Design and Performance Comparisons of Brushless Doubly-Fed Generators with Different Rotor Structures

The Brushless Doubly-Fed Generator (BDFG) shows the great potential for use in large variable speed wind turbines due to its high reliability and cost benefits of a partially-rated power electronics converter. However, it suffers from the compromised efficiency and power factor in comparison with conventional doubly fed induction or synchronous generators. Therefore, optimizing the BDFG, especially the rotor, is necessary for enhancing its torque density and market competitiveness. In this paper, a novel cage-assisted magnetic barrier rotor, called the hybrid rotor, is proposed and analyzed. The detailed analytical design approaches based on the magnetic field modulation theory are investigated. In addition, the machine losses and mutual inductance values using the proposed rotor designs are calculated and their performance implications evaluated. Finally, the comparative experimental results for two BDFG prototypes are presented to verify the accuracy and effectiveness of the theoretical studies

A comprehensive review on brushless doubly-fed reluctance machine

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. The Brushless Doubly-Fed Reluctance Machine (BDFRM) has been widely investigated in numerous research studies since it is brushless and cageless and there is no winding on the rotor of this emerging machine. This feature leads to several advantages for this machine in comparison with its induction counterpart, i.e., Brushless Doubly-Fed Induction Machine (BDFIM). Less maintenance, less power losses, and also more reliability are the major advantages of BDFRM compared to BDFIM. The design complexity of its reluctance rotor, as well as flux patterns for indirect connection between the two windings mounted on the stator including power winding and control winding, have restricted the development of this machine technology. In the literature, there is not a comprehensive review of the research studies related to BDFRM. In this paper, the previous research studies are reviewed from different points of view, such as operation, design, control, transient model, dynamic model, power factor, Maximum Power Point Tracking (MPPT), and losses. It is revealed that the BDFRM is still evolving since the theoretical results have shown that this machine operates efficiently if it is well-designed

A comprehensive review on brushless doubly-fed reluctance machine

The Brushless Doubly-Fed Reluctance Machine (BDFRM) has been widely investigated in numerous research studies since it is brushless and cageless and there is no winding on the rotor of this emerging machine. This feature leads to several advantages for this machine in comparison with its induction counterpart, i.e., Brushless Doubly-Fed Induction Machine (BDFIM). Less maintenance, less power losses, and also more reliability are the major advantages of BDFRM compared to BDFIM. The design complexity of its reluctance rotor, as well as flux patterns for indirect connection between the two windings mounted on the stator including power winding and control winding, have restricted the development of this machine technology. In the literature, there is not a comprehensive review of the research studies related to BDFRM. In this paper, the previous research studies are reviewed from different points of view, such as operation, design, control, transient model, dynamic model, power factor, Maximum Power Point Tracking (MPPT), and losses. It is revealed that the BDFRM is still evolving since the theoretical results have shown that this machine operates efficiently if it is well-designed

Fractional kVA Rating PWM Converter Doubly Fed Variable Speed Electric Generator Systems:An Overview in 2020

Variable speed generator systems (VSGs) are at work in the now 600 GW installed wind power plants (parks). Also, they are used as vehicular and on ground stand-alone generators. VSGs imply full kVA rating PWM converters in permanent magnet (PM) or in electrically excited synchronous or in cage rotor inductance generators. But, to reduce cost in absence of PMs at a reasonable initial cost (weight) and efficiency, the fractional kVA PWM converter doubly fed induction generators (DFIG) cover now about 50% of all installed power in wind generators. The present paper reviews recent progress in DFIG and various forms of brushless DFGs (doubly fed generators) characterized in terms of topology, design, performance and advanced control for healthy and faulty load conditions in the hope of inspiring new, hopefully ground breakings, progress for wind and hydro energy conversion and in vehicular and on the ground stand-alone generator applications

Effects of Design Parameters on Performance of Brushless Electrically Excited Synchronous Reluctance Generator

