master of Science

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Back, Erik. "A new DC-DC converter technology suitable to support grid connection of wave power energy converter." Thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-182937.

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Since 2002, the department of electricity at Uppsala university has pushed the Lysekil project. The project has a number of wave energy converters installed in the sea southwest of Lysekil. The purpose of this work is to design, build and test a DC-DC converter, which will later be used as a necessary part of the grid connection of a wave energy converter. Since a wave energy converter does not generate electricity at a constant frequency, it is not possible to use a gearbox. Instead, power is rectified and, if there are several wave power energy converters, are put together with the others before it is inverted and transformed to the correct voltage level, and finally connected to the grid [1]. The designed DC-DC converter is a converter of the type "inverting buck-boost", i.e. a converter that can both lower and raise the voltage, and inverts the polarity of the output. Although the voltage in normal circumstances will only be increased, the simulations showed that the efficiency and cost of components did not differ much between a "boost" and "buck-boost" converter, thus considered flexibility to be able to lower the voltage if needed. The project also includes a small part to the construction of a bridge rectifier, but as the most difficult moment in the project is the DC-DC converter, the greatest focus will be there.

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Spies, Andries Theodorus. "An investigation into the grid compliance of the slip synchronous permanent magnet wind generator." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80075.

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Thesis (MScEng)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The slip synchronous permanent magnet generator (SSG) is a direct-driven direct-grid connected generator developed to alleviate the need for expensive gearboxes and solid-state power converters on wind turbine generators. This study identifies certain key areas where the current wind turbine generator (WTG) system does not comply with the grid code for wind energy facilities (WEF) as specified by the National Energy Regulator of South Africa. The current WTG system does not have a reactive power compensation device. The main focus in this study is the development of an on-load tap changer (OLTC) transformer to control the terminal voltage of the generator. By controlling the terminal voltage of the generator the excitation-mode of the SSG can be changed allowing for control over the reactive power output of the SSG. An OLTC transformer utilising a solid-state assisted mechanical diverter circuit is built and tested to determine the viability of using an OLTC as a reactive power control device. Practical test results show that the OLTC can successfully control the terminal voltage of the SSG without interrupting the load current. The required accuracy regarding power factor control capability was not met due to the large change in reactive power output per tap change operation. A method of using small shunt capacitor banks to provide additional reactive power in between consecutive tap changes is evaluated in simulation. Simulation results show that the addition of these small shunt capacitor banks dramatically improves the reactive power control accuracy. Additionally the grid code specifies that a WEF must have the ability to curtail the active power output during frequency disturbances. The effects of frequency disturbances on the SSG output is simulated and it was found that the SSG will comply with the minimum connection requirements as specified in the grid code. A method of using an IGBT switched DC load to limit the active power output of the WEF is developed and simulated. From the simulation results it was found that the proposed active power curtailment device will meet the minimum power curtailment response time requirements as specified in the grid code.
AFRIKAANSE OPSOMMING: Die glip sinchroon permanente magneet generator (SSG) is ŉ direkte dryf, direkte netwerk gekoppelde wind generator wat ontwikkel is om behoefte aan duur ratkaste en drywing elektroniese omsetters te verlig. Hierdie studie identifiseer sekere sleutel areas waar die huidige wind generator opstelling nie aan die netwerk kode spesifikasie soos uiteengesit deur die Nasionale Energie Reguleerder van Suid-Afrika voldoen nie. Die wind turbine generator stelsel beskik nie oor ŉ reaktiewe drywing beheer meganisme nie. Die belangrikste fokus in hierdie studie is die ontwikkeling van ŉ transformator tap wisselaar wat gebruik sal word om die generator se terminale spanning te beheer. Deur die terminaal spanning te beheer kan die opwekking modus van die generator verander word om dan die uittree reaktiewe drywing te beheer. ŉ Tap wisselaar wat gebruik maak van ŉ drywingelektronies gesteunde meganiese skakelaar is ontwikkel en getoets om die lewensvatbaarheid van die tegniek te ondersoek. Praktiese toets resultate toon dat die tap wisselaar suksesvol beheer oor die generator se terminaal spanning kon uitvoer, sonder om die las-stroom te onderbreuk. Ongelukkig is die vereiste akkuraatheid ten opsigte van die reaktiewe drywing beheer nie gehaal nie. Die rede hiervoor is dat die verandering in uittree reaktiewe drywing baie groot is vir opeenvolgende tap verstellings. ŉ Metode waar twee klein kapasitor banke geskakel word om reaktiewe drywing te lewer, tussen opeenvolgende tap veranderinge, is deur middel van simulasie ondersoek. Die simulasie resultate toon aan dat die toevoeging van die kapasitors ŉ drastiese verbetering in die beheerbaarheid van die uittree reaktiewe drywing het. Verder spesifiseer die netwerk kode ook dat ŉ wind plaas oor die vermoë moet beskik om die aktiewe drywing te verminder tydens ŉ netwerk frekwensie versteuring. Die effek wat ŉ frekwensie versteuring op die SSG het, is deur middel van simulasie ondersoek en daar is gevind dat die SSG aan die netwerk verbinding spesifikasie sal voldoen. ŉ Metode waarby ŉ IGBT geskakelde GS las gebruik word om die aktiewe drywing van die wind generator te beperk is ondersoek en gesimuleer. Vanaf die simulasie resultate is daar gevind dat die drywing beperkings toestel aan die minimum drywing en reaksie tyd spesifikasies soos vereis sal voldoen.

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Perera, Sam Prasanna Kurukulasuriya, and Sumith Ruwan Dharmasiri Kachchakaduge. "SMART VAR Generator to Manage Grid Voltage Stability issue of Low Frequency Switching Photovoltaic Inverters." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-20595.

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Solar power, clean and abundant, is considered as a vital contributor in the effort of transforming world energy-mix to pollution-free and natural-regenerative sources. The solar micro inverters have gained greater visibility during the past several years due to their higher efficiency, greater performances, longer life expectancy and many other benefits. But, integrating small scale [<15kW] renewable energy sources, especially the low frequency switching solar inverters to the low voltage distribution grid has its own challenges due to their inability to generate reactive power to maintain the static voltage stability of the grid. Higher level of solar penetration has identified as a potential cause of low voltage grid instability due to lack of reactive power feeding and their tendency to keep on increasing the voltage higher than grid at the point of common connection [PCC] in order to inject the current to the grid. The studies and experience in voltage stability issues has resulted in introducing many new grid regulations to manage the grid voltage stability throughout the world. The new regulation, VDE-AR-N-4105-2011 is a German grid regulation standard specifically focuses on the low voltage grid connected power generators. This regulation has addressed the reactive power requirements in terms of power factor and supply management to maintain the grid static voltage variation less than 3% at the PCC, when connecting any type of distributed power generators to the low voltage network. This report discuss about the voltage stability issues related to low frequency switching inverters and present a solution to comply with low voltage grid regulation - VDE-AR-N-4105-2011; a SmartVar Generator concept, theory, design and functionality.

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Fan, Zaiming. "Investigation on smart bi-directional inverter with quantitative reactive power compensation and interleaved DC/DC converter for micro-grid system." Thesis, University of Cumbria, 2016. http://insight.cumbria.ac.uk/id/eprint/3326/.

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The PhD project aims to develop a smart grid-connected inverter (SGCI) for a micro-grid, which can be applied in a built environment such as a community, and associated power electronic DC/DC converters. The micro-grid generally includes distributed renewable power generators and battery storage. The SGCI is a bi-directional DC/AC inverter for distributed generation with battery storage installed at its DC side. In one aspect, it is expected the DC/AC inverter functions as a controlled inverter that can deliver expected real power to the power grid with quantitative reactive power compensation (RPC). In other words, all the SGCIs in the community microgrid can share the reactive power of the whole community because a SGCI can quantify its active and reactive power output. It is also expected that the inverter can work in both on-grid and off-grid modes. In other words, the DC/AC inverter functions as a controlled rectifier with high quality power factor correction (PFC), which can deliver expected DC power from the AC power grid at unity power factor. With the above features, battery storage on the DC bus of the SGCI can be charged/discharged through a four-phase, interleaved, bi-directional, boost/buck DC/DC converter (IBDBBC) for distributed renewable power system, either wind or solar PV or hybrid wind/solar PV system. The IBDBBC can discharge power from a low voltage battery to a high voltage DC bus as the IBDBBC operates in boost mode, or it can also draw power from the DC bus to charge the battery as the IBDBBC operates in buck mode. Based on MATLAB/Simulink, a mathematical model was developed for the grid-connected bi-directional DC/AC inverter that operates as a rectifier with PFC and as a grid-connected inverter (GCI) with expected real power output and quantitative RPC. In a practical application, the sampling of input signal through AD converter usually has some noise due to common-mode interference; simulation results demonstrate that the second order generalised integrator (SOGI) has great advantages to prevent interference. Therefore, SOGI can be utilised to construct a pair of orthogonal signals in a single-phase system to instantaneously split grid’s active and reactive power to achieve RPC for local community loads. The methodology of the constructed the pair of orthogonal signals was also used to generate the required reference current for the DC/AC inverter when which operated as a single-phase rectifier with PFC. Using three TI C2000 Solar Inverter DSK Boards, a small lab scale distributed power system was developed. In the lab distributed power system, the operating mode of the inverters could be switched between on-grid and off-grid through instruction from the control centre. The lab test outcomes demonstrate that each distributed power system unit worked properly under loss of power grid signal, simulating grid failure.

