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Rasmussen, Måns, and Gustaf Holte. "Kontroll av inverterad pendel med inlärning." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254831.
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Den inverterade pendeln fäst på en vagn som kan röra sig längs en riktning, även kallad CartPole, anses vara det mest grundläggande exemplet inom reglerteknik och optimering. I denna rapport var målet att försöka lösa detta instabila, olinjära stabiliseringsproblemet med hjälp av maskininlärning, mer specifikt med ett artificiellt neuronnät. I början av varje simulation ändrades vagnens massa samt pendelns massa och längd slumpmässigt. Dessutom undersöktes hur robust modellen var, genom att ta reda på hur långt man kunde ändra CartPole parametrarna utanför de gränser som modellen har tränats för. Detta uppnåddes genom att göra tusentals simuleringar, allt kodat i Python med paket som TFLearn, Tensorflow och gym från openAI. Resultaten visade att det faktiskt är möjligt att kontrollera CartPole-systemet med hjälp av ett neuronnät, samt visade att det är en robust modell som klarar av nya CartPole parametrar som går långt utanför det område som neuronnätet hade tränats för.<br>The inverted pendulum attached to a cart moving in one dimension, also called a CartPole, is considered to be the most fundamental example on control theory and optimization. In this report the goal was to try and solve the unstable, non-linear stabilization problem using machine learning, more specifically using artificial neural networks. Using this to control the CartPole to be able to swing up and stabilize the pendulum where the mass of the cart as well as the mass and length of the pendulum was set randomly at the start of each simulation. Furthermore, to find out how far it is possible to push the artificial neural network outside of the limits of training and still get a stable result. This was accomplished by doing thousands of simulations, coded in Python using packages like TFLearn, Tensorflow and the gym environment from openAI. The results showed that it is in fact possible to control the CartPole system using artificial neural networks, also showing that it is robust against new CartPole parameters going far outside of what the network had been trained for.
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Hellmers, Robin, and Viktor Boström. "Konstruktion och reglering av inverterad pendel." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355380.
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Syftet med projektet är att konstruera en inverterad pendel som sedan med hjälp av reglertekniska metoder ska stabiliseras. De linjära regulatorer som prövats är Proportionell, Integrerande och Deriverande (PID) -regulatorn och Linnear Quadratic Gaussian (LQG) -regulatorn som båda är populära och beprövade i industrin. PID-regulatorn är den absolut mest använda regulatorn medan LQG-regulatorn är mer raffinerad och i vissa avseenden en optimal regulator. Regulatorerna programmerades in i mikrokontrollern Arduino Nano som skickar signaler till en motordrivare som styr den stegmotor som ska balansera pendeln. Mycket av arbetet har handlat om att skapa en uppställning som tillåter goda förutsättningar för att pröva regulatorerna. I uppställningen finns delar som utformats i Computor-Aided design (CAD) -verktyget OpenSCAD och skrivits ut på en 3D-skrivare. Den givare vi använt för att mäta pendelns vinkel är en potentiometer infäst i dessa 3D-utskrivna delar. Motorn kunde styras till sin maximala kapacitet och en uppställning har skapats. Dock skulle en starkare motor och en mer robust uppställning möjliggöra en avsevärt bättre reglering. Regulatorerna klarade inte av att stabilisera systemet mer än ett fåtal sekunder, detta bland annat pågrund av tidsbrist till att justera regleringsvariablerna.
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Clauson, Carl, and Malte Sloma. "Simulering av inverterad pendel med analytisk mekanik." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-255691.
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Analytisk mekanik är ett alternativ till klassisk (Newtonsk) mekanik för att beräkna rörelsen av partiklar och system av partiklar. I den här rapporten analyserar vi tre olika mekaniska system med analytisk mekanik. Vi implementerar sedan detta i den maple-baserade programvaran "Sophia" för att ytterligare analysera hur ändringar av vissa parametrar förändrar systemets beteende. Ett av våra huvudsyften med den här rapporten är att studera stabiliteten hos en inverterad pendel. År 1951 fann den ryska fysikern Pyotr Kapitza att pendeln kunde stabiliseras i dess upp-och-ner-läge genom att tvinga den till en snabb vertikal svängning. Vi studerar gränserna för denna stabilitet och undersöker om pendeln istället kan stabiliseras genom en elliptisk svängning.<br>Analytical mechanics is an alternative to Classical (Newtonian) mechanics for calculating the movement of particles and systems of particles. In this paper we analyze three different mechanical systems using analytical mechanics. We then implement this into the maple based software "Sophia" to further analyze how changing some of the parameters alter the behavior of the system. One of our main focuses in the report is studying the stability of an inverted pendulum. In 1951 the Russian physicist Pyotr Kapitza, figured out that the pendulum could be stabilized in the upside-down position by forcing it into a rapid vertical oscillation. We examine the boundaries of this stability and explore if the pendulum can instead be stabilized using an elliptical oscillation
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Darth, Johan, John-Eric Eriksson, Ludwig Lindebratt, Zebastian Lovén, and Joakim Trobeck. "Konstruktion av en självbalanserande inverterad pendel-robot." Thesis, KTH, Maskinkonstruktion (Inst.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-184182.
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Som en del av kandidatexamensarbetet i mekatronik har ett projekt med syfte att utveckla och tillverka en självbalanserad robot genomförts. Projektet löpte under perioden 28/03/2012 -15/05/2012 och utfördes av fem teknologer på Kungliga Tekniska Högskolan, Stockholm. Tidigare under kandidatexamensarbetet fördjupade sig samtliga gruppmedlemmar i varsitt mekatroniskt område: töjningsgivare, accelerometer, MP3, likströmsmotor och RFID. I detta projekt ingick följande delsystem: Gyro- och accelerometer, Bluetooth, likströmsmotor, fotoresistor, rotationsenkoder, motorstyrning i form av h-bryggor, Logiken behandlades av en mikroprocessor av modell Atmega16 från tillverkaren Atmel. Den färdiga produkten har tagits fram utifrån egenskaperna att ha två hjul i bredd, likt en Segway, med en kropp som går upp dem emellan. Den aktiva balanseringen styrs av en mikroprocessor som matas med en vinkel ortogonal mot horisontalplanet. En vinkel framställs med hjälp av en gyrometer och en accelerometer.<br>As part of a Degree Project in mechatronics a self-balanced robot was developed and manufactured. The project ran for the period 28.03.2012 - 05.15.2012 and was performed by five students at the Royal Institute of Technology, Stockholm. The project includes the following subsystems: gyro- and accelerometer, Bluetooth communication, DC motors, phototransistor, encoders and motor control using H-bridges. The finished product has been developed based on properties of having two wheels side by side, like a Segway, with a body that goes in between them. The active balancing was controlled by a microprocessor fed by an angle orthogonal to the ground plane. The angle was calculated using the Kalman filter algorithm.
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Carlsson, Ulla. "A general interface for computer control in real time." Thesis, University West, Department of Technology, Mathematics and Computer Science, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-388.
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Ali, ZAKI. "Självbalansering av MinSeg." Thesis, Högskolan i Gävle, Elektronik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-29910.
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Gustavsson, Martin, and Viktor Frimodig. "Virtual Prototyping and Physical Validation of an Inverted Pendulum : "Sea-Calf Bot"." Thesis, Högskolan i Halmstad, Akademin för informationsteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-27946.
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The work is motivated by the goal of linking reality and model, and to see if there is an opportunity to develop an inexpensive educational tool for training in cyber-physical systems. This project has investigated the possibilities to build a cheap inverted pendulum with controller and connect this with the modeling language Acumen. Acumen models is used for comparison with the actual prototype. To solve these problems has a 3D printer been used to create hardware, Arduino UNO for control and Raspberry Pi for enable communication with Acumen over WLAN. The result was a cheap inverted pendulum, which can be built for a cost around 750 SEK. Graphs created in Acumen and from data collected from sensors can be analyzed. With a model of the inverted pendulum system, the results show that Acumen can be used in the development of cyber-physical systems. There are differences between model and reality but also similarities.<br>Arbetet motiveras av målet att knyta samman verklighet och modell, samt att se om det finns möjlighet att utveckla ett billigt utbildningsverktyg för utbildning i cyberfysiska system. Detta projekt har undersökt möjligheter att bygga en billig inverterad pendel med regulator samt koppla samman denna med modelleringsspråket Acumen. I Acumen skapa en modell av systemet och jämföra den med en fysisk prototyp. För att lösa dessa problem har en 3D skrivare använts för att skapa hårdvara. Arduino UNO för styrning och Raspberry Pi för att möjligöra kommunikation med Acumen över WLAN. Resultatet blev en billig inverterad pendel, som kan byggas för en kostnad runt 750 kr. Grafer från Acumen, och från data samlad från sensorer kan analyseras. Med en modell av en inverterad pendel visar resultaten att Acumen kan användas i utveckling av cyberfysiska system. Skillnader finns mellan modell och verklighet men även likheter.
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Reimers, Axel, and Isak Gustafsson. "Indexing and Search Algorithmsfor Web shops :." Thesis, KTH, Data- och elektroteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-193373.
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Web shops today needs to be more and more responsive, where one part of this responsivenessis fast product searches. One way of getting faster searches are by searching against anindex instead of directly against a database. Network Expertise Sweden AB (Net Exp) wants to explore different methods of implementingan index in their future web shop, building upon the open-source web shop platformSmartStore.NET. Since SmartStore.NET does all of its searches directly against itsdatabase, it will not scale well and will wear more on the database. The aim was thereforeto find different solutions to offload the database by using an index instead. A prototype that retrieved products from a database and made them searchable through anindex was developed, evaluated and implemented. The prototype indexed the data with aninverted index algorithm, and was made searchable with a search algorithm that mixed typeboolean queries with normal queries.<br>Webbutiker idag behöver vara mer och mer responsiva, en del av denna responsivitet ärsnabb produkt sökningar. Ett sätt att skaffa snabbare sökningar är genom att söka mot ettindex istället för att söka direkt mot en databas. Network Expertise Sweden AB vill utforska olika metoder för att implementera ett index ideras framtida webbutik, byggt ovanpå SmartStore.NET som är öppen käll-kod. Då Smart-Store.NET gör alla av sina sökningar direkt mot sin databas, kommer den inte att skala braoch kommer slita mer på databasen. Målsättningen var därför att hitta olika lösningar somavlastar databasen genom att använda ett index istället. En prototyp som hämtade produkter från en databas och gjorde dom sökbara genom ettindex var utvecklad, utvärderad och implementerad. Prototypen indexerade datan med eninverterad indexerings algoritm, och gjordes sökbara med en sök algoritm som blandar booleskafrågor med normala frågor.<br><p></p><p></p><p></p>
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Klisjina, Polina. "Finns det ett samband mellan andel topikaliseringar i elevtexter och betyg? : En kvantitativ textlingvistisk undersökning av nationella provtexter från grundskolans årskurs 9." Thesis, Uppsala universitet, Institutionen för nordiska språk, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-323813.
