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Design aspects and optimisation of an axial field permanent magnet machine with an ironless statorWang, Rong-Jie 04 1900 (has links)
Thesis (PhDEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The advent of new high energy product permanent magnet materials has opened great opportunities
for novel electrical machine topologies with advantageous features such as high efficiency
and high power/weight ratio. Amongst others, axial field permanent magnet (AFPM)
machines with ironless stators are increasingly being used in power generation applications.
Because of the absence of the core losses, a generator with this type of design can operate at a
substantially high efficiency. Besides, the high compactness and disc-shaped profile make this
type of machine particularly suitable for compact integrated power generation systems. Due
to construction problems, the generator application of this type of machine has been limited
to quite a low power range. There is a need to investigate the performance capability of this
type of AFPM machine in the upper medium power level.
The focus of this thesis is on the design optimisation of the air-cooled AFPM generator with
an ironless stator. A design approach that directly incorporates the finite element field solution
in a multi-dimensional optimisation procedure is developed and applied to the design
optimisation of a 300 kW (at unity power factor) AFPM generator. To enable an overall
design optimisation of the machine, different design aspects, such as the cooling capacity, the
mechanical strength and eddy loss, are also studied in this research.
To enable the free movement of the rotor mesh with respect to the stator mesh, the air-gap
element originally proposed by Razek et. al. is derived for Cartesian coordinate systems. For
minimising the large computation overhead associated with this macro element, a number of
existing time-saving schemes have been utilised together with the derived Cartesian air-gap
element. The developed finite element time-step model is applied to calculating the steadystate
performance of the AFPM machine.
Since the flux distribution in an AFPM machine is three dimensional by nature, calculating
the eddy current loss by merely using a simple analytical method may be subject to a significant
error. To overcome this problem, the two dimensional finite element field modelling
is introduced to perform accurate field analysis. To exploit the full advantages of the twodimensional
finite element modelling, a multi-layer approach is proposed, which takes into account the variation of the air-gap flux density in the conductors with regard to their relative
positions in the air-gap. To account for the radial variation of the field, a multi-slice finite
element modelling scheme is devised.
The thermal analysis is an important aspect of the design optimisation of AFPM machines.
From a design point of view, it is preferable to have a simple but effective method for cooling
analysis and design, which can easily be adapted to a wide range of AFPM machines. In
this thesis a thermofluid model of the AFPM machine is developed. The fluid flow model is
needed for calculating the air flow rate, which is then used to find the convective heat transfer
coefficients. These are important parameters in the subsequent thermal calculations.
Experimental investigations have been carried out to verify each of the above-mentioned
models/methods. With these models implemented, the design optimisation of an air-cooled
ironless stator 300 kW (at unity power factor) AFPM generator is carried out. The performance
measurements done on the fabricated prototype are compared in this thesis with
predicted results. The study shows that the proposed design approach can be applied with
success to optimise the design of the AFPM machine. The advantages of high power density,
high efficiency, no cogging torque and good voltage regulation make this type of AFPM machine
very suitable for power generator applications. The optimum steady-state performance
of the AFPM machine shows that this machine with an ironless stator is an excellent candidate
for high speed power generator applications, even in the upper medium power level.
The good cooling capacity of this type of machine holds the promise of its being a self-cooled
generator at high power ratings. / AFRIKAANSE OPSOMMING: Die uitvinding van nuwe hoë energiedigtheid permanent magneet materiale het groot geleenthede
vir nuwe elektriese masjien topologië laat ontstaan met voordelige eienskappe soos hoë
benuttingsgraad en hoë drywing/gewig verhouding. Onder andere word die aksiaalveld permanente
magneet (AVPM) masjiene met kernlose stators toenemend gebruik vir elektriese
generator toepassings. As gevolg van die afwesigheid van kernverliese kan 'n generator met
hierdie tipe ontwerp teen 'n aansienlik hoë benuttingsgraad werk. Daarbenewens maak die
hoë kompaktheid en skyfvorm-profiel die masjien in besonder geskik vir die ontwikkeling van
kompak geïntegreerde drywing generator stelsels. As gevolg van konstruksie probleme is die
toepassing van hierdie tipe masjien as generator beperk tot redelik lae drywingsgebiede. Dit
is nodig om die werkverrigtingsvermoë van hierdie tipe AVPM masjien in die boonste medium
drywingsgebied te ondersoek.