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Mohseni, Mansour. "Enhanced control of DFIG-based wind power plants to comply with the international grid codes." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1878.

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A review of the latest international grid codes shows that large wind power plants are stipulated to not only ride-through various fault conditions, but also exhibit adequate active and reactive power responses during the fault period in order to support the network stability. In particular, modern grid codes require wind power plants to: (1) ride-through various voltage sag and swell conditions, (2) inject reactive current into the grid during the fault period, and (3) attain swift active power restoration after the fault clearance. This thesis proposes a transient control scheme for DFIG-based wind power plants to comply with these requirements.In the first part of this thesis, the latest regulations enforced on large wind power plants are studied and compared. This study identifies the most stringent regulations defined by the international grid codes, to be further investigated in the following chapters. In the second part of this thesis, extensive simulation studies are carried out to examine the transient response of DFIG-based wind turbines under various symmetrical and asymmetrical fault conditions. Supplementary theoretical analyses are also presented to justify the observations made in the time-domain simulations results. For the first time, the impacts of phase-angle jump, voltage recovery process and sag parameters on the DFIG response are explored. The results of this study can assist researcher to identify the difficulties that hinder successful fault ride-through response of DFIG-based wind turbines, as requested by the international grid codes.In the third part of the thesis, an enhanced hysteresis-based current regulator (referred to as VBHCR) is proposed to be implemented in the rotor-side and grid-side converters of DFIG-based wind turbines. The main advantages of this current regulator are very fast transient response, simple control structure and insensitivity to the machine parameters variations. Simulation results show that on one hand the VBHCR has very good steady-state performance and on the other hand, it presents very fast/robust tracking response. Therefore, the DFIG equipped the proposed current regulator can fulfill the most stringent low-voltage ride-through requirements imposed by the international grid codes, i.e., those stipulated by the Australian grid code. In the fourth part of the thesis, a new hybrid current control scheme is introduced to enhance both low and high voltage ride-through capabilities of DFIG-based wind turbines. The proposed control scheme uses the standard PI current regulators under steady-state conditions but upon a voltage sag or swell occurrence, the supervisory control unit transfers the switching strategy of the rotor-side and grid-side converters to the hysteresis-based method. The VBHCR remains in action until the oscillation in the rotor current and dc-link voltage of DFIG suppress below the safety limit and then, the PI current regulator are activated through a re-initialization process.Finally, the conventional vector control scheme of DFIG-based wind power plants is modified to fulfill the regulations imposed on the active and reactive power responses of wind farms subject to various faults. New design strategies are suggested and their corresponding P-Q capability curves are thoroughly studied. Simulations results show that the proposed control scheme can meet the Australian regulations as the most demanding grid code. The best design strategy, with enhanced active and reactive power responses, permits the rotor-side and grid-side converters of DFIG to be temporarily overloaded during the fault period and also exploits the free capacity of the GSC to inject further reactive power to the grid. As a result, the active power generation of DFIG-based wind power plant can be retained during the fault period while its reactive power injection capacity of DFIG is also increased to further support the grid.

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Ro, Kyoungsoo. "Two-Loop Controller for Maximizing Performance of a Grid-Connected Photovoltaic-Fuel Cell Hybrid Power Plant." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30378.

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The study started with the requirement that a photovoltaic (PV) power source should be integrated with other supplementary power sources whether it operates in a stand-alone or grid-connected mode. First, fuel cells for a backup of varying PV power were compared in detail with batteries and were found to have more operational benefits. Next, maximizing performance of a grid-connected PV-fuel cell hybrid system by use of a two-loop controller was discussed. One loop is a neural network controller for maximum power point tracking, which extracts maximum available solar power from PV arrays under varying conditions of insolation, temperature, and system load. A real/reactive power controller (RRPC) is the other loop. The RRPC meets the system's requirement for real and reactive powers by controlling incoming fuel to fuel cell stacks as well as switching control signals to a power conditioning subsystem. The RRPC is able to achieve more versatile control of real/reactive powers than the conventional power sources since the hybrid power plant does not contain any rotating mass. Results of time-domain simulations prove not only effectiveness of the proposed computer models of the two-loop controller, but also their applicability for use in transient stability analysis of the hybrid power plant. Finally, environmental evaluation of the proposed hybrid plant was made in terms of plant's land requirement and lifetime CO2 emissions, and then compared with that of the conventional fossil-fuel power generating forms.
Ph. D.

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Waseem, Irfan. "Impacts of Distributed Generation on the Residential Distribution Network Operation." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/36394.

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In this research, the impacts of installing DG on a residential distribution circuit are explored. The work is focused on analyzing the impact of DG installation on distribution network operation including voltage analysis, electric losses and reliability of the system. First, various DG penetration levels and the impact of distributing the DG across several locations are explored. Secondly, the impacts of installing DG on any one phase on the voltage profiles of the unbalanced three-phase distribution network are investigated. Thirdly, the losses of the system are analyzed. Next, the reliability analysis (SAIDI, CAIDI, ENS, and AENS) of the system is performed by installing DGs as backup generators. Different DG penetration levels, locations and the impacts of installing one large-scale DG on the main distribution line vs. several small-scale randomly distributed DGs are explored. A residential distribution circuit in Blacksburg, VA was built using its one-line diagram in DEW (Distributed Engineering Workstation) to perform detailed analysis. The research involves several case studies that explore the impacts of installing distributed generation (DG) on residential distribution network operation including the voltage profile, losses, and reliability indices of the system.
Master of Science

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Moghadasiriseh, Amirhasan. "Analysis and Modeling of Advanced Power Control and Protection Requirements for Integrating Renewable Energy Sources in Smart Grid." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2469.

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Attempts to reduce greenhouse gas emissions are promising with the recent dramatic increase of installed renewable energy sources (RES) capacity. Integration of large intermittent renewable resources affects smart grid systems in several significant ways, such as transient and voltage stability, existing protection scheme, and power leveling and energy balancing. To protect the grid from threats related to these issues, utilities impose rigorous technical requirements, more importantly, focusing on fault ride through requirements and active/reactive power responses following disturbances. This dissertation is aimed at developing and verifying the advanced and algorithmic methods for specification of protection schemes, reactive power capability and power control requirements for interconnection of the RESs to the smart grid systems. The first findings of this dissertation verified that the integration of large RESs become more promising from the energy-saving, and downsizing perspective by introducing a resistive superconducting fault current limiter (SFCL) as a self-healing equipment. The proposed SFCL decreased the activation of the conventional control scheme for the wind power plant (WPP), such as dc braking chopper and fast pitch angle control systems, thereby increased the reliability of the system. A static synchronous compensator (STATCOM) has been proposed to assist with the uninterrupted operation of the doubly-fed induction generators (DFIGs)-based WTs during grid disturbances. The key motivation of this study was to design a new computational intelligence technique based on a multi-objective optimization problem (MOP), for the online coordinated reactive power control between the DFIG and the STATCOM in order to improve the low voltage ride-through (LVRT) capability of the WT during the fault, and to smooth low-frequency oscillations of the active power during the recovery. Furthermore, the application of a three-phase single-stage module-integrated converter (MIC) incorporated into a grid-tied photovoltaic (PV) system was investigated in this dissertation. A new current control scheme based on multivariable PI controller, with a faster dynamic and superior axis decoupling capability compared with the conventional PI control method, was developed and experimentally evaluated for three-phase PV MIC system. Finally, a study was conducted based on the framework of stochastic game theory to enable a power system to dynamically survive concurrent severe multi-failure events, before such failures turn into a full blown cascading failure. This effort provides reliable strategies in the form of insightful guidelines on how to deploy limited budgets for protecting critical components of the smart grid systems.