Permanent magnet synchronous generators, doubly fed induction generators, and traditional electrically excited synchronous generators are widely used for wind power applications, especially large offshore installations. In order to eliminate brushes and slip rings for improved reliability and maintenance-free operation, as well as to avoid costly permanent magnets, a novel brushless electrically excited synchronous reluctance generator having many outstanding advantages has been proposed in this paper. The fundamental operating principles, finite element analysis design studies and performance optimization aspects have been thoroughly investigated by simulations and experimentally under different loading conditions. The effects of different pole combinations and rotor dimensions on the magnetic coupling capacity of this machine have been specifically addressed and fully verified by off-line testing of the 6/2 pole and 8/4 pole prototypes with magnetic barrier reluctance rotor and a new hybrid cage rotor offering superior performance

Design development of brushless doubly fed machines

Thesis (PhD)--Stellenbosch University, 2022.ENGLISH ABSTRACT: Doubly fed induction generators (DFIGs) are the most widely used generators in large wind turbines, because of their cheap constructions, smaller converter sizes, and wide speed range. However, DFIGs have well known reliability issues stemming from their slip ring and brush failures. This is particularly problematic in remote areas like offshore wind sites. Currently, the operational and maintenance costs of DFIG based wind turbines are the highest among commonly used offshore wind topologies, due to the slip ring and brush failures. It should be noted that offshore wind power is getting increasing attention, and significant increases in offshore wind installations are projected in the coming years. The use of brushless doubly fed (induction) machines (BDFMs) has been proposed as an alternative to DFIGs, especially in remote areas like offshore sites, as they do not have slip rings and brushes. BDFMs, which are typically medium speed machines, also have better low voltage ride through characteristics compared to DFIGs, which could help reduce cost and complexity of their drivetrains. However, BDFMs have a more complex structure to DFIGs, with considerably lower power densities. Also, BDFMs have higher total harmonic distortions and vibrations compared to DFIGs. With their development still being at experimental stages, there is no well-defined way to design BDFMs, with the design of certain parts still debated. In this project, the start to finish design process of BDFMs is investigated. The thought process behind certain decisions like the placement of the stator windings are highlighted. The design of a suitable rotor topology per BDFM application isresearched. The rotor design is conducted with power density and harmonics/vibrations considered. A proper method for BDFM design evaluation is demonstrated especially when considering grid complaint operations. This evaluation method is compared with evaluation methods com monly used in available literature to demonstrate its suitability. With proper evaluation deter mined, the optimization of BDFM designs is investigated using different models. A coupled circuit model is developed for use in the rotor design. Results from finite element analysis models are used to develop response surface approximations which are coupled with a genetic algorithm for power density optimizations. There are established values of certain input parameters such as the electric and magnetic loadings in