Elkvalitet beror på flera olika faktorer, exempelvis kortvarig spänningshöjning, kortvarig spänningssänkning, snabba spänningsvariationer (flimmer), spänningssprång, transienter, övertoner eller spänningsosymmetri. Den vanligaste åtgärden för att förbättra elkvaliteten i ett industrinät med ljusbågsugn och höga nivåer av snabba spänningsvariationer är att använda sig av reaktiv effektkompensering.  Denna studie undersöker snabba spänningsvariationers eventuella påverkan på elektrisk utrustning, både gällande användning och livslängd. Vidare undersöks även elkvaliteten i Sandviks industrinät där elektrisk utrustning upplevs ha blivit defekt tidigt under dess livslängd. Detta för att finna åtgärder som kan förbättra elkvaliteten för industrinätet, där en ljusbågsugn används i produktionen. I studien har mätdata gällande elkvalitet från Sandvik jämförts med mätdata från andra industrier vilket sedan analyserat utifrån gällande elkvalitetsnormer. Data om vilken typ av utrustning som kan ha påverkats och information om hur elnätsföretag upplever industriers påverkan på elkvalitet har samlats in genom intervjuer med personal på Sandvik och Vattenfall. Även tidigare forskning behandlas i denna studie. Resultatet visar att Sandviks elkvalitet påverkas av när ljusbågsugnen körs. Flimmernivån är den elkvalitetsstörning som återkommande överstiger normen vid anslutningspunkten av utrustning som tidigt blivit defekt. Tidigare forskning visar att användandet av utrustning kan påverkas av snabba spänningsvariationer till exempel i form av mindre hastighetsförändringar i motorer. I jämförelsen mellan Sandvik och de andra industriernas mätdata framkommer bland annat att höga flimmernivåer är vanligt förekommande i industrinät med ljusbågsugn. För att åtgärda Sandviks flimmernivåer och förbättra deras elkvalitet kan en reaktiv effektkompensering i form av en STATCOM installeras. Det finns inte forskning i tillräcklig stor grad för att kunna dra säkra slutsatser gällande hur snabba spänningsvariationer påverkar elektrisk utrustnings livslängd. Det finns dock forskning som indikerar att så är fallet. Denna studies insamlade data leder inte heller till några säkra slutsatser gällande detta men tydliggör att nuvarande testprocedurer om utrustnings immunitet mot snabba spänningsvariationer inte går att jämföra med de verkliga förhållandena i ett industrinät. Slutsatsen är även att fler studier i ämnet krävs. / Power quality depends on several different factors, such as voltage sags, voltage dips, voltage fluctuation (flicker), rapid voltage changes, transients, harmonics or voltage asymmetry. To improve the power quality in an industrial network one common mitigation is reactive power compensation.     This study examines the possible effects of voltage fluctuations on electronic equipment, both in terms of use and service life. Furthermore, Sandvik's power quality in their industrial network is also examined, where electronic equipment is perceived to have become defective early in its service life. To improve the power quality the goal is to find suitable mitigation for the arc furnace in the industrial network. In this study, the power quality at Sandvik was compared with the power quality from similar industries and analyzed based on current power quality standards. Through interviews with staff at Sandvik and Vattenfall data was provided regarding which type of equipment that may have been affected and information on how electricity network companies experience the impact from industries on power quality. Previous research is also covered in this study. The result shows that the power quality at Sandvik is affected when the arc furnace is active. The flicker level is the power quality disturbance that repeatedly exceeds the norm at the connection point of equipment that has become defective at an early stage. Previous research shows that the use of equipment can be affected by voltage fluctuations, for example in the form of minor speed changes in motors. The comparison between Sandvik and the similar industries reveals that industrials networks with an arc furnace often is affected by high flicker levels. By installing a reactive power compensator, in form of a STATCOM, the high flicker level of Sandvik’s industrial network can be mitigated. There is not enough research to be able to draw definite conclusions if voltage fluctuation affects the lifespan of electronic equipment. However, there is research that indicates that this is the case. The data collected in this study also do not lead to any definite conclusions regarding this but clarifies that current test procedures on equipment immunity to voltage fluctuations cannot be compared with the actual conditions in an industrial network. The conclusion is also that more studies on the subject are required.

This thesis provides a basic overview of the ancillary services in a transmission system. It summarizes changes regarding the implementation of European directives SOGL and EBGL. It describes in detail a portfolio of non-frequency ancillary services used in the distribution systems. It evaluates the demand of E.ON distribution system potential for those services in particular locations. Practical part is focused on a potential of reactive power management in this distribution area. It evaluates reactive power flow into transmission system and indicates the most critical substations. This thesis also covers analysis of existing resources in this distribution area and assign their possible potential in reactive power management.

