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  • 1.
    Andersson, Carl Fredrik
    University West, Department of Engineering Science.
    50 kVA eller 100 kVA: En teknisk och ekonomisk jämförelse av distributionstransformatorer2010Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Rapporten utreder om distributionstransformatorer med märkeffekten 50 kVA i Vattenfall Eldistribution AB:s elnät kan avskaffas till förmån för märkeffekten 100 kVA. Transformatorer med märkeffekten 50 kVA förekommer vid nedtransformering av spänningen från 22 kV och 11 kV till hushållens huvudspänning 0,4 kV.

    50 kVA-transformatorer skiljer inte särskilt mycket från transformatorer med den högre märkeffekten i fråga om storlek och pris, och de bedöms kunna bytas ut utan större praktiska svårigheter.

    Fördelen med 100 kVA är att de elektriska belastningsförlusterna blir lägre i och med den högre märkeffekten. Dessutom innebär ett byte vissa elkvalitetsförbättringar.

    Nackdelarna med 100 kVA är att de elektriska tomgångsförlusterna är högre och att inköpspriset är högre än för 50 kVA. I övrigt kan kostnaderna likställas för de två alternativen.

    Endast kostnader för aktiva effektförluster berördes i rapporten då de ekonomiska kostnaderna för reaktiva effektförluster kunde försummas för de aktuella transformatorerna.

    För att nå ett svar på frågan om det kan vara lönsamt att avskaffa 50 kVA-transformatorerna studerades fem verkliga fall i Vattenfalls svenska elnät. Dessutom studerades eventuella elkvalitetsvinster med ett byte.

    Svaret blev att inte för något av de fem studerade fallen var det lönsamt med ett byte till 100 kVA-transformator. Rörande elkvalitetsaspekten blev svaret att ett byte visserligen innebär en skillnad men att andra faktorer oftast har större betydelse. Rapportens rekommendation blev att behålla 50 kVA-transformatorn i distributionsnätet. 

  • 2.
    Andersson, Tommy
    et al.
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Lindell, Erik
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Kartläggning av begränsande faktorer vid fellokalisering med pulsekometod på mellanspänningskablar2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    As the medium voltage network cables in Sweden is buried down in the earth, the demand of fault localization expertise increases. To keep downtimes in the network short, the importance of effective fault localization is necessary. This work is aimed to map and visualize limiting factors within fault localization with focus on the TDR -

    Time Domain Reflectometry. This work is a collaboration with Vattenfall Eldistribution AB.

    Problems with fault localization on medium voltage cables with the TDR have been detected. A multiple factors are contributing to this problem. The results of this study show that the cable construction is a significant part in which extent the TDR can be used. The report are also accounting for basic information about construction and types.

    The mapping also illustrates water treeing and how it affects cables in a negative way. Visualization of what causes water treeing and several actions such as triple extrusion, jacket testing and insulation testing is included in the essay. Further information about fault types, cable types, cable generations, instrument types and method types is given. All of them are affecting factors within the area of fault localization.

    Documentation is highly important for a successful fault localization procedure, which is clarified in the report. Besides documentation the cable condition and the influence on it affecting the result of fault localization is stated.

    A number of measuring methods and instruments are available to use when fault localization and testing are occurring. Every instrument has their own advantages and disadvantages. They also have their own respective area of usage. The basic principle of TDR is studied and explained accordingly. The other measuring methods, which are used in fault localization and testing, are shown more generally

  • 3.
    Carlson, Christer
    et al.
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Lundgren, Clas
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Alternativa metoder för att öka strömmar vid fel och förbättra elkvalitet i lågspänningsnät2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this study are rebuilding methods to improve existing low voltage networks (0,4 kV) investigated. The background, causing the need of improvement, is the existence of lines where the trigger condition is not satisfied. Due to the length of the line and its area a problem with power quality is also often present in these lines. The meaning in this context of not satisfying the trigger condition is that intended fuse will not disconnect in prescribed time of 5 seconds when a single phase fault to ground occurs at the line. Why this problem is emerged can depend of load increases by time, thus the fuse size has been increased which causes the demand of a higher fault current to disconnect. In this study a large part of the focus is placed in satisfying the trigger condition and a small part of the focus is placed in improving the power quality.

    The traditional solution to solve above problem is to expand the medium voltage network, closer to the customer, or reinforce the low voltage network, two comparative expensive solutions.

    The studied methods are named alternative as either the methods are less known or entire new which are not fully developed so far. Respective method consists of a device that by design, and chosen point of connection at the line, is considered to afford a gained single phase fault to ground current. Four devices are studied and named

    Isolertransformator (eng. Isolating transformer), Sparkopplad transformator (eng. Auto transformer), Magtech Voltage Booster and Black box. The devices are studied in computer aided simulations with the program PSCAD/EMTDC and the result shows that all devices increase the fault current. The device Isolertransformator affords the highest gain. Further an economic comparison is performed regarding purchase cost and no-load losses, the result is that the devices Sparkopplad transformator and Black box has the lowest costs and losses

  • 4.
    Carse, Eddie
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Garsallawi, Naman
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Wennström-Juslin, Christina
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Förslag till övervakningslösning med värmekameror för Magnetgärdets transformatorstation2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The substation called Magnetgärdet is located in Ludvika, Sweden and it is owned by Västerbergslagens Energi AB. The substation has recently been renovated and is now placed indoors, which reduces the influence of weather on the station. To decrease the need for personal supervision and increase the availability of the station a monitoring solution is needed.