Die fokus van hierdie tesis is op die ontwerp-optimering van 'n lugverkoelde AVPM generator
met 'n kernlose stator. 'n Ontwerpsbenadering wat die eindige element veldoplossing
in 'n multi-dimensionele optimeringsprosedure insluit, is ontwikkel en toegepas op die ontwerpsoptimering
van 'n 300 kW (by eenheidsarbeidsfaktor) AVPM generator. Om 'n globale
ontwerpsoptimering van die masjien te kan doen is verskillende ontwerpsaspekte soos die
verkoelingskapasiteit, meganiese sterkte en werwelverliese ook in hierdie navorsing bestudeer.
Om die vrye beweging van die rotormaas ten opsigte van die statormaas te verseker is die
lugspleet-element, soos oorspronklik deur Razek et al voorgestel, afgelei vir Cartesiaanse
koórdinaat stelsels. Om die lang berekeningstyd geassosieer met hierdie makro-element te
minimaliseer is 'n aantal bestaande tydbesparende metodes saam met die ontwikkelde Cartesiaanse
lugspleet-element gebruik. Die ontwikkelde eindige element tydstapmodel is toegepas
om die bestendige werkverrigting van die AVPM masjien te bereken.
Aangesien die vloedverspreiding in 'n AVPM masjien van nature drie-dimensioneel is, kan
die berekening van die werwelstroomverliese tot aansienlike foute lei as eenvoudige analitiese
metodes gebruik word. Om hierdie probleem te oorkom is twee-dimensionele eindige element
modellering gebruik om akkurate veld-analise te doen. Om die volle voordele van die twee- dimensionele eindige element modellering te eksploiteer is 'n multi-laag benadering voorgestel
wat die variasie van die lugspleetvloeddigtheid in die geleiers met betrekking tot hulle relatiewe
lugspleetposisies in ag neem. Om voorsiening te maak vir die radiale variasie van die
veld, is 'n multi-skyf eindige element modelleringstegniek ontwikkel.
Die termiese analise is 'n belangrike aspek van die ontwerpsoptimering van AVPM masjiene.
Vanuit 'n ontwerpsoogpunt is dit verkieslik om 'n eenvoudige maar tog effektiewe metode van
verkoelingsanalise en -ontwerp te hê wat maklik toegepas kan word op 'n wye reeks van AVPM
masjiene. In hierdie tesis word 'n termovloeimodel van die AVPM masjien ontwikkel. Hierdie
vloeimodel is nodig vir die berekening van die lugvloeitempo, wat op sy beurt weer nodig is
om die konveksie hitte-oordrag koëffisiënte te bepaal. Hierdie is belangrike parameters in die
opvolgende termiese berekeninge.
Eksperimentele ondersoek is uitgevoer om elkeen van die bogenoemde modelle en metodes
te verifieer. Nadat hierdie modelle geïmplimenteer is, is die ontwerpsoptimering van 'n 300
kW (by eenheidsarbeidsfaktor) lugverkoelde kernlose stator AVPM generator uitgevoer. Die
werkverrigtingmetings gedoen op 'n vervaardigde prototipe masjien, word in hierdie tesis
vergelyk met voorspelde resultate. Daar word getoon dat die voorgestelde ontwerpsbenadering
met sukses toegepas kan word om die ontwerp van die AVPM masjien te optimeer. Die
voordele van hoë drywingsdigtheid, hoë benuttingsgraad, geen vertandingsdraaimomente en
goeie spanningsregulasie maak hierdie masjien baie aantreklik vir generator toepassings. Die
optimum bestendige werkverrigting van die AVPM masjien toon dat hierdie masjien met 'n
kernlose stator 'n goeie kandidaat is vir hoë spoed generator toepassings, selfs in die boonste
medium drywingsgebied. Die goeie verkoelingskapasiteit van hierdie tipe masjien hou die
belofte in van'n selfverkoelde generator by hoë drywing aanslae.
