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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Создание и исследование имитационной модели разрывной машины для статических испытаний металлов Р-10 : магистерская диссертация / Creation and study of a simulation model of a tensile testing machine for static testing of metals R-10

Мальцева, О. Н., Maltseva, O. N. January 2023 (has links)
В данной работе были рассмотрены различные испытательные машины, изучен принцип и особенности работы разрывной машины для статических испытаний металлов Р-10. Проведены расчеты геометрических параметров гидроцилиндров (основного рабочего и захватов), прочностной и расчет на устойчивость. Также, исходя из перечисленных расчетов подобран рабочий насос и среда – масло. Смоделированы детали модели в пакете программ SolidWorks, а в пакете MATLAB Simscape составлена сборка разрывной машины и добавлена система с гидроприводом. В результате исследования была получена имитационная модель статической разрывной машины для металлов, при помощи которой было проведено моделирование испытания на растяжение. Для этого был выбран образец стали известной марки с заранее определенными геометрическими параметрами. После чего к образцу были приложены различные усилия, и сняты показания удлинения образца. На основе этого был получен график. Затем с помощью данных усилие/перемещение и начальных геометрических параметров были рассчитаны пределы пропорциональности, текучести, прочности на основании которых и был определен материал образца. Данный пример демонстрирует правильность разработки подобных моделей в системе MATLAB, которые могут позволить провести детальные исследования процессов работы механизмов машины во время испытаний, в том числе оценить характеристики гидравлической системы разрывной испытательной машины. / In this dissertation, various testing machines were considered, the principle and features of the operation of a tensile testing machine for static testing of metals R-10 were studied. Calculations of the geometrical parameters of hydraulic cylinders (main working and grippers), strength and stability calculations were carried out. Also, based on the above calculations, a working pump and a medium - oil were selected. The details of the model were modeled in SolidWorks, and the tensile testing machine assembly was assembled in MATLAB Simscape and the hydraulic actuator system was added. As a result of the study, a simulation model of a static tensile testing machine for metals was obtained, with the help of which a simulation of a tensile test was carried out. For this, a sample of well-known brand steel with predetermined geometric parameters was selected. After that, various forces were applied to the sample, and indications of the elongation of the sample were taken. Based on this, a graph was obtained. Then, using the force / displacement data and the initial geometric parameters, the limits of proportionality, yield, strength were calculated, on the basis of which the sample material was determined. This example demonstrates the correctness of developing such models in MATLAB. They can make it possible to conduct detailed studies of the operation of the machine mechanisms during testing, including the evaluation of the characteristics of the hydraulic system of the tensile testing machine.
272

Development of Friction/Blended Braking Capability for an Electric Driveline Model for Multi-Scale Road-Cargo Simulations / Utveckling av friktion/blandad Bromsförmåga för en elektrisk Drivlinjemodell för Multi-Scale Road-Cargo Simuleringar