    The purpose of this degree thesis is to examine if it is possible to monitor the condition of critical items in the station with infrared cameras. To determine this, theory on condition monitoring, thermography and thermal imaging cameras has been compiled together with relevant measurements and tests. The results are then discussed to see if a possible solution can be presented. Important criteria for making condition monitoring with infrared cameras possible have also been formulated in this degree thesis.

    The conclusion is that it is possible, but a complicated system is required. The solution we have given is based on different parts interplaying with each other and it should become a powerful monitoring system. It is however uncertain whether infrared cameras are the only and best tools, therefore other tools should be considered. It might be possible to use thermistors with, or instead of infrared cameras.

  • 5.
    Changala, Mayani
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Investigation of power quality in the auxiliary and distribution networks at Kafue Gorge Power Station in Zambia2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Zambia Electrical Supply Company (ZESCO) Limited has partly replaced electrical components from analogue to digital in the auxiliary system at Kafue Gorge Power Station. Later, it was discovered that there was an increase in component breakdowns in the parts of the monitoring system connected to the auxiliary system. The company seeks baseline data for Power Quality to help determine the cause of these frequent breakdowns.

    Unilyser 902 and PQ Secure were used to monitor and analyse the power quality outlook in both the auxiliary and distribution systems. Data was collected on 3 deferent points of the systems. These points were different both in space and electrically and were connected to loads with different electricalcharacteristics. There were inconsistences in the data collection procession such as deferent lengths in times of motoring per point and difficulties in reaching one of the pre-selected points. Furthermore, the monitoring instrument could not be correctly configured because a correct IP address could not be obtained. This led to inconsistencies in data collection such as failure to obtain certain power quality parameter readings. No particular power quality issues could be pin pointed in the system that could be linked to the problem at the station. However, due to the above mentioned challenges in the data collection process, these results were inconclusive for the purpose of the study. The results arrived at cannot serve as baseline data for trouble shooting the system. More concrete and updated monitoring of power quality is needed to draw conclusion about the wellbeing of the system from the power quality point of view.

    In view of the above, it was recommended that permanent power quality monitors are more suitable tools for the purpose as they give more updated data. The updated data can be relied upon and compared with other points monitored at the same time and this gives a more fair understanding of instantaneous and non-repetitive events in the power system

  • 6.
    Chavier, Emmanuel
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Investigations of POSEYE: a photogrammetry position measuring system2005Report (Other (popular science, discussion, etc.))
    Abstract [en]

    In this report, we present a photogrammetric system that can be used during welding operation with a robot. It should be able to give the position and the orientation of the Tool Center Point with a high accuracy (less than 0.5 mm). After a view on the historic of PosEye®, we describe its two different ways of working: using active or passive markers. We then explain one way to improve the accuracy of the sensor by taking in account the distortion of the image due to the projection. This part is followed by investigations on a so-called “flash collar” which permits to fix diodes when we use passive markers. We finish by some tests to have a better idea of the accuracy of the sensor. This accuracy is only available for the position, as it has been realized on a Coordinate Measuring Machine which is only able to give information on its position.

  • 7.
    Ehnberg, Jimmy S.G.
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Autonomous power systems based on renewables: On generation reliability and system control2007Doctoral thesis, comprehensive summary (Other academic)
  • 8.
    Elofsson, Rickard
    et al.
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Karlsson, Anders
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Undersökning av intermittenta och transienta jordfelsfunktioner för reläskydd2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The hurricane Gudrun in 2005 left major damages on the Swedish grid. Therefore new grid regulations concerning downtime were implemented in Sweden. Resulting overhead lines were replaced with underground cables. The first well known effect of underground cables during a fault is the generation of capacitive earth fault current in the grid. The second well known effects are intermittent and transient earth faults in the underground cables. These faults usually occur in cable joints or other insulation defects in cables. It has been found that the recent earth fault protections have problems with detecting intermittent and transient earth fault, this in turn causes disconnection of the power transformer which yields a non-selective disconnection at the distribution system. This work has been carried out at Göteborg Energi Nät AB. The purpose of this work is to study and examine how some of the most common earth fault relays on market detects and manages intermittent and transient earth faults. The study shows that the fault detection became more complex by increased generation of capacitive earth fault currents. The main reason is that the resistive part of the fault current is too small in comparison to the capacitive part. Therefore the Petersen coil compensation calibration is vital in order to minimize the generation of capacitive earth fault currents. The study finds only minor theoretical differences between the intermittent and transient fault detection. One deviation found was in the protection MiCOM P132 which is designed and constructed with an analogue detection circuit in order to enhance the protection functionality. The remaining earth fault relays are designed and constructed with digital technology. The major difference between the digital technique relays is that the sampling rate is different in different models. A well calibrated compensation simplifies fault detection which results in simpler earth fault protection relays meet the detection requirements of the represented company. To achieve accurate results, live tests are highly recommended

  • 9.
    Forsmark, Anders
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Sidemark, Tim
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Anslutning av vindkraft till ett svagt nät i Tidaholm2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    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.

  • 10.
    Fuentes Martinez, Ana
    et al.
    Lunds universitet, Lund, Sverige.
    Kuchcinski, Krzysztof
    Lunds universitet, Lund, Sverige.
    Multifrequency Test and Diagnosis of Analog Circuits Using Constraint Programming and Interval Arithmetic2003Conference paper (Other academic)
    Abstract [en]

    Analog circuits are often specified using non-linear equations, which are difficult to analyze. Therefore, test generation and diagnosis are problematic issues in practice. In this paper we propose a new method for diagnosis of analog circuits that uses combined information from tests at different frequencies. By solving simultaneously the resulting equations (one for each test frequency), we get a reliable method that decreases the number of possible answers to the diagnosis problem. The min-max optimization algorithm that we implemented for non-linear transfer functions gives good average runtime for diagnosis parametric faults.