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Kapidou, Alexandra. "Application for Wind Farm Integration Complying with the Grid Code by Designing an Outer Control Strategy for the Converter." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-187686.

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The continuously increasing energy penetration from wind farms into the grid raises concerns regarding power quality and the stable operation of the power system. The Grid Code´s requirements give strict guidelines for a wind farm´s behaviour under faulty or abnormal operating conditions.The primary purpose of this project is the application of a STATCOM for wind farm integration complying with the Grid Code. Towards that, an outer control strategy for the converter is designed so as to regulate the voltage at the point of common coupling by providing reactive power compensation. Thus the safe operation of the grid will be ensured since the wind farm will follow the Grid Code´s standards.The existing Grid Code requires only a positive sequence current controller. This study attempts to investigate whether this is sufficient or not and to examine the possibility of extending the Grid Code requirements so as to incorporate a negative sequence current controller as well. The results support the latter suggestion. Also, the use of SiC devices was also considered in this project.
Den ständigt ökande penetrationen av vindenergi i elnätet väcker farhågor om elkvalitet och stabil drift av kraftsystemet. Nätkoden (Grid Code) ger strikta riktlinjer för en vindkraftsparks beteende i felfall och under onormala driftsförhållanden.Huvudsyftet med detta projekt är att använda en STATCOM för integration av vindkraftsparker så att nätkoden uppfylls. I detta projekt utformas en yttre reglerstrategi för omriktaren för att reglera spänningen vid anslutningspunkten för vindkraftsparken genom att tillhandahålla reaktiv effektkompensering. Därigenom uppnås en säker drift av nätet eftersom vindkraftparken kommer att följa nätkoden.Den befintliga nätkoden kräver endast styrning av plusföljdskomponenten av strömmen. Denna studie försöker undersöka om detta är tillräckligt samt undersöka möjligheten för att utvidga nätkoden genom att införa ett krav på styrning av negativ-sekvens ström. Resultaten stöder det sistnämnda förslaget. Även användningen av halvledarkomponenter av kiselkarbid-SiC studerades i detta projekt.

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Shen, Ming. "Distributed Solar Photovoltaic Grid Integration System : A Case Study for Performance." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/945.

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The needs to the sustainable development of electricity, energy efficiency improvement, and environment pollution reduction have favored the development of distributed generation (DG). But the problems come with increasing DG penetration in distribution networks. This thesis presents the Solar Energy Grid Integration System (SEGIS) Stage III project done by Portland General Electric (PGE), Advanced Energy, Sandia National Lab on a PGE selected distribution feeder. The feeder has six monitored commercial solar PV systems connected. The total power output from the PV systems has the potential to reach 30% of the feeder load. The author analyzes the performance of the solar feeder on both generation and voltage effects. As a project report, it introduced a new islanding detection done by other team members to give an islanding solution of future high penetration distribution networks. At last, the author describes micro-grid and grid support concepts in a SEGIS concept paper with some examples.

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Guo, Yue. "Capability assessment of VAr support and demand response to transmission network using flexible tap changing techniques in distribution networks." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/capability-assessment-of-var-support-and-demand-response-to-transmission-network-using-flexible-tap-changing-techniques-in-distribution-networks(5a373163-d2c9-4e13-9720-0c4fa0456c3f).html.

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Due to the increasing integration of renewable energy generations, the overvoltage and overload issues in transmission networks have become more significant, and they may occur at various locations. To mitigate the overvoltage issues, traditional solutions which often consider the installation of reactive power compensators such as shunt reactors, SVC, STATCOM may not be cost-effective. To mitigate the overload issues, traditional methods using direct or price-based demand control will affect customersâ electrical experience in that they are inconvenienced greatly. This thesis discusses the flexible tap changing techniques that utilise existing parallel transformers in distribution networks to provide reactive power absorption and demand response services for transmission systems. Among them, the tap stagger technique operates parallel transformers in small different tap positions, i.e. staggered taps, to result in more reactive power absorption from upstream networks. In addition, the tap changing technique changes voltages in the range of statutory limits through the adjustment of tap positions in order to change network demands without directly affecting customers. The aggregated reactive power absorption or demand response from many pairs of parallel transformers in distribution networks could be sufficient to provide VAr or demand support to transmission networks. Network capability studies have been carried out in OpenDSS simulation software to investigate the VAr absorption capability by using tap staggering technique and the demand reduction capability by using tap changing technique. The studies are based on two UK HV distribution networks (132-33kV) with 11 and 28 primary substations (33/11 or 6.6 kV) respectively, and the techniques are applied to parallel transformers in primary substations. Based on the results of the two networks, the capabilities of the whole ENW and the UK distribution networks have been estimated respectively by using linear estimation method. In addition, the VAr absorption capability of the tap stagger technique has been validated by using site trial data. The results show an average VAr absorption capability of 0.89MVAr for a primary substation, 315MVAr for ENW networks and about 2500MVAr for the UK at stagger level 4 and show an average demand reduction capability of 3.1% of the original demand at tap down level 3. The results of capability studies together with the validations results confirm that the flexible tap changing techniques are able to provide transmission networks with effective VAr support and demand response services. To assess network VAr absorption and demand response capability more precisely, this thesis also proposes an online load profile estimation method to estimate the load profiles of the network more accurately if not all substations in the network are monitored. The method uses Peak Load Share values, Euclidean Distance, and some load measurements to estimate load profiles. The method has been validated and compared with a traditional aggregation-based method. The results show an average estimation error of 13% ~ 23% in different conditions using the proposed method, and show an average estimation error reduction from about 47% (using the traditional method) to about 13% (using the proposed method). The results indicate that the developed method has a considerable improvement on the accuracy of load profile estimation.

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Forsmark, Anders, and Tim Sidemark. "Anslutning av vindkraft till ett svagt nät i Tidaholm." Thesis, Högskolan Väst, Avd för elektro- och automationsteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-4148.

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Vindkraftverk ansluts idag i snabb takt till elnät runt om i världen. Elnäten är ofta inte tillräckligt dimensionerade på platser där vindkraftutbyggnad är lämplig vilket leder till ett behov av nätförstärkning. Förstärkning sker konventionellt genom att övergå till en högre spänning, något som kan vara förenat med stora kostnader och ledtider. Bland annat därför har en filosofi med beteckningen smarta elnät uppstått, som handlar om hur elnätsystemet ska se ut när det är mer anpassat till de nya energikällornas karaktär och samtidigt medför ett mer effektivt totalutnyttjande. För vindkraftverk kan det då handla om att i högre grad än idag reglera produktionen och understödja nätet, t.ex. via intelligenta kontrollsystem, kraftelektronik och energilager. I den här rapporten undersöks hur mycket vindkraft som kan anslutas till ett svagt elnät då principer för smarta elnät tillämpas och för att se om kostnaden blir lägre än anslutning via konventionella nätförstärkningsmetoder. Det svaga elnätet som studien bygger på ligger i Tidaholm. Vindkraftseffekten som ska anslutas är på 62 MW. Begränsningar i befintliga regionnätets ledningar gör att 60,3 MW kan anslutas med principer för smarta elnät, fast det finns flera skäl till att anta att den fulla mängden vindkraft går att ansluta. Detta till en kostnad som väsentligt understiger kostnaden att förstärka nätet på konventionellt sätt, kostnadsbesparingen uppgår till ca 58 % eller ca 95 Mkr.

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Гейруш, Гергей Гаврилович, and Herhei Heirush. "Забезпечення ефективності системи електропостачання виробництва покрівельного прокату в ТОВ «Євро-прокат»." Master's thesis, Тернопільський національний технічний університет імені Івана Пулюя, кафедра електричної інженерії,Тернопіль, Україна, 2021. http://elartu.tntu.edu.ua/handle/lib/36670.