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Inverterad ordföljd i svenskan upplevs ofta som svår och kan ta lång tid att lära sig för andraspråksinlärare. Problem med ordföljden kan påverka inlärares tal och texter negativt och orsaka missförstånd i kommunikationen. Syftet med denna studie är att undersöka hur ofta och hur korrekt elever som läser svenska som andra språk i årskurs 9 använder inverterad ordföljd vid topikaliseringar i påstående huvudsatser i skrift och se om det finns ett samband mellan elevtexternas betyg och andel korrekta påstående huvudsatser med inverterad ordföljd i dessa texter. Materialet består av fyrtio nationella provtexter från år 2013 skrivna av elever som läser svenska och svenska som andra språk. Metoden är en kvantitativ analys av elevtexter. Resultatet tyder på att det inte finns något tydligt samband mellan andelen korrekta användningar av inverterad ordföljd vid topikaliseringar i påstående huvudsatser och betyg. Slutsatsen är att betyg påverkas av många olika faktorer och korrekta användningar av inverterad ordföljd vid topikaliseringar i påstående huvudsatser är inte den avgörande faktorn för elevtexters betyg.
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JOHNSSON, ALEXANDER, and TAGE RÅHLÉN. "Inverted Pendulum Stability Regarding Bandwidth and Center of Mas." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279825.
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This bachelor thesis at the Royal Institute of Technology in Stockholm, Sweden, aims to clarify how the minimum bandwidth of a stabilised mobile inverted pendulum is affected by the position of its center of mass and the frequency of measuring the state variables. The scope is to apply basic theories in automation control and electronic systems when designing the system. The mechatronical system in the experimental trials is constructed with the main components consisting of bipolar stepper motors, stepper motor drivers (DRV8825), potentiometer and Arduino UNO. The mobile pendulum in question consists of a cart on a rail with a potentiomoter and a rod mounted to it. In the experimental trials in this paper, three different radial positions of the center of mass are analysed with regards to the bandwidth of relevant measurements. A variety of PID parameters, for both the angle and position regulation, are the essential basis on which these stability trials are performed. The results are limited to the resolution of the potentiometer outputs, the length of the rail and the stiffness of the rod. The result is presented by comparisons between data of the greatest angles which are stabilised and the corresponding maximal latency of the angle corrections. These data concludes to that the minimum required bandwidth to sustain stability decreases for an increasing length between the center of mass and the point of rotation.<br>Denna kandidatexamensuppsats genomfördes på Kungliga Tekniska Högskolan, i Stockholm, Sverige, och har som mål att klargöra hur den minsta bandbredden för en stabiliserad inverterad pendel påverkas av positionen av dess tyngdpunkt samt nätfrekvensen av tillståndsvariablerna. Projektet omfattar grundläggande teorier om reglerteknik och elektriska system. Det mekatroniska systemet som används i experimenten är uppbyggt av följande nyckelkomponenter: bipolära stegmotorer, stegmotordrivare (DRV8825), potentionmeter och Arduino UNO. Den mobila pendeln består av en stång och en potentiometer som är monterad på en vagn löpandes på en räls. I de utförda experimenten i denna rapport analyseras tre radiella positioner på masscentrum med hänsyn till bandbredden och relevanta mätningar. En reglering med olika PID parametrar, för både vinkel- och positionsreglering, är den kritiska process som lade grunden för analyserna av stabiliteten. Resultaten är begränsade av upplösningen hos potentiometerns utsignal, längden av rälsen och stångens styvhet. Resultaten presenteras genom jämförelser mellan data för de största vinklarna som stabiliseras och de motsvarande maximala fördröjningarna. Sammanfattningsvis minskar den minst nödvändiga bandbredden för att upprätthålla stabilitet för ökande längder mellan pendelns tyngdpunkt och rotationspunkten.
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Klasson, Svensson Emil, and Anton Persson. "En statistisk analys av islastens effekt på en dammkonstruktion." Thesis, Linköpings universitet, Statistik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129963.
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En damm används i huvudsak för att magasinera vatten i energiutvinningssyfte. Dammen rör sig fram och tillbaka i ett säsongsmönster mestadels beroende på skillnader i utomhustemperatur och vattentemperaturen i magasinet. Det nordiska klimatet innebär risk för isläggning i magasinet, för vilken lasten är relativt outforskad. Denna rapport syftar till ett med multipla linjära regressionsmodeller samt dynamiska regressionsmodeller avgöra vilka variabler som förklarar en specifik svensk dammkonstruktions rörelse. Dammens rörelse mäts genom att mäta dammens förflyttning kontra berggrunden med data från dammens inverterade pendlar. Av särskilt intresse är att avgöra islastens påverkan på rörelsen. Resultaten visar att multipla linjära regressions-modeller inte fullständigt lyckas modellera dammens rörelse, då de har problem med autokorrelerade residualer. Detta hanteras med hjälp av autoregressiva regressionsmodeller där de initiala förklarande variablerna inkluderas, kallat dynamisk regression. Denna rapports resultat visar att de autoregressiva parametrarna fungerar mycket väl för att förklara pendlarna, men att även tid, temperatur, det hydrostatiska trycket samt istjocklek är användbara förklarande variabler. Istjockleken visar signifikant påverkan på 5 % signifikansnivå på två av de undersökta pendlarna, vilket är ett noterbart resultat. Författarna menar att rapportens resultat indikerar att det finns anledning att fortsätta forska kring islastens påverkan på dammkonstruktioner.<br>A dam is a structure mainly used for storing water and generating electricity. The structure of a dam moves in a season-based pattern, mainly because of the difference in temperature between the air on outside of the dam and the water on the inside. Due to the Nordic climate, occurrences of icing on the water in the basin is fairly frequent. The effects of ice on the structural load of the dam are relatively unexplored and are the subject to this bachelor’s thesis. The goal of this project is to evaluate which predictors are significant to the movement of the dam with multiple linear regression models and dynamic regressions. The movement is measured by inverted pendulums that register the dam’s movement compared to the foundation. It is of particular interest to determine if the ice load influences the movement of the dam. The multiple regression models used to explain the dam’s movement were all discarded due to autocorrelation in the residuals. This falsifies the models, since autocorrelation means that they don’t meet the needed assumptions. To counteract the autocorrelation, dynamic models with autoregressive terms were fitted. These models showed no problem with autocorrelation. The result from the dynamic models were successful and managed to significantly explain the movement of the dam. The autoregressive terms proved to be efficient explanatory variables. The dynamic regression models also show that the time, temperature, hydrostatic pressure and ice thickness variables are also useful explanatory variables. The ice thickness shows a significant effect at the 5 % significance level on two of the investigated pendulums. The report's results indicate that there is reason to continue research on the ice load impact on dam constructions.
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Haraldsson, Jonathan, Julia Nordin, and Johanna Blomstedt. "Expressive Arduino Controlled Self-Balancing Robot." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-298757.
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A robot capable of balancing itself on two wheels has been built and programmed. While balancing, the robot keeps within a limited area. The robot has a face with two eyes and a mouth, consisting of LED-matrices, which switch between six different facial expressions. The robot is programmed using Arduino boards, one of which implements PID regulators to control the motors.
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Mansfield, Keith. "COMPARISON OF SINGLE STAGE AND TWO STAGE STAGE GRID-TIE INVERTERS." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2730.
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This thesis compares two methods of designing grid-tie inverters. The first design topology is a traditional two stage approach consisting of an isolated DC-DC converter on the input followed by a high switching frequency SPWM (Sinusoidal Pulse Width Modulation) stage to produce the required low frequency sine wave output. The novel second design approach employs a similar DC-DC input stage capable of being modulated to provide a rectified sine wave output voltage/current waveform. This stage is followed by a simple low frequency switched Unfolding Stage to recreate the required sine wave output. Both of the above designs have advantages and disadvantages depending on operating parameters. The following work will compare the Unfolding Output Stage and the SPWM Output Stage at various power levels and power densities. Input stage topologies are similarly examined in order to determine the best design approach for each output stage under consideration.<br>M.S.E.E.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering MSEE
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Rydving, Martin. "Kunskapspalatset : Ett vuxengymnasium i norra Fatbursparken." Thesis, KTH, Arkitektur, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-208364.