  • 11.
    Gustafsson, Jonas
    University West, Department of Engineering Science.
    Beredning för nybyggnation av två stycken vindkraftverk i Lyrestad, Mariestad.2011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Detta examensarbete är en beredning för Fortum Distribution AB. Avsikten är att ansluta två stycken nybyggda vindkraftverk till det befintliga elnätet. Samtidigt genomförs en förstärkning av distributionsnätet genom kablifiering (kabelförläggning i mark) samt rasering av det befintliga luftnätet. Platsen för projektet är belägen strax norr om Mariestad.

    Projektet är uppdelat i tre deletapper. Deletapp ett (huvudprojektet) heter Vindkraft Lyrestad – Värlsen. De nybyggda vindkraftverken i huvudprojektet kommer att anslutas till ställverket i Lyrestad.

    Gällande deletapp 2/3, högspänningen 10 kV, kommer matningen till distributionsnätet från en befintlig stolpstation L9083-40054 som står i Ödegården. Stolpstationen som står i Ödegården kommer även att mata fem nya markstationer längs sträckningen. Lågspänningen 0,4 kV kommer idag från stolpstationer som kommer att raseras och ersättas med markstationer.

    Beredning är utförd av Jonas Gustafsson på konsult företaget PSN Kraftkonsult i Vedum.

    Hela projektet omfattar ett 15-tal berörda lågspänningskunder som kommer få sin servis nedgrävd samt en schaktsträcka för högspänningskabel på ca 8 km. Detta är fördelat på sträckningen mellan Lyrestad – Värslen via fem stycken nya markstationer. 

  • 12.
    Gustafsson, Stig
    University West, Department of Engineering Science.
    Driftoptimering av effektkondensatorbatterier och transformatorer på mottagningsstationer2010Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report contains a study of power flows in Uddevalla Energi AB receiving stations and optimization of the operation control of its power capacitor batteries and transformers.

    For the past thirty years, Uddevalla Energi AB has employed power capacitor batteries almost all year around and these need soon to be replaced due to ageing. Uddevalla Energi Elnät AB has a need for new procedures for the operation control of the power capacitor batteries following new regulations introduced by Svenska Kraftnät and Vattenfall AB for reactive power flows on the grid.

    In the study of power capacitor batteries, there has been an investment calculation with three alternative purchase options. Option one is central phase compensation at the receiving station, option two is phase compensation at the receiving station supplemented with phase compensation at subscriber stations and option three is a local phase compensation at subscriber stations. The investment calculation shows that the second option: Central phase compensation supplemented with phase compensation at subscriber stations is the most favourable to implement.

    It has previously been found that, during certain times of the year, there has been a low load on some of the transformers of the receiving stations. It has never been investigated if it is profitable to turn off one of the transformer for the entire, or part of the year.

    In the investigation of the operation control of the transformers at the receiving stations, three alternatives have been considered. One alternative is that one transformer is in idle operation without load, the second alternative is that one transformer is completely turned off. The third alternative is to make no change. The study showed that the preferred alternative is to make no change, because the risks of turning off transformers are greater than the economic gain, that is approximately 101000 SEK.

  • 13.
    Hatefipour, Saeid
    et al.
    University West, Department of Engineering Science, Division of Automation Systems. saeid@termisk.se.
    Ahlberg, Jörgen
    Linköping University.
    Wren, Joakim
    University West, Department of Engineering Science, Division of Automation Systems.
    Runnemalm, Anna
    University West, Department of Engineering Science, Division of Automation Systems.
    Thermal non-destructive testing: modeling, simulation and experiments for improved localization of hidden defects2014In: The 12th International Conference on Quantitative Infrared Thermography, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

    During the last decades, a substantial amount of research and practical work has been conducted on non-destructive testing of materials using thermography. The performed studies elucidate the potential of various types of thermal non-destructive testing (TNDT) for different materials and applications, including various types of defects. This paper presents a method for detecting in-depth defects in metallic materials and a simulation model for the heat transfer in the material. Experiments are performed on a test specimen with artificial defects (flat-bottom holes). The detection method exploits spatiotemporal analysis in order to find deviations from a model of normality, and shows novel results. Thermal modelling is performed in order to have a base-line simulation model enable us to (a) investigate affecting parameters without repeating the experiments and (b) generalize the results and extend their validity to other cases. Results show that there is an acceptable compliance between simulated and measured thermal data. 

  • 14.
    Hedlund, Petter
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Studie av alternativ vid konstruktion av testutrustning för generatorskydd2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna studie utreder alternativ för hur en testutrustning för generatorskydd skulle kunna konstrueras. Den är utförd på uppdrag av Siemens Industrial Turbomachinery, SIT. Målet är att underlätta konfigureringen av generatorskyddet för de konstruktörer som arbetar på SIT samt förebygga fel i provningsfasen som försenar färdigställandet av de turbinanläggningar i vilka generatorskydden skall användas. Testutrustningen behöver vara billig vilket medfört att fokus har legat på att undersöka möjligheten för konstruktion av en egen lösning av signalgenereringen, som är den del av utrustningen som kostar mest.