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Системи електропостачання - це сукупність джерел електричної енергії, силових трансформаторів, повітряних та кабельних ліній електропередачі, розподільних пристроїв, перетворювачів струму та напруги, засобів захисту та управління, допоміжних пристроїв та інших технічних засобів, призначена для забезпечення споживачів електроенергією у необхідній кількості необхідної якості. Якість електроенергії - це сукупність властивостей електричної енергії, що відображає ступінь відповідності встановленим значенням параметрів електричної енергії, кількісно характеризує властивості електричної енергії (частоту, напругу, форму кривої напруги), є мірою електромагнітного впливу системи електропостачання на прилади, апарати, засоби управління, зв’язку та ін., проявляється у вигляді кондуктивних електромагнітних завад. Зниження якості електроенергії у системах електропостачання може призвести до зміни режимів роботи електроприймачів і в результаті – до скорочення терміну служби електрообладнання, підвищення ймовірностей аварій тощо. В реальних системах електропостачання підтримання якості електроенергії в заданих межах забезпечується автоматичним регулюванням окремих показників якості [5]. Нині з’явилися нові технології, які суттєво впливають на забезпечення надійності електроенергетичної системи. Насамперед слід зазначити: нове покоління комутаційної апаратури для всіх класів напруги з практично необмеженим ресурсом та електронні КРП, що дозволяє переглянути завдання надійності підстанцій; стрімкий розвиток силової електроніки та нових матеріалів; значний прогрес у галузі ізоляції електрообладнання [23]. Системи електропостачання промислових підприємств не повинні бути багатоступінчастими, мережі живлення не повинні бути довгими, а спосіб прокладання мережі повинен бути максимально простим. Крім того, система зобов’язана забезпечувати можливість впровадження нового обладнання, тобто повинна бути масштабованою
У кваліфікаційній роботі розроблена модернізація ефективної системи електропостачання підприємства з технологією виробництва покрівельного прокату. Проаналізований технологічний процес порошкового фарбування листового металопрокату. Розраховані електричні навантаження силової та освітлювальної мереж, струми короткого замикання; проведений вибір ефективних перерізів кабельно–провідникової продукції. Проведений розрахунок ефективного схемо–технічного рішення електромережі підприємства з дворівневим розміщенням установок компенсації реактивної потужності.
In the qualification work the modernization of the efficient power supply system of the enterprise with the technology of roofing production is developed. The technological process of powder coating of rolled sheet metal is analyzed. Electrical loads of power and lighting networks, short-circuit currents; the choice of effective cross-sections of cable-conductor products is calculated. The calculation of the effective circuit-technical solution of the power grid of the enterprise with two-level placement of reactive power compensation units is carried out.
ВСТУП ... 6 1 АНАЛІТИЧНИЙ РОЗДІЛ ... 9 1.1 Аналіз енергетичної ефективності систем електропостачання .... 9 1.2 Аналіз методів дослідження ефективності систем електропостачання промислових підприємств ... 12 1.3 Аналіз технологічного процесу порошкового фарбування листового металопрокату ... 14 1.4 Автоматичний пристрій регенерації порошкової фарби ... 18 1.5 Аналіз енергетичних переваг застосування полімерних порошкових покриттів ... 21 1.6 Загальна характеристика електроприймачів ... 23 1.7 Загальна характеристика електроспоживання підприємства ... 24 1.8 Вибір схеми електропостачання ... 24 1.9 Висновки до розділу ... 25 2 РОЗРАХУНКОВО–ДОСЛІДНИЦЬКИЙ РОЗДІЛ ... 26 2.1 Загальна характеристика потужностей основного виробництва.. . 26 2.2 Розрахунок електричних навантажень основного виробництва ... 27 2.3 Розрахунок центрів електричних навантажень ... 28 2.4 Визначення розрахункових навантажень виробничого обладнання ... 30 2.5 Розрахунок електричного освітлення виробничих дільниць ... 33 2.6 Розрахунок навантаження щитка освітлення ... 35 2.7 Розрахунок потужності розподільчих пристроїв ... 35 2.8 Розрахунок навантаження силового трансформатора ... 36 2.9 Схемо-технічні рішення ефективних електромереж промислових підприємств ... 37 2.10 Висновки до розділу ... 44 3 ПРОЕКТНО-КОНСТРУКТОРСЬКИЙ РОЗДІЛ ... 46 3.1 Вибір захисної апаратури електромережі підприємства ... 46 3.2 Проєктне рішення ... 49 3.3 Розрахунок максимальних струмів кіл навантаження силового трансформатора ... 50 3.4 Вибір компенсувальних пристроїв реактивної потужності ... 54 3.5 Вибір площі перерізу проводів і жил кабелів ... 56 3.6 Кабельний журнал ... 58 3.7 Перевірка струмовідних частин на термічну стійкість ... 59 3.8 Релейний захист трансформаторів підстанції ... 60 3.9 Висновки до розділу ... 60 4 ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ ... 61 4.1 Аналіз і заходи з усунення шкідливих факторів виробництва фарбованого покрівельного прокату ... 61 4.2 Електробезпека на виробництві. Технічні засоби електробезпеки ... 64 4.3 Стійкість виробництва фарбованого металопрокату в умовах дії надзвичайних ситуацій ... 66 4.4 Вимоги щодо улаштування системи електрозабезпечення виробництва у надзвичайних ситуаціях ... 67 ЗАГАЛЬНІ ВИСНОВКИ ... 69 ПЕРЕЛІК ПОСИЛАНЬ ... 71

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Stefopoulos, Georgios Konstantinos. "Quadratic power system modeling and simulation with application to voltage recovery and optimal allocation of VAr support." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29695.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Meliopoulos, A. P. Sakis; Committee Member: Deng, Shijie; Committee Member: Divan, Deepakraj; Committee Member: Harley, Ronald; Committee Member: Taylor, David. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Hudji, Muadh. "Analys av elnät för begränsning av reaktiv effekt." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-396215.

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Ystad Energi har ansvaret över elnätet i Ystads kommun. Med ökande efterfråga om el har samhället blivit sårbart. Därför jobbar myndigheterna och elleverantörer alltid för att säkerställa en trygg och säker elleverans. Variationer i energibehovet under de olika årstider sätter elsystemet i en svår situation gällande elleveranssäkerhet. Ystad Energi har noterat att elnätet matar ut reaktiv effekt mot överliggande nät under sommarperioden. Vilket kan påverka förlusterna och systemets drifttillstånd i både lokal – och regionnät. Därför fokuserar detta arbete på att utföra analyser av reaktiv effekt i nätledningarna som ligger mellan fördelningsstationerna och nätstationerna, d.v.s. i 10.7 kV – nivå av den s.k. distributionsnätet. För att minska elavbrott i systemet på grund av väder och annan yttre påverkan har Ystad Energi grävt ner alla ledningar i nätet. Datainsamlingen från Ystad Energi visar att den reaktiva effektinmatningen ökar mest under sommaren jämfört med andra årstider. Utifrån vetenskapliga teorier och tidigare arbeten anses kablifiering som en viktig orsak till reaktiv effektinmatning i ett elsystem. Datainsamlingen visar även avsevärda variationer i energiförbrukningen mellan vinter- och sommarhalvåret, där energiförbrukningen är mycket lägre under sommaren på grund av klimatet och livsstilen. Därför leder detta till spänningsförhöjning i elnätet som vidare kan leda till kapacitiv reaktiv effektgenerering. I arbetet utförs även analyser på nätet med anslutna produktionsanläggningar såsom vindkraft som kan påverka effektflödet i nätet. Rapporten skall presentera vilka möjliga lösningar som kan vara lämpliga för att minska den reaktiva effekten i nätet. Kraven som ställs från myndigheterna kring reaktiv effekt redovisas även i rapporten.
Ystad Energy is responsible for the power grid in Ystad municipality. With increasing demand for electricity, society has become more vulnerable. Therefore, authorities and electricity suppliers always work to ensure safe and secure electricity supply. Variations in energy demand and climate change put the electrical system in a difficult situation regarding electricity supply safety. Ystad Energy has noted that the power grid has high values of reactive power over a part of year, which may affect the losses and system operating conditions in both local and regional networks. Therefore, this work focuses on performing reactive power analysis in the power cables located between the high voltage substations and the low voltage substations, i.e. in the 10.7 kV level of the distribution network. All overhead lines in Ystad municipality are already buried in the ground to reduce line faults in the system due to weather and other influences. The data collection from Ystad Energy shows that the reactive power input increases most during the summer. Underground cables are considered an important cause that contributes to reactive power input in an electrical system. Data collection also shows significant variations in energy consumption between the winter and summer months, where energy consumption is much lower in the summer due to the climate and human habits. Therefore, this leads to a voltage increase in the mains that can further lead to a capacitive reactive power generation. In the project, an analysis of the power grid has been performed, considering the current grid topology. Simulations of different scenarios with production plants, such as wind power, which can affect the power flow in the network, are also carried out. It was proved that the reactive power in the grid is produced by the underground cables. The report also presents some possible solutions that may be appropriate to reduce the reactive power in the network.

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Silwal, Hari. "MULTISTEP FRAMEWORK FOR SHORT-TERM LOAD FORECASTING USING MACHINE LEARNING ALGORITHM." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2312.