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Tänk, en plats, ett palats för kunskap. En byggnad gjord för lärande, förståelse och insikt: Kunskapspalatset! Kunskapspalatset är först och främst ett vuxengymnasium där man läser in kurser från grundskolan eller gymnasiet. Parallellt är det en byggnad för konferenser, mässor, möten, föreläsningar och annan kunskapsspridning. Jag tog utgångspunkt i Rafaels Skolan i Aten som inspiration, där kunskapen finns som i luften. Kunskapspalatset är ett försök på att i nutiden skapa en realitet av den bilden. Byggnaden ger plats åt och släpper in parken utanför, och är inspirerad av en kombination av antik arkitektur och postmodernism. För att anknyta till det antika har jag också haft i åtanke Vitruvius grundelement för arkitektur: firmitas (kvalitet/hållbarhet), utilitas (användbarhet/funktion) och venustas (det vackra/skönhet), som tillsammans skapar en välfungerande helhet. Av olika arkitektoniska stilar är det den antika, med de klassiska kolonnerna, som kanske mest associeras med värdighet och stolthet, något som vuxenutbildning förtjänar mer av. Genom att leka med arkitektoniska traditioner med ett eftertänksamt förhållande till platsen skapas en byggnad som både sticker fram näsan och ger utrymme, och kombinationen av det antika och klassiska med det postmoderna och nyskapande blir en självklarhet. Folkflödet längs det centrala stråket genom parken mellan de två noderna Medborgarplatsen i öst och Södra Station i väst hälsas nu av Kunskapspalatsets front av vad jag har kallat för ”inverterade pelare”. Byggnaden är avlång, ren, helgjuten, utan utstickande delar. En byggnad som triggar tänkande. Vuxenutbildningen står där med stolthet och dignitet i hjärtat av Södermalm. Tänk om man kunde stiga in i Kunskapspalatset ...<br>Imagine, a place, a palace, made for knowledge. A building made for learning, understanding and insight. A Palace of Knowledge! The Palace of Knowledge is a building for adult education, for grown-ups taking up courses from ordinary school. It is at the same time a building for conferences, trade fairs, events, meetings, lectures and other means of the growth of knowledge. As an outset for the project I took inspiration from Rafael’s School of Athens, where knowledge is to be felt in the air. The Palace of Knowledge is an attempt to, in present time, make it a reality. The building lets the park outside in while at the same time giving it room. It is inspired by a combination of antique architecture and postmodernism. In order to link to the antique, I have had in mind Vitruvius’ elements of architecture: firmitas (strength) utilitas (utility) venustas (beauty), that together form a unified whole. Among the variety of architectural styles, it is the antique, with its classical columns, that perhaps is most readily associated with dignity and pride—something that adult education deserves more of. Through a playfulness with architectural traditions and a thoughtful relationship with its context, a building is formed that makes a bold mark while simultaneously giving room, and the combination of the antique and classical with the postmodern and original is thereby given. The constant flow of people along the central path through the park between the two nodes Medborgarplatsen in the east and Södra Station in the west is now greeted by the Palace of Knowledge and its front with what I have termed “inverted pillars”. The building is clean, as if cast in one piece, without protruding parts. A building that triggers thinking. Adult education is now standing with pride and dignity in the heart of Södermalm. If only one could step inside the Palace of Knowledge ...
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Mattsson, Malin. "Flipped classroom i matematik i gymnasieskolan : Studie av en gymnasieklass som undervisats enligt olika undervisningsupplägg i matematikkurserna Ma 1c, Ma 2c respektive Ma 3c." Thesis, Karlstads universitet, Fakulteten för humaniora och samhällsvetenskap (from 2013), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-28741.
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I föreliggande studie undersöks hur ett undervisningsupplägg baserat på flipped classroom påverkar resultatet i en matematikklass på det naturvetenskapliga programmet, samt hur eleverna förhåller sig till ett sådant undervisningsupplägg. Klassen undervisades av samma lärare, men med olika undervisningsupplägg, i tre olika matematikkurser: Traditionell undervisning med klassrumsbaserade genomgångar i Ma 1c; inverterad undervisning i Ma 2c där eleverna före lektionstillfället tog del av en videogenomgång, för att frigöra tid för uppgiftslösning i klassrummet; inverterad undervisning i Ma 3c med tillägget att man i klassrummet använde sig av undervisningsverktyget peer instruction. En enkät gjordes angående elevernas attityder till de olika undervisningsuppläggen. Vidare gjordes en jämförelse av klassens resultat på de nationella proven med resultaten i riket, samt med resultaten för en elevgrupp som undervisats traditionellt. Enkätsvaren visar att eleverna var mycket nöjda med flipped classroom, och att majoriteten ansåg att de lärde sig mer med flipped-classroom-baserad undervisning än med traditionell undervisning. Detta gäller elever på alla betygsnivåer; elever med såväl som utan tillgång till matematikhjälp hemma; pojkar såväl flickor. Elevernas inställning till peer instruction var mera splittrad. Jämförelsen av resultat på de nationella proven visar en tydlig nedgång i elevernas prestation mellan Ma 1c och Ma 3c. Den största delen av nedgången skedde mellan Ma 1c och Ma 2c, dvs. då undervisning baserad på flipped classroom infördes. Denna nedgång skulle givetvis kunna ha andra orsaker än att flipped classroom införts i undervisningen. Slutsatsen att flipped classroom, såsom det implementerats i klassen, inte tycks ha någon positiv inverkan på elevernas akademiska resultat tycks dock motiverad.<br>A flipped classroom based teaching structure in a natural science programme class at a higher secondary school has been studied in terms of influence on academic results and pupil attitudes. The class of was taught in mathematics by the same teacher using different teaching structures in three different mathematics courses: In Ma 1c, the teaching followed a traditional structure with classroom based lectures; in Ma 2c, the teaching structure was flipped, in that the pupils watched lecture podcasts prior to the lesson in order to make more time available for problem solving in class; Ma 3c also had a flipped structure, with the addition of peer instruction exercises in the classroom. A survey was performed relating to the pupils’ attitudes to the different teaching structures. Furthermore, the results of the class at the national tests in mathematics were compared a control group consisting of pupils who had been traditionally taught, as well as control groups derived from national statistics. The survey revealed that the pupils were very positive to flipped classroom teaching. The comparison of the results on national tests revealed that the academic results of the class declined between Ma 1c and Ma 3c, with the largest part of the decline occurring between Ma 1c and Ma 2c, i.e. when flipped classroom was introduced. At least part of this decline could possibly be ascribed to other factors than the change of teaching structure. However, the conclusion that flipped classroom as implemented in the class at study does not have a positive influence on the academic results of the pupils seems motivated.
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Majer, Šimon. "Síťová podpora distribuovaných zdrojů řízením jejich výkonu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-400587.
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This thesis is focused on voltage regulation in low voltage distribution system. It describes power management methods using photovoltaic inverters. The thesis describes the working PQ space of the inverter and the regulation characteristics of the active and reactive power in dependence on the voltage. The practical part focuses on the simulation of specific PQU control settings on the test models created in PSCAD. The model is used as a basis for real measurement. Outputs obtained from measurement and simulation are validated in the text. The last part of the thesis identifies limits for connecting resources with and without support.
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Bielskis, Edvardas. "Galios elektronikos mokymo laboratorinės įrangos prototipų kūrimas." Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110804_092454-45181.
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Šis elektros inžinerijos bakalauro darbas yra aktualus, nes yra kuriami nauji laboratorinių darbu stendai galios elektronikos, kurių dar katedra neturėjo. Taip kuriant naujus mokomuosius stendus bus galima padidinti studijų kokybę, nes bus lengviau paaiškinti vykstančius sudėtingus procesus, kurie yra reikalingi gauti reikiamą valdymo dėsnį. Iki šiol panašūs laboratoriniai darbai buvo atlikinėjami programinėmis įrangomis imituojant elektrines grandines, tačiau toks mokymo būdas yra suidealizuotas, todėl nelabai atitinka tikrovę.
Buvo nutarta pagaminti du stendus, susijusius su galios elektronikos disciplinos studijomis. Tai būtų tiristorinio lyginimo tiltelio stendas ir inverterio stendas. Pradinėje gamybos stadijoje programine įranga „MULTISIM“ buvo modeliuojamos stendų atitinkamos elektrinės grandinės ir žiūrima ar rezultatai tenkina norimus gauti parametrus. Toliau sumodeliavus atitinkamas elektrines grandines, buvo braižomos elektrinės schemos, pagal kurias buvo gaminami realūs laboratoriniai stendai. Toliau pagaminti stendai buvo išbandomi ir jų rezultatai palyginami su žinomomis teorinėmis reikšmėmis.
Darbo metu buvo pagaminti minėti du stendai. Buvo išbandyta ar jie tinkamai veikia tikrinant oscilografu atitinkamų dalių elektrinės grandinės taškų signalus. Taip pat buvo sukurti stendų aprašai, pagal kuriuos studentai galios elektronikos laboratoriniuose darbuose susipažins su šių stendų įranga bei naudojimosi algoritmu. Be to buvo sukurtos laboratorinių darbų užduotis... [toliau žr. visą tekstą]<br>The Bachelor’s work in Electrical Engineering is relevant, whereas new power electronics equipment for laboratory works were developed. So far, the department did not have such kind of equipment. Thus, developing the new, it will be possible to improve the study quality, whereas is will be easier to explain the operation of complicated processes. Herewith, similar virtual experimentation was performed using electrical circuit simulation software. However such method of teaching was idealised, therefore it did not meet the reality very much.
It was intended to develop two different laboratory equipment sets in relation with the requirements of the Power Electronics course. These include SCR control and voltage inverter modules. In the initial stage, the respective electrical circuits were simulated using “MULTISIM”. Further, the real electrical circuits were designed, made and tested. The simulation and real systems analysis results were in good agreement.
The descriptions of the equipment were prepared, which can be used for the laboratory practice. The students will have to perform respective tasks and measurements and familiarise themselves with the principles of power electronic circuit operation.
Conclusions:
The equipment testing results were in conformity with the theory, therefore they are operating appropriately.
Students will be able to obtain appropriate knowledge concerning power electronics devices in the real environment.
The price of production of the... [to full text]
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Stahre, Christoffer. "Interaktioner i det inverterade klassrummet." Thesis, Malmö högskola, Lärarutbildningen (LUT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-35812.
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Denna uppsats har som syfte att undersöka om, och i så fall hur, matematiklärare upplever att interaktionen mellan dem och deras elever förändras då de övergår till att arbeta med det inverterade klassrummet som undervisningsmodell i grundskolans senare år och i gymnasiet. Det empiriska materialet har samlats in genom semistrukturella, kvalitativa intervjuer med fem lärare. Utifrån tidigare litteratur kring denna undervisningsform, Deweys tankar kring det demokratiska klassrummet samt en sociokulturell syn på lärande, analyseras dessa fem lärares uppfattningar kring interaktioner i det inverterade klassrummet, möjligheter att skapa fler samtal i klassrummet, elevcentrerad undervisning och ett mer jämlikt och demokratiskt klassrum. Resultatet visar att tankarna kring vad denna undervisningsmodell kan bidra med är vitt skilda hos studiens informanter. Vissa ser modellen endast som ett sätt att organisera sin undervisning medan andra ser modellen som en möjlighet att påverka långtgående relationella maktstrukturer.
