Analysis and performance evaluation of large-scale wound rotor synchronous wind generator with non-overlap winding technology
| dc.contributor.advisor | Kamper, Maarten | en_ZA |
| dc.contributor.author | Garner, Karen | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. | en_ZA |
| dc.date.accessioned | 2021-12-08T07:45:23Z | |
| dc.date.accessioned | 2021-12-22T14:34:32Z | |
| dc.date.available | 2021-12-08T07:45:23Z | |
| dc.date.available | 2021-12-22T14:34:32Z | |
| dc.date.issued | 2021-12 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: This thesis covers the analysis, performance evaluation and design optimisation of a wound rotor synchronous generator (WRSG) for medium-speed wind generator drive train applications. Permanent magnet synchronous generators (PMSG) have been the preferred choice because of their high performance and low maintenance costs. The high market price and fluctuating availability of rare-earth permanent magnets have become drivers for alternative wind generator designs. WRSGs are rare-earth free, which lowers the material costs. WRSGs have a flux variation capability that allows for reactive power control without the need of a solid-state converter when direct electrical grid connection is considered. This research adopts the use of non-overlap coils in the stator winding of the WRSG and the use of a phase-shift technique between the coil currents to reduce certain harmful harmonics. Non-overlap windings are selected due to the associated lower manufacturing cost and lower copper losses compared to conventional overlap wind-ings. The study applies the phase-shifting technique to a 375 r/min wound rotor synchronous generator with a 16/18 pole/slot combination. The objective is to find an optimum design for possible direct grid connection, complying with key South African grid requirements, that is an attractive non-permanent magnet option. Various winding designs for synchronous generators are analysed theoretically and finite element analysis is used in the modelling and design optimisation of the generator. The focus is on (i) methods to minimise the losses in non-overlap windings of WRSGs and (ii) to compare the performance of these generators with that of conventional synchronous generators. The phase-shifting technique is shown to reduce sub- and higher-order harmonics in the MMF harmonic spectrum. The application also improves the working harmonic of the 16/18 pole/slot combination that is noted in the lowered torque ripple and improved machine performance of the 3 MW model. However, the rotor core losses are slightly increased after the application. The effect of the rotor yoke design on the rotor core losses is investigated. Placing flux barriers in the inner core of a large rotor yoke largely reduces the rotor core losses without affecting the machine performance negatively. The intent of the study is to test at a 3 kW power level but also to determine the design up to 3 MW. The conducted design optimisation results in a WRSG with a lower torque ripple and improved efficiency. The optimised 3 MW 16/18 WRSG with the phase-shifted non-overlap winding fairs competitively against the 3 MW 16/72 WRSG in terms of active mass, power factor, efficiency and torque ripple. However, the per unit synchronous reactance of the 3 MW 16/18 WRSG design of this study is considered too high for direct grid connection. This can be overcome by increasing the air gap length, subject to lowering the power density. To validate the 2D-FEA predictions, the 3 kW prototype is manufactured and tested. Based on the practical measurements, the theoretical results of design aspects are confirmed. A consolidated conclusion and further recommendations for the future of the design conclude the work in this study. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Hierdie tesis dek die analise, prestasie-evaluering en ontwerp optimalisering van ’n wondrotor-sinchrone kragopwekker (WRSG) vir mediumspoed windgenerator- aandryftoepassings. Permanente magneet sinchroon kragopwekkers (PMSG) was die voorkeurkeuse vanweë hul hoë prestasie en lae instandhoudingskoste. Die hoë markprys en wisselvallig beskikbaarheid van seldsame aarde permanente magnete het die dryfveer geword vir alternatiewe windgeneratorontwerpe. WRSG’s is skaars aarde-vry, wat verlaag die materiaalkoste. WRSG’s het ’n vloedvariasievermoë wat dit moontlik maak reaktiewe kragbeheer sonder dat ’n vastetoestandomskakelaar nodig is wanneer direkte elektriese netwerkverbinding word oorweeg. Hierdie navorsing aanvaar die gebruik van nie-oorvleuelende spoele in die stator- wikkeling van die WRSG en die gebruik van ’n faseverskuiwingstegniek tussen die krulstrome na verminder sekere skadelike harmonieke. Nie-oorvleuelende windings word gekies as gevolg van die gepaardgaande laer vervaardigingskoste en laer koper- verliese vergeleke met konvensionele oorvleueling. Die studie pas die faseverskuiwing toe tegniek aan ’n 375 r / min wondrotor sinchrone kragopwekker met ’n 16/18 paal / gleufkombinasie. Die doel is om ’n optimale ontwerp vir moontlike direkte netwerk- verbinding, wat voldoen aan die belangrikste Suid-Afrikaanse netwerk vereistes, dit is ’n aantreklike nie-permanente magneet-opsie. Verskeie kronkelende ontwerpe vir sinchrone kragopwekkers word teoreties ontleed en eindige elementontleding word gebruik in die modellering en ontwerpoptimalisering van die kragopwekker. Die fo- kus is op (i) metodes om die verliese in nie-oorvleuelende windings van WRSG’s en (ii) om die prestasie hiervan te vergelyk kragopwekkers met die ́ van konvensionele sinchrone kragopwekkers. Die faseverskuiwingstegniek toon dat dit sub- en hoër-orde verminder harmonieke in die MMF harmoniese spektrum. Die toepassing verbeter ook die werkharmo- niese van die 16/18 paal / gleufkombinasie wat in die verlaagde wringkrag rimpel opgemerk word en verbeterde masjienverrigting van die 3 MW-model. Die rotor- kern egter verliese word effens verhoog na die toediening. Die effek van die rotor jukontwerp op die rotorkernverliese word ondersoek. Plaas vloedversperrings in die binnekern van ’n groot rotorjuk verminder die rotorkernverliese grootliks sonder om die masjien se werkverrigting negatief te beïnvloed. Die doel van die studie is om op ’n 3 kW-kragvlak te toets, maar ook om bepaal die ontwerp tot 3 MW. Die optimale ontwerpoptimalisering lei tot ’n WRSG met ’n laer wringkrag rimpel en verbeterde doeltreffendheid. Die geoptimaliseerde 3 MW 16/18 WRSG met die faseverskuiwende nie-oorvleuelende kronkelbeurte mededin- gend teenoor die 3 MW 16/72 WRSG in terme van aktiewe massa, drywingsfaktor, doeltreffendheid en wringkrag rimpel. Die sinchroniese reaktansie per eenheid van die 3 MW 16/18 Die WRSG-ontwerp van hierdie studie word as te hoog vir direkte rooster beskou verbinding. Dit kan oorkom word deur die luggaping te vergroot lengte, onderhewig aan die verlaging van die kragdigtheid. Om die 2D-FEA voorspellings te bevestig, word die 3 kW prototipe vervaardig en getoets. Op grond van die praktiese metings is die teoretiese resultate van ontwer- paspekte word bevestig. ’n Gekonsolideerde gevolgtrekking en verder aanbevelings vir die toekoms van die ontwerp sluit die werk in hierdie studie af. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.format.extent | 120 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/124008 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Winding machines | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.subject | Wind power | en_ZA |
| dc.subject | Wound rotor synchronous generator | en_ZA |
| dc.subject | Synchronous generators -- Performance -- Evaluation | en_ZA |
| dc.title | Analysis and performance evaluation of large-scale wound rotor synchronous wind generator with non-overlap winding technology | en_ZA |
| dc.type | Thesis | en_ZA |