    Konstruktionen är tänkt att fungera genom användandet av ett styrsystem vars analoga utsignaler förstärks till nivåer passande generatorskyddet. Spänningssignalerna transformeras upp med hjälp av en transformator och strömsignalerna förstärks genom användande av en förstärkarkrets innehållandes transistorer och en operationsförstärkare.

    Kostnaden för konstruktionen är låg jämfört med att köpa in en utrustning motsvarande det reläprovningsinstrument som används i provningsfasen. Det upptäcktes dock att det fanns möjlighet att köpa in ett begagnat reläprovningsinstrument till ett likvärdigt pris. Då detta instrument är av samma fabrikat som det reläprovningsinstrument som används av SIT vid funktionsprovning och dessutom en väl beprövad produkt anses det lämpligare att istället köpa in ett sådant.

  • 15.
    Hermansson, Andreas
    University West, Department of Engineering Science, Division of Computer, Electrical and Surveying Engineering.
    Simulation of line fault locator on HVDC Light electrode line2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this bachelor thesis, cable fault locators are studied for use on the overhead electrode lines in the HVDC (High Voltage Direct Current) Light project Caprivi Link. The cable fault locators studied operates with the principle of travelling waves, where a pulse is sent in the tested conductor. The time difference is measured from the injection moment to the reflection is received. If the propagation speed of the pulse is known the distance to the fault can be calculated. This type of unit is typically referred to as a TDR (Time Domain Reflectometer). The study is performed as a computer simulation where a simplified model of a TDR unit is created and applied to an electrode line model by using PSCAD/EMTDC. Staged faults of open circuit and ground fault types are placed at three distances on the electrode line model, different parameters of the TDR units such as pulse width and pulse amplitude along with its connection to the electrode line are then studied and evaluated. The results of the simulations show that it is possible to detect faults of both open circuit and ground fault types with a suitable TDR unit. Ground faults with high resistance occurring at long distances can be hard to detect due to low reflection amplitudes from the injections. This problem can somewhat be resolved with a function that lets the user compare an old trace of a “healthy” line with the new trace. The study shows that most of the faults can be detected and a distance to the fault can be calculated within an accuracy of ± 250 m. The pulse width of the TDR needs to be at least 10 μs, preferable 20 μs to deliver high enough energy to the fault to create a detectable reflection. The pulse amplitude seams to be of less significance in this simulation, although higher pulse amplitude is likely to be more suitable in a real measurement due to the higher energy delivered to the fault. The Hipotronics TDR 1150 is a unit that fulfil these requirements and should therefore be able to work as a line fault locator on the electrode line.

  • 16.
    Hällsten, Christoffer
    University West, Department of Engineering Science, Division of Computer, Electrical and Surveying Engineering.
    Jordfelssimulering och modell-validering med PSCAD av ett impedansjordat distributionsnät2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis has been carried out at Vattenfall Eldistribution at the department Control and Protection with the objective to design and evaluate a network model for ground fault simulations in PSCAD. The reconversion from overhead lines to underground cables has led to increased capacitances in the distribution network and this places greater demands on the feeder protection unit and network analyzes in order to assure that faulted feeders are disconnected according to regulatory requirements. The aim of this work has been to determine how a network model could be designed for analysis of stationary signal characteristics and evaluate how great accuracy the power system model have compared to real earth fault test results.

    Earth fault simulations are performed with fault resistances of 3 kΩ and 5 kΩ. The power system model have been created to emulate a real impedance grounded network according to the π-model in PSCAD based on system information from Vattenfalls network management program Netbas. Results from the simulations have been compared against results obtained from real earth faults from the physical network with different settings on the central compensation equipment placed between the transformers neutral and ground. Simulations show, despite assumptions and some uncertainty about the actual zero sequence components similar results when fault resistance was 3 kΩ, both when compensation coil are fully tuned and out of tune ± 30 A corresponding to the feeder capacitance. The overall signal sequence conform quite well to the real network but at the same time simulations with 5 kΩ obtains greater deviations when results are represented in percentage. Particularly prominent abnormalities could be identified in the phase angle between zero sequence voltage and zero sequence current.

    An analysis of deviations from the simulations in the digital network model against the real system indicates that the model probably could be further optimized if zero sequence impedances, dc components, and tolerances that occur in the real systems reactive compensation equipment and measuring circuits are taken into account.

  • 17.
    Ivarsson, Johanna
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Improvement of Commutation Failure Prediction in HVDC Classic Links2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis, an evaluation of the existing control system for ABB: s HVDC Classic Links is performed in order to investigate whether a possible improvement to commutation failure prediction is possible and to be recommended.

    The thesis starts with a theoretical approach to the complexity of consequences of increasing the extinction angle (γ) in order to prevent commutation failure in inverter operation, which is later confirmed through using the simulation software PSCAD to evaluate coherence between simulation results and theory.

    Dynamic power studies are performed through simulations in the electromagnetic time domain transient tool PSCAD in order to establish a possible improvement to the existing commutation failure prediction today used in ABB control systems for HVDC applications.

  • 18.
    Johansson, Niklas
    University West, Department of Engineering Science.
    Selektivplaner för Uddevalla Energi Elnät AB:s högspänningsnät.2011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 19.
    Johansson, Tobias
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Modernisering av el- och belysningssystem i en industrifastighet2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis has been carried out in AB Järn & Rörs premises in Lilla Edet, The project was to modernize the electricity and lighting in the premises, and also calculate how much a modernized lighting solution can save in energy. The premises included a metal workshop, garage, hallway, bath and dressing room, staff room, office and a storage room. The project has been carried out in accordance with current regulations, standards and recommendations from the Swedish National Electrical Safety Board and the Swedish work environment authority. The number of power outlets have been increased in all of the rooms to comply with current standards. The Lightning has been changed from 69 luminaries equipped with two 33 W T5 Light Tubes each and a few halogen lamps, to 59 luminaries equipped with LED light tubes of varying power. This change has decreased the amount of power required by the lighting system from 4167 W to 2246 W, which is a decrease of 1921 W or 46%. The electrical blueprints have all been created in the program EasyEl. The placement of the luminaries and the light calculations have all been made in the program DIALux.