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Jonassen, Simon. "Distribuerte Inverterte Indekser." Thesis, Norwegian University of Science and Technology, Department of Computer and Information Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10426.
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<p>Masteroppgaven presenterer en litteraturstudie på sammenligning mellom globale og lokale inverterte filer, samt alternative metoder som samlebåndsbaserte prosessering av globale inverterte filer og hybride inverterte filer. Arbeidet ble videreført med en simuleringsmodel som ble brukt til å utføre en rekke eksperimenter for metodene beskrevet i oppgaven. En virkelig dokumentsamling og en virkelig lastsamling ble brukt under eksperimenter. Resultater fra simuleringsmodellen ble diskutert mot de mest sentrale resultatene som presentert i litteraturstudiet.</p>
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Eurenius, Mario. "Inverted dart." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-9752.
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The field I’m working in is “design through construction”. Construction as a field in fashion design when creating has expanded and there are many views upon how one can work whit-in this field. I’m working with a cut and then bending or displacing it through placing it on the body so it creates volume which starts from its vertex. One could say that it works like an inverted dart. This way to work has a potential to create volume that stands out from the body without using standard ways e.g. like adding a new pattern piece or build a crinoline. It might answer to the question: How can one create shape or arrange shape without adding anchor points? Therefor I explore the relation between body and shape through inverted dart. I’ve been executing experiments through a trial and error method diverged in three steps when in the physi- cal part examine my aim in tests based on the body pressing a cut apart which gives an effect in the vertex of the cut. Through my research I’ve have come to a conclusion that the body in itself can transform garment trough an inverted dart by stepping into it. The relation between the body and material through the inverted dart has qualities were body can arrange dress and define it trough folding fabric and body can through the inverted dart make room for itself. This idea and development is relating to the basics when make dress, body and material and how we can work whit these opponents. Instead of thinking about new variables like new technical tools, e.g. the laser cutter when pushing boundaries one can also take new turns with basics. In this work the body defines dress through the inverted dart (an interaction between body and dress) and create new ways of handling fabric and shape. This perspective on design and art can also been used when working in other fields when distort basic prin- ciples to create new expression. As an example there might be possibilities to develop basics in architecture by studying society and therefore understand fundamental values in this field and, how you by change these variables can develop design.
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Saghaleini, Mahdi. "Switching Patterns and Steady-State Analysis of Grid-Connected and Stand-Alone Single-Stage Boost-Inverters for PV Applications." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/796.
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Renewable or sustainable energy (SE) sources have attracted the attention of many countries because the power generated is environmentally friendly, and the sources are not subject to the instability of price and availability. This dissertation presents new trends in the DC-AC converters (inverters) used in renewable energy sources, particularly for photovoltaic (PV) energy systems. A review of the existing technologies is performed for both single-phase and three-phase systems, and the pros and cons of the best candidates are investigated.
In many modern energy conversion systems, a DC voltage, which is provided from a SE source or energy storage device, must be boosted and converted to an AC voltage with a fixed amplitude and frequency. A novel switching pattern based on the concept of the conventional space-vector pulse-width-modulated (SVPWM) technique is developed for single-stage, boost-inverters using the topology of current source inverters (CSI). The six main switching states, and two zeros, with three switches conducting at any given instant in conventional SVPWM techniques are modified herein into three charging states and six discharging states with only two switches conducting at any given instant. The charging states are necessary in order to boost the DC input voltage. It is demonstrated that the CSI topology in conjunction with the developed switching pattern is capable of providing the required residential AC voltage from a low DC voltage of one PV panel at its rated power for both linear and nonlinear loads.
In a micro-grid, the active and reactive power control and consequently voltage regulation is one of the main requirements. Therefore, the capability of the single-stage boost-inverter in controlling the active power and providing the reactive power is investigated. It is demonstrated that the injected active and reactive power can be independently controlled through two modulation indices introduced in the proposed switching algorithm. The system is capable of injecting a desirable level of reactive power, while the maximum power point tracking (MPPT) dictates the desirable active power.
The developed switching pattern is experimentally verified through a laboratory scaled three-phase 200W boost-inverter for both grid-connected and stand-alone cases and the results are presented.
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Hallstedt, Karin, and Jessika Runesson. "Kinetisk validering av den inverterade pendelmodellen för transfemoralt amputerade." Thesis, Hälsohögskolan, Högskolan i Jönköping, HHJ, Avd. för rehabilitering, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-40117.
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Bakgrund: Transfemoralt amputerade har nedsatt balans och ökad fallrisk, men väldigt lite forskning är gjord om detta. Inverted pendulum model (IPM) är en balansmodell för icke-amputerade som bygger på ett känt samband mellan Center of Pressure (CoP) och Center of Mass (CoM). Syftet med denna studie är att kinetiskt validera den inverterade pendelmodellen för transfemoralt amputerade. Metod: I studien deltog amputerade (n=5) och en matchande kontrollgrupp (n=5). Man samlade in data genom att deltagarna fick stå stilla på två stycken kraftplattor under tre styckern villkor; öppna ögon, stängda ögon och weight-bearing feedback. Man undersökte sedan korrelationen mellan avståndet från CoM till CoP och CoMacc i både anterioposterior (A/P) riktning samt medio-lateral (M/L) riktning och analyserade datan med trevägsvariansanalys (ANOVA). Resultat: Resultatet visade att det fanns en signifikant interaktionseffekt mellan villkor och position i M/L-riktning. I A/P-riktning fanns det en signifikant interaktionseffekt mellan grupp och position samt villkor och position. Slutsats: Resultatet innebär att IPM är kinetiskt validerat i A/P-riktning sett till hela kroppen men inte på den amputerade sidan. Hur det intakta benet förhåller sig till IPM för amputerade är tvivelaktigt.<br>Background: It is known that transfemoral prosthesis users lack normal balance control and are more likely to fall. Research on this topic is insufficient. The Inverted Pendulum Model (IPM) is a commonly used biomechanical model for assessment of balance and postural control for healthy individuals based on an assumption that Center of Pressure (CoP) and Center of Mass (CoM) are inter-dependent. The aim of the study is to validate IPM kinetically for transfemoral prosthesis users. Method: Amputees (n=5) and a control group (n=5) participated. During data collection, participants stood on two force plates with eyes open, eyes closed and with weight-bearing feedback. Correlation of the distance CoP-CoM and CoMacc were calculated for anteroposterior and mediolateral directions and evaluated with three-way ANOVA. Result: Results showed significant interaction effects between condition and position plus group and position in anteroposterior direction and condition and group in mediolateral direction. Conclusion: Results indicate kinetic validity of IPM for transfemoral amputees when looking at the whole body but not at the amputated side in the A/P direction. Kinetic validity of IPM for the intact leg is questionable.
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Faraci, William Eric. "Design of a Resonant Snubber Inverter for Photovoltaic Inverter Systems." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/47800.
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With the rise in demand for renewable energy sources, photovoltaics have become increasingly popular as a means of reducing household dependence on the utility grid for power. But solar panels generate dc electricity, a dc to ac inverter is required to allow the energy to be used by the existing ac electrical distribution. Traditional full bridge inverters are able to accomplish this, but they suffer from many problems such as low efficiency, large size, high cost, and generation of electrical noise, especially common mode noise. Efforts to solve these issues have resulted in improved solutions, but they do not eliminate all of the problems and even exaggerate some of them.
Soft switching inverters are able to achieve high efficiency by eliminating the switching losses of the power stage switches. Since this action requires additional components that are large and have additional losses associated with them, these topologies have traditionally been limited to higher power levels. The resonant snubber inverter is a soft switching topology that eliminates many of these problems by taking advantage of the bipolar switching action of the power stage switches. This allows for a significant size reduction in the additional parts and elimination of common mode noise, making it an ideal candidate for lower power levels. Previous attempts to implement the resonant snubber inverter have been hampered by low efficiency due to parasitics of the silicon devices used, but, with recent developments in new semiconductor technologies such as silicon carbide and gallium nitride, these problems can be minimized and possibly eliminated.
The goal of this thesis is to design and experimentally verify a design of a resonant snubber inverter that takes advantage of new semiconductor materials to improve efficiency while maintaining minimal additional, parts, simple control, and elimination of common mode noise. A 600 W prototype is built. The performance improvements over previous designs are verified and compared to alternative high efficiency solutions along with a novel control technique for the auxiliary resonant snubber. A standalone and grid tie controller are developed to verify that the auxiliary resonant snubber and new auxiliary control technique does not complicate the closed loop control.<br>Master of Science
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Pettersson, Martin. "Analyser av två VSC-HVDC-stationer genom långtidsmätningar med elkvalitetsmätare." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70056.
