This thesis is about reactive power compensation in industrial network. Task is design reactive power compensation devices, so that the power factor, which is main indicator of power quality, was within the limits required by the distributor. This is applied to wholesale customers of electrical energy. Reactive power consumed by appliances increased the current that flows through the network, transmission losses and voltage drop. Reactive power compensation is a measure reducing load current and ohmic losses in a supply line. Given that the compensation is one of the significant cost-saving measures in electric power distribution. Distributor requires electric power consumption with a lagging power factor in the range from 0,95 to 1. Other values of power factor are penalized.

This master’s thesis is focusing on compensation of reactive power, especially on creating demonstrative model of static var compensation unit (SVC). Main topic of thesis is to apply this device for fast balancing dynamic conversions of recieved reactive power. In theoretical part is described suitable method for determination of instantaneous power. Next, there is basic description of all means used for compensation of reactive power and detailed description of the SVC compensator. Practical part includes design of compensation unit and control program in LabVIEW. The pq theory is implemented for detection instantaneous power. The results of validating functionality of compensator are presented in the last part of thesis.

Voltage stability is the ability of a power system to maintain acceptable voltages at all buses under normal and abnormal operating conditions. The scarcity of reactive power or reactive power imbalance is the main reason of voltage instabilities. The energy supply of Germany will be dominated by renewable energy sources (RES) within energy transition actions leading to a decrease in conventional power plants especially in the transmission grid. Since the conventional power plants are still main reactive power sources, key challenge in the future will be the provision of system services such as control of reactive power to maintain voltage stability in the transmission networks. A wide range of technology that is able to provide the required dynamic reactive power compensation is already available. However, in order to find the most effective implementation, it is necessary to investigate and compare these different technologies for a voltage stable grid operation. The main challenge regarding comparative studies that incorporate reactive power compensation devices is the development and the implementation of reliable comparison strategies. This thesis analyses the impact of reactive power on the voltage stability phenomena both in long-term and short-term time frames under various grid situations. Voltage stability margins in the long-term time frame are quantified by gradually increasing the reactive power injection into certain buses until the voltage collapses. Voltage stability in the short-term time frame is assessed by applying grid faults and simulating the time-domain grid response. A transient voltage severity ratio (TVSR) is developed in this thesis as the main comparison metric to evaluate and compare the performance of investigated compensation devices. Additionally, TVSR and other developed comparison metrics in this thesis are used to determine the optimal settings of the controller parameters of compensation devices. As a result, the submitted thesis shows a practical and reliable approach to analyze the performance of different compensation devices under different grid situations.

Rapporten redogör för en solcellsanläggnings generering av reaktiv effekt samt för de växelriktarbaserade kontrollmetoderna P(U), Konstant Q, Konstant Cosφ, Cosφ(P), Q(P) samt Q(U) för reaktiv effektkontroll. Rapporten redogör även för möjligheterna till att utnyttja solcellsanläggningen till reaktiv effektkompensation för spänningsreglering för det lokala elnätet. Rapportens syfte är att specificera en eller flera kontrollmetoder som möter både solcellsanläggningens och det lokala elnätets reglerbehov.Rapporten behandlar relevanta elektriska storheter, ger en kort introduktion till Sveriges elnät, elområden samt metoder för frekvens- och spänningsreglering. Solinstrålningens variation samt vanligt förekommande komponenter i en solcellsanläggning kartläggs och rapporten diskuterar även vilka effekter en hög andel solel kan ha på ett elnät.Utgångspunkt för rapporten är HSBs solcellsanläggning i Strängnäs samt Strängnäs lokalnät. Efter samtal med Strängnäs lokalnät konstateras att elnätet inte är i behov av ökad reglerkapacitet för spänningsreglering, dock visar insamlat data att det finns ett reglerbehov för kapacitiv reaktiv effekt. Enligt insamlat data över HSBs solcellsanläggning konstateras att så även är fallet för solcellsanläggningen.Det är därmed fördelaktigt för både HSBs solcellsanläggning och Strängnäs lokalnät med reaktiv effektkompensation med induktiv reaktiv effekt. Eftersom solcellsanläggningen inte behöver ta hänsyn till lokalnätets spänning kan anläggningen välja att styra genereringen av reaktiv effekt med kontrollmetoderna Konstant Q, Konstant Cosφ, Cosφ(P) samt Q(P). Här har kontrollmetoderna Cosφ(P) samt Q(P) fördelen att genereringen av reaktiv effekt baseras på solcellsanläggningens produktion av aktiv effekt och kan därmed implementeras utan risk för att strypa produktionen av aktiv effekt.