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Development of a novel air-cored permanent magnet linear generator for direct drive ocean wave energy convertersVermaak, Rieghard 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In hierdie tesis word ’n nuwe lug kern permanent magnet (PM) lineêre generator (LG) vir toepassing tot direk
aangedrewe (DA) oseaan golf energie omsetters (GEO) ontwikkel. Die nuwe LG word ontwikkel vanaf die
lineêre dubbel-kant topologie in ’n poging om probleme met die huidige longitudinale vloed (LV) yster kern
LGs, wat tot dusvêr oorheersend voorkom in eksperimentele DA-GEOs, te oorkom. Die grootste probleem met
hierdie LGs is die masiewe aantrekkings kragte tussen hul yster stators en die PM transleerders. ’n Groot hoeveelheid
strukturuele staal word benodig om die luggaping te handhaaf, terwyl die las op die laars ook ’n groot
probleem is. Die nuwe LG gebruik ’n lug kern stator wat alle aantrekkings kragte tussen die stator en transleerder
elimineer en dus die nodige strukturuele material verminder. Die topologie van die transleerder is ook
van so ’n aard dat die netto aantrekkings kragte op enige spesifieke PM ideaal nul is; dit verminder die strukturuele
materiaal selfs verder. Die transleerder het ook ’n nuwe transversale vloed pad wat die sogenaamde paarwyse
vloed koppeling wat in LV-LGs voorkom, en die negatiewe effekte daarvan, verhoed.
’n Aantal nuwe bydraes tot die veld van LGs vir DA-GEO word in hierdie tesis gemaak. ’n Nuwe topologie lug
kern PMLG is ontwikkel soos bespreek. Dit sluit in die ontwikkeling van analitiese en eindige element modelle
en ’n optimerings prosedure wat vinnig optimale dimensies vir minimum aktiewe massa van die nuwe LG vind.
In die ontwerp word dit ook gevind dat die drywingsdigtheid van LGs verbeter kan word deur zero oorvleuling
tussen die die stator en transleerder by die slag endte toe te laat. ’n 1 kW prototipe van die nuwe LG word ontwerp
en gebou; die uitvoerbaarheid van die konstruksie vir die nuwe topologie op ’n klein skaal word dus gedemonstreer.
’n Unieke toets opstelling word ook ontwerp en is gebasseer op bestaande toerusting in die vorm van
’n wind turbine generator en rug-aan-rug spannings bron omsetters. Met die toets opstelling word ’n enkel frekwensie
golf ge-emuleer om die teorie en simulasies te verifieer en word ook ’n voorspellende beheer strategie
geimplementeer, wat vir die eerste keer gedemonstreer word vir LGs vir DA-GEOs. Goeie ooreenstemming tussen
die gemete en gesimuleerde data bevestig die voorgestelde modellerings en ontwerps metodes. / AFRIKAANSE OPSOMMING: In this thesis, a novel air-cored permanent magnet (PM) linear generator (LG) is developed with application to
direct drive (DD) wave energy converters (WECs). The novel LG is developed from the linear double-sided topology
in an attempt to overcome the problems with current longitudinal flux (LF) iron-cored LGs, which have
so far been dominant in experimental DD-WECs. The biggest problem with these LGs is the massive attraction
forces between their iron stators and PM translators. A large amount of structural steel is required to maintain the
air gap, while the load on the bearings is also a large concern. The novel LG uses an air-cored stator which
eliminates any attraction forces between the stator and translator and hence reduces the required structural material.
Furthermore, the topology of the translator is such that the net attraction force on any particular PM is ideally
zero, which even further reduces the structural material required for the translator. A new transverse circulating
flux path is also introduced in the translator which prevents pair-wise flux coupling and its negative effects
as observed in LF-LGs.
A number of new contributions are made to the field of LGs for DD-WECs in this thesis. A novel topology aircored
PMLG is developed as described. This includes the development of analytical and finite element models
and an exhaustive optimisation procedure for quickly finding optimal dimensions for minimum active mass of
the novel LG. In the design it is also found that the power density of LGs can be improved by allowing zero
overlap between the stator and translator at the stroke ends. A 1 kW prototype of the novel LG is designed and
built; the feasibility of constructing the novel LG on a small scale is as such demonstrated. A unique test rig is
designed based on existing equipment in the form of a wind turbine generator and back-to-back voltage source
converters. The test rig allows emulation of a monochromatic wave for verifying the theory and simulations and
also allows for implementation of a predictive control strategy, which is for the first time demonstrated for LGs
for DD-WECs. Good agreement between measured and simulated data confirms the presented modelling and design
methods.