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Gotland har länge präglats av mycket speciella lösningar och legat i framkant vad gäller ny teknik. Under ca 20 år har Gotland haft en VSC-HVDC-station som har stabiliserat spänningen i det gotländska nätet. HVDC Light har löst en del av de tekniska begränsningarna som hindrat utvecklingen av vindkraftverk. Anläggningen börjar lida mot slutet av sin tekniska livslängd och examensarbetet är ett första steg i utredningen för en eventuell ersättning. Med hjälp av elkvalitetsmätare kartlagdes prestanda och eventuella förbättringsområden. Den svenska stamnätsoperatören Svenska kraftnät har sedan 2016 haft en VSC-HVDC-station som använts för att utväxla energi till asynkrona systemet i Östeuropa. Svenska kraftnät har på senare tid velat utnyttja spänningsregleringsmöjligheterna och utreda mättekniska metoder. Elkvalitetsmätare placerades ut på lämpliga mätpunkter för att utreda anläggningens beteenden. ELSPEC G4500 elkvalitetsmätare installerades på Nordbalt och Gotlands HVDC Light för att mäta under sensommar till hösten 2017. Skillnader mellan CVT och IVT samt Rogowskispole och CT mättes. Valet av ELSPEC lämpade sig bra eftersom att inga triggningsvillkor behövdes som tillåter att man kan upptäcka små men viktiga avvikelser. Gotlands HVDC Light stabiliserar nätet främst mot spänningsdippar efter kortslutningar i 10 kV-elnätet och flimmer ifrån vindkraftsparkerna i ände 2. Märkeffekten för en uppdaterad anläggning kommer baseras på den kortslutningseffekt i 10 kV-nätet som kan utvecklas under anläggningens livstid. Spänningsregleringen ska baseras på en PI-regulator och ska kunna reglera fullt på 40 ms. Komponentspänningar kan användas för att ge reaktiv effekt på de faser som behöver det. Behovet mot flimmer ska baseras på en mätning i närmaste konsumtionscentrum, två mil från ände 2. Om behovet finns, ska en separat loop för flimmerkontroll som motverkar 1,5 Hz-komponenter implementeras utifrån en punkt ca 1,5 mil ifrån ände 2. Teknikvalet står mellan two-level generation 3 eller MMC, beroende på uppgradering eller ersättning. Många olika framtida scenarion påverkar HVDC Lights roll och oavsett, kommer mycket resurser behövas för Gotlands och HVDC Lights framtid. Det har observerats två beteenden på Nordbalt varav ena är långsam och det andra beteendet är snabbt. Det snabba beteendet uppstår när lågohmiga fel sker som också synkronmaskinerna tar hand om. Nordbalt kan hjälpa till för mindre spänningsvariationer om den varit snabbare likt beteendet vid lågohmiga fel. En stabilitetsbedömning behövs dock eftersom att snabbare beteende ökar risken för instabilitet. Eftersom att data mellan CVT och IVT skiljde sig mycket, upplystes mättekniska problem. Några lösningar diskuteras varav RCVT och PQSensor gås igenom grundligt. Alternativa lösningar som MoW och mobila enheter presenteras också vagt. Samtliga lösningar visade sig ha praktiska hinder, vilket försvårar genomförandet. Det uppmanas därför att man bör testa teknikerna i laborationsmiljö eftersom begränsat med studier gjorts på dessa samt att konkurrerande tillverkare uppger olika uppgifter.<br>Gotland has long been known for various special solutions and been on the leading edge regarding new technology. For the past 20 years Gotland has had a VSC-HVDC station that has stabilized the voltage in the Gotlandic grid. HVDC Light has solved some of the technical limitations that has hindered the growth of wind turbines. The station has almost reached the end of its technical lifespan and the thesis is a first step in the investigation for an eventual replacement. With power quality analyzers performance and improvements were investigated. The Swedish transmission system operator Svenska kraftnät have since 2016 had a VSCHVDC station that have been used to exchange energy to the asynchronous system in Eastern Europe. Svenska kraftnät has of lately wanted to take advantage of the voltage control capabilities and investigate measurement technologies. Power quality analyzers were installed on suitable connection points to investigate the behavior of the station. ELSPEC G4500 power quality analyzers were installed on Nordbalt’s and Gotland’s HVDC Light to measure during the late summer to fall of 2017. The differences between CVT and IVT, and Rogowski coil and CT were captured. The choice of ELSPEC suited well since no trigger conditions are needed which allows small but important errors to be discovered. Gotland’s HVDC Light stabilizes the grid mostly against voltage sags for faults in the 10 kVgrid and flicker from the wind farms in node 2. The rated power for an upgrade should be based on the 10 kV-grid short-circuit power to be developed during the station’s life span. The voltage control should be based on a PI-controller and should be able to transmit full power in 40 ms. Component voltages can be used to produce reactive power on the phases in need. The need against flicker should be based on measurements in the closest center of consumption, 2 miles from node 2. If it’s needed, a separate loop for flicker-control that prevents 1.5 Hz-components based on a point 1.5 mile from node 2 should be implemented. Depending on an upgrade or replacement, the topology can either be “two-level generation 3” or MMC. Many different future scenarios affect HVDC Light’s role and more resources will be required for Gotland’s and HVDC Light’s future. Two behaviors have been observed on Nordbalt where one is slow and the other behavior is fast. The fast behavior was only observed when low impedance faults occurs, that the synchronous generators also handles. Nordbalt can contribute to small voltage variations if it was faster, like the behavior for low impedance faults. A consideration in stability is needed since a faster behavior can lead to stability problems. Since the data between CVT and IVT differed a lot, metrology problems were discovered. Some solutions were discussed, of which RCVT and PQSensor was thoroughly reviewed. Alternative solutions like MoW and mobile units were also presented vaguely. All solutions showed practical difficulties, which complicates the implementation. It is therefore encouraged to test the technologies in a laboratory environment since few studies have been made on these and competing manufactures state different information.
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Christodoulides, Nico. "Inverted theory networks." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/4872.
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Includes bibliographical references (leaves 147-152).<br>The logicatom is defined, and it is argued that this represents the quantum of knowledge. Theory networks encapsulating a set of logicatoms and the dynamic relations between them, are defined. It is shown that these structures call emulate cellular automaton systems and in particular, simulate universal Turing machines. The regulating priuciple of natural selection is formalised together with its necessary and sufficient conditions. It is proven that there exists inverted theory networks (an analogous construct to theory networks) that satisfy all the requirements specified for natural selection to regulate their dynamics. The applicability of inverted theory networks to modelling thought is analysed. Further, inverted theory networks are proposed as a candidate for the pregeometry hypothesised by Wheeler.
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Chen, Baifeng. "High-efficiency Transformerless PV Inverter Circuits." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/56686.
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With worldwide growing demand for electric energy, there has been a great interest in exploring photovoltaic (PV) sources. For the PV generation system, the power converter is the most essential part for the efficiency and function performance. In recent years, there have been quite a few new transformerless PV inverters topologies, which eliminate the traditional line frequency transformers to achieve lower cost and higher efficiency, and maintain lower leakage current as well.
With an overview of the state-of-the-art transformerless PV inverters, a new inverter technology is summarized in the Chapter 2, which is named V-NPC inverter technology. Based this V-NPC technology, a family of high efficiency transformerless inverters are proposed and detailly analyzed. The experimental results demonstrate the validity of V-NPC technology and high performance of the transformerless inverters.
For the lower power level transformerless inverters, most of the innovative topologies try to use super junction metal oxide semiconductor field effect transistor(MOSFET) to boost efficiency, but these MOSFET based inverter topologies suffer from one or more of these drawbacks: MOSFET failure risk from body diode reverse recovery, increased conduction losses due to more devices, or low magnetics utilization. By splitting the conventional MOSFET based phase leg with an optimized inductor, Chapter 3 proposes a novel MOSFET based phase leg configuration to minimize these drawbacks. Based on the proposed phase leg configuration, a high efficiency single-phase MOSFET transformerless inverter is presented for the PV micro-inverter applications. The PWM modulation and circuit operation principle are then described. The common mode and differential mode voltage model is then presented and analyzed for circuit design. Experimental results of a 250 W hardware prototype are shown to demonstrate the merits of the proposed MOSFET based phase-le and the proposed transformerless inverter.
New codes require PV inverters to provide system regulation and service to improve the distribution system stabilization. One obvious impact on PV inverters is that they now need to have reactive power generation capability. The Chapter 4 improves the MOFET based transformerless inverter in the Chapter 3 and proposed a novel pulse width modulation (PWM) method for reactive power generation. The ground loop voltage of this inverter under the proposed PWM method is also derived with common mode and differential mode circuit analyses, which indicate that high-frequency voltage component can be minimized with symmetrical design of inductors. A 250-W inverter hardware prototype has been designed and fabricated. Steady state and transient operating conditions are tested to demonstrate the validity of improved inverter and proposed PWM method for reactive power generation, high efficiency of the inverter circuit, and the high-frequency-free ground loop voltage.
Besides the high efficiency inverter circuit, the grid connection function is also the essential part of the PV system. The Chapter 5 present the overall function blocks for a grid-connected PV inverter system. The current control and voltage control loop is then analyzed, modeled, and designed. The dynamic reactive power generation is also realized in the control system. The new PLL method for the grid frequency/voltage disturbance is also realized and demonstrate the validity of the detection and protection capability for the voltage/frequency disturbance.
At last, a brief conclusion is given in the Chapter 6 about each work. After that, future works on device packaging, system integration, innovation on inverter circuit, and standard compliance are discussed.<br>Ph. D.
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Fors, Rickard. "Flippad matematik : Elevers uppfattningar av det inverterade klassrummet." Thesis, Stockholms universitet, Institutionen för matematikämnets och naturvetenskapsämnenas didaktik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-78380.
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I det inverterade klassrummet flyttas genomgångarna från klassrummet till videofilmer som eleverna ser på hemma. Lektionerna ägnas till stor del åt sådant som annars hade utgjort hemarbete för eleven. I denna studie analyseras gymnasieelevers uppfattning av denna undervisningsmodell i matematikämnet med fokus på videogenomgångarna och förändringar i hem- och skolarbete. Det framkommer att elevernas uppfattningar av videogenomgångarna kan kategoriseras utifrån deras grad av aktivitet under videogenomgången samt deras beroende av relationen mellan elev och lärare. I en jämförelse mellan enkla filmer, digitala animationer och klassrumsgenomgångar framhålls de enkla filmernas tydlighet och fokus på matematik, samt klassrumsgenomgångarnas flyktiga natur. Dessa resultat diskuteras utifrån en kognitiv modell för överbelastning av arbetsminnet. Eleverna uppfattar att deras arbetsbelastning är lägre i det inverterade klassrummet än i ett traditionellt klassrum eftersom det finns mer tid för egen räkning i klassrummet. Dessutom uppfattas videogenomgångar som mer effektiva än klassrumsgenomgångar trots att de är betydligt kortare. Den tid som frigörs när klassrummet inverteras har inte förändrat elevernas sätt att arbeta inom matematikämnet. Elevers respons på förändrade undervisningsvillkor analyseras med hjälp av en kognitiv teori för elevers reglering av sitt eget lärande. Utifrån denna teori diskuteras hur lärare kan ta tillvara på de ökade tidsresurserna och förändra elevers tänkande om matematik och deras lärande.