Wu, Fangge January 2023 (has links)
This thesis focuses on the critical development of friction and blended braking capabilities for an electric driveline model intended for multiscale road-cargo simulations. In the rapidly evolving landscape of transportation, electric driveline technology has emerged as a key player in achieving sustainability and efficiency goals. This study addresses the pivotal aspect of braking performance within this context, aiming to optimize energy utilization and enhance road safety. Using a systems engineering approach, MATLAB, and Simulink, the work in this thesis focused on the construction of a comprehensive model of a Volvo FH truck with friction/blended braking and an Anti-lock Braking System (ABS). The model underwent rigorous validation against the New European Driving Cycle (NEDC) and subsequent simulation under NEDC, US06, WLTC3 driving cycles. The primary objective was to assess the impact of activating or deactivating the blended control system on the State of Charge (SOC) and energy consumption. Through iterative refinement, the model's energy consumption per kilometer closely approximated actual FH truck test values. Activating the blended control system consistently led to reduced energy consumption across all driving cycles, underscoring its potential to enhance sustainable and safe transportation solutions. Importantly, the ABS system functioned effectively throughout the simulations, ensuring vehicle safety, while the model maintained a consistent output speed aligned with the input speed. This abstract summarizes the research's focus, methodology, and key findings, highlighting the successful development and validation of a Volvo FH truck model with friction/blended braking and ABS systems. The results underscore the blended control system's capacity to improve energy efficiency, contributing to the pursuit of sustainable and efficient transportation solutions in the evolving landscape of electric driveline technology. / Detta examensarbete fokuserar på utvecklingen av en elektrisk drivlinemodell som inkluderar mixning av konventionell friktionsbromssystem och den elektriska drivlinans moment under regenerering. Modellen är avsedd för multiskaliga väg-och godstransportsimuleringar. I den snabbt föränderliga transportsektorn är elektrisk drivlineteknologi en viktig del för att uppnå hållbarhets- och effektivitetsmål. Detta arbete behandlar den avgörande aspekten av bromsprestanda i detta sammanhang och har som mål att optimera energianvändningen och kontrollera vägsäkerheten. Genom att använda s.k. systems engineering-metodik, MATLAB och Simulink, utvecklades en dynamisk modell av en Volvo FH-lastbil med friktions-/mixad bromsning och system för låsningsfria bromsar (ABS). Modellen genomgick en rigorös validering mot New European Driving Cycle (NEDC) och efterföljande simuleringar enligt NEDC, US06 och WLTC3-körcykler. Det primära målet var att bedöma effekten av att aktivera eller inaktivera det mixade kontrollsystemet på laddningsnivå (SOC) och energiförbrukning. Genom iterativ förbättring approximerade modellen energiförbrukningen per kilometer nära de faktiska provvärdena för FH-lastbilar. Aktivering av det blandade kontrollsystemet ledde konsekvent till minskad energiförbrukning för alla körcykler och underströk dess potential att förbättra hållbara och säkra transportsystem. Det är viktigt att notera att ABS-systemet fungerade effektivt genom alla simuleringar och säkerställde fordonssäkerheten, samtidigt som modellen beräknade en hastighet i linje med körcykelns specificerade hastigheten. Denna sammanfattning sammanfattar forskningens fokus, metodik och huvudsakliga resultat och lyfter fram den framgångsrika utvecklingen och valideringen av en Volvo FH-lastbilsmodell med friktions-/mixad bromsning och ABS-system. Resultaten understryker det blandade kontrollsystemets förmåga att förbättra energieffektiviteten och bidra till strävan efter hållbara och effektiva transportsystem i den snabbt föränderliga världen av elektrisk drivlineteknologi.
273

Model-Based Testing of Dosing System : An Introductory Review on Model-Based Automatic Test Case Generation with Matlab Simulink Proof-of-concept / Modellbaserad Testning av doseringssystem : En översiktlig genomgång av modellbaserad automatisk testfallgenerering med Matlab Simulink proof-of-concept

Setyawan, Albertus Adrian January 2021 (has links)
A modern truck contains a large number of functionalities implemented in its electronics system. Thus, testing all of these functions employs a considerable effort. The execution of tests against the system has been automated for a long time. Unfortunately, most of the test is still designed manually these days. This manual test design is sometimes not comprehensive enough to cover all possible scenarios within a complex system. At the moment, there is also a growing trend in the development process based on the model. Furthermore, model-based software can handle events and signal behaviour more robustly[1]. This thesis investigates the technique in model-based testing. The study evaluates the requirement modelling and automated abstract test generation of model-based testing over the existing testing method. A cause-effect graph is utilized for the modelling in Matlab Simulink tool with DesignVerifier feature. The case study is the truck dosing system in Scania. The results are the following. The temporal and static requirements modelling are capable of being modelled using the cause-effect graph in Matlab Simulink. Compared to the traditional method, the MBT method can achieve higher requirement coverage and more rigorous test with optimized test case generation. The MBT method also has a rapid test case generation time suitable for quick design iteration. However, the total test development time (including test case generation time) of using MBT is 12.5% higher than the manual method. Using a model-based platform like Matlab Simulink is recommended to assist the manual testing, not to replace the test flow entirely with the current research state. / En modern truck innehåller ett stort antal funktioner implementerade i dess elektroniksystem. Att testa alla dessa funktioner kräver därför en avsevärd ansträngning. Utförandet av tester mot systemet har varit automatiserat under lång tid. Tyvärr är det mesta av testet fortfarande utformat manuellt nu för tiden. Denna manuella testdesign är ibland inte tillräckligt omfattande för att täcka alla möjliga scenarier inom ett komplext system. För tillfället finns det också en växande trend i utvecklingsprocessen utifrån modellen. Dessutom kan modellbaserad programvara hantera händelser och signalbeteende mer robust[1]. Detta examensarbete undersöker tekniken i modellbaserad testning. Studien utvärderar kravmodellering och automatiserad abstrakt testgenerering av modellbaserad testning över den befintliga testmetoden. En cause-effect graph används för modelleringen i Matlab Simulink-verktyget med Design Verifier-funktionen. Fallstudien är lastbilens doseringssystem i Scania. Resultaten är följande. Den tidsmässiga och statiska kravmodelleringen kan modelleras med hjälp av cause-effect graph i Matlab Simulink. Jämfört med den traditionella metoden kan MBT-metoden uppnå högre kravtäckning och mer rigorösa test med optimerad testfallsgenerering. MBT-metoden har också en snabb genereringstid för testfall som är lämplig för snabb designiteration. Den totala testutvecklingstiden (inklusive genereringstid för testfall) för att använda MBT är 12,5% högre än den manuella metoden. Att använda en modellbaserad plattform som Matlab Simulink rekommenderas för att underlätta den manuella testningen, inte för att ersätta testflödet helt med det aktuella forskningsläget.
274