  • 20.
    Karlsson, Lars
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Fallstudie i Järbo: En utredning av förutsättningarna för återstart av ett nedlagt småskaligt vattenkraftverk2009Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The prospects of achieving a restart of the two small hydropower plants studied in this report are good. The basic conditions are favourable in the sense that the plans for a restart are well in line with accepted procedures such as established by decisions in the highest courts regarding similar cases. The owner plans to run the operation in essentially the same way it was originally run, a circumstance which has proven to be important when seeking to get restart of discontinued hydropower activities approved. These power plants are small, very small. This means that investment costs has to be minimized if there is to be any chance of achieving an acceptable pay-off time for the investment. Some can't be affected at all, such as the cost for getting connected to the power network. Some, such as those of new tubes, intake bars and electrical wiring and equipment for the plants, can be affected to some extent by carefully choosing the suppliers of the equipment and choosing the most cost-efficient (in most cases synonymous with the simplest but yet functional) solutions. A few components, such as the generator, can possibly be obtained as used equipment, which helps keeping the costs down. Lastly, the potential of saving money by doing as much as possible of the work yourself should not be underestimated.

  • 21.
    Karlsson, Lars
    et al.
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Norbäck, Elin
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Förutsättningar för mikroproduktion med solceller för Byggnad 73 på Innovatum2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis is done at University West in Trollhättan. The purpose of this investigation was to find out the conditions for micro production with solar cells for Building 73 at Innovatum in Trollhättan.

    The technology for a solar cell system and its main components have been investigated and reported. Example of two important components in addition to the solar cell module is the inverter and the AC switch. The inverter serves to convert the voltage to an alternating voltage. The AC switch is important for the ability to disconnect the solar cell from overhead electricity network if necessary.

    There are laws and regulations that may affect a planned building permission. In this case the building belongs to an old industrial area where design issues are important.

    Another item discussed is building-specific conditions. For example, measurement of free roof space, roof pitch, cardinal point and ceiling coverings.

    Subsequently conducted a market research. Two different options for micro production where made.

    One of the proposals is a facility with solar cells at 30kW from the dealer Nordic Solar on racks at an angle of 30°. The proposal includes a package of solar cells modules manufactured by Eopply. The second proposal is a package of solar cells at 100kW from the dealer Svea Solar, for installation directly on the roof with the roof's existing slope. This package has solar cells modules manufactured by CSUN. A big difference besides the effect on solar cells installations is that the Svea Solar has an attachment that does not require drilling for attachment to the roof.

    At first glance, the proposal with solar cells modules of 100kW feels optimally, given the installed power, and that the damage to the roof is minimized. However, there are aspects like snow removal in the winter. These enable the second option with solar cells modules at 30kW mounted on racks will be more appropriate in this comparison

  • 22.
    Keränen, Tommy
    et al.
    University West, Department of Engineering Science.
    Magnusson, Jakob
    University West, Department of Engineering Science.
    Elkvalitetsanalys av VBG Groups maskinhall2010Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Examensarbetet har utförts på uppdrag av NEA Gruppen och är en elkvalitetsanalys av VBG Groups maskinhall. Målet med analysen var att uppvisa elkvaliteten i maskinhallen.

    Perfekt elkvalitet kan definieras som total frånvaro av elektriska störningar. Av elektriska störningar är det framförallt spänningsstörningar, såsom kortvariga spänningsvariationer, spänningsosymmetrier, spänningstransienter och likspänningskomponnenter, som orsakar mest besvär för elnät och anslutna laster. Även övertoner, som kan delas i spännings- och strömövertoner, påverkar elsystem på ett negativt sätt.

    Analysen visar att maskinhallens spänning är stabil. Detta var väntat då kortslutningseffekten är hög jämfört med anläggningens storlek. Det matande nätet kan alltså anses starkt.

    Maskinhallens laster alstrar strömövertoner av framförallt ordningstalen 5 och 7 men eftersom det matande nätet är starkt ger dessa inte upphov till några spänningsövertoner som ligger utanför rekommenderade gränser.

    I maskinhallens ena inmatningspunkt, T1A15, finns ett kondensatorbatteri anslutet för reaktiv effektkompensering. Vid den andra inmatningspunkten, transformatorstation T3, finns idag ingen kompenseringsutrustning. Behovet är inte heller stort då belastningsgraden av T3 idag är under 10%. Man kan dock se att den reaktiva effekten redan nu är lika stor som den aktiva vilket medför att effektfaktorn är ca 0,7 och inom en nära framtid kommer fler laster att anslutas till T3 vilket innebär att ett kondensatorbatteri kan vara en lönsam investering.

    Maskinhallens belysning alstrar strömövertoner av framförallt ordningstal tre. Övertoner av detta ordningstal har egenskapen att de ger upphov till strömmar i neutralledaren, i värsta fall så stora att neutralledaren blir överbelastad. Någon risk för överbelastning av neutralledaren för maskinhallens belysningsgrupp finns dock inte.