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Transformerless series dip/sag compensation with ultracapacitorsBecker, Martin Gerhard 12 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This thesis covers the development of a transformerless series dip compensator. Of all known power
quality problems, voltage dips are the greatest reason for concern. Series injection dip compensators
offer the advantage of only having to compensate for the decrease in supply voltage during a dip.
This results in significant reduction in converter ratings and energy storage requirements. The aim of
this thesis was to take up previous developments and combine them with new technologies to
maximize their functionality. The new design was implemented with ultracapacitors to offer a
maintenance-free device lifespan of 20 years. As they are very expensive, a new topology was
introduced in this thesis to maximize their use so that they become viable for industry. Furthermore,
a new method of daisy chaining switches was introduced to minimize costs involved in controlling
them. A single-phase compensator, with this new topology and the new way of controlling switches,
was designed and built according to specifications stated by Eskom. This ultracapacitor-based dip
compensator was tested with a dip generator, developed by the University of Stellenbosch for
different load currents. The experimental results confirmed simulations made with identical
parameters. This thesis presents a reliable and cost effective solution for dip compensation. / AFRIKAANSE OPSOMMING: Hierdie tesis dek die ontwikkeling van ’n transformatorlose duik kompenseerder. Van al die bekende
toevoerkwaliteit probleme wek duike in die spanning die meeste kommer. Serie-injeksie
kompenseerders het die voordeel dat hulle net kompenseer vir die verlies in die toevoerspanning
tydens die duik. Dit het ’n beduidende vermindering in die omsetterkenwaardes en
energiestoorvereistes tot gevolg. Hierdie tesis mik om vorige soortgelyke ontwikkelings op te volg
en te verbeter met nuwe tegnologie om die funktionliteit te maksimeer. Die ontwerp is
geimplementeer met ultrakapasitore wat die onderhoudsvrye toestel ‘n leeftyd van 20 jaar toelaat.
Omdat ultrakapasitore so duur is moes ‘n nuwe topologie onwikkel word om die gebruik van
ultrakapasitore meer ekonomies aantreklik te maak. Daar is ook ‘n nuwe manier van skakelaar
beheer ontwikkel wat toelaat dat baie skakelaars oor een optise veesel beheer kan word. ‘n Enkel
fase dip kompensaeerder is toe onwikkel en gebou volgens Eskom se spesifikasies. Die
ultrakapasitor gebaseerde omsetter is getoets met ‘n dip generator wat deur die Universiteit van
Stellenbosch ontwikkel is. Die praktiese resultate bevestig die simulasies wat gedoen is met dieselfe
parameters. Hierdie tesis lei tot ‘n betroubaare en ekonomiese oplossing vir duik kompensasie.
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Optimisation methods applied to compensator placementBurger, I. 12 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The optimal placement of different types of compensators on electrical networks is a complex
task faced by network planners and operations engineers. The successful placement of these
devices normally involves a large number of power flow studies and relies heavily on the
experience of the engineer. Firstly the operation and application of the different types of
compensators must be clearly understood. Secondly the application of combinations of
different compensators on a specific network must be investigated. Then the dynamics of the
network and interaction between the network and the compensator/s must be studied under a
wide variety of network conditions and load levels. This task is further complicated by the
non-linear nature of the mathematical equations that govern the power flow and voltage
distribution on an electrical network. Yet another complication is the fact that some of the
variables that describe an electrical network can be non smooth or discrete. For instance, the
discrete value of a tap position of a power transformer can only assume an integer value. To
simplify the problem of compensator placement, advanced software tools are available that
are capable of solving power flows of networks containing compensators. To a large degree,
however, these tools still rely on the user to make intelligent decisions as to the configuration
of networks and the placement of compensators. In many cases trial and error is the only way
to find a good solution.