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Sirisukprasert, Siriroj. "Optimized Harmonic Stepped-Waveform for Multilevel Inverter." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35333.
Full textAbstract:
The concept of multilevel voltage source inverters and their modulation topologies are described. The concept of the Optimized Harmonic Stepped-Waveform (OHSW) technique for a multilevel inverter is presented. By applying this concept, specific harmonics can be eliminated, and the output voltage THD can be improved. A procedure to achieve the appropriate switching angles of the OHSW is proposed. Experimental results are presented to verify the concept. The proposed OHSW technique is implemented on a multilevel inverter using cascaded-inverter with separated dc sources. Comparison between the Selective Harmonic Eliminated PWM and the OHSW is also presented.<br>Master of Science
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Tang, Yuqing. "High Power Inverter EMI Characterization and Improvement by Auxiliary Resonant Snubber Inverter." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/31022.
Full textAbstract:
Electromagnetic interference (EMI) is a major concern in inverter motor drive systems. The sources of EMI have been commonly identified as high switching dv/dt and di/dt rates interacting with inverter parasitic components. The reduction of parasitic components relies on highly integrated circuit layout and packaging. This is the way to deal with noise path. On the other hand, switching dv/dt and di/dt can be potentially reduced by soft-switching techniques; thus the intensity of noise source is reduced.
<p>
In this paper, the relation between the dv/dt di/dt and the EMI generation are discussed. The EMI sources of a hard-switching single-phase PWM inverter are identified and measured with separation of common-mode and differential-mode noises. The noise reduction in an auxiliary resonant snubber inverter (RSI) is presented. The observation of voltage ringing and current ringing and the methods to suppress these ringing in the implementation of RSI are also discussed. The test condition and circuit layout are described as the basis of the study. And the experimental EMI spectra of both hard- and soft-switching inverter are compared. The effectiveness and limitation of the EMI reduction of the ZVT-RSI are also discussed and concluded.
<p>
The control interface circuit and gate driver design are described in the appendix. The implementation of variable charging time control of the resonant inductor current is also explained in the appendix.<br>Master of Science
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Paquette, Andrew Donald. "Power quality and inverter-generator interactions in microgrids." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51803.
Full textAbstract:
This research addresses some of the difficulties faced when operating voltage controlled inverters with synchronous generators in microgrids. First, an overview of microgrid value propositions is provided, and the problems faced when attempting to use microgrids to provide improved power quality are discussed. Design considerations for different types of microgrids are provided to enable microgrids to deliver the desired functionality without adding unnecessary cost. The main body of this research investigates the poor transient load sharing encountered between voltage controlled inverters and synchronous generators in islanded operation. Poor transient load sharing results in high peak inverter rating requirements and high cost. The tradeoff between power quality and power sharing is highlighted, and methods to improve transient load sharing are proposed. The use of current limiting to protect inverters during faults and overloads is also investigated. Stability problems are identified when using simple inverter current limiting methods when operating in parallel with synchronous generators. Virtual impedance current limiting is proposed to improve transient stability during current limiting. The methods proposed in this thesis for mitigating inverter overloads and faults will allow for more reliable and cost effective application of inverter based distributed energy resources with synchronous generators in microgrids.
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Cortes, Avellaneda Douglas D. "Inverted base pavement structures." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37305.
Full textAbstract:
An inverted base pavement is a new pavement structure that consists of an unbound aggregate base between a stiff cement-treated foundation layer and a thin asphalt cover. Unlike conventional pavements which rely on upper stiff layers to bear and spread traffic loads, the unbound aggregate inter-layer in an inverted base pavement plays a major role in the mechanical response of the pavement structure. Traditional empirical pavement design methods rely on rules developed through long-term experience with conventional flexible or rigid pavement structures. The boundaries imposed on the unbound aggregate base in an inverted pavement structure change radically from those in conventional pavements. Therefore, current empirically derived design methods are unsuitable for the analysis of inverted base pavements. The present work documents a comprehensive experimental study on a full-scale inverted pavement test section built near LaGrange, Georgia. A detailed description of the mechanical behavior of the test section before, during and after construction provides critically needed understanding of the internal behavior and macro-scale performance of this pavement structure. Given the critical role of the unbound aggregate base and its proximity to the surface, a new field test was developed to characterize the stress-dependent stiffness of the as-built layer. A complementary numerical study that incorporates state-of-the-art concepts in constitutive modeling of unbound aggregates is used to analyze experimental results and to develop preliminary guidelines for inverted base pavement design. Simulation results show that an inverted pavement can deliver superior rutting resistance compared to a conventional flexible pavement structure with the same fatigue life. Furthermore, results show that an inverted base pavement structure can exceed the structural capacity of conventional flexible pavement designs for three typical road types both in rutting and fatigue while saving up to 40% of the initial construction costs.
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Firch, Robert S. "Inverted Cotton Futures Markets." College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/203915.
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Vaynzof, Yana. "Inverted hybrid solar cells." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609823.
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Li, Bo. "Rotational Double Inverted Pendulum." University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1375188910.
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Fillmore, Paul F. "Design, construction, and testing of a hysteresis controlled inverter for paralleling." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03sep%5FFillmore.pdf.
Full textAbstract:
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 2003.<br>Thesis advisor(s): Robert Ashton, Xiaoping Yun. Includes bibliographical references (p. 69-70). Also available online.
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Bodiker, Goldie Marie. "FMRI Analysis of Inverted and Non-inverted Left-handed Subjects During Language Tasks." University of Toledo Health Science Campus / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=mco1096298665.
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Larsen, Alexander, and Pontus Lindquist. "Forecasting mismatch losses: An empirical study investigating module level inverter- and string inverter systems." Thesis, KTH, Energiteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-148089.
Full textAbstract:
The purpose of this thesis is to investigate the correlation between irradiance and power output for a system with a module level inverter and a string inverter, respectively. An empirical study has been conducted and inverters in photovoltaic systems will be discussed and divided into two types; module level and string inverters. Different sources of mismatch such as degradation, partial shading and manufacturing issues are also part of the study. The predicted mismatch for the string inverter system is 2,6 %, based on flash test data for fresh cells, although that value is likely to be underrated due to aging effects not accounted for in the model. The system equipped with module level inverters generated 6,1 % more energy during the measured period. Although the period of measuring is short and the number of systems compared is small, this study has identified multiple sources that explain why the string inverter system is inferior and is outperformed by the module level inverter system regarding power output.<br>Syftet med detta arbete är att utforska korrelationen mellan solinstrålning och producerad effekt för två olika system. Det ena systemet består av lokala växelriktare och det andra av en strängomriktare. En empirisk studie har utförts och i detta arbete diskuteras växelriktare i fotovoltaiska system. Olika orsaker till varför förlorad effekt uppstår mellan modulerna så som ålder, skuggning och tillverkningsfel omfattas även av detta arbete. Det förutspådda värdet på effektförluster mellan modulerna i strängomriktarsystemet uppgick till 2,6 %, vilket är baserat på flash tester för nya solceller. Detta värde är troligtvis underskattat med tanke på att de celler som använts är föråldrade och att effekten av detta inte är medtaget i beräkningarna. Systemet med lokala växelriktare genererade 6,1 % mer elektricitet under den uppmätta perioden. Fastän den uppmätta perioden var kort och antalet system som studerades var litet så kunde flera faktorer identifieras som förklarar varför strängomriktare är underlägsna lokala växelriktare sett till producerad effekt.
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Krogemann, Markus. "The parallel resonant DC link inverter : a soft-switching inverter topology with PWM capability." Thesis, University of Nottingham, 1997. http://eprints.nottingham.ac.uk/13526/.
Full textAbstract:
Soft-switching inverters have over the last decade received a lot of attention by researchers owing to the reduction or virtual elimination of switching losses that these circuits can achieve. Possible improvements in EMC performance due to the reduced levels of dv/dt have among other advantages triggered the development of a still growing number of zero-voltage or zero-current switching inverter circuits. More recently, the trend seems to have shifted from continuously resonant systems over to quasi-resonant topologies due to advantages in terms of device stresses and PWM compatibility. In this work, continuously resonant as well as quasi-resonant techniques are reviewed. A quasi-resonant circuit will be implemented in a three-phase PWM inverter system controlled by a network of transputers. It will be examined to which degree the working principle of this Parallel Resonant DC Link (PRDCL) inverter affects the PWM compatibility and a suitable PWM strategy will be presented and implemented. The modified PWM technique shows output quality comparable to standard PWM methods while being fully compatible with the operation of the resonant link. The conversion efficiency and EMC performance of a PWM inverter drive based on the PRDCL circuit will be measured and compared to its hard-switched equivalent. It will be shown that improvements over hard-switching inverters are possible. However, the investigation of the PRDCL PWM inverter also reveals a number of drawbacks which limit the achievable switching frequency and adversely affect the conversion efficiency. Despite the many previous publications these problems have generally been overlooked in the past.
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Thomschke, Michael. "Inverted Organic Light Emitting Diodes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-106255.
Full textAbstract:
This study focuses on the investigation of the key parameters that determine the optical and electrical characteristics of inverted top-emitting organic light emitting diodes (OLED). A co-deposition of small molecules in vacuum is used to establish electrically doped films that are applied in n-i-p layered devices. The knowledge about the functionality of each layer and parameter is important to develop efficient strategies to reach outstanding device performances.
In the first part, the thin film optics of top-emitting OLEDs are investigated, focusing on light extraction via cavity tuning, external outcoupling layers (capping layer), and the application of microlens films. Optical simulations are performed to determine the layer configuration with the maximum light extraction efficiency for monochrome phosphorescent devices. The peak efficiency is found at 35%, while varying the thickness of the charge transport layers, the
semitransparent anode, and the capping layer simultaneously. Measurements of the spatial light distribution validate, that the capping layer influences the spectral width and the resonance wavelength of the extracted cavity mode, especially for TM polarization. Further, laminated microlens films are applied to benefit from strong microcavity effects in stacked OLEDs by spatial mixing of external and to some extend internal light modes. These findings are used to demonstrate white top-emitting OLEDs on opaque substrates showing power conversion efficiencies up to 30 lm/W and a color rendering index of 93, respectively.