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Traditional forecasting approaches forecast the total system load directly without considering the individual consumer's load. With the introduction of the smart grid, lots of renewable energy resources such as wind and solar are added to the system from consumer side fluctuates the system load and makes forecasting more complex. Thus, it is necessary to forecast individual consumers load. Here, a framework is presented in which individual customer loads is forecasted rather than the system load. At first, a hierarchical cluster analysis is performed to classify daily load patterns into different groups for all the individuals. Then an association analysis is performed to determine critical influential factors that affect the load curve for given day. The next step is the application of a decision tree to establish classification rules between the different groups of the load curve and the critical influential factors. Then, appropriate forecasting models are chosen for different load patterns and the individual load is forecasted. Finally, the forecasted total system load is obtained through an aggregation of an individual load forecasting results. The relative error of forecasting the system load using this framework is compared with the relative errors using SVM regression and this framework had better accuracy. This framework is also used for forecasting the power output of the renewable generation. Also, the results of the day ahead forecast of system load and renewable generation is used for economic power scheduling for the microgrid and peak shaving for the utilities.

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Benedito, Ricardo da Silva. "Análise de um mecanismo de compensação de reativos incorporado aos inversores de um sistema fotovoltaico conectado à rede elétrica." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/106/106131/tde-16122014-000110/.

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No Brasil, quando uma unidade consumidora (UC) sob regime de microgeração ou de minigeração distribuída tem parte ou a totalidade da sua demanda por potência ativa suprida pela planta geradora, mas sua demanda por potência reativa é atendida exclusivamente pela rede elétrica, verifica-se uma aparente deterioração do fator de potência dessa UC, sob a ótica da concessionária. Esse efeito decorre do fato de que o fator de potência, de acordo com a regulamentação vigente, é determinado apenas a partir das medições dos fluxos de potência ativa e reativa trocados entre a UC e a rede elétrica e não também entre a planta geradora e UC. Para consumidores do Grupo A (tensão de fornecimento igual ou superior a 2,3 kV) nessa situação, de acordo com o perfil da carga, pode haver cobrança por excedentes de reativos, constituindo-se assim uma barreira. Especificamente no caso de sistemas fotovoltaicos conectados à rede, existe a possibilidade de se utilizar os próprios inversores c.c.-c.a para suprir a demanda de reativos da UC e, dessa forma, minimizar o problema apresentado. Com o objetivo de se avaliar essa alternativa no contexto brasileiro, tendo-se em vista condições reais de operação e os limites normativos de injeção de potência reativa para inversores de sistemas fotovoltaicos, foi realizado um estudo de caso de uma planta fotovoltaica instalada no telhado do prédio da Administração do Instituto de Energia e Ambiente da Universidade de São Paulo. O estudo mostrou que a compensação realizada por meio do inversor selecionado evitou a cobrança de excedentes de reativos sem afetar de forma significativa a produtividade do sistema fotovoltaico. Do ponto de vista elétrico, verificou-se que a injeção de reativos pelo inversor não provocou variações significativas de tensão no ponto de acoplamento ou no alimentador e, ainda, se verificou considerável liberação de capacidade do sistema supridor da concessionária. Dessa forma, a análise dos resultados indica uma tendência a se considerar a compensação de reativos proporcionada pelo próprio inversor a opção mais viável para se lidar com os excedentes de reativos, comparativamente a métodos convencionais de compensação ou à situação em que nenhuma ação compensatória seja implementada.
In Brazil, when a consumer unit (CU) under a distributed microgeneration or minigeneration scheme has part or all of its demand for active power supplied by the generating plant, but its demand for reactive power is served exclusively by the grid, the power factor of this CU appears deteriorated, from the perspective of the utility. This effect is due to the fact the power factor, according to the current regulations, is determined only from measurements of the flows of active and reactive power exchanged between the UC and the grid and not also between the generating plant and UC. Users of group A (supply voltage equal to or greater than 2.3 kV) in this situation, according to the CU load profile, may be charged due the reactive power excess, thus constituting a barrier. Specifically in the case of grid-connected photovoltaic systems, there is the possibility of using the d.c.- a.c. inverters to suply the CU reactive power demand and, thus, minimizing the presented problem. In order to evaluate this alternative in the Brazilian context, keeping in view real operating conditions and regulatory limits for the reactive power injection for photovoltaic inverters, we conducted a case study with a photovoltaic plant installed on the roof of the University of São Paulo Institute for Energy and Environment administration building. The study showed that the compensation performed by the selected inverter prevented the reactive power excess charging without affecting significantly the photovoltaic system productivity. From an electrical point of view, it was found that the injection of reactive power by the inverter did not cause significant voltage variations at the coupling point or at the transformer and, additionally, there was a significant release in the utility suply system capacity. Thus, the analysis results indicates a tendency to consider the compensation provided by the inverter itself the most viable option for dealing with the surplus of reactive power compared to conventional compensation methods or to the situation in which no compensatory action is implemented.

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Koziel, Sylvie Evelyne. "From data collection to electric grid performance : How can data analytics support asset management decisions for an efficient transition toward smart grids?" Licentiate thesis, KTH, Elektroteknisk teori och konstruktion, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-292323.

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Physical asset management in the electric power sector encompasses the scheduling of the maintenance and replacement of grid components, as well as decisions about investments in new components. Data plays a crucial role in these decisions. The importance of data is increasing with the transformation of the power system and its evolution toward smart grids. This thesis deals with questions related to data management as a way to improve the performance of asset management decisions. Data management is defined as the collection, processing, and storage of data. Here, the focus is on the collection and processing of data. First, the influence of data on the decisions related to assets is explored. In particular, the impacts of data quality on the replacement time of a generic component (a line for example) are quantified using a scenario approach, and failure modeling. In fact, decisions based on data of poor quality are most likely not optimal. In this case, faulty data related to the age of the component leads to a non-optimal scheduling of component replacement. The corresponding costs are calculated for different levels of data quality. A framework has been developed to evaluate the amount of investment needed into data quality improvement, and its profitability. Then, the ways to use available data efficiently are investigated. Especially, the possibility to use machine learning algorithms on real-world datasets is examined. New approaches are developed to use only available data for component ranking and failure prediction, which are two important concepts often used to prioritize components and schedule maintenance and replacement. A large part of the scientific literature assumes that the future of smart grids lies in big data collection, and in developing algorithms to process huge amounts of data. On the contrary, this work contributes to show how automatization and machine learning techniques can actually be used to reduce the need to collect huge amount of data, by using the available data more efficiently. One major challenge is the trade-offs needed between precision of modeling results, and costs of data management.

QC 20210330

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Al-Saedi, Waleed Abood Baddai. "Optimal Control of Power Quality in Microgrids Using Particle Swarm Optimisation." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/611.

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Driven by environmental protection, economic factors, conservation of energy resources, and technical challenges, the microgrid has emerged as an innovative small-scale power generation network. Microgrids consist of a cluster of Distributed Generation units that encompass a portion of an electric power distribution system and may rely on different energy sources. Functionally, the microgrid is required to provide adequate levels and quality of power to meet load demands. The issue of power quality is significant as it directly affects the characteristics of the microgrid’s operation. This problem can be defined as an occurrence of short to long periods of inadequate or unstable power outputs by the microgrid. In a stand-alone operation mode, the system voltage and frequency must be established by the microgrid, otherwise the system will collapse due to the variety in the microgrid component characteristics. The harmonic distortion of the output power waveforms is also a serious problem that often occurs because of the high speed operation of the converter switches. The long transient period is a critical issue that is usually caused by changing the operation mode or the load demand. Power sharing among the Distributed Generation units is also an important matter for sharing the load appropriately, particularly given that some renewable energy resources are not available continuously. In a utility connected microgrid, the reliable power quality mainly depends on the regulation of both active and reactive power, because the microgrid’s behaviour is mostly dominated by the bulk power system. Therefore, an optimal power control strategy is proposed in this thesis to improve the quality of the power supply in a microgrid scenario. This controller comprises an inner current control loop and an outer power control loop based on a synchronous reference frame and conventional PI regulators. The power control loop can operate in two modes: voltage-frequency power control mode and active-reactive power control mode. Particle Swarm Optimisation is an intelligent searching algorithm that is applied here for real-time self-tuning of the power control parameters. The voltage-frequency power controller is proposed for an inverter-based Distributed Generation unit in an autonomous operation mode. The results show satisfactory system voltage and frequency, high dynamic response, and an acceptable harmonic distortion level. The active-reactive power controller is adopted for an inverter-based Distributed Generation unit in a utility operation mode. This controller provides excellent regulation of the active and reactive power, in particular when load power has to be shared equally between the microgrid and utility. The voltage-frequency and active-reactive power control modes are used for a microgrid configured from two DG units in an autonomous operation mode. The proposed control strategy maintains the system voltage and frequency within acceptable limits, and injects sustained output power from one DG unit during a load change. The reliability of the system’s operation is investigated through developing a small-signal dynamic model for the microgrid. The results prove that the system was stable for the given operating point and under the proposed power controller. Consequently, this research reveals that the microgrid can successfully operate as a controllable power generation unit to support the utility, thus reducing the dependency on the bulk power system and increasing the market penetration of the micro-sources.