This thesis deals with the reactive power compensation, namely the possibility of reactive power compensation in Petrochemie company using a passive power factor correction system instead of synchronous generators, as part of the contract Kompel company. The thesis analyzes problems of definition of power in circuits with sinusoidal and nonsinusoidal voltages and currents. Furthermore, this thesis describes the power factor correction systems used in the low and medium voltage industrial and distribution networks. The last four chapters contain description of the existing state of power plant in Petrochemie company. There are considered the possibility of use of existing power factor correction system owned by company. The new static power factor correction system is suggested and functionality of power factor correction systems is verified through the simulations.

This thesis is focused on issues with transmission of reactive power though the distribution line of E.ON area. The goal is to find out where and in what rate are overflows of reactive power and to project the correctional steps to minimize this overflow. In this solution, there were used data of dispatcher measurement, which were processed by created source code in Matlab. The processing was analyzed for final conclusion. There were discovered shortages in overflow of reactive power in transfer between distribution and transmission line and in unsuitably regulated capacity power factor in Planá power plant and wrong automatic regulation of turns in 440/110kV substation Dasný. The action to minimize overflows of reactive power was projected by decompensation reactor placed in T101 and T102 transformers in substation Tábor.

This work deals with the deployment of distributed power sources into the electric power grid. The nature of these sources causes that the massive integration may experience problems with power quality in the local context, and also overall reliability of supply in the range of interconnected power systems may be endangered. Work is focused on local voltage quality problems with special emphasis on analysis and design of tools (e.g. reactive power compensation units of power plants or dynamic voltage control by transformers 110/22kV) for voltage control in power distribution systems. These tools should be used as a part of uniform concept of voltage control. The proposed concept is involved.

Orientador: Júlio Borges de Souza / Resumo: Este trabalho apresenta uma avaliação dos aspectos da instalação de sistemas de geração distribuída fotovoltaica (GDFV) em unidades consumidoras sujeitas à cobrança de reativos no Brasil. A avaliação dos possíveis impactos técnicos e financeiro é realizada sob o alicerce da legislação e normativas aplicáveis. São abordados os modos de medição, sistema tarifário aplicado à unidade em estudo, bem como um comparativo com outros tipos de unidades consumidoras com geração distribuída (GD). São realizadas projeções de funcionamento em condições definidas, faz-se uso do equacionamento definido pela legislação e normas vigentes. Também é realizado um estudo de caso em uma unidade consumidora real. Como resultado apresentam-se gráficos que ilustram o comportamento da curva de geração fotovoltaica, consumo demandado, consumo medido, bem como o comportamento do fator de potência em unidades com GDFV instalada. Isto viabiliza a aferição de eventuais pontos positivos e negativos da instalação de GD nesse tipo de unidade consumidora. No estudo de caso também são apresentadas, em forma de tabela, os valores e percentuais de economia da unidade, comparando com o período sem GDFV. Por fim, são avaliados os possíveis impactos no tempo de retorno do investimento, contribuições negativas na qualidade de energia do sistema elétrico e apresentadas propostas de soluções para sanar ou atenuar os problemas encontrados. / Abstract: This paper presents an evaluation of the aspects of the installation of photovoltaic distributed generation systems in consumer units subjected to reactive charging in Brazil. The assessment of possible technical and financial impacts is carried out on the basis of applicable legislation and regulations. Measurement modes are addressed, the tariff system applied to the unit studied, a comparison is made with other types of consumer units with distributed generation (DG). Operating projections are carried out under defined conditions, using the equation defined by current legislation and standards. A case study is also performed in a real consumer unit. As a result we present graphs that illustrate the behavior of the photovoltaic generation curve, demanded consumption, measured consumption, as well as the behavior of the power factor in units with installed photovoltaic distributed generation system. This makes it possible to measure any positive and negative points of the installation of DG in this type of consumer unit. In the case study are also presented in table form the values and percentages of economy of the unit, comparing with the period without distributed photovoltaic generation. Finally, the possible impacts on return on investment time, negative contributions on the electric power quality of the electric system are evaluated and proposals of solutions to solve or mitigate the problems are presented. / Mestre

This research work focuses on the reactive power compensation of the permanent magnet synchronous generator (PSG) in wind power plants. PSG feeds a fixed voltage dc grid through a rectifier bridge. In variable speed operation, the PSG will be able to build torque only in small speed range. This is due to the fixed magnet of the PSG. External reactive power compensation provides an attractive solution to overcome this problem. Different reactive power compensation configurations were examined. Statics synchronous series compensation and a shunt passive filter were chosen as a compensation method. Simulation and implementation of small wind power plant were performed. The wind power plant consists of the synchronous generator, inverter, rectifier, coupling transformers and shunt passive filter. The experimental results agree to the proposed theory and simulation results. / Der Schwerpunkt meiner Promotion ist die Blindleistungskompensation bei einem permanenterregten Synchrongenerator. Der Synchrongenerator speist das Gleichsspannungsnetz über ein Gleichrichter. In der Drehzahlvariablen Betriebsverhalten können Nachteile auftreten. Die Folge ist, dass bei konstanter Gleichspannung und fester Erregung durch die Permanenterregung nur ein sehr kleiner Drehzahlbereich mit vernünftiger Drehmomentausbeute bedienbar ist. Ein möglicher Ausweg wäre eine variable Kompensationsspannung. Verschiedene Kompensationsverfahren wurden untersucht. Ein Series Active Filter und ein Shunt Passive-Filter wurden als Blindleistungskompensation gewählt. Im Rahmen meiner Dissertation beschäftige ich mich mit dem Aufbau und der Simulation einer Windkraftanlage. Diese besteht aus einem permanenterregten Synchrongenerator, einem Wechselrichrter, einem Gleichrichter, drei Transformatoren und einem passiven Filter. Das Versuchsergebnis zeigt, dass die Theorie mit der Simulation übereinstimmt.