In the second part, the charge carrier management of n-i-p layered diodes is investigated as it strongly deviates from that of the p-i-n layered counterparts. The influence of the bottom cathode material and the electron transport layer is found to be negligible in terms of driving voltage, which means that the assumption of an ohmic bottom contact is valid. The hole transport and the charge carrier injection at the anode is much more sensitive to the evaporation sequence, especially when using hole transport materials with a glass transition
temperature below 100°C. As a consequence, thermal annealing of fabricated inverted OLEDs is found to drastically improve the device electronics, resulting in lower driving voltages and an increased internal efficiency. The annealing effect on charge transport comes from a reduced charge accumulation due to an altered film morphology of the transport layers, which is proven for electrons and for holes independently. The thermal treatment can further lead to a device degradation. Finally, the thickness and the material of the blocking layers which usually control the charge confinement inside the OLED are found to influence the recombination much more effectively in inverted OLEDs compared to non-inverted ones.
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Lundberg, Kent Howard. "Linear dual inverted pendulum control." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10767.
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Breda, David Pedro. "Simulation of a resonant inverter." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/15931.
Full textAbstract:
Mestrado em Engenharia Electrónica e de Telecomunicações<br>Mostly developed since the Industrial Revolution, the automation of
systems and equipment around us is responsible for a technological
progress and economic growth without precedents, but also by a relentless
energy dependence.
Currently, fossil fuels still tend to come as the main energy source,
even in developed countries, due to the ease in its extraction and the
mastery of the technology needed for its use. However, the perception
of its ending availability, as well as the environmental impact of this
practice has led to a growing energy production originated from renewable
sources.
Easy maintenance, coupled with the fact that they are virtually inexhaustible,
makes the solar and wind energy very promising solutions.
In this context, this work proposes to facilitate energy production from
these sources.
To this end, in this work the power inverter is studied, which is an
equipment responsible for converting DC power available by solar or
wind power in traditional AC power. Then it is discussed and designed
a new architecture which, in addition to achieve a high energy e -
ciency, has also the ability to adapt to the type of conversion desired
by the user, namely if he wants to sell electricity to the power grid, be
independent of it or bet on a self consumption system.
In order to achieve the promised energy e ciency, the projected inverter
uses a resonant DC-DC converter, whose architecture signi cantly decreases
the energy dissipated in the conversion, allowing a higher power
density.
The adaptability of the equipment is provided by an adaptive control
algorithm, responsible for assessing its behavior on every iteration and
making the necessary changes to achieve maximum stability throughout
the process.
To evaluate the functioning of the proposed architecture, a simulation
is presented using the PLECS simulation software.<br>Desenvolvida maioritariamente a partir da Revolução Industrial, a automatização dos sistemas e equipamentos que nos rodeiam e responsável por um progresso tecnológico e crescimento económico sem precedentes, mas também por uma incessante dependência energética. Atualmente, combustíveis fosseis ainda tendem a surgir com principal fonte de energia, mesmo em países desenvolvidos, devido a facilidade na sua extração e domínio da tecnologia necessária a sua utilização. No entanto, a perceção quer da sua findável disponibilidade, quer do impacto ambiental desta pratica, tem levado a uma crescente produção de energia proveniente de fontes renováveis. A sua fácil manutenção, aliada ao facto de serem praticamente inesgotáveis, faz das energias solar e eólica uma solução muito promissora. Neste contexto, esta dissertação propõe facilitar a produção de energia proveniente destas fontes. Assim, neste trabalho são estudados os inversores de potencia, equipamentos responsáveis por converter energia DC disponibilizada por uma fonte solar ou eólica em energia AC tradicional. Seguidamente e discutida e projetada uma nova arquitetura que, para al em de conseguir um alto rendimento energético, tem também a capacidade de se adaptar face ao tipo de conversão pretendida pelo utilizador, caso este queira vender energia a rede elétrica, ser independente desta ou apostar num sistema de auto consumo. Para alcançar o alto rendimento energético prometido, o inversor projetado faz uso de um conversor DC-DC ressonante, cuja arquitetura diminui consideravelmente a energia dissipada na conversão, permitindo assim uma maior densidade de potencia. A versatilidade do equipamento e disponibilizada por um algoritmo de controlo adaptativo, responsável por avaliar o comportamento deste a cada iteração e fazer as alterações necessárias para alcançar a máxima estabilidade ao longo de todo o processo. Para uma avaliação do funcionamento da arquitetura proposta, apresenta-se a simulação da mesma utilizando o software de simulação PLECS.
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Joel, Jaldemark. "Remote control of frequency inverter." Thesis, Högskolan i Halmstad, Akademin för informationsteknologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-41400.
Full textAbstract:
Emotron has a frequency inverter on the market that different industries uses in their factories. In case of errors they need to send out service to the factories in order to examine the inverter and find the error. They now want a solution that makes it possible for them to give support without leaving the office by connecting their devices to the cloud which eliminates the need to send out staff to industries. Emotron gave this task to HMS and has been possible with their product Anybus wiress bolt. By connecting the Anybus wireless bolt to the inverter it was possible to communicate with the cloud, MicrosoftAzure, where a static webb application is hosted. The application is made to look like the terminal on the inverter and has similiar structures and functionality. Through the application users can communicate withthe inverter by means of controlling the connected motor, reading registers and also write to certain registers. These registers contain different measurement and option parameters. The purpose of this thesis was to create a Proof-of-Concept solution using the Anybus wireless bolt. The thesis has shown of industries can use Anybus wireless bolt and the tag engine to make it possible to create a link between machines and the ever- growing cloud and is also the first part of a bigger project.
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Chbeir, Richard, Yi Luo, Joe Tekli, et al. "SemIndex: Semantic-Aware Inverted Index." Springer International Publishing, 2015. http://hdl.handle.net/10757/344330.
Full textAbstract:
carlos.raymundo@upc.edu.pe<br>This paper focuses on the important problem of semanticaware
search in textual (structured, semi-structured, NoSQL) databases.
This problem has emerged as a required extension of the standard containment
keyword based query to meet user needs in textual databases
and IR applications. We provide here a new approach, called SemIndex,
that extends the standard inverted index by constructing a tight coupling
inverted index graph that combines two main resources: a general
purpose semantic network, and a standard inverted index on a collection
of textual data. We also provide an extended query model and
related processing algorithms with the help of SemIndex. To investigate
its effectiveness, we set up experiments to test the performance
of SemIndex. Preliminary results have demonstrated the effectiveness,
scalability and optimality of our approach.
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Stenbeck, Filip, and Aron Nygren. "Controller Analysis with Inverted Pendulum." Thesis, KTH, Maskinkonstruktion (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-184515.
Full textAbstract:
The aim of this thesis is to examine if feedback of the angle from an inverted pendulum is sufficient to control its angle at an unstable equilibrium with statics and force impulses, and through different approaches and choice of controller find the most suitable one for these types of applications. The controllers that were tested was, the PID regulator and the state space regulator. The results would show that the mathematical approach to find a controller is difficult and time consuming, and it is often better to use a trial and error approach to find a regulator if repeated test on the system is possible. The core of the thesis lies in the mathematical approximations of the mechanical and electrical system, the analysis of the controller and the choice and usage of components. Analysis of the combined electrical and mechanical systems were made in Simulink and Matlab and was then generated to mechanical code to an micro controller controlling the voltage to a dc-motor. The system is non linear but can be linearised around the equilibrium point that we want to maintain, which is a good approximation for small angles. This thesis describes the electrical and mechanical components used to build a rotary inverted pendulum and how to produce an effective controller in detail.<br>Målet med examensarbetet är att utvärdera om återkoppling av vinkeln frånen inverterad pendel är tillräcklig för att kontrollera denna kring en instabil jämviktspunkt med störningar samt pålagda kraftimpulser, och genom val av olika tillvägagångssätt och regulatorer finna den mest lämpliga för dessa typer av tillämpningar. De regulatorer som användes i projektet var PID-regulatorn samt state space regulatorn. Resultaten kom att visa att ett matematisk tillvägagångsätt att skapa en regulator är svårt och tidskrävande, och det är ofta mer effektivt att testa sig fram till en regulator om systemet tillåter. Kärnan i arbetet ligger i de matematiska approximationerna av de mekaniska och elektriska system, analysen av kontrollern och valet samt tillämpningen av komponenter. Analysen av det kombinerade elektriska och mekaniska systemen gjordes i Simulink och Matlab och var därefter genererad till mekanisk kod till en mikro-kontroller för att regulera spänningen till en likströmsmotor. Den inverterade pendeln är ett olinjärt system men kan med god approximation och litet fel linjariseras runt dess instabila jämnviktspunkt. Detta examensarbete kommer i huvudsak handla om hur man konstruerar en regulator genom simulering samt analys av systemet. Alla komponenter såväl elektriska som mekaniska kommer att beskrivas i detalj.
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Heredero, Peris Daniel. "Control contributions to AC microgrid inverters." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/405898.
Full textAbstract:
This thesis is focused on the microgrid control framework. Specifically, it is concentrated on alternative current microgrids. As a result of the author involvement in different industrial projects concerning microgrids during the last years, the goal of the thesis is to apply and expose the acquired experiences for exploring new control possibilities. The followed methodology is detailed in the next lines.
Primarily, the thesis presents two chapters whose purpose is to introduce the concept of operation and to analyse the context and challenges posed by microgrids from a top to bottom approach. The first chapter is oriented in general terms while the second one devotes more efforts in the alternative current microgrids particular case. After identifying the different actors that play an key role in the alternative current microgrids it is disclosed that the inverter becomes a key element. In this sense, the first two chapters allows to pave the way addressing how an inverter installed in an alternative current microgrid can be considered and operated. In this direction, the named grid-tied operation mode reflects the most complex configuration. Considering that the scope of the thesis is focused on voltage source inverters, the grid-tied configuration may not only consider the grid-connected or grid-disconnected operation mode but also the transients between them. Thus, important challenges such as the inverter operation itself, the anti-islanding detection capability according to the behaviour of the inverter and the galvanic isolation restriction in a microgrid framework are dealt.