Modelling and Dynamic Performance of Hydropower in Frequency Regulation : Modelling of Double Regulated Hydropower Turbines

Ormsson, Kristinn Arnar January 2021 (has links)
The frequency of the Nordic power system has been increasingly deviating outside the normal frequency band (50 ± 0.1 Hz) in the past two decades. In an effort to counteract this, the Nordic Transmission System Operators (TSOs) have proposed new and stricter requirements on the units participating in Frequency Containment Reserve (FCR) market. The implication of these new requirements is that all units participating in the FCR markets must be re-evaluated and early predictions state that double regulated (DR) hydropower turbines, such as Kaplan and Bulb types, will have problems meeting these new requirements. To limit the amount of work required to re-evaluate all DR turbines, which might ultimately show that the unit will not pass the requirements, it is highly beneficial for power producing companies to be able to simulate the turbine response accurately enough, without full-scale physical testing, to filter out the possible cases from the impossible ones. This thesis is aimed at finding a hydropower turbine model that could accurately predict the FCR prequalification outcome for a DR hydropower turbine in Simulink from only pre-existing testing and design data. Three hydropower turbine models, one single regulated (SR) and two DR, were tested and validated for FCR Normal operation (FCR-N). The validation was performed by comparing the model results to field test data attained from a full-scale FCR-N test performed on one of Fortum’s DR hydropower units. Furthermore, two of these models were simulated and tested with regard to the FCR Disturbance (FCR-D) requirements but not validated as no such data was available. The results showed that simulating DR turbines with SR models can give inaccurate results as the SR model could not capture the more complex dynamics of the DR turbine accurately enough. The SR model underestimated the active power response drastically while at the same time overestimating the dynamic stability. The DR turbine models managed to capture the dynamics better with the most prominent model, DR Model 2, giving less than 3 % overestimation of the FCR-N capacity and a correctly predicting that the unit would fail the dynamic stability for FCR-N. The thesis results further showed that when modelling DR turbines, the calculation of the net head is vital for accurate model response. Finally, both the SR and DR model agreed that the unit would likely not pass the FCR-D requirements and therefore confirm the early predictions that DR hydropower turbines, such as the one modelled in this thesis, may have problems passing the new FCR prequalification requirements. Ultimately this might impact electrical price or frequency quality negatively. / Frekvenskvaliteten i det nordiska kraftsystemet har stadigt avvikit alltmer från det normala frekvensbandet (50 ± 0,1 Hz) under de två senaste decennierna. I ett försöka att motverka denna trend har de nordiska kraftsystemoperatörerna (TSO) föreslagit nya och striktare krav på aggregat som deltar i frekvensreservsmarknaden (FCR). Dessa nya krav innebär att alla aggregat som redan deltar på FCR-marknaden måste omvärderas och de bedömningar som har gjorts antyder att dubbelreglerade (DR) vattenkraftturbiner, som kaplan- och bulbturbiner, kommer att ha svårt med att uppfylla dessa nya krav. För att begränsa mängden arbete som krävs för att omvärdera alla DR-turbiner, som i slutändan kan visa att aggregatet inte kommer att klara kraven, är det mycket för fördelaktigt för kraftföretag att kunna noggrant simulera turbinresponsen innan de fysiska testerna utförs, för att filtrera bort de omöjliga fallen från de möjliga. Detta examensarbetes syfte var att hitta en turbinmodell som med bra noggrannhet kan förutsäga FCR förkvalificeringsresultatet for en dubbelreglerad vattenkraftturbin, med hjälp av Simulink från endast befintliga driftdata och information om aggregatets konstruktion. Tre turbinmodeller, en enkelreglerade (SR) och två dubbelreglerade, testades och validerades för FCR Normal drift (FCR-N). Valideringen utfördes genom att jämföra modellresultaten med fälttestdata från ett fullskaligt FCR-N-test som utfördes på en av Fortums dubbelreglerade vattenkraftturbiner. Dessutom simulerades även två av dessa modeller och testades med avseende på frekvensreglering vid störd drift (FCR-D) men validerades inte på grund av avsaknad av fälttestdata. Resultaten visade att simulering av dubbelreglerade turbiner med enkelreglerade turbinmodeller kan vara problematisk eftersom enkelreglerade modellen inte kunde fånga dubbelregleringsturbinernas mer komplexa dynamik tillräckligt bra. Enkelreglerade modellerna tydligt underskattade den aktiva effektresponsen samtidigt som de överskattade den dynamiska stabiliteten. De dubbelreglerade turbinmodellerna fångade däremot dynamiken bättre, där den mest framstående modellen, DR model 2, gav mindre än 3 % överskattning av FCR-N-kapaciteten och en korrekt förutsägelse att enheten skulle misslyckas uppfylla den dynamiska stabiliteten för FCR-N. Resultaten visade vidare att beräkningen av nettofallhöjden är avgörande för korrekt modellrespons. Slutligen var både singel- och dubbelreglerade modellerna överens om att aggregatet sannolikt inte skulle klara FCR-D-kraven och bekräftar därmed de tidiga bedömningarna att dubbelreglerade aggregat, som den som modellerades i denna avhandling, kan ha svårt att klara de nya FCR kraven. I slutändan kan det påverka såväl elpris som frekvenskvalitet negativt.
275