The purpose of this thesis is to show the different techniques available to implement
intelligent algorithms capable of finding optimal solutions specific to the placement of voltage
regulators. State of the art algorithms are implemented in Matlab that can place voltage
regulators on sub transmission, reticulation and low voltage networks. The sub transmission
and reticulation placement algorithm is a combination of an SQP technique and a simple
combinatorial algorithm. The low voltage placement program is based on a simple genetic
algorithm with a few customized features that has been developed to ensure fast convergence.
The programs developed were used to do optimal voltage regulator placement on a number of
networks. As far as possible real world networks were used. Where real world networks
were not available test networks were used that closely resemble real networks, as they exist
on typical networks owned by Eskom Distribution.
It was found that SQP is a very efficient algorithm for optimising large non-linear problems
such as the placement of a Step Voltage Regulator on a large electrical network. This
algorithm however does not handle discrete variables very well and is also limited in handlingany reconfiguration of the network due to the placement of series devices such as voltage
regulators. To cater for reconfiguration, it is necessary to combine the SQP algorithm with a
combinatorial algorithm.
The genetic algorithm used to do optimal placement of multiple Electronic Voltage
Regulators on low voltage networks was found to be very efficient and robust. This can be
attributed to the simplicity of the algorithm as well as the fact that it does not rely on the
availability of derivative and second derivative information to move towards an optimal
solution. Instead, it only uses fitness values obtained from function evaluations to optimise
the placement problem. Another useful feature of using a genetic algorithm is that the
algorithm does not get stuck in sub optimal areas in the solution space. Both the placement
programs developed are relatively simple and do not consider all the factors involved in the
placement of voltage regulators. However, the addition of any number of factors is however
possible with further development of the programs as presented in this thesis. / AFRIKAANSE OPSOMMING: Die optimale plasing van verskillende kompenseerders op elektriese kragstelsels is ´n
moeilike probleem vir beplanners en operasionele personeel. Die plasing van
kompenseerders gaan gewoonlik gepaard met ´n groot hoeveelheid netwerk studies en die
sukses daarvan berus gewoonlik op die ondervinding van die ingenieur. Eerstens moet die
werking en toepassing van elke kompenseerder behoorlik verstaan word. Tweedes moet die
plasing van ´n enkele asook kombinasies van verskillende kompenseerders ondersoek word.
Dan moet die dinamika van die netwerk en interaksie met die kompenseerder/s bestudeer
word vir al die moontlike netwerk konfigurasies en belasting vlakke. Die taak word verder
bemoeilik deur die nie-liniêre vorm van die wiskundige vergelykings wat die netwerk vrag en
spanning verspeiding beskryf. Nog ´n komplikasie is die feit dat van die veranderlikes wat
die probleem beskryf, diskreet is. Byvoorbeeld die tap posisie van ´n transformator kan slegs
´n heel getal aanneem. Om die plasing van kompenseerders te vergemaklik is gevorderde
sagteware beskikbaar wat simulasies kan doen van netwerke wat kompenseerders bevat. Tot
´n groot mate is die sagteware nog steeds afhanklik van intellegente besluitneming deur die
gebruiker. In die algemeen moet ´n groot hoeveelheid studies nog steeds gedoen work om ´n
goeie oplossing te vind.
Die doel van hierdie tesis is om die verskillende tegnieke te wys wat beskikbaar is om
intelligente algoritmes te implementeer wat optimale oplossings kan vind vir spesifiek die
plasing van spanning reguleerders. Moderne algoritmes is in Matlab geimplementeer wat
spanning reguleerders op sub transmissie, retikulasie en laag spanning netwerke kan plaas.
Die sub transmissie en retikulasie plasings algoritme is gebaseer op ´n kombinasie van ´n
sekwensieële kwadratiese programmering metode en ´n eenvoudige kombinatoriese metode.
Die laag spanning plasings program is gebaseer op ´n eenvoudige genetiese algoritme met ´n
paar unieke verstellings om vinnige konvergensie te verseker. Die twee programme wat
ontwikkel is word dan gebruik on spanning reguleerders te plaas op ´n paar netwerke. So ver
moontlik is bestaande netwerke gebruik. Waar bestaande netwerke nie beskikbaar was nie is
toets netwerke saamgestel wat gebaseer is op bestaande Eskom netwerke.
