Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The growing contribution of wind energy to utility grids has sparked interest in small-scale wind
turbines and thus a growing global cumulative installed capacity. Small-scale wind turbines find
use in the saving of cost of electricity or for the carbon footprint reduction of small farms and
small-holdings, as well as the electrification of rural communities.
A goal of any wind turbine is to produce power at as low of a cost per unit energy as possible.
Thus, a generator with a high power density and high efficiency is essential. The reluctance
synchronous machine (RSM) is a strong competitor in this regard. Additionally, the RSM is
a robust brushless topology that has good properties of manufacturability. However, studies
published on the use of RSMs as generators in wind turbines is limited. This study serves to
explore the performance and controllability of an RSM as a generator in a small-scale 9:2 kW
wind turbine.
For maximum power capture, it is desirable to have a wind turbine vary its rotor speed.
However, there is a limit to the power that the generator may produce and so techniques
are employed to reduce the captured power when operating above the rated wind speed. A
turbine controller is developed that employs a speed-controlled maximum power point tracking
(MPPT) technique for maximum power capture and soft-stalling of the blades to reduce power
capture at excessive wind speeds. The RSM is modelled along with a turbine simulation model,
complete with a wind source generator, to evaluate the performance of the system.
Speed-controlled MPPT is known to sacrifice torque smoothness for fast tracking performance.
To mitigate these harsh effects on the drivetrain, the speed reference of the generator
is filtered to provide an average response to the optimal speed reference. This is shown to
reduce the frequent and excessive speed, torque, and electrical power variations though optimal
performance is not possible. However, any reduction on drivetrain fatigue that will maximise
operation time of the turbine is considered an important gain.
The RSM proves to have qualities that are applicable to wind turbine applications with its
high efficiency, good manufacturability properties, low cost, and high robustness. Its higher
power density over induction machines is also favourable though power electronics are required
for optimal operation of the machine. / AFRIKAANSE OPSOMMING: Die groeiende bydrae van wind energie te nut roosters het aanleiding gegee tot belangstelling in
kleinskaalse wind turbines en dus 'n groeiende w^ereldwye kumulatiewe geïnstalleerde kapasiteit.
Kleinskaalse wind turbines vind ook gebruik in die besparing van koste van elektrisiteit, of vir
die koolstofvoetspoor vermindering van klein plase en klein-hoewes, sowel as die elektrifisering
van landelike gemeenskappe.
Een van die doelwitte van enige wind turbine is om krag te produseer teen so laag van
'n koste per eenheid energie as moontlik. Dus, 'n kragopwekker met 'n hoë krag digtheid
en hoë doeltreffendheid is noodsaaklik. Die reluktansie sinchroonmajien (RSM) is 'n sterk
mededinger in hierdie verband. Daarbenewens is die RSM 'n robuuste borsellose topologie
wat goeie eienskappe van vervaardigbaarheid het. Maar studies oor die gebruik van RSMs as
kragopwekkers gepubliseer in die wind turbines is beperk. Hierdie studie dien om die prestasie
te ondersoek en die beheerbaarheid van 'n RSM as 'n a kragopwekker in 'n klein-skaal 9:2 kW
wind turbine te verken.
Vir maksimum krag vang is dit wenslik dat die wind turbine sy rotor spoed wissel. Maar daar
is 'n beperking op die krag wat die kragopwekker kan produseer en daarom work tegnieke gebruik
om die gevange krag te verminder wanneer daar bo die gegradeerde wind spoed gewerk word.
'n Turbine beheerder word ontwikkel wat werk om 'n spoedbeheer maksimum kragpunt dop
tegniek vir maksimum krag vang en die sagtestaking van die lemme krag vang deur oormatige
wind spoed te verminder. Die RSM is gemodeleer saam met 'n turbine simulasie model kompleet
met 'n wind bron kragopwekker om die prestasie van die stelsel te evalueer.
Spoedbeheerde maksimum kragpunt dop is bekend om wringkrag gladheid vir 'n vinnige dop
prestasie te offer. Om hierdie harde gevolge op die kragoorbringstelsel te versag is die spoed
verwysing van die kragopwekker gefiltreer om 'n gemiddelde reaksie op die optimale spoed
verwysing te verskaf. Dit word getoon om gereelde en hoë spoed, wringkrag en elektriese krag
variases te verminder al is optimale prestasie nie moontlik nie. Enige afname van aandrystelsel
moegheid wat operasie tyd van die turbine maksimeer word beskou as 'n belangrike gewin.
Die RSM bewys eienskappe wat van toepassing is op die turbine aansoeke na aanleiding met
sy hoë doeltreffendheid, goeie vervaardigbaarheid eienskappe, lae koste end ' hoë robuustheid.
Sy hoër krag digtheid oor induksiemasjien is ook gunstig al is drywingselektronika nodig vir
optimale werking van die masjien.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/97015 |
| Date | 03 1900 |
| Creators | Du Plooy, Jon-Pierre |
| Contributors | Gule, Nkosinathi, Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 92 pages : illustrations |
| Rights | Stellenbosch University |
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