Performance evaluation of ANF-PLL, SFE and SFE-PLL filter structures to suppress harmonic content on hall sensor signals when controlling BLDC motors / Prestandautvärdering av ANF-PLL, SFE och SFE-PLL filterstrukturer för att dämpa övertonsinnehåll på hallsensorsignaler vid reglering av BLDC-motorer

Rangaraju, Gowtham Raj January 2024 (has links)
High-performance variable-speed drives, such as PMSM and BLDC, rely on instantaneous torque control. Over the years, several strategies have been investigated in this domain, with the prominent strategies being field-oriented control and direct torque control. Regardless of the strategy employed, a precise rotor position during operation is an essential requirement. While a wide range of sensing technologies to monitor the rotor position have been employed, industries at large presently focus on Hall effect sensors for this application because they are highly cost-effective, low maintenance, noninvasive, and occupy very little space compared to its alternatives. However, the downside of using Hall effect sensors is their low accuracy. In particular, in the application of handheld battery-powered tools, output signals are affected by vibrations and harmonics from the electromagnetic field. Approaches that are being investigated to reduce or eliminate this noise from the signals can be broadly categorized into 1) installation position optimization, 2) filter methods, and 3) measurement model methods. As they are widely cited and easy to implement in the application of handheld battery-powered tools, four filter structures, namely, ANF with PLL, only PLL, SFE, and SFE with PLL, have been investigated in this thesis. This thesis evaluated the filter’s performance when applied to a real-world application of battery-powered tools. The filters were evaluated for their ability to preserve fundamental frequency components and reject harmonic content up to the 5th order. Visual inspections of Lissajous curves, rotor angle curves and generated reference signals provided insights into peculiarities during operation. Operations were categorized into four scenarios to facilitate the examination of filter response during acceleration and steady state in forward and reverse directions. Only performances of ANFPLL and SFE-PLL proved to be satisfactory with some limitations. The SFE filter yielded insignificant results which could be attributed to a lack of feedback mechanism. While the findings presented in this thesis contribute to the understanding of the viability of filter applications in batterypowered tools, additional testing is imperative. This entails the conversion of filter structures into algorithms suitable  for integration within software frameworks, ensuring their practical applicability and efficacy in real-world scenarios. / Högpresterande frekvensomriktare, såsom Permanent Magnet Synchronous Motor (PMSM) och Brushless DC Electric Motor (BLDC), förlitar sig på momentan vridmomentkontroll. Under årens lopp har flera strategier undersökts inom detta område, där de framträdande strategierna är fältorienterad kontroll och direkt vridmomentkontroll. Oavsett vilken strategi som används är en exakt rotorposition under drift ett väsentligt krav. Medan ett brett utbud av avkänningstekniker för att övervaka rotorns position har använts, fokuserar industrier i stort på Hall-effektsensorer för denna applikation eftersom de är mycket kostnadseffektiva, låga underhållskostnader, ickeinvasiva och upptar mycket lite utrymme jämfört med dess alternativ. Men nackdelen med att använda Hall-effektsensorer är deras låga noggrannhet. I synnerhet vid tillämpning av handhållna batteridrivna verktyg påverkas utsignalerna av vibrationer och övertoner från det elektromagnetiska fältet. Tillvägagångssätt som undersöks för att minska eller eliminera detta brus