Daar is gevind dat sekwensieële kwadratiese programmering ´n effektiewe algoritme is om
groot nie liniêre optimerings probleme, soos die plasing van spanning reguleerders, op te los.
Hierdie algoritme is egter nie geskik om diskrete veranderlikes te hanteer nie. Dit is verder
ook nie geskik om enige netwerk rekonfigurasie te hanteer tydens die plasing van seriesgeskakelde kompenseerders soos spanning reguleerders nie. Om die rekonfigurasie moontlik
te maak is dit nodig om die sekwensieële kwadratiese programmering te kombineer met ´n
kombinatoriese algoritme. Daar is verder gevind dat die genetiese algoritme wat gebruik is
om elektroniese spanning reguleerders te plaas op laag spanning netwerke baie effektief en
robuust is. Dit is as gevolg van die eenvoudigheid van die algoritme en die feit dat dit nie
afhanklik is van afgeleide en tweede afgeleide informasie om na die optimale oplossing te
beweeg nie. Die algoritme gebruik slegs fiksheid waardes bereken van funksie evaluasies om
die probleem te optimeer. Nog ´n voordeel van genetiese algoritmes is dat dit nie in sub
optimale gebiede van die oplossing ruimte stil staan nie.
Beide die programme wat ontwikkel is, is redelik eenvoudig en neem nie al die faktore in ag
wat gepaard gaan met die plasing van spanning reguleerders nie. Addisionele faktore kan
egter maklik ingesluit word deur verdere ontwikkeling van die bestaande programme.
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Independent formant and pitch control applied to singing voiceCalitz, Wietsche Roets 12 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: A singing voice can be manipulated artificially by means of a digital computer for the
purposes of creating new melodies or to correct existing ones. When the fundamental frequency
of an audio signal that represents a human voice is changed by simple algorithms,
the formants of the voice tend to move to new frequency locations, making it sound unnatural.
The main purpose is to design a technique by which the pitch and formants of a
singing voice can be controlled independently. / AFRIKAANSE OPSOMMING: Onafhanklike formant- en toonhoogte beheer toegepas op ’n sangstem: ’n Sangstem kan
deur ’n digitale rekenaar gemanipuleer word om nuwe melodie¨e te skep, of om bestaandes
te verbeter. Wanneer die fundamentele frekwensie van ’n klanksein (wat ’n menslike stem
voorstel) deur ’n eenvoudige algoritme verander word, skuif die oorspronklike formante
na nuwe frekwensie gebiede. Dit veroorsaak dat die resultaat onnatuurlik klink. Die hoof
oogmerk is om ’n tegniek te ontwerp wat die toonhoogte en die formante van ’n sangstem
apart kan beheer.
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Electricity theft detection on a low voltage reticulation environmentDoorduin, Riaan 12 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Electricity theft in South Africa has become a major problem. This led to several developments
from both industries and research institutes to counter these actions. Since equipment is already
installed and major capital has been invested to provide electricity for a broad spectrum
of consumers, the challenge is to find a low cost solution harnessing current investments and
technology to detect electricity theft more accurately.
This thesis investigates into the electricity theft topic. Two different methods, Time Domain
Pulse Reflectometry and a data driven platform based on the Theory of Constraints philosophy,
were investigated to provide means to detect and determine the impact of illegal electricity
usage. Both methods required detailed designs to conduct preliminary proof of concept tests in
a laboratory environment.
These methods are evaluated against their economical viability, possible practical implications
and applications. This thesis presents a practical approach to electricity theft detection
and provides the basic tools for management of this ever-increasing problem. / AFRIKAANSE OPSOMMING: Suid Afrika se elektrisiteit diefstal statistiek het die afgelope jare skrikwekkend gegroei. Dit het
die industrie genoop om baie meer navorsing in die area te doen. Met reeds gevestigde toerusting
en tegnologie om di´e energie medium so effektief moontlik te versprei, is die uitdaging juis
om ’n ekonomiese oplossing te vind om reeds beskikbare tegnologie¨e meer doeltreffend aan te
wend.