DFIG design. This is however not the case with BDFMs. Consequently, in this project, practical values of these parameters are researched for different BDFM power ratings. The disparities in power density between BDFMs with different pole pair combinations and DFIGs at corresponding rated speeds across different power ratings are mapped out. These disparities in power density are used to recommend the best performing pole pair combinations at different power ratings.AFRIKAANSE OPSOMMING: Dubbel gevoerde induksie generators (DGIGs) word gereeld in groot wind turbines gebruik omdat dit goedkoop is om aan mekaar te sit, kleiner omskakelaar groottes het, en ‘n wye spoed verskeidenheid het. Ten spyte hiervan het DGIGs betroubaarheid probleme wat veroorsaak word deur die gly ring en borsel mislukkings. Dit is veral ‘n probleem in afgesonderde areas soos buitelandse wind plase. As gevolg hiervan is DGIG gebaseerde wind turbines se kostes die hoogste onder algemeen gebruikte buitelandse wind tipologiee.¨ Dit is belangrik om in ag te neem dat daar meer aandag aan buitelandse wind krag gegee word en dus word daar ‘n beduidende toename in buitelandse wind installasies vir die komende jare geprojekteer. Die gebruik van borsellose dubbel gevoerde (induksie) masjiene (BDGMe) is al as ‘n alterna tiewe opsie vir DGIGs voorgestel, veral vir afgesonderde areas omdat hulle nie gly ringe of borsels het nie. BDGMe, wat tipies medium spoed masjiene is, het ook beter lae spanning rit deur eienskappe as DGIGs wat kan help om die kostes en kompleksiteit van die dryf stelsels te verminder. Daar moet egter in ag geneem word dat BDGMe ‘n baie meer komplekse struktuur het met laer krag digthede. BDGMe het ook hoer¨ totale harmoniee¨ versteurings en vibrasies wanneer dit met DGIGs vergelyk word. Met die masjiene se ontwikkeling wat nog in ekspe rimentele fases is, is daar nog nie ‘n goed-gedefinieerde manier om BDGMe te ontwerp nie, veral omdat sekere dele se ontwerpe nog gedebatteer word. In die projek word die proses van BDGMe ontwerp van begin tot einde ondersoek. Die proses van sekere besluite wat gemaak is, soos die plasing van die stator windings, word uitgelig. Die ontwerp van ‘n toepaslike rotor topologie per BDGM toepassing word ook in die studie nagevors. Die rotor ontwerp is met die inagneming van krag digtheid en harmoniee/vibrasies ¨ uitgevoer. ‘n Gepaste metode vir die evaluering van BDGM ontwerp is gedemonstreer, veral wanneer krag-netwerk voldoende bedrywighede in ag geneem word. Die evaluasie metode is met ander metodes wat algemeen in beskikbare literatuur gebruik word vergelyk om die geskiktheid daarvan te demonstreer. Met die gepaste evaluasie wat bepaal is, is die optimalisering van BDGM ontwerpe ondersoek deur gebruik te maak van verskeie modelle. ‘n Gekoppelde baan model is vir die gebruik in rotor ontwerp ontwikkel. Resultate van beperkte element analise modelle is gebruik om reaksie oppervlak benaderings te ontwerp wat aan die genetiese algoritme vir krag digtheid optimaliserings ontwikkel is. Daar is bepaalde waardes van sekere inset parameters, soos die elektriese en magnetiese ladings in die DGIG ontwerp. Dit is egter nie die geval vir BDGMe nie. As gevolg hiervan word daar in die projek praktiese waardes van die parameters vir verskillende BDGM krag grade rings nagevors. Die ongelykhede in krag digtheid tussen BDGMe met verskillende pool paring kombinasies en DGIGs teen ooreenstemmende gegradeerde spoed oor verskillende krag graderings is uiteengesit. Die ongelykhede is gebruik om die beste pool paring kombinasies teen verskillende spoed graderings voor te stel.Doctora

