High Frequency (MHz) Planar Transformers for Next Generation Switch Mode Power Supplies by Radhika Ambatipudi -Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.(Power Electronics)

 High Frequency (MHz) Planar Transformers for Next Generation Switch Mode Power Supplies

by Ambatipudi, Radhika

Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.(Power Electronics) 2013 (English) Doctoral thesis

 ABSTRACT

 Increasing the power density of power electronic converters while reducing or maintaining the same cost, offers a higher potential to meet the current trend in relation to various power electronic applications. High power density converters can be achieved by increasing the switching frequency, due to which the bulkiest parts, such as transformer, inductors and the capacitor's size in the converter circuit can be drastically reduced. In this regard, highly integrated planar magnetics are considered as an effective approach compared to the conventional wire wound transformers in modern switch mode power supplies (SMPS). However, as the operating frequency of the transformers increase from several hundred kHz to MHz, numerous problems arise such as skin and proximity effects due to the induced eddy currents in the windings, leakage inductance and unbalanced magnetic flux distribution. In addition to this, the core losses which are functional dependent on frequency gets elevated as the operating frequency increases. Therefore, this thesis provides an insight towards the problems related to the high frequency magnetics and proposes a solution with regards to different aspects in relation to designing high power density, energy efficient transformers.

The first part of the thesis concentrates on the investigation of high power density and highly energy efficient coreless printed circuit board (PCB) step-down transformers useful for stringent height DC-DC converter applications, where the core losses are being completely eliminated. These transformers also maintain the advantages offered by existing core based transformers such as, high coupling coefficient, sufficient input impedance, high energy efficiency and wide frequency bandwidth with the assistance of a resonant technique. In this regard, several coreless PCB step down transformers of different turn’s ratio for power transfer applications have been designed and evaluated. The designed multilayered coreless PCB transformers for telecom and PoE applications of 8, 15 and 30W show that the volume reduction of approximately 40 - 90% is possible when compared to its existing core based counterparts while maintaining the energy efficiency of the transformers in the range of 90 - 97%. The estimation of EMI emissions from the designed transformers for the given power transfer application proves that the amount of radiated EMI from a multilayered transformer is less than that of the two layered transformer because of the decreased radius for the same amount of inductance.

The design guidelines for the multilayered coreless PCB step-down transformer for the given power transfer application has been proposed. The designed transformer of 10mm radius has been characterized up to the power level of 50W and possesses a record power density of 107W/cm3 with a peak energy efficiency of 96%. In addition to this, the design guidelines of the signal transformer for driving the high side MOSFET in double ended converter topologies have been proposed. The measured power consumption of the high side gate drive circuit together with the designed signal transformer is 0.37W. Both these signal and power transformers have been successfully implemented in a resonant converter topology in the switching frequency range of 2.4 – 2.75MHz for the maximum load power of 34.5W resulting in the peak energy efficiency of converter as 86.5%.

This thesis also investigates the indirect effect of the dielectric laminate on the magnetic field intensity and current density distribution in the planar power transformers with the assistance of finite element analysis (FEA). The significance of the high frequency dielectric laminate compared to FR-4 laminate in terms of energy efficiency of planar power transformers in MHz frequency region is also explored.

The investigations were also conducted on different winding strategies such as conventional solid winding and the parallel winding strategies, which play an important role in the design and development of a high frequency transformer and suggested a better choice in the case of transformers operating in the MHz frequency region.

In the second part of the thesis, a novel planar power transformer with hybrid core structure has been designed and evaluated in the MHz frequency region. The design guidelines of the energy efficient high frequency planar power transformer for the given power transfer application have been proposed. The designed core based planar transformer has been characterized up to the power level of 50W and possess a power density of 47W/cm3 with maximum energy efficiency of 97%. This transformer has been evaluated successfully in the resonant converter topology within the switching frequency range of 3 – 4.5MHz. The peak energy efficiency of the converter is reported to be 92% and the converter has been tested for the maximum power level of 45W, which is suitable for consumer applications such as laptop adapters. In addition to this, a record power density transformer has been designed with a custom made pot core and has been characterized in the frequency range of 1 - 10MHz. The power density of this custom core transformer operating at 6.78MHz frequency is 67W/cm3 and with the peak energy efficiency of 98%.

LINK ORIGINAL NA WEB:

https://www.diva-portal.org/smash/get/diva2:665725/FULLTEXT01.pdf

Étude et élaboration d’un système de surveillance et de maintenance prédictive pour les condensateurs et les batteries utilisés dans les Alimentations Sans Interruptions (ASI) by Mohamed Karim Abdennadher - Study and elaboration of a monitoring and predictive maintenance system for capacitors and batteries used in Uninterruptible Power Supplies (UPS)

 

Étude et élaboration d’un système de surveillance et de maintenance prédictive pour les condensateurs et les batteries utilisés dans les Alimentations Sans Interruptions (ASI) Mohamed Karim Abdennadher

Study and elaboration of a monitoring and predictive maintenance system for capacitors and batteries used in Uninterruptible Power Supplies (UPS)

THESE DE DOCTORAT Présentée devant L’UNIVERSITE CLAUDE BERNARD LYON 1 Pour l’obtention du grade de DOCTEUR de l’UNIVERSITE de LYON 1 (Arrêté du 07 Août 2006) Spécialité : GENIE ELECTRIQUE Préparée au sein de L’ECOLE DOCTORALE ELECTRONIQUE, ELECTROTECHNIQUE, AUTOMATIQUE DE LYON Par M. Mohamed Karim ABDENNADHER