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Sousa, Thales. "Valoração do fornecimento de serviços ancilares a partir de usinas hidroelétricas." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-07122006-144442/.

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O presente trabalho propõe o desenvolvimento de uma metodologia de valoração da reserva de potência ativa e do suporte de potência reativa a partir de plantas hidroelétricas. Inicialmente foi apresentado um histórico que descreveu o que foi definido e regulamentado sobre estes serviços em diferentes mercados de energia. Em seguida, com o objetivo de valorar o serviço de reserva de potência ativa foi realizada a mensuração da perda de eficiência, resultante do fornecimento deste serviço, que após convertida em MWh foi relacionada à perda de oportunidade, caso essa energia fosse comercializada no mercado de energia. Para a valoração do suporte de potência reativa foi utilizada a teoria de Fluxo de Potência Ótimo com objetivo de minimizar as perdas do sistema e relacionar essa minimização à redução do suporte de potência reativa. Em seguida, foi apresentada uma metodologia de valoração e alocação dos custos do suporte de potência reativa entre as barras responsáveis pela necessidade adicional deste suporte. Foram realizados vários testes para validação e verificação das metodologias propostas.
The present study proposes valuation methodologies for the spinning reserve and for the reactive power support regarding hydroelectric plants. Initially, a revision describing what was defined and regulated on these services in different energy markets is presented. In order to valuate the spinning reserve service, the measurement of efficiency losses stemming from this service supply was done. Thereafter, the efficiency losses were converted into MWh and related to the opportunity loss, in case this energy was commercialized in the energy market. As for the reactive power support valuation, the Optimal Power Flow was used. The objective was to minimize the system losses and relate such a minimization to the reactive power support. Subsequently, methodologies for the reactive power support costs and for the cost allocation among the responsible buses for additional requirement of this support are also presented. Various tests to validate and verify the above mentioned methodologies were carried out.

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Costa, Jean Patric da. "Contribuição ao estudo do gerador de indução duplamente alimentado: operação durante distúrbios na rede elétrica." Universidade Federal de Santa Maria, 2010. http://repositorio.ufsm.br/handle/1/3665.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The Doubly Fed Induction Generator (DFIG) is one of the most frequently deployed large grid connected Wind Turbines (WT) concept. The implementation of classical vector control techniques, have been proven to work well for considering the initial grid code requirements. However, recently many grid operators are requiring WT to remain connected during grid faults, resulting in low voltage fault ride through capability (LVRT). In addition, it is required for WTs to contribute with reactive support during the fault. As a result, the improvements of the transient behavior of the DFIG, the power converter protection and the controller design have become a challenge for WT manufactures. This work presents a high performance stationary frame non-linear controller for doubly fed induction generator, which improves the steady state and transient behavior of the grid connected wind turbines especially under unbalance voltage dips resulting from network unbalance faults. A controller design procedure that guarantees the DFIG stability under uncertainties and disturbances at grid side is presented in details. Furthermore, it is demonstrated in the thesis that with the proposed controller different goals such as control of grid side active and reactive power, minimization of torque pulsation under unbalance operation and improvement of the low voltage ride through capability can be easily achieved. Simulations and experimental results are given to illustrate the good performance of a grid connected DFIG with the proposed controller.
Turbinas eólicas modernas que utilizam o Gerador de Indução Duplamente Alimentado (GIDA) são amplamente empregadas para geração de energia elétrica. Essa grande parcela de aero-geradores baseados na tecnologia GIDA e técnicas de controle vetorial clássicas já comprovaram ao longo dos últimos anos que este conceito apresenta méritos e foi capaz de satisfazer requisitos de conexão de turbinas eólicas com a rede elétrica inicialmente elaborados. No entanto, atualmente, os operadores do sistema estão revisando os códigos de rede em muitos países, introduzindo novos requisitos e estreitando os limites definidos inicialmente. Basicamente, os geradores eólicos estão assumindo maiores responsabilidades no sistema de potência. A capacidade de sobrevivência e suporte de reativos durante afundamentos de tensão, introduzidos nos novos códigos de rede, tornaram-se os maiores desafios para os fabricantes de aero-geradores com tecnologia GIDA. Essa tese de doutorado tem como principal objetivo desenvolver estratégias de controle para melhorar o desempenho dinâmico do Gerador de Indução Duplamente Alimentado conectado a rede elétrica frente aos requisitos de sobrevivência aos afundamentos de tensão no Ponto de Conexão (PC). Para isso, essa tese propõe um controlador não linear de alto desempenho baseado em modos deslizantes para o controle do GIDA em eixos estacionários. O controlador proposto melhora o comportamento transitório do GIDA principalmente durante distúrbios na tensão no PC. O projeto do controlador é desenvolvido de forma a garantir a estabilidade do GIDA conectado à rede elétrica mesmo considerando incertezas associadas ao modelo nominal. Outras características do controlador proposto, além da robustez, são a sua simplicidade de implementação e a sua excelente resposta transitória. Ainda, dois modos de operação são propostos para geração de referência do GIDA, MODO 1 para operação em condições normais da tensão da rede elétrica, MODO 2 com uma metodologia para o cálculo das referências de corrente de forma a dar suporte de reativos durante faltas próximas ao PC. O comportamento dinâmico do sistema e o desempenho da estratégia de controle são verificadas através de simulações e também experimentalmente.

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El, achkar Maria. "Contribution au Dimensionnement et à la Commande d’un Générateur de type Cascade de Machines Asynchrones à Double Alimentation." Thesis, Cergy-Pontoise, 2016. http://www.theses.fr/2016CERG0814/document.

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Le travail présenté dans cette thèse est une contribution au dimensionnement et à la commande d’un générateur de type Cascade de Machines Asynchrones à Double Alimentation. Le modèle de la machine pour les simulations est basé sur une représentation modulaire qui découle du modèle de Park de deux machines asynchrones doublement alimentées distinctes, en respectant deux systèmes de référence. Le modèle dynamique est ensuite étendu pour décrire la machine dans un repère unifié. Cette représentation est cruciale pour le dimensionnement de la machine et la synthèse de la commande. Le domaine de fonctionnement de la cascade en régime permanent est exploré. Une méthode analytique générique est proposée pour établir les plages de puissances active-réactive. Les courbes limites sont définies par rapport aux grandeurs nominales de la machine. L’étude prend en compte l’effet de saturation du circuit magnétique. Il est prouvé que la capacité en puissance de la machine est déterminée par les valeurs maximales des courants statoriques et peut être soumise à plusieurs limitations. L’approche analytique est testée et validée par des mesures expérimentales. Deux cas sont considérés pour la commande de la cascade : un générateur raccordé au réseau et un générateur autonome. Pour la connexion au réseau l’application visée est les éoliennes de grande puissance. Une nouvelle méthode pour l’extraction de la puissance maximale d’une éolienne à vitesse variable est proposée. Le système est contrôlé dans le but de fournir une puissance maximale quasi-constante indépendamment des fluctuations du vent. En plus de l’optimisation de la puissance, le facteur de puissance est également ajusté selon les normes de raccordement standard imposées par les services système, et les limites de fonctionnement de l’unité intégrée. Une commande vectorielle sans capteur de tension, basée sur une orientation suivant un flux virtuel, est appliquée pour la régulation découplée des puissances active et réactive. Pour le fonctionnement en mode isolé, l’application visée est la génération électrique pour système avionique embarqué. Deux réseaux de distribution sont traités : réseau AC à fréquence fixe et réseau DC. Dans les deux cas, la commande est élaborée dans le but de maintenir une tension de sortie constante. Le fonctionnement de la cascade alimentant une charge triphasée déséquilibrée est également étudié. Des schémas de contrôle servant à la compensation du déséquilibre des tensions statoriques sont développés. Deux méthodes de compensation sont proposées : l’une basée sur le principe de deux repères tournants et l’autre sur un correcteur répétitif. Les approches présentées sont validées par simulation avec Matlab/Simulink et par expérimentation
This thesis is a contribution to the power sizing and the control of a Cascaded Doubly Fed Induction Generator (CDFIG). The machine model for simulation is based on a modular representation, derived from the Park model of two distinct Doubly Fed Induction Machines expressed in their own reference frames. The dynamic model of the cascaded machine is then extended to be described in a unified reference frame. This representation is convenient for the sizing of the machine and for the design of the controller. The steady state power operating margins of the cascaded machine are investigated. A generic analytic method is suggested to derive the active-reactive power domain. The limit curves are defined in terms of the rated quantities of the machine. The study takes into account the magnetic circuit saturation effect. It is proven that the power capability of the machine is determined by the stator current maximum values and is subject to several limitations. The analytical approach is tested and validated by experimental measurements. The CDFIG is controlled in grid-connected and standalone operation modes. In grid-connected application, the attention is paid to high power wind generation systems. A new maximum power tracking of a variable speed wind turbine is suggested. The generating plant is carried to provide a quasi-constant maximum power regardless wind fluctuations. In addition to active power optimization the power factor is adjusted according to the grid code requirements and the operating domain of the integrated unit. A virtual flux oriented vector control is applied for the decoupled regulation of active and reactive powers, leading to grid voltage sensorless operation. In standalone operating mode, the study treats in particular the embedded aircraft power system generation. Two distribution networks are considered: constant frequency AC network and DC network. In both cases, the control aims to maintain a constant output voltage. The operation of the CDFIG supplying unbalanced three-phase load is further explored. Control schemes to cope with unbalanced stator voltage conditions are developed. Two compensation methods are elaborated: the first dealing with dual rotating frames and the second is based on repetitive controller. Simulations with Matlab/Simulink software and experiments validate the control approaches