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.

[pt] O fenômeno de estabilidade de tensão é um problema associado ao fluxo de potência ativa e reativa nas linhas de transmissão. A manifestação mais conhecida do fenômeno é a existência de uma máxima carga que pode ser alimentada pela rede. Outra possibilidade é a existência de uma máxima injeção de potência ativa e reativa fornecida por geradores e compensadores. A curva QV possibilita o cálculo da margem Q, que corresponde à distância entre o caso-base e ponto de fronteira da curva. A margem Q, supostamente, é um índice para avaliação da estabilidade do sistema, determinando uma operação normal quando a inclinação da curva é positiva. O método da matriz D também fornece a relação Q e V de cada barra, avaliando, supostamente, as condições de estabilidade do sistema. Nesta dissertação foi proposta a análise desses dois índices, com o objetivo de explicitar as premissas, similaridades e diferenças das duas maneiras de se calcular a relação VQ. E assim, avaliar e identificar possíveis resultados não coerentes. / [en] The phenomenon of voltage stability is a problem associated with active and reactive power flow in transmission lines. The best-known manifestation of the event is the existence of a maximum load that can be supplied by the grid. Another possibility is the existence of a maximum injection of active and reactive power provided by generators and compensators. The QV curve enables the calculation of the Q margin, which corresponds to the distance between the base case and the curve s inflection point. The Q margin, supposedly, is an index for evaluating the system stability, consisting of normal operation when the slope of the curve is positive. The matrix method D also provides the relation Q and V of each bar evaluating, supposedly, conditions of system stability. In this dissertation, an analysis of these two indices was proposed to clarify the assumptions, similarities, and differences between the two ways of calculating the VQ relation. And so, evaluate and identify possible non-coherent results.

[pt] No novo modelo do Setor Elétrico é essencial desenvolver novas técnicas que estimem valores futuros, a curto e longo-prazos, das potências ativa e reativa. Com base nisso, este trabalho tem por objetivo apresentar uma nova técnica de previsão horária de potência reativa a curto-prazo, por subestação, baseada na linearidade existente entre as potências ativa e reativa. O modelo proposto, denominado de Modelo Híbrido de Previsão de Reativo, é dividido em duas etapas: A primeira etapa é feita uma classificação dos dados através de uma rede neural não supervisionada Mapas Auto-Organizáveis de Kohonen (SOM); A segunda etapa, utiliza-se um modelo de defasagem distribuída auto-regressivo (ADL) com estimação de Mínimos Quadrados Reponderados Iterativamente (IRLS) acoplado a uma correção para autocorrelação serial dos resíduos - Método Iterativo de Cochrane-Orcutt. Este Modelo Híbrido tem como variável dependente a potência reativa, e como variáveis explicativas dados horários de potência ativa e reativa no instante atual e defasadas no tempo. A previsão de potência reativa a curto-prazo é dividida em in sample e em out of sample. A previsão out of sample é aplicada a períodos horários em até um mês à frente. O modelo proposto é aplicado aos dados de uma concessionária específica de Energia Elétrica e os resultados são comparados a um modelo de Regressão Dinâmica convencional e a um modelo de Redes Neurais Artificiais Feedforward de Múltiplas camadas (MLP) com um algoritmo de retropropagação do erro. / [en] The forecasting of reactive and active power is an important tool in the monitoring of an Electrical Energy System. The main purpose of the present work is the development of a new short-term reactive power hourly forecast technique, which can be used at utility or substations levels. The proposed model, named A Hybrid Model for Reactive Forecasting, is divided in two stages. In the first stage, the active and reactive power data are classified by an unsupervised neural network - the Self-Organized Maps of Kohonen (SOM). In the second stage, a Autoregressive Distributed Lags Model (ADL) is used with its parameters estimated by an Iteratively Reweighted Least Square (IRLS). It also includes a correction lag structure for serial autocorrelation of the residuals as used in the Cochrane-Orcutt formulation. The short term reactive power forecasting is divided in in sample and out of sample. The out of sample forecast is applied to hourly periods until one month ahead. The proposed model is applied to real data of one substation and the results are compared with two other approaches, a conventional Dynamic Regression and a Feedforward Multi-layer Perceptron (MLP) Artificial Neural Network model.