från signalerna kan brett kategoriseras i 1) installationspositionsoptimering, 2) filtermetoder och 3) mätmodellmetoder. Eftersom de är allmänt citerade och lätta att implementera i tillämpningen av handhållna batteridrivna verktyg, fyra filterstrukturer, nämligen Adaptive Notch Filter (ANF) med Phase Locked Loop (PLL), endast PLL, Synchronous Frequency Extractor (SFE) och SFE med PLL, har undersökts i denna avhandling. Denna avhandling utvärderade filtrets prestanda när det tillämpades på en verklig tillämpning av batteridrivna verktyg. Filtren utvärderades med avseende på förmågan att bevara grundfrekvenskomponenten och avvisa övertonsinnehåll upp till 5:e ordningen. Visuella inspektioner av Lissajous-kurvor, rotorvinkelkurvor och genererade referenssignaler gav insikter om egenheter under drift. Operationer kategoriserades i fyra scenarier för att underlätta undersökning av filterrespons under acceleration och stationärt tillstånd i framåt- och bakåtriktning. Endast prestanda av ANF-PLL och SFE-PLL visade sig vara tillfredsställande med vissa begränsningar. SFE-filtret gav obetydliga resultat som kunde tillskrivas bristen på återkopplingsmekanism. Även om resultaten som presenteras i denna avhandling bidrar till förståelsen av användbarheten av filtertillämpningar  i batteridrivna verktyg, är ytterligare tester absolut nödvändiga. Detta innebär omvandling av filterstrukturer till algoritmer lämpliga för integration inom mjukvaruramverk, vilket säkerställer deras praktiska tillämpbarhet och effektivitet i verkliga scenarier.
276

Имитационная модель приводного механизма рабочей клети стана ХПТ-90 : магистерская диссертация / Simulation model of the drive mechanism of the working stand of a cold pipe rolling mill (ХПТ-90)

Шапоренко, А. О., Shaporenko, A. O. January 2024 (has links)
В данной работе изучено общее строение станов ХПТ и в частности строение приводного механизма. На основе этих данных созданы модели деталей привода в системе трехмерного моделирования КОМПАС-3D. В программе Mathcad рассчитаны данные переходных процессов пуска двигателя, а в программе для моделирования систем Simulink смоделирован двигатель. Далее в среде для имитационного моделирования многозвенных трёхмерных механических систем Simscape Multibody собрана блок-схема приводного механизма рабочей клети стана ХПТ, к ней подключён электродвигатель. В результате исследования была получена имитационная модель приводного механизма рабочей клети стана ХПТ-90, проведена симуляция и исследование её работы. Данная модель позволяет: наглядно продемонстрировать работу механизма; обнаружить ошибки в работе; определить оптимальные параметры прокатки; оптимизировать процессы; снизить стоимость испытаний механизма; снизить затраты времени при проектировании. / In this work, the general structure of cold pipe rolling mills and, in particular, the structure of the drive mechanism were studied. Based on these data, models of drive parts were created in the KOMPAS-3D three-dimensional modeling system. The motor starting transient data was calculated using Mathcad, and the motor was simulated using the systems modeling software Simulink. Next, in the simulation environment for multi-link three-dimensional mechanical systems Simscape Multibody, a block diagram of the drive mechanism of the working stand of a cold pipe rolling mill was assembled, and an electric motor was connected to it. As a result of the study, a simulation model of the drive mechanism of the working stand of the cold pipe rolling mill (ХПТ-90) was obtained, a simulation and study of its operation was carried out. This model allows you to: clearly demonstrate the operation of the mechanism; detect errors in operation; determine optimal rolling parameters; optimize processes; reduce the cost of testing the mechanism; reduce time spent on design.
277