Comparison of doubly-fed induction generator and brushless doubly-fed reluctance generator for wind energy applications

Phd ThesisThe Doubly-fed Induction Generator (DFIG) is the dominant technology for variable-speed wind power generation due in part to its cost-effective partially-rated power converter. However, the maintenance requirements and potential failure of brushes and slip rings is a significant disadvantage of DFIG. This has led to increased interest in brushless doubly-fed generators. In this thesis a Brushless Doubly-Fed Reluctance Generator (BDFRG) is compared with DFIG from a control performance point of view. To compare the performance of the two generators a flexible 7.5kW test facility has been constructed. Initially, a classical cascade vector controller is applied to both generators. This controller is based on the stator voltage field orientation method with an inner rotor (secondary stator) current control loop and an outer active and reactive power control loop. The dynamic and steady state performance of two generators are examined experimentally. The results confirm that the BDFRG has a slower dynamic response when compared to the DFIG due to the larger and variable inductance. Finally a sensorless Direct Power Control (DPC) scheme is applied to both the DFIG and BDFRG. The performance of this scheme is demonstrated with both simulation and experimental results.Engineering and Physical Sciences Research Council (EPSRC) and Overseas Researcher Scholarship (ORS

Brushless doubly-fed reluctance machine modeling, desing and optimization

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2015.Esta tese aborda a modelagem, o projeto e a otimização, com validação experimental, de máquinas de relutância duplamente alimentadas sem escovas (BDFRM) para sistemas de geração de energia eólica. O objetivo principal dela é de contribuir para o domínio de técnicas de projeto otimizado para a BDFRM através da proposição de uma metodologia baseada em diferentes níveis de modelagem e em otimização. Discute-se como técnicas de otimização podem ser aplicadas em todas as fases de desenvolvimento com objetivos distintos. Especificamente, a metodologia proposta se concentra na definição e na solução iterativa de problemas de otimização com restrições nas saídas utilizando um algoritmo determinístico acoplado a modelos semi-analíticos de diferentes níveis. Como conclusão geral, pode-se afirmar que a BDFRM é potencialmente uma boa candidata para ser utilizada em sistemas de geração de energia eólica. Contudo, aspectos técnicos e econômicos sobre essa escolha devem ainda ser avaliados, comparando-se as diferentes topologias existentes sob o mesmo enfoque metodológico.Abstract : This thesis addresses the modeling, design and optimization with experimental validation of the Brushless Doubly-Fed Reluctance Machine (BDFRM) for wind power systems. Its main goal is to contribute on mastering the BDFRM optimized design by proposing a methodological approach based on different modeling levels and on optimization. More precisely, it draws its attention on setting the optimization problem and on the iterative solution of a constrained inputs/outputs problem by using a deterministic algorithm. As a general conclusion, the results show that the BDFRM is potentially a good candidate to be used in wind power systems. However, the technical and economic aspects on this choice must be still assessed, analyzing and comparing the overall system solution of distinct topologies within the same framework

Sensorless adaptive control of brushless doubly-fed reluctance generators for wind power applications

A novel model reference adaptive system for the rotor position/speed estimation and sensorless operation of a brushless doubly fed reluctance generator with maximum power point tracking is presented. Its main advantage over the existing designs are the inherent robustness and stability afforded by the complete parameter independence of the reference model using only the measured currents of the converter-fed (secondary) winding. In addition, the respective stationary frame current components are estimated by the adaptive model using the voltage and current measurements of the grid-connected (primary) winding at line frequency, offering higher accuracy. The simulation and experimental results have demonstrated the excellent real and reactive power controller performance for typical operating characteristics of wind turbines

A Review of Control Techniques Future Trends in Wind Energy Turbine Systems with Doubly Fed Induction Generators (DFIG)

تعتبر طاقة الرياح حاليا واحدة من أكثر مصادر الطاقة الخضراء النظيفة الملاءمة على نطاق واسع في العالم. تم تطوير العديد من مبادئ توربينات الرياح بستخدام  المولدات المختلفة لتحويل طاقة الرياح المتاحة إلى طاقة كهربائية. يعد نظام المولد الحثي ذي التغذية المزدوجة DFIG لتوربينات الرياح ذات السرعة المتغيرة نسبيا (VSWT) هو الأكثر ملاءمة لطاقة توربينات الرياح بسبب فوائده العديدة مقارنة بتوربينات الرياح ذات السرعة الثابتة نسبيا (FSWT). تقدم هذه الورقة مراجعة و مقارنة عن طاقة توربينات الرياح المختلفة وملخصًا قيمًا للعمل الأخير المتعلقة بأنظمة طاقة الرياح المختلفة (WECS) لنمذجة DFIG وأقصى نقطة طاقة MPP وأحدث نظام تحكم للتشغيل. ومن ناحية أخرى تم في الدراسة الحالية تقديم مقارنات ومناقشات بين توربينات الرياح المختلفة لتكون مفيدة للدراسات البحثية.Wind energy is currently widely regarded as one of the most favorable green clean sources of energy. Several wind turbine principles with various generator architectures have been evolved to exchange the available wind energy into electric power. The DFIG partial Variable-Speed Wind Turbine (VSWT) system is most proper for wind turbine energy because of its numerous benefits over Fixed-Speed Wind Turbines (FSWT). This paper introduces a comparative review of the different wind turbine conversion energy and a valuable summary of the recent work in the literature on different Wind Energy Conversion Systems (WECS) of a DFIG modeling, Maximum Power Point (MPP), and the latest control system for operation. On the other side, comparisons and discussions between different wind turbines have been presented in the current study to be beneficial for research studies