Ce travail est le résultat d'une collaboration entre le laboratoire LAPLACE, la "Seconda Università degli Studi di Napoli" (SUN) et la Société National des Chemins de fer Français SNCF. Le sujet de recherche concerne l'utilisation de dispositifs électroniques de puissance dans les sous stations ferroviaires 25kV/50Hz afin d’améliorer la qualité de l'énergie électrique. Dans le transport ferroviaire, le système d'électrification monophasé 25kV/50Hz est largement diffusé en particulier pour les lignes ferroviaires à grande vitesse. Bien qu'aujourd'hui les systèmes d’alimentation en courant continu soient encore largement utilisés, l'adoption du courant alternatif monophasé offre des avantages économiques pour les infrastructures d'environ 30% en termes d'investissement, d'exploitation et d'entretien. Initialement, compte tenu de la simplicité du circuit, il n'y avait aucune nécessité d'intégrer de l'électronique de puissance dans les sous stations. Toutefois, au cours de la décennie passée, l'intérêt pour ces équipements est apparu car ils peuvent apporter une solution d'optimisation du réseau lorsque le trafic augmente ou lorsqu’une nouvelle sous station est envisagée. Deux principaux types de dispositifs sont installés aujourd'hui sur le réseau ferré français : les compensateurs de puissance réactive et les compensateurs de déséquilibre de tension. Cette thèse présente de nouvelles topologies de compensateurs basées sur le concept d’impédances contrôlées par gradateur MLI. Comparées aux solutions existantes, ces topologies ont des caractéristiques particulièrement intéressantes en termes de pertes dans les semi-conducteurs et de volume des composants réactifs. Le manuscrit contient trois parties principales: La première partie présente le principe de l’électrification en 25kV/50Hz et souligne l’intérêt d’installer des moyens de compensation statique dans les sous stations. Après une description des solutions actuellement utilisées, le concept d’impédance contrôlée par gradateur MLI (CCI : Chopper Controlled Impedance ) est ensuite présenté. La deuxième partie du travail concerne l'utilisation du concept de CCI pour la compensation de puissance réactive. La sous-station SNCF de Revest est considérée comme cas d’étude. Celle-ci est équipée d'un transformateur monophasé de 60MVA dont le primaire est connecté à une ligne de transport 225kV. Deux topologies de compensateur de puissance réactive, basées sur des montages abaisseur ou élévateur de tension sont présentées. Le dimensionnement des gradateurs est effectué sur la base d'une campagne de mesures réalisée à la sous station. Des simulations numériques utilisant des formes d’ondes réelles de courant et de tension sont présentées. Des résultats expérimentaux effectués à la plateforme de test de la SNCF sur un prototype de 1,2MVAR permettent de valider le concept de CCI. La dernière partie du travail concerne le problème du déséquilibre de tension en amont de la sous station. Un circuit de Steinmetz « actif », toujours basée sur des gradateurs MLI, est présenté et étudié. La sous station SNCF d'Evron est alors considérée comme cas étude. Celle-ci comporte un transformateur de 32MVA et est connectée à une ligne de transmission 90kV. Les mesures effectuées sur le site permettent le dimensionnement du compensateur ainsi que l’utilisation des formes d'onde réelles de courant et de tension dans les simulations numériques. Une comparaison avec des solutions classiques basées sur des onduleurs 2 niveaux et 3 niveaux souligne les avantages de la solution proposée. Ainsi, les résultats des calculs et des simulations montrent que l'énergie stockée dans les éléments réactifs est réduite d’un facteur six et que les pertes dans les semi-conducteurs sont réduites de 40%. Des résultats expérimentaux obtenus sur une maquette de 1.5 kVA permettent de valider le principe du circuit de Steinmetz actif. / This work is the result of collaboration between the LAPLACE laboratory, the “Seconda Università degli Studi di Napoli” (SUN) and the French national railways operator SNCF. The research topic treated herein concerns the use of power electronic devices in 25kV/50Hz railways substations to achieve power quality improvements. In railway transportation, single-phase 25kV-50Hz electrification system is widely diffused especially for high-speed railway applications. Although electrified DC systems are still widely applied, the adoption of AC single-phase system offers economical advantages for the infrastructures of about 30% in terms of investment, exploitation and maintenance. In early ages, due to its very simple diagram, there was no necessity to integrate power electronics in substations. However, for the last decade, the interest in power electronic equipments raised since they can provide the solution for network optimization when traffic increases or when a difficulty is foreseen for a substation implementation. Two types of devices are implemented today on the French Railway Network: Reactive Power compensators and Voltage Unbalance compensators. This thesis presents an investigation into new topologies based on the concept of “Chopper Controlled Impedances”(CCI). Compared to existing solutions, the new topologies show interesting features in terms of semi-conductor losses reduction and volume of reactive components. The manuscript is developed through three main parts: Firstly, the French railways system is introduced and the interest in installing power electronic compensators in substations is highlighted. After a brief description of currently used solutions, the CCI concept is presented: the use of Pulse Width Modulated AC Choppers allows achieving structures which behave as variable impedances. In the second part, the use of CCI structures in reactive power compensation is investigated. The SNCF substation of Revest is under study. It is equipped by a 60MVA single phase transformer with the primary side connected to a 225kV transmission line. Based on the step-down or step-up functioning mode of CCIs, two topologies of reactive power compensator are presented. The converter design is developed on the base of a measurement campaign carried out at the substation. Numerical simulations using real current and voltage waveforms are presented. Finally, experimental results carried out at the SNCF test platform on a 1.2MVAR prototype are shown. In the last part, the problem of voltage unbalance is treated. Using the concept of CCI, the feasibility of an active Steinmetz circuit based on AC choppers is explored. As a case study, the substation of Evron is considered. It is a 32MVA substation connected to a 90kV transmission line. Measurements carried out on the substation site allow the compensator design and the possibility to consider real waveforms for current and voltage in numerical simulations. A comparison with classical solution based on two levels VSI and three levels NPC-VSI highlights the advantages of the proposed solution. Calculation and simulation results show that the stored energy in reactive elements is reduced by a factor six whereas the semiconductor losses are 40% lower. Experimental results obtained on a scaled demonstrator (1.5 kVA) validate the principle of the active Steinmetz circuit.

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 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 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.

It is necessary to judge the influences of producers on the electric compounds while creating electrical energy or during the regulation of those existing. These analyses are sorted out by so called studies of connectivity. These calculations analyze the degree of connection of the producer and the standby unit during a break-down. The results of this report are several recommendations for creating such unit and succeeding steps leading to secure the stability and safety of the electric compound operation. The aim of this thesis is to discuss about software for PC solutions for static and dynamic network model, to draft power outlet into a network of generating high voltage, to complete a study of connectivity with respect to all the distortion factor, as increased voltage, inrush current at startup, flicker, harmonic currents, interference ripple, contribution to short-circuit current, reactive power control options, and demands for compensation.