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Critical Evaluation of DC-Grid and Strong Grid-Forming Wind Generator Systems
Thesis (PhD)--Stellenbosch University, 2026.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1867613800086110208 |
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| access_status_str | Open Access |
| author | Dube, Lucky |
| author2 | Garner, Karen S. |
| author_browse | Dube, Lucky Garner, Karen S. |
| author_facet | Garner, Karen S. Dube, Lucky |
| author_sort | Dube, Lucky |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2026. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/135787 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:41:53.663Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/135787 Critical Evaluation of DC-Grid and Strong Grid-Forming Wind Generator Systems Dube, Lucky Garner, Karen S. Kamper, Maarten J. Stellenbosch University. Faculty of Engineering. Dept. of Electrical & Electronic Engineering. Thesis (PhD)--Stellenbosch University, 2026. Dube, L. 2026. Critical Evaluation of DC-Grid and Strong Grid-Forming Wind Generator Systems. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/2d20a8f2-a691-4721-812f-611038231b4a The global transition to renewable energy has intensified challenges related to grid stability and material sustainability in wind power systems. This research addresses two critical issues: the declining grid strength due to inverter-based resource integration, and the dependency on rare-earth permanent magnets in wind generators. The research proposes and evaluates alternative system architectures and generator technologies through comprehensive theoretical analysis, numerical simulation, and experimental validation. The first part of this work develops novel strong grid-forming (SGF) wind energy systems based on synchronous machine interfaces. Three distinct configurations are investigated: a variable DC grid wind-cluster with motor-generator (MG) drive, a ground-mounted SGF (G-SGF) system, and a top-tower-mounted SGF (T-SGF) system. These systems demonstrate the capability to provide 24/7 grid strength, inertia, and reactive power support while maintaining maximum power point tracking (MPPT). A key finding reveals that the fundamental power factor of diode rectifier-connected generators deviates from the commonly assumed unity value, which is crucial for accurate system modeling. Stability analysis proves that overdamped operation is achieved through proper grid frequency feedback in the MG control. The second part presents the design of a non-permanent magnet alternative through a triple-three-phase wound rotor synchronous generator (T-WRSG) optimized for DC grid applications. A multi-stage optimization methodology combining the coordinate descent method and NSGA-II algorithms successfully reduces the synchronous reactance from 2.82 per unit (pu) to 0.94 pu for a 5-MW T-WRSG, enabling effective operation with passive diode rectifiers. Experimental validation using a 4.2-kW T-WRSG prototype confirms a measured synchronous reactance of 1.0 pu. The derived DC grid voltage versus speed function enables model-based MPPT control. This research contributes to the design of more resilient and sustainable wind energy systems by providing viable solutions for grid strength enhancement and rare-earth material independence. The integrated approach from theoretical design to practical implementation establishes a foundation for next-generation wind energy technologies suitable for large-scale offshore applications. Doctoral 2026-04-10T09:19:51Z 2026-04-10T09:19:51Z 2026-03 Thesis https://scholar.sun.ac.za/handle/10019.1/135787 en Stellenbosch University 144 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Dube, Lucky Critical Evaluation of DC-Grid and Strong Grid-Forming Wind Generator Systems |
| title | Critical Evaluation of DC-Grid and Strong Grid-Forming Wind Generator Systems |
| title_full | Critical Evaluation of DC-Grid and Strong Grid-Forming Wind Generator Systems |
| title_fullStr | Critical Evaluation of DC-Grid and Strong Grid-Forming Wind Generator Systems |
| title_full_unstemmed | Critical Evaluation of DC-Grid and Strong Grid-Forming Wind Generator Systems |
| title_short | Critical Evaluation of DC-Grid and Strong Grid-Forming Wind Generator Systems |
| title_sort | critical evaluation of dc grid and strong grid forming wind generator systems |
| url | https://scholar.sun.ac.za/handle/10019.1/135787 |
| work_keys_str_mv | AT dubelucky criticalevaluationofdcgridandstronggridformingwindgeneratorsystems |