Die doel van die tesis is om die gebied van elektrisiteit diefstal na te vors. Twee verskillende
metodes is ondersoek, naamlik Tydgebied-pulse-reflektometrie en ’n informasie gebaseerde
stelsel wat op die Randvoorwaarde Teorie gebaseer is, om effektief die omvang van elektrisiteit
diefstal in ’n mikro, asook makro omgewing te bepaal. Die twee metodes is in ’n beheerde
omgewing getoets sodat die konsepte wat ontwikkel is bewys kon word.
Die metodes is ge-evalueer in terme van die ekonomiese lewensvatbaarheid daarvan met inagneming
van die praktiese implikasies. Die tesis bied bestuur die nodige kennis om elektrisiteit
diefstal in die praktyk doeltreffend die hok mee te slaan.
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Bidirectional converter for a stirling energy systemRedecker, H. H. (Hans Henning) 12 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This thesis discusses a 23 kW three-phase AC bus system that is utilized together with the
“Stirling Energy System (SES) Integrated Solar Dish-Stirling Module” to function as a
mini-grid for off-grid locations. The system is designed to supply power to 27 rural
households. This three-phase AC bus system includes a bidirectional 4-wire PWM
converter and a battery bank for energy storage. The simulations and results presented
show that the system can function as a rectifier and as an inverter. The system operates as
an inverter when the SES starts up and when different AC loads are connected to the AC
bus. The unit functions as a rectifier when the battery bank is charged. The design was
implemented successfully in a practical system and measurements revealed that the
system functioned as a standalone unit. / AFRIKAANSE OPSOMMING: Hierdie tesis bespreek ‘n 23 kW drie-fase vier-draad WS bus stelsel wat saam met die
“Stirling Energy System (SES) Integrated Solar Dish-Stirling Module” gebruik word om
as ‘n alleenstaande stelsel in ’n plattelandse omgewing te laat funksioneer. Die sisteem is
ontwerp om vir 27 plattelandse huise drywing te lewer. Hierdie stelsel behels ‘n drie-fase
GS na WS omsetter, saam met loodsuur batterye as energiestoor. Die simulasies en
resultate wat gegee word, dui aan dat die omsetter as ‘n wisselrigter en ook as ‘n
gelykrigter kan werk. Die stelsel funksioneer as ‘n wisselrigter as die SES aanskakel, en
as ekstra laste op die WS bus gekoppel word. Die sisteem funksioneer as ‘n gelykrigter as
die batterye gelaai word. Die ontwerp is suksesvol in ‘n praktiese stelsel geimplimenteer
wat as ‘n alleenstaande stelsel funksioneer.
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Design and implementation of a DSP based controller for power electronic applicationsVan Heerden, Gerhard Johann 04 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: In the field of power electronic engineering, there is a need for a reconfigurable power electronic
controller. Such a controller will enable engineers to stay focussed on their main field
of study, not being side-tracked by the process of designing a high-speed digital controller to
implement their ideas with. The design, construction and implementation of such a controller is
presented in this paper. The design process involved defining the specifications of the controller
and finding electronic components to satisfy them. After suitable components had been identified,
a schematic design of the system was done. The netlist of the schematic was exported
to a printed circuit board (PCB) design program, where the final layout was done and the connections
between the devices routed. Before the PCB was manufactured, the firmware for the
programmable logic devices (PLDs) was written to ensure that it fits in the selected PLDs of
the system. After the PCB was manufactured and all its components fitted, it was tested and
eventually used to implement the control of a shunt active power filter. / AFRIKAANSE OPSOMMING: Wanneer navorsing gedoen word in die drywings-elektronika gebied, word ’n behoefte vir ’n
heropstelbare drywings-elektroniese beheerder ondervind. So ’n beheerder sal ingenieurs in
staat stel om gefokus te bly op hulle hoof studieveld, sonder dat hulle aandag hoef te skenk
daaraan om ’n ho¨e spoed digitale beheerder te ontwerp om hulle idees mee te implementeer.
Die ontwerp, konstruksie en implementering van so ’n beheerder word in hierdie tesis voorgelˆe.