The control of the voltage source inverters operated in an alternative microgrid results crucial. For this reason, a full chapter carries out a study proposing and delving into various type of controllers according to different possibilities exposed in the literature. It is conducted a stability analysis for stationary reference frame resonant current and voltage controllers. The chapter concludes with a new hybrid formulation based on fractional calculus and conventional resonant control. This novel formulation allows to enhance the controllable frequency bandwidth range decreasing inter-harmonic excitations and reducing the controller order in respect with other classical formulations.
The fourth and fifth chapters are involved into discussing and presenting different operation options when the inverter is considered as a current or as a voltage source. The fourth chapter poses over how to tackle the problem of transients when a current source grid-tied inverter is assumed while grid-connected operated. Two situations are studied; the flying transference from current to voltage source and how to extend the maximum power point extraction when a back-up system supports the inverter operation. A set of different scenarios conducted in simulation and in a real experimental platform complements the two considered situations.
The fifth chapter analyses the operation of the inverter from an opposite perspective. The considered inverter is operated by using a hybrid combination between alternative current droop control strategy when grid-connected and voltage-frequency control when grid-disconnected. In this way it is possible to preserve dynamics capabilities in both operation modes meanwhile the inverter is treated as a voltage source in any case. A predominant resistive model applying virtual resistance is considered for the case of alternative current droop control. For both operation modes an LCL-type coupling filter is assumed, complementing the control strategy with an active damping mechanism to mitigate possible resonances. Then, a three-phase four-wire four-leg inverter is proposed to match better with a proper approximation to an AC microgrid with over-load supervisor when grid-connected and sinusoidal short-circuit proof when grid-disconnected operated<br>Aquesta tesi s'emmarca en el control de microxarxes. Específicament, es focalitza en microxarxes de corrent altern. La tesi es divideix en sis capítols principals que permeten afrontar amb èxit els reptes considerats per l'operació d'una microxarxa de corrent altern. En primer lloc, la tesi presenta dos capítols el propòsit dels quals és introduir el concepte d'operació i analitzar el context i els reptes que planteja una microxarxa des d'una aproximació de dalt a baix. El primer capítol està orientat als conceptes generals, mentre que en el segon es dediquen més esforços als detalls del cas particular de les microxarxes de corrent altern. Després d'identificar els diferents actors que juguen un paper important en les microxarxes de corrent altern se'n despren que l'inversor n'esdevé clau. Els dos primers capítols permeten entendre de quina forma un inversor instal·lat en una microxarxa de corrent altern pot ser considerat i operat. En aquest sentit, el mode de funcionament anomenat -lligat a la xarxa- reflexa la configuració més complexa a tenir en compte. Tenint present que l'abast de la tesi es centra en els convertidors de font de tensió, en la configuració lligada a la xarxa s'ha de considerar, no sols, el mode de funcionament connectat a la xarxa o desconnectat, sinó, també, el transitori entre ells. Per tant, es tracten importants reptes com ara poden ser la seva operació, la capacitat de detecció d'illa d'acord amb el comportament de l'inversor i la restricció d'ús d'aïllament galvànic en el marc de les microxarxes. El control dels inversors de font de tensió utilitzats per operar una microxarxa de corrent altern resulta crucial. Per aquesta raó, es porta a terme un estudi proposant i aprofundint en diversos tipus de controladors d'acord amb l'exposat en la literatura. En aquest capítol es porta a terme una anàlisi d'estabilitat pel cas de controladors ressonants de corrent i voltatge en el marc de la referència estacionaria. El capítol conclou amb una nova formulació híbrida basada en el càlcul fraccional i el control ressonant convencional. Aquesta nova formulació permet millorar el rang d'ample de banda en freqüència controlable disminuint les excitacions inter-harmòniques i reduint, al seu torn, l'ordre del controlador respecte d'altres formulacions clàssiques. Els capítols quart i cinquè estan involucrats en la discussió i la presentació de diferents opcions d'operació quan l'inversor es considera com una font de corrent o de tensió. El quart capítol planteja com abordar el problema dels transitoris quan es suposa que un inversor lligat a la xarxa opera com a font de corrent mentre es troba connectat a la xarxa. S'estudien dos situacions; la transferència al vol de font de corrent a voltatge i la forma d'extendre l'operació des del punt de màxima potència quan s'admet un sistema d'emmagatzematge com a suport en l'operació de l'inversor. El cinquè capítol analitza el funcionament de l'inversor des d'una perspectiva oposada. L'inversor considerat funciona mitjançant l'ús d'una combinació híbrida entre l'estratègia de control droop per microxarxes de corrent altern quan es troba connectat a la xarxa i el control de voltatge-freqüència quan es troba desconnectat. Així, és possible preservar capacitats dinàmiques en els dos modes de funcionament mentre que l'inversor és tractat com una font de tensió en ambdós casos. Pel cas concret del droop aplicat a xarxes de corrent altern s'ha fet ús d'un model predominantment resistiu aplicant el concepte de resistència virtual. Els dos modes de funcionament consideren l'ús d'un filtre d'acoblament del tipus LCL el control del qual es complementa mitjançant esmorteïment actiu per mitigar possibles ressonàncies. Així, es proposa un inversor trifàsic de quatre fils i quatre branques perquè coincideixi millor l'operació d'aquest amb una aproximació adequada a una microxarxa de corrent altern real amb capacitat de sobrecàrrega i curtcircuit controlats
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Abeyasekera, Tusitha Darshana. "Improvements to grid connected photovoltaic inverters." Thesis, University of Newcastle Upon Tyne, 2005. http://hdl.handle.net/10443/585.
Full textAbstract:
This thesis presents investigations into issues of power quality and reliability of grid connected inverters and proposes improved topological and control solutions to improve performance and cost effectiveness of these systems. Synchronisation of inverters to the grid can be problematic in its operational reliability. Of all grid synchronisation techniques phase locked loop based method offers a simple, robust and flexible solution. However the conventional PLL approach is inherently difficult to tune, due to the influence of its parameters on loop dynamics, filtering properties and output waveform spectral purity. The improved PLL proposed in the thesis, relieves the tuning task by decoupling the effect of its loop parameters from performance characteristics. Inverter power quality issues are addressed beginning from sources of harmonic distortion, classified as intrinsic and extrinsic. A potential intrinsic source is a look-up table generated reference sinusoid accessed in non-uniform increments resulting in harmonic, inter-harmonic or subharmonic distortion. The effect is studied in detail with analytical derivations and experimental results. On the other hand, extrinsic distortions are mainly caused by the distorted grid voltage. The effect of inductor current feedback, output current feedback and capacitor current feedforward on harmonic impedance is studied. The combination of inductor current feedback and capacitor current feedforward demonstrates good disturbance rejection and damped load transient performance on a low power grid connected inverter. It is shown that by carefully selecting the feedforward coefficient, the structure of the control system could be varied between the feedback and feedforward schemes. Theoretical concepts are validated on a purpose built 50OW 3-level grid connected inverter controlled through a generalised controller board based on TMS320C31 DSP. Multi-level inverters are presented as a favourable topological alternative to H-bridge grid connected inverters at medium and high power levels. The effect of number of levels, topology and switching strategy on switching losses, spectral performance and cost is analysed. Simulation results reveal that Boolean manipulation of PWM signals can be used to re-distribute harmonic energy for common mode cancellation, resulting in low switching harmonic amplitudes. Such a scheme - Carrier anti-phase sine (CAS) PWM is proposed and used in the prototype 3-level inverter.
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Yuan, Xiaoming. "Soft switching techniques for multilevel inverters." Florianópolis, SC, 1998. http://repositorio.ufsc.br/xmlui/handle/123456789/77541.
Full textAbstract:
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica.<br>Made available in DSpace on 2012-10-17T05:11:34Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-08T23:47:23Z : No. of bitstreams: 1
262713.pdf: 5373844 bytes, checksum: a249dd10d0242685c395874b9c696d96 (MD5)
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Zeng, Yu. "Droop control of parallel-operated inverters." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/11810/.
Full textAbstract:
Several critical issues for the droop control of parallel-operated inverters are addressed in this thesis, including the power quality, the parallel operation of inverters with different types of output impedance, the power sharing, the voltage and frequency regulation, as well as the current limiting.
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Barbosa, José Nilton Tavares. "PV inverters for module level applications." Master's thesis, FCT-UNL, 2011. http://hdl.handle.net/10362/7083.
Full textAbstract:
Dissertação para obtenção do Grau de Mestre em
Energias Renováveis – Conversão Eléctrica e Utilização Sustentáveis<br>Nowadays, the photovoltaic (PV) energy is presented as one of the most promising source of clean energy, and so a good way for greenhouse gas emissions mitigation and reduce the fossil fuel dependence. Within it, the photovoltaic energy has caused a huge interest in the electronic converters, and the need to improve their efficiency and reducing their cost. With this work I present a solution for a module scale grid-connected single-phase inverter. The solution consists in a two-stage inverter insolated with a grid line transformer. The two-stage inverter is composed by a DC-DC converter and a DC-AC converter connected through a DC-link capacitor. The DC-DC converter in case is a boost converter used to elevate the voltage from the PV module to a higher level. For the DC-AC converter it is used a full-bridge inverter, and both the DC-DC and the DC-AC converters use the IGBTs form an integrated module with its respective drivers. To the boost control it is implemented a Maximum Power Point Tracking algorithm that can optimize the power extraction from the PV source and for the inverter it is used a sliding mode hysteretic control. Once this inverter is conceived to work connected to the grid, a single-phase PLL system is used to synchronize the injected current to grid voltage. All the control part is made digitally using an Arduino Uno board, which uses an Atmel microcontroller.
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姚建明 and Jianming Yao. "Control schemes and performance improvement of resonant snubber soft-switching inverters." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31220198.
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