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44

Dallmer-Zerbe, Kilian. "Probabilistische Modellierung dezentraler Energieanlagen und Sekundärtechnik für die Verteilnetzplanung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-227470.

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Der Ausbau dezentraler Energieanlagen wie fotovoltaischen Anlagen beeinflusst die Netzzustände signifikant. Dabei ist unsicher, wo und in welchem Maße deren Ausbau zukünftig erfolgt. Es ist nun an den Netzbetreibern gleichzeitig die aktuellen Herausforderungen zu meistern und die Netzplanung und -regelung für die Zukunft zu aktualisieren. Eine statistische Methode wird entwickelt, die Verteilnetzplanung unter Einsatz von quasi-stationär modellierten ”Smart Grid”-Lösungen wie Blindleistungsreglern und regelbaren Ortsnetztransformatoren ermöglicht. Durch Stichprobenverfahren werden Unsicherheiten wie Ort, Größe und Leistungsprofile der Energieanlagen in das Netzmodell eingebunden. Diese als probabilistischer Lastfluss bekannte Methode wird durch Gütemaße im Bereich geringer Kombination evaluiert. Beispiele probabilistischer Netzplanung werden an Netztopologien präsentiert
Development of distributed energy units such as photovoltaic systems affects grid states significantly. It is uncertain, where and to what extent the development of these units is carried out in the future. It is now up to the distribution system operator to cope with todays grid challenges and to update grid planning and control for the future. A statistical method is developed, which incorporates quasi-stationary modeled ”smart grid” solutions such as reactive power controllers and on-load tap-changers. Uncertainties such as location, size and power profiles of energy systems are integrated into the grid model by sampling. This method is known as probabilistic load flow and is evaluated by quality measures at low combinations. Examples on probabilistic grid planning of different grid topologies are presented

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Alves, Marcos Gutierrez [UNESP]. "Sistema de geração distribuída fotovoltaica com acumulação, controle da injeção de potências ativa e reativa, com capacidade de operação conectada e ilhada." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/151952.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Frente aos novos desafios impostos ao cenário energético mundial, esta tese de doutorado implementa e analisa uma micro-rede de geração distribuída (GD), com acumulação e capacidade de operação conectada ou desconectada da rede de distribuição de energia elétrica (RDEE). A energia é fornecida à RDEE através de seis inversores monofásicos, constituindo uma rede trifásica, sendo três deles com capacidade de operação ilhada e conectada, e outros três com características de fonte de corrente que podem injetar energia de forma controlada, ativa ou reativa, no ponto de conexão comum (PCC). Através do sistema de acumulação com baterias do tipo chumbo-ácido, também é possível que o sistema minimize o consumo de energia da RDEE, mesmo quando não há energia solar, extraindo potência das baterias. Tendo em vista que a quase totalidade dos inversores utilizados em um sistema de GD fornecem somente potência ativa, ou trabalhem com fator de potência fixo, este trabalho também implementa o controle dinâmico de P e Q na micro-rede, atuando como compensador de tensão no PCC e promovendo melhorias na qualidade da energia elétrica. A micro-rede é gerenciada por um programa desenvolvido para o controle de todos os dispositivos essenciais presentes na GD, incluindo controle da carga e descarga do sistema de acumulação, controle dos contatores de conexão de todo o sistema, e controle do firmware dos inversores conectados, permitindo total liberdade de gestão da energia disponível, resultando numa importante ferramenta acadêmica de aprendizagem. Adicionalmente, a planta de GD é monitorada por meio de um programa de aquisição de dados do fluxo de energia elétrica que flui entre a GD e a RDEE, armazenando os dados relevantes em um banco de dados de informações para análises em longo prazo. É apresentada uma revisão bibliográfica para o cenário energético mundial e no Brasil, além das configurações de micro-rede com GD mais utilizadas no setor atualmente. O diagrama geral da micro-rede com GD é exposto, com descrição de cada equipamento e dimensionamento das fontes de energia solar. Finalmente, resultados experimentais e estruturas dos códigos são apresentados e discutidos.
Considering the new challenges imposed in the energetic scenario around the world, this PhD thesis implements and analyzes a micro-grid of Distributed Generation (DG) plant with accumulation and capability of operation connected or islanded from the electric power distribution grid. The system will supply power to the utility grid and local loads through six single-phase inverters, constituting a three-phase system, among which three are with capability to operate in islanded and connected mode, and the other three single-phase inverters with current source characteristic that can inject active or reactive power in a controlled manner at the point of common coupling (PCC). Through the accumulation system with lead-acid batteries technology, it is also possible that the system minimizes the utility grid consumption, though without solar energy. Given that most of the available inverters for DG are designed only to provide active power or to operate with a fixed power factor, this work, in the meantime, implements the dynamic control of the supplied active and reactive power (P and Q) in micro-grid, acting as a voltage compensator at the PCC to improve the quality of electric power. The micro-grid is managed by software designed to control and communicate with all essential devices in DG, including control of charge and discharge of the accumulation system, control of the whole system connection contactors, and the firmware control of grid connected inverters, which allow a wide control over the available energy and provide a significant academic studying platform. In addition, the energy flow between the DG and the utility grid is monitored through a power quality monitoring device, which is capable to send daily reports by email. In this way, a program was developed to store and recover all the relevant data in a database for the long-term analysis, compiling the results for easy interpretation. A literature review is presented for the world energy scenario, with more focus in Brazil, besides the micro-grid configurations with DG most used in the sector currently. This work also shows the general diagram of the micro-grid with DG describing the equipment and dimensioning the solar energy sources. Finally, it demonstrates and discusses experimental results and code structures.

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46

Alves, Marcos Gutierrez. "Sistema de geração distribuída fotovoltaica com acumulação, controle da injeção de potências ativa e reativa, com capacidade de operação conectada e ilhada /." Ilha Solteira, 2017. http://hdl.handle.net/11449/151952.

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Orientador: Carlos Alberto Canesin
Resumo: Frente aos novos desafios impostos ao cenário energético mundial, esta tese de doutorado implementa e analisa uma micro-rede de geração distribuída (GD), com acumulação e capacidade de operação conectada ou desconectada da rede de distribuição de energia elétrica (RDEE). A energia é fornecida à RDEE através de seis inversores monofásicos, constituindo uma rede trifásica, sendo três deles com capacidade de operação ilhada e conectada, e outros três com características de fonte de corrente que podem injetar energia de forma controlada, ativa ou reativa, no ponto de conexão comum (PCC). Através do sistema de acumulação com baterias do tipo chumbo-ácido, também é possível que o sistema minimize o consumo de energia da RDEE, mesmo quando não há energia solar, extraindo potência das baterias. Tendo em vista que a quase totalidade dos inversores utilizados em um sistema de GD fornecem somente potência ativa, ou trabalhem com fator de potência fixo, este trabalho também implementa o controle dinâmico de P e Q na micro-rede, atuando como compensador de tensão no PCC e promovendo melhorias na qualidade da energia elétrica. A micro-rede é gerenciada por um programa desenvolvido para o controle de todos os dispositivos essenciais presentes na GD, incluindo controle da carga e descarga do sistema de acumulação, controle dos contatores de conexão de todo o sistema, e controle do firmware dos inversores conectados, permitindo total liberdade de gestão da energia disponível, resultando numa ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Considering the new challenges imposed in the energetic scenario around the world, this PhD thesis implements and analyzes a micro-grid of Distributed Generation (DG) plant with accumulation and capability of operation connected or islanded from the electric power distribution grid. The system will supply power to the utility grid and local loads through six single-phase inverters, constituting a three-phase system, among which three are with capability to operate in islanded and connected mode, and the other three single-phase inverters with current source characteristic that can inject active or reactive power in a controlled manner at the point of common coupling (PCC). Through the accumulation system with lead-acid batteries technology, it is also possible that the system minimizes the utility grid consumption, though without solar energy. Given that most of the available inverters for DG are designed only to provide active power or to operate with a fixed power factor, this work, in the meantime, implements the dynamic control of the supplied active and reactive power (P and Q) in micro-grid, acting as a voltage compensator at the PCC to improve the quality of electric power. The micro-grid is managed by software designed to control and communicate with all essential devices in DG, including control of charge and discharge of the accumulation system, control of the whole system connection contactors, and the firmware control of grid connected inverters, which allow a wid... (Complete abstract click electronic access below)
Doutor