    Totalt sett är anläggningens elkvalitet god och inga akuta åtgärder behöver vidtas.

  • 23.
    Larsson, Hans
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Fjärrfrånskiljares inverkan på kundavbrottstiden i Vattenfall Eldistributions lokalnät2009Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    An alternative approach in Vattenfall Eldistribution’s network has evolved from the increased demands on reducing network downtime. Eldistribution are using remote controlled disconnectors / reclosers in Finland to reduce the system average interruption duration index (SAIDI). The initial section of the report includes a study on the source of downtime and SAIDI-statistics in Eldistribution’s network. A comparison with network and the climate in Finland is carried out which indicate different conditions in the two countries. The weather comparison shows that it’s more difficult to use non-insulated overhead-lines in Sweden because of the climate conditions. The result shows a maximum reduction of SAIDI by 36% and a minimum of 17% based on calculations on six example-lines. If all the lines would be possible to build under similar principles it would result in a reduction of Eldistributions SAIDI by approximately 12 % if the 200 worst lines was supplemented with remote controlled disconnectors with a corresponding amount of reduced SAIDI-minutes. Comparisons with cable alternatives show that it’s more cost-effective to invest in remoted controlled disconnectors if the target is a quick and cheap reduction of SAIDI. As a general recommendation the backup powering of a network should be remote controlled and the lines should have at least one outsourced remote controlled disconnector. This will split the line in multiple remote controlled areas, which will reduce disruption time for customers connected to the line. If a line doesn’t have any backup powering it should be investigated whether it’s possible to connect the line to another line to ensure backup-feeding if this is possible to do at acceptable costs. If there are more locations on the line suitable for supplementation of remote controlled disconnectors, those places should be used to get as much reduced SAIDI as possible at a cost-effective level. It's difficult to give a general advice concerning the number of remote controlled disconnectors but the first disconnector is generally more cost-effective than the subsequent ones. Reclosers should be deployed at appropriate locations to be equally costefficient as remoted controlled disconnectors. Examples of such places can be when switching from cable to non-insulated line and before a section where errors often occur.

  • 24.
    Larsson, Lena
    et al.
    University West, Department of Engineering Science, Division of Industrial Engineering and Management, Electrical- and Mechanical Engineering.
    Larsson, Mikaela
    University West, Department of Engineering Science, Division of Industrial Engineering and Management, Electrical- and Mechanical Engineering.
    Wiberg, Caroline
    University West, Department of Engineering Science, Division of Industrial Engineering and Management, Electrical- and Mechanical Engineering.
    Beredning av lokalnät Ängås, Etapp 32018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis concerns a preparation work for TROLK El and Tele AB, commissioned by Ellevio. The preparation work covers field visits, construction maps, power grid calculation, state and contract search. The thesis work has been accomplished in addition to the same stage already being prepared by preparers at the company, which enabled comparison in the final phase of our work with the company's preparation. The purpose of this work is to achieve higher operational reliability and thus replace existing overhead cable with underground cable. This is to reduce the long interruptions in the area, which today is a problem, partly due to the ages of the lines and the salty winds. The current area is located in Ängås, Svanesund in the south eastern part of Orust. The work has been limited to Stage 3, which concerns a total of 43 subscribers and is one of four stages in the area. Today, the power grid consists mostly of overhead lines, both low and medium voltage, 0.4 to 12 kV. The stage consists of four pole-mounted and two ground stations replaced by four seriesatellite- and two ELIT-stations. There are also 12 new cable cabinets. The result of the preparation is that approximately 10.6 km of overhead lines is scheduled to be demolished and approximately 12.8 km of underground cable is being prepared. These cables have been dimensioned to meet the conditions for network calculations. A cost calculation for the preparation has been planned according to Ellevio's internal unit price list. The total final cost of the project amounts to SEK 3.1 million. A preparation binder has been established where all material is available at TROLK El and Tele AB in Uddevalla

  • 25.
    Larsson, Mats
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Holm, Oskar
    University West, Department of Engineering Science, Division of Automation Systems.
    Förstudie gällande konvertering till bränslecellsbaserad elkraftsproduktion på Stena Vision.2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This feasibility study has been carried out onboard Stena Vision and it aims to investigate if a fuel cell conversion of the ships electrical power production plant is technically possible.

    Through studies of the ships construction, as well as laws and regulations regarding ships installations, the authors has constructed a proposal for a new design for the electrical system. The proposal is presented in "bilaga B2".

    The authors also presents a design proposal for a new fuel system, adapted for the new fuel hydrogen. The new fuel system proposal is presented in "bilaga D".

    One of the most important conclusions in this thesis is that a full conversion, including the emergency generator, would demand a law amendment.

  • 26.
    Myrén, Henrik
    et al.
    University West, Department of Engineering Science.
    Svensson, Veronica
    University West, Department of Engineering Science.
    Installation av feldetektorer i Vänersborgs elnät för reducering av samhällskostnader vid störningar2011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Det finns inom Vattenfall Eldistribution AB ett intresse att automatisera felsökning i elnätet. Syftet med detta examensarbete är att utreda möjligheten att utplacera feldetektorer i Vänersborgs centrala elnät. Ett förslag på en optimal placering av feldetektorerna utifrån ett tekniskt och ekonomiskt perspektiv presenteras. Den föreslagna placeringen av feldetektorer bygger på det befintliga signalkabelsystems struktur.