Die ontwerp behels die bepaling van die spesifikasies van die beheerder en die opsporing van
elektroniese komponente wat hierdie spesifikasies sal bevredig. Nadat geskikte komponente
gevind is, is ’n skematiese ontwerp van die hele beheerder gedoen. Die lys van die verbindings
tussen die komponente (Eng. netlist) is na die stroombaanbord ontwerp program gestuur, waar
die finale uitleg van die bord gedoen is. Voordat die bord gemaak kon word, is die programmatuur
vir die programmeerbare logikatoestelle geskryf om te verseker dat dit in die toestelle
wat in die sisteem gebruik word, sal pas. Nadat die stroombaanborde vervaardig is en al die
komponente daarop gemonteer is, is die bord getoets en uiteindelik gebruik om die beheer van
’n aktiewe drywingsfilter te implementeer.
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Dynamics and Energy Management of Electric VehiclesVan Schalkwyk, Daniel Jacobus 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / The work presented in this thesis forms part of the participation of the University of Stellenbosch in an electric vehicle project. The thesis deals with three aspects of the dynamics and energy management of the electric vehicle. The three aspects that are dealt with are the suspension system of an electric vehicle with in-wheel propulsion, the traction control of an electric vehicle and the energy system of such a vehicle.
An investigation is presented in the thesis on the effect the mass of the hub motors has on the safety, stability and comfort of the electric vehicle. The investigation is done through a system frequency analysis and a comparative simulation. A comparison is made between a standard vehicle and a vehicle with in-wheel propulsion. A vehicle model is derived for the simulation of the vehicle. Finally, a few of the results of physical measurements performed are also presented.
The traction control requirements of an EV are investigated. A discussion is given on the parts that make up an EV’s traction control system. A few examples of possible traction control systems are given through a step by step evolution of a traction control system. A vehicle model is derived for both static and kinetic friction conditions. The model is used in simulations to illustrate the need for traction control in EV’s.
The thesis presents two methods for choosing a battery pack size, in terms of energy capacity etc. The difficulties associated with choosing a battery pack, using each of these methods are given. A battery pack choice for the specific electric vehicle, is presented. The measurements of one of the required charge-discharge cycles are presented to illustrate the charge and discharge curves of the battery cells used.
The management of energy flow within the energy system of the EV is crucial, especially if regenerative braking is utilized. This is to protect the battery cells as well as to extend the range of the vehicle. The thesis presents the evaluation of an energy management system (EMS) using ultra capacitors as auxiliary storage device. An electronic load system is designed to simulate the operation of the vehicle motors. The transfer functions for the EMS and load system are derived and used to design the respective control algorithms. The control algorithms were implemented in both simulation as well as a laboratory setup to show the operation of the EMS.
A new energy system configuration is presented. The aim of the new configuration is to solve certain problems encountered when implementing a conventional EMS. The operation of the new configuration is discussed. A comparative study is made between the conventional and the new configurations.
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Design of a haptic controller for excavatorsVan der Zee, Lodewyk Francois 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / The input orientation of the excavators in use today usually comprises
two joysticks that control the actuator links individually. In order to perform
an excavation task, several different combinations of joystick inputs
are required, placing high psychomotor demands on the operator.
In training an operator this creates a steep learning curve, with a lengthy
training time and a reasonable amount of experience being required to
perform an excavation task skilfully. In this master’s thesis a haptic1 device
was developed, resolving input ergonomics and creating a single
input device capable of providing feedback to the operator. The design
and construction of the haptic device, with the related control scheme, is
presented and discussed. The control scheme combines position and rate
control, and relates all the actuator joint positions to a single end-effector
point. The control and ergonomic aspects of the haptic device were tested
and compared to the traditional two joystick control setup by means of
the implementation of a virtual excavator simulator. The simulation was
developed in MATLAB, and virtual excavator displayed in an openGL
window. The objective of this study was to evaluate the human factors
related to the input orientation. Ten inexperienced test subjects were recruited
to perform four sets of tests, where each test required a different
level of operator skill. The results indicated that, on average, the test subjects
had an increased level of performance after training on the haptic
device. These results strongly support the hypothesis that haptic control
simplifies the operational tasks required for operating an excavator.
1The word haptic means of, or relating to, the sense of touch, or tactile
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