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47

Möst, Dominik, and Peter Schegner. "Energiewende Sachsen – Aktuelle Herausforderungen und Lösungsansätze: Beiträge der Abschlusskonferenz des ENERSAX-Projektes." Technische Universität Dresden, 2014. https://tud.qucosa.de/id/qucosa%3A28425.

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Die Bundesregierung plant im Rahmen der Energiewende den Anteil von erneuerbaren Energien an der Stromerzeugung in Deutschland von heute rund 25% auf 80% bis zum Jahr 2050 auszubauen. Damit stehen auch dem Stromsektor in Sachsen grundlegende Veränderungen bevor. Derzeit leistet im Freistaat Sachsen die Braunkohle den größten Beitrag zur Elektrizitätsbereitstellung. Mit dem zunehmenden Ausbau an erneuerbaren Energien steigt der Anteil dargebotsabhängiger Energieträger. Daraus resultieren technische und wirtschaftliche Herausforderungen für das bestehende Energiesystem, wie z.B. die künftige Bereitstellung von Systemdienstleistungen. Mit diesen und weiteren Fragestellungen zur Transformation des Elektrizitätssystems haben sich Nachwuchswissenschaftler der TU Dresden in den vergangenen zwei Jahren im Rahmen des vom Europäischen Sozialfonds – ESF geförderten Projekts EnerSAX auseinander gesetzt. Neben der Erstellung einer Potenzialanalyse für Sachsen wurden sowohl technische Fragestellungen,wie z.B. die Auswirkungen der Integration erneuerbarer Energien auf die Übertragungs-, Verteilungs-und Niederspannungsnetze, als auch ökonomische Fragestellung, wie z.B. die künftige Ausgestaltung der Regelenergiemärkte, untersucht. Durch die Zusammenarbeit der Nachwuchsforscher aus den Bereichen der Elektrotechnik und Energiewirtschaft konnten so integrierte Lösungsansätze zur Ausgestaltung einer weitgehend auf erneuerbaren Energien beruhenden Energieversorgung mit dem Fokus auf Sachsen im transnationalen Kontext erarbeitet werden. Die wesentlichen Ergebnisse aus dem Projekt werden in diesem Buch vorgestellt.

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48

Moger, Tukaram. "Reactive Power Planning And Operation of Power Systems with Wind Farms for Voltage Stability Improvement." Thesis, 2015. http://hdl.handle.net/2005/2674.

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In recent years, the electric power industry around the world is changing continuously due to transformation from regulated market structure to deregulated market structure. The main aim of the transformation of electric supply industry under open access environment is to overcome the some of the limitations faced by the vertically integrated system. It is believed that this transformation will bring in new technologies, integration of other sources of energy such as wind, solar, fuel cells, bio-gas, etc., which are self sustainable and competitive, and better choice for the consumers and so on. As a result, several new issues and challenges have emerged. One of the main issues in power systems is to support reactive power for maintaining the system voltage profile with an acceptable margin of security and reliability required for system operation. In this context, the thesis addresses some of the problems related to planning and operation of reactive power in power systems. Studies are mainly focused on steady state operation of grid systems, grid connected wind farms and distribution systems as well. The reactive power support and loss allocation using Y-bus approach is proposed. It computes the reactive power contribution from various reactive sources to meet the reactive load demand and losses. Further, the allocation of reactive power loss to load or sink buses is also computed. Detailed case studies are carried out on 11-bus equivalent system of Indian southern region power grid under different loading conditions and also tested on 259-bus equivalent system of Indian western region power grid. A comparative analysis is also carried out with the proportional sharing principle and one of the circuit based approach in the literature to highlight the features of the proposed approach. A new reactive power loss index is proposed for identification of weak buses in the system. The new index is computed from the proposed Y-bus approach for the system under intact condition as well as some severe contingencies cases. Fuzzy logic approach is used to select the important and severe line contingencies from the contingency list. The validation of weak load buses identification from the proposed reactive power loss index with that from other well known existing methods in the literature such as Q-V sensitivity based modal analysis and continuation power flow method is carried out to demonstrate the effectiveness of the proposed index. Then, a short-term reactive power procurement/optimal reactive power dispatch analysis is also carried out to determine the optimum size of the reactive compensation devices to be placed at the weak buses for reactive compensation performance analysis in the system. The proposed approach is illustrated on a sample 5-bus system, and tested on sample 10-bus equivalent system and 72-bus equivalent system of Indian southern region power grid. A comprehensive power flow analysis of PQ type models for wind turbine generating units is presented. The diﬀerent PQ type models of fixed/semi-variable speed wind turbine generating units are considered for the studies. In addition, the variable speed wind turbine generating units are considered in fixed power factor mode of operation. Based on these models, a comparative analysis is carried out to assess the impact of wind generation on distribution and transmission systems. 27-bus equivalent distribution test system, 93-bus equivalent test system and SR 297-bus equivalent grid connected wind system are considered for the studies. Lastly, reactive power coordination for voltage stability improvement in grid connected wind farms with different types of wind turbine generating units based on fuzzy logic approach is presented. In the proposed approach, the load bus voltage deviation is minimized by changing the reactive power controllers according to their sensitivity using fuzzy set theory. The fixed/semi-variable speed wind turbine generating units are also considered in the studies because of its impact on overall system voltage performance even though they do not support the system for voltage unlike variable speed wind generators. 297-bus equivalent and 417-bus equivalent grid connected wind systems are considered to present the simulation results. A comparative analysis is also carried out with the conventional linear programming based reactive power optimization technique to highlight the features of the proposed approach.

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Huang, Yung-Hao, and 黃勇豪. "Diesel Generator Grid-Connected Digital Controller with Reactive Power Compensation." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/44946607627249342961.

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碩士
國立彰化師範大學
電機工程學系
102
This thesis proposes a diesel generator grid connection digital controller with reactive power compensation. The proposed system is mainly constructed by a digital signal processor dsPIC30F4011, a frequency/phase measurement circuit, a voltage measurement circuit, an active power measurement circuit, a reactive power measurement circuit, an excitation regulators drive circuit, an electronic valve drive circuit and an electromagnetic switch drive circuit to achieve the functions of grid connected, active power control and reactive power compensation. Finally, a prototype is designed and implemented and installed a 15kW diesel generator for testing to verify the feasibility. Experimental results show that the proposed system can really achieves functions of grid connected, active power control and reactive power compensation.

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50

Lin, Chi-Hsiang, and 林吉祥. "Active and Reactive Power Control Strategies for Grid-Connected Microgrid." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/4cj43b.

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碩士
國立臺灣科技大學
電機工程系
105
This thesis investigates the active/reactive power control strategies for a grid-connected microgrid to let the photovoltaic (PV) system more flexible in operation and control through power electronics. It is to refer to the voltage level of the microgrid in the Taiwan Institute of Nuclear Energy Research. The grid-connected microgrid is established by the Matlab/Simulink, which includes PV system, smart inverter, battery energy storage system (BESS) and LCL filter. It is connected to the utility through the distributed transformer. Finally, the results present that the PV array is kept at the maximum power point by the maximum power point trakers. The smart Inverter has active/reactive power control function. The BESS stabilizes DC voltage and absorbs or releases the PV power to promote the power generation efficiency of PV and reliability of system. The LCL Filter effectly reduces the total harmonic distortion of current (ITHD).

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Dissertations / Theses on the topic 'Grid reactive power support'

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