    Signalkabelsystemet för Vänersborgs centralort finns dokumenterat i Vattenfalls

    dokumentationssystem. Samhällskostnader har beräknats och sammanställts för berörda ledningar. I beräkningsmodellen har olika alternativ med utplacerade feldetektorer simulerats. Alternativen utvärderas därefter i relation till felsökningstid, felfrekvens och samhällskostnad. Med framtagen beräkningsmodell erhålls samhällskostnaden för varje ledning, för ett genomsnittligt avbrott. Beräkningsmodellen visar även hur samhällskostnaden reduceras vid alternativa utplaceringar av feldetektorer.

    För det optimala alternativet med utplacerade feldetektorer i Vänersborgs centralort har den reducerade samhällskostnaden ställts i relation till investeringskostnaden. Därefter har den ekonomiska besparingen kunnat fastställas. Det har visat sig enligt detta examensarbete, att det med avseende på samhällskostnader och kundnytta är en bra investering att installera feldetektorer. Med den föreslagna optimala placeringen av feldetektorer, passeras återbetalningstiden för investeringen efter sex till sju år. Det genererar samtidigt en förhöjd kundnytta. Ett minskat antal provinkopplingar medför dessutom att kablar och elapparater inte på samma vis utsätts för höga kortslutningsströmmar, vilket resulterar i en längre livslängd för elnätet. 

  • 27.
    Mård, Mathias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Automation i Distributionsnät2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    As a part of Göteborg Energi’s work towards a smarter electric grid, the company has chosen to investigate the possibilities of automation in their middle voltage grid. In Europe, there are example cases where these technologies already are installed which many articles on the CIRED conference 2011 proved. Netcontrol Oy in Finland has, together with Tekla, created an automated SCADA system that Vattenfall in Finland today uses. The grid mainly consists of 10 kV open loop fed city grid and this automation is mainly designed for this type of grid. The intention of the automation is to when a fault occurs, the automation disconnects the faulted cable in the loop and then reconnects, this in as little time as possible in order to not make customers suffer.There are several different theories about how automation can be implemented, the two main principles are local automation and centralized automation. The local automation is implemented at station level with fault detectors that communicate with each other and thus disconnects a fault in the circuit using logic steps. This is the fastest option and Göteborg Energi has already installed several devices in the grid, which could make this option possible to realize. The other alternative is to let the SCADA do the sectionalizing using information from the indicators in the loop. This poses a problem though when the system becomes more complex. The operational staff might have problems with letting the SCADA make its own decisions and thereby lose control over the events in the grid. What the system could do instead is to make a suggestion on how the operational staff should handle the situation. However, the fault durations in this case will end at its best around 2-5 minutes and this makes the customer suffer for a longer time than the earlier principle.Hence, local automation is recommended, partly because it is today implemented in the grid and also because the fault duration is much shorter. This option can, with today’s technology disconnect a single-phase to ground fault without a power failure, and thus does no customer suffer during the fault. This should be supplemented with some sort of residual current compensation of the earth fault in order to remove the active fault current, thus minimizing the probability of a double earth fault or short circuit. Göteborg Energi should contact the suppliers of these devices and find out what they consider appropriate, and implement the technology in a loop as a pilot project to investigate its function.

  • 28.
    Nilsson, Daniel
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Berg, Sebastian
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Standardisering och modularisering av lågspänningsställverken i ABB:s HVDC-stationer.2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates the possibilities to standardize and modularize the low-voltageswitchgear in ABB’s HVDC-stations. The reason for this is that the customized solutionthey use today take too much engineering and production time to meet the expectedincrease of projects.The report is based on thirteen stations in eight different closed or ongoing projects. Theselection was based on the station size, geographical location, commissioning year andstation type.In order to obtain a correct representation of the loads in the low-voltage switchgear, therelevant station documentation was reviewed and compiled in a database. The data wasthen analyzed to determine the most frequently occurring loads and their characteristics.The thesis shows that it’s possible to standardize some components in the low-voltageswitchgear. However, this report doesn’t take into consideration any possible increase oftotal size and cost. It also shows the most frequent sizes of the circuit breakers for each ofthe common loads.The standard proposition for the common loads was developed to cover all the occurringsizes of the circuit breakers in the stations. For the converter transformers coolingequipment there’s two different cubicles to choose from, while the remaining loads islimited to a single alternative.An alternative solution could be to develop a standard for each occurring station type.However, this would require that the data from a larger number of projects, for all stationtypes, are reviewed and compiled.

  • 29.
    Nilsson, Rikard
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Rekommendationer inför konstruktion av mellanspänningsställverk: ett underhållsperspektiv2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    OKG AB is the owner of the three boiling water reactors Oskarshamn 1, 2 and 3. The nuclear power plant is located in Simpevarp north of Oskarshamn. The thesis has been carried out at Oskarshamn 1 within a project called CEM. Oskarshamn 1 started to produce electricity in 1972 and can today deliver an electrical power of 491 MW.

    The thesis considers maintenance aspects which are to be taken into consideration before planning and construction of the new automatic gas turbine secured switchgears in system 642. The switchgears are the main distribution switchgears within Oskarshamn 1 and are to be replaced because of high age and lack of spare parts.

    In purpose to achieve high availability performance and availability for the switchgears, aspects which improves the reliability, maintainability and maintenance supportability has been specified. Suggestion of new distribution of the loads between the busbars and arrangement of the cubicles has also been carried out and specified.

    The results of the thesis are the specified maintenance aspects which can be used when planning and constructing the switchgears. The most important maintenance aspects are that the equipment has high personnel safety, that there is enough space in the cubicles to perform maintenance and that a complete documentation is delivered together with the equipment. Suggestion of new load distribution between the busbars has been carried out with the help of a technical specification. The suggestion of new arrangement for the switchgears implies that there is enough space in the existing electrical room for the switchgears.