Autonomous air-to-air refueling : a comparison of control strategies

Venter, Jeanne Marie 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The air-to-air refuelling of large aircraft presents challenges such as a long fuel transfer time, slow aircraft responses and a large distance between the aircraft CG and the receptacle position. This project addresses some of these issues by adding a control system to keep the receiver aircraft in the correct position relative to the tanker to enable fuel transfer. This project investigates different control strategies which are designed to control the A330-300 during refuelling at one trim condition. The controllers are based on a mathematical aircraft model which was derived from a simulation model received from Airbus. The first set of controllers uses the aircraft actuators directly. Controllers that are based on the CG dynamics and the receptacle dynamics are compared. Due to the large distance between the CG and the receptacle it was found to be essential to control the receptacle position, and not only the CG position. Also, a controller that is based on a model of the receptacle dynamics performs better. The second set of controllers uses the aircraft manual control laws as an inner loop controller. This set of controllers and the last direct actuator controller use the same axial controller that uses the engine thrust to control axial position. It was found that both the direct actuator controller and the manual control laws controller are able to keep the receptacle within the disconnect envelope in moderate turbulence. In both sets of controllers the axial controller fails to keep the receptacle reliably within the disconnect envelope in light turbulence. From the results it is concluded that both the direct actuator control and manual control laws can be used to successfully control the receptacle position in the normal and lateral positions as long as the receptacle kinematics are included in the control design. Using only the engine thrust for axial control is insufficient. Several recommendations are made to improve the axial control and also how these results can be used in future work. / AFRIKAANSE OPSOMMING: Die lug-tot-lug brandstof hervulling van groot vliegtuie het uitdagings soos ’n lang hervullingstyd, stadige vliegtuig dinamika en ’n groot afstand tussen die hervullingspoort en die vliegtuig massamiddelpunt. Hierdie projek spreek sommige van hierdie uitdagings aan deur ’n beheerstelsel by te voeg wat die vliegtuig in die korrekte posisie relatief tot die tenker hou vir brandstofoordrag om plaas te vind. Hierdie projek ondersoek verskillende beheerstrategieë wat ontwerp is om die A330- 300 te beheer by ’n enkele gestadigde toestand. Die beheerders is gebaseer op ’n wiskundige vliegtuigmodel wat vanaf ’n simulasiemodel afgelei is. Die simulasiemodel is vanaf Airbus verkry. Die eerste stel beheerders beheer direk die vliegtuig se beheeroppervlakke. Beheerders wat onderskeidelik die massamiddelpunt en die hervullingspoort beheer word vergelyk. Daar is gevind dat dit essensieel is om die hervullingspoort te beheer en nie slegs die massamiddelpunt nie, as gevolg van die groot afstand tussen hierdie twee punte. Die tweede stel beheerders gebruik die vliegtuig se eie beheerwette as ’n binnelusbeheerder en vorm self die buitelus. Albei stelle beheerders gebruik dieselfde aksiale beheerder wat enjin stukrag gebruik om die aksiale posisie te beheer. Daar is gevind dat beide stelle beheerders die hervullingspoort binne die ontkoppelingsbestek kan hou in die normale en laterale rigtings tydens matige turbulensie. In beide stelle beheerders is dit die aksiale beheerder wat faal om die hervullingspoort betroubaar in posisie te hou, selfs in ligte turbulensie. Vanaf die resultate word afgelei dat beide die direkte beheerder en die buitelusbeheerder gepas is om die laterale en normale posisiebeheer toe te pas mits die dinamika van die hervullingspoort in ag geneem word. Om slegs stukrag te gebruik vir aksiale beheer is nie voldoende nie, en verskeie voorstelle word gemaak om die aksiale beheer te verbeter in toekomstige navorsing.
278