  • 30.
    Pettersson, Mattias
    University West, Department of Engineering Science, Division of Natural Sciences and Electrical and Surveying Engineering.
    Ombyggnation och modernisering av transformatorstation för anslutning av vindkraft2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This bachelor´s thesis is carried out on behalf of Rejlers Ingenjörer in Gothenburg. The work aims to overall present the realization of two station design proposals, including components, functions, financial aspects and plans, in connection with a reconstruction and expansion of a substation. The substation currently has two voltage levels of 40 kV and 10 kV. In connection with the reconstruction, the station is supplemented by a further voltage level of 20 kV, for connection of a number of wind turbines. For the installation to meet basic requirements, the work is performed by sorting and putting together relevant information from applicable regulations, standards and technical guidelines. Further information is obtained through additional information from literature, catalogues, product sheets and verbal contact with the job requestor. In the thesis the two station design proposals are presented in compliance with the aim. The high voltage equipment is dimensioned and presented, and the relay protection functions are identified. In both options, the transformers are located outdoors with a station building that houses 10 kV, 20 kV switchgear, a battery room and a control room. The main difference between the alternatives is that one of the options has an outdoor air insulated 40 kV switchgear, while the second one has a more compact indoor air insulated switchgear. The total estimated cost, including operation and maintenance costs, over a 25-year period is estimated at 22.7 million Swedish kronor for the outdoor option and 22.4 million Swedish kronor for the indoor alternative. The difference in costs is expected to rise to the advantage of the indoor option if social costs during a power failure also are taken into account in the calculation. It is recommended that the substation be built according to the indoor option, since this is considered to provide the best overall economy, safety of operation and protection against unauthorized access.

  • 31.
    Puumala, Johan
    et al.
    University West, Department of Engineering Science, Division of Computer, Electrical and Surveying Engineering.
    Wahrnberg, Magnus
    University West, Department of Engineering Science, Division of Computer, Electrical and Surveying Engineering.
    En jämförelse av SLAAC och DHCPv6 vid tilldelning av IPv6-adresser2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A computer connecting to a network can be assigned an IP address automatically in several ways. In networks that use IPv4 this is accomplished with the Dynamic Host Configuration Protocol (DHCP). In IPv6 networks this can be done with DHCPv6 or Stateless Address Autoconfiguration (SLAAC).

    Because these two methods are different in operation it is interesting to investigate which method is the most effective. In this report we compare DHCPv6 and SLAAC on two different platforms consisting of a PC with Windows 7 and a Raspberry Pi with the Linux distribution Raspbian.

    Specifically we are measuring the time it takes for a computer to receive an IP address and get access to the Internet when connecting to a network. To compare this with the most commonly used IP protocol we also did measurements on DHCP for IPv4.

    Results from testing done in a lab environment show that SLAAC is the more effective of the two methods used and that the PC is considerably faster than the Raspberry Pi for both methods in IPv6. However, both computers show similar results when using DHCP in IPv4.

  • 32.
    Reddy, Damodhar
    et al.
    School of Electrical Engineering, Vellore Institute Technology, Vellore, 632014, India.
    Ramasamy, Sudha
    University West, Department of Engineering Science, Division of Production Systems.
    A back propagation network based MPPT algorithm for grid-tied wind energy system with Vienna Rectifier2019In: International Journal of Renewable Energy Research, ISSN 1309-0127, Vol. 9, no 2, p. 1097-1107Article in journal (Refereed)
    Abstract [en]

    This paper presents a boost type Vienna Rectifier with a back propagation network algorithm for maximum power point tracking (MPPT) from the wind energy system. The preferred control algorithm deals with non-linear problems with improved conversance precision and reduced learning time. In this system, boost type Vienna Rectifier is employed as a machine side converter for single stage energy conversion of AC to DC with the enhanced output voltage and a grid side converter worked for DC to AC conversion. Vienna Rectifier facilitates power flow with high power density, continuous sinusoidal input current, improved power factor and offers low voltage stress across the switches. The proposed system is designed to meet the load power demand of 1kW Active power with the combined contribution of the wind and the main grid. The resulting analysis of the Vienna Rectifier with the aforementioned control algorithm is validated through Matlab-Simulink for variable wind speeds. © 2019, International Journal of Renewable Energy Research.

  • 33.
    Reddy, Damodhar
    et al.
    HITAM, Department of Electrical and Electronics Engineering, Hyderabad, India.
    Ramasamy, Sudha
    University West, Department of Engineering Science, Division of Production Systems.
    Comparative Analysis of P & O and RBFN MPPT Controller Based Three Level SEPIC Topology for 1.2kW Solar PV System2019In: Gazi University Journal of Science, E-ISSN 2147-1762, Vol. 32, no 3, p. 853-869Article in journal (Other academic)
    Abstract [en]

    This paper accords an intelligent controller based 3-level SEPIC configuration for energy transformation in the solar PV system. An artificial intelligence based radial basis function network is engaged as a control algorithm for the maximum power extraction and the converter control can be done based on the duty cycle generated by the controller. In this system, a SEPIC topology is used for high voltage gain with reduced switching losses. In this paper, an RBFN controller based 3-level SEPIC topology is designed for 1.2kW solar PV system over the traditional P & O (Perturb & Observe) control method and the comparative result analysis is done though the simulation output for the corresponding input parameters.

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