INVESTIGATION OF THE EFFECT OF THE TRANSFORMER CONNECTION TYPE ON VOLTAGE UNBALANCE PROPAGATION: CASE STUDY AT NÄSUDDEN WIND FARM

Styliaras, Nikolaos January 2016 (has links)
The objective of this Thesis is to investigate the phenomenon of voltage unbalance on electrical wind power systems. A large part of this work is the literature review of all relative work that has been done so far. This serves first as a guideline to define and measure voltage unbalance and second as a tool to spot open research questions that can inspire future work. A case study is then used to investigate the voltage unbalance at a wind farm in Näsudden, Gotland. Using real-time measurements and a simulation of the power system in MATLAB/Simulink, an evaluation of the propagation of the voltage unbalance from the distribution to the turbine level is carried out. The effect that different transformer connection types have on the propagation is studied through simulations. Many assumptions and simplifications had to be made due to several limiting factors during this work, mainly related to time and data restrictions. The main result shows that when Delta – Wye Grounded and Wye – Wye Grounded transformers are used, the unbalance is halved when it passes to the turbine side. On the other hand, when Wye Grounded – Wye Grounded configuration was used, the unbalance was unaffected. The results also include a comparison of the use of different indices to quantify a voltage unbalance.
279

Study of a battery energy storagesystem in a weak distributiongrid

Lindstens, Jonas January 2017 (has links)
The awareness of the problems with fossil energy sources have increased the past decades. To decrease the effects of the fossil fuels on the climate and the environment, the use of intermittent energy sources such as solar- and wind power are increasing. Intermittent generation creates instability in the power grid, which cause fluctuations in the voltage and the frequency of the power grid. To be able to handle these fluctuations, regulating capacity such as for example pumped storage or batteries are needed. This thesis has investigated how the placement and the power capacity of a battery energy storage system affects the possibility for frequency and voltage regulation in a weak distribution grid. The investigation was made in MATLAB Simulink by creating a weak radial distribution grid with a high penetration of solar power. The distribution grid had variable loads with different power consumption at each bus, creating instability in the distribution grid. The optimal placement of a battery energy storage system is firstly at the largest load and secondly as far away from the other power generation units as possible. A battery storage with a power capacity that can handle all consumption is optimal. It is possible to have a smaller power capacity if the grid is stable enough to withstand the appearing fluctuation of frequency or voltage. The frequency variations are more dependent on the power capacity and the voltage variations are more dependent on the placement of the battery energy storage system. ISSN:
280

Simulink Simulation of an Airgapless Motor

Chuyue Tang (5931140) 16 January 2019 (has links)
<div>Nowadays, electrical motors are widely used in the automotive industry because of their high efficiency and lossless characteristics. One downside is that the system is complicated to control and it requires more complex control strategies. Moreover, compared to other motors, electrical motors produce less torque, which limits its capability.</div><div><br></div><div>Therefore, in this thesis, an air-gapless electric motor is presented. Instead of having a static air gaps between the rotor and the stator, the gap changes dynamically creating contact which generates higher torques. A SIMULINK simulation method is used for this motor in order to show the systems dynamic behaviors.</div><div><br></div><div>Five blocks are used in the system: the block to nd phase currents, the block to find phase torque, the block to find self-inductance, the block to obtain mechanical speed of the motor and the block to simulate the saturation effect. These blocks are developed based on the analytical relationships between components, which are shown in Chapter two.</div><div><br></div><div>Moreover, saturation effect in the iron cores is taken into consideration in this thesis due to the fact that it always effects the shape of the magnetic eld curves. And four different materials are discussed and compared in Chapter three. The findings in this chapter is that carbon steel and silicon steel serve as better materials of the rotor in the air-gapless motor than soft ferrite and nickel steel because they tend to have higher torques under same levels of the currents and they have larger torque stability regions.</div><div><br></div><div><div>As for Chapter four, a current control strategy is proposed with an inverter, this could simulate the current controller in a real application. Trial and error PID controller tuning method is discussed in Chapter four.</div></div>

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