Résumé

 To ensure power quality and permanently, some electronic system supplies exist. These supplies are the Uninterrupted Power Supplies (UPS). An UPS like any other system may have some failures. This can be a cause of redundancy loss. This load loss causes a maintenance downtime which may represent a high cost. We propose in this thesis to work on two of the most sensitive components in the UPS namely electrolytic capacitors and lead acid batteries. In a first phase, we present the existing surveillance systems for these two components, highlighting their main drawbacks. This allows us to propose the specifications which have to be implemented for this system. For electrolytic capacitors, we detail different stages of characterization ; the aging accelerated standard experimental procedure and their associated results. On the other hand, we present the simulation results of monitoring and failure prediction system retained. We discuss the experimental validation, describing the developed system. We detail the electronic boards designed, implemented algorithms and their respective constraints for a real time implementation. Finally, for lead acid batteries, we present the simulation results of the monitoring system adopted to obtain the SOC and SOH. We describe the aging experimental procedure of charging and discharging cycles of the batteries needed to find a simple and accurate electric models. We explain the aging experimental results and in the end we give suggestions for improving our system to get a more accurate SOH.

LINK:  https://tel.archives-ouvertes.fr/tel-00532642v2/document

SISTEMA FOTOVOLTAICO DE PEQUENO PORTE INTERLIGADO À REDE ELÉTRICA by Eldin Mario Miranda Terán Dissertação submetida à Universidade Federal do Ceará como parte dos requisitos para obtenção do grau de Mestre em Engenharia Elétrica. Orientador: Prof. Dr. René Pastor Torrico Bascopé

INTRODUÇÃO GERAL 

Em meados do século XVIII a Grã Bretanha presenciou o inicio da Revolução Industrial: um conjunto de avanços tecnológicos que mudaram todo o sistema produtivo conhecido até então. O motor a vapor e depois o motor a combustão foram os principais atores nesta revolução. Esta revolução espalhou-se rapidamente pela Europa, pelos Estados Unidos e pelo mundo todo no século XIX. Paralelamente, grandes avanços na área da eletricidade foram realizados e a máquina elétrica foi desenvolvida. Já no século XX muitos países atingiram altos níveis de industrialização enquanto a energia elétrica mudou o estilo de vida da humanidade toda. A energia primária que foi usada para impulsionar esta revolução e que ainda continua alimentando o sistema produtivo do planeta é baseada em combustíveis fósseis e carvão. No ano de 2009 aproximadamente 88% do consumo energético mundial teve origem nestas fontes (petróleo, carvão e gás natural) [1]. É sabido que esta dependência global dos combustíveis fósseis tem provocado sérios problemas no clima do planeta e que no futuro o custo da sua produção vai aumentar mais e mais, a medida que seja mais complexo realizar a exploração destes recursos, ocasionando problemas econômicos e sociais. Diante deste panorama, as fontes de energia renovável, como a solar, hidráulica e eólica entre outras, perfilam-se a ser a solução à demanda energética no futuro, sendo uma resposta tecnicamente viável e amigável com o meio ambiente, porém cara, quando comparada com as tecnologias convencionais na atualidade, precisando de subsídios e apoio dos governos para serem implementadas1 [2]. Em países altamente desenvolvidos como Espanha, Alemanha, Itália, Japão e outros, há diversos incentivos tributários a produção de energia renovável, entretanto, na América do Sul ainda não se conta com legislações que incentivem a produção de energia renovável em grande escala. A eletrônica de potência desempenha um papel importante na atividade de processamento da energia renovável, particularmente das energias fotovoltaica e eólica. No caso da energia fotovoltaica tem-se uma fonte de corrente contínua que deve ser transformada em corrente alternada para ser interligada aos sistemas elétricos e às cargas elétricas convencionais. Este processamento de energia é realizado mediante o uso da eletrônica de potência, através de conversores estáticos. Assim, neste trabalho foi desenvolvido um sistema de energia fotovoltaica de pequeno porte interligado à rede elétrica, formado por dois estágios de processamento de energia:  O primeiro estágio é um conversor cc-cc elevador (Boost) responsável por aumentar a tensão entregue pelos painéis fotovoltaicos a uma tensão adequada para ser transformada em corrente alternada e, por extrair a máxima potência elétrica disponível nos painéis fotovoltaicos.  O segundo estágio é um conversor cc-ca Full-Bridge (ponte completa) responsável por transformar a corrente continua entregue pelo primeiro estágio em corrente alternada num nível de tensão, frequência e fase úteis à rede elétrica de baixa tensão. No capítulo 1 do trabalho tem-se uma revisão bibliográfica geral focada na área da eletrônica de potência, ou seja, nas topologias de conversores aplicáveis em sistemas fotovoltaicos interligados à rede elétrica. Além disso, apresenta-se informação sobre energia solar fotovoltaica com foco nas técnicas de rastreamento de máxima potência, os objetivos do trabalho e a proposta do estudo. Nos capítulos 2 e 3 são apresentados o primeiro estágio (cc-cc) e segundo estágio (cc-ca) de processamento de energia, respectivamente. As topologias escolhidas são analisadas qualitativa e quantitativamente e os projetos dos conversores são realizados; também é detalhada a técnica de rastreamento de máxima potência (MPPT) usada no primeiro estágio e a metodologia de controle aplicada no segundo estágio. Finalmente, no capitulo 4 são apresentados resultados de simulação complementados com resultados experimentais para validar os estudos teóricos feitos nos capítulos anteriores. 

  LINK: http://www.repositorio.ufc.br/bitstream/riufc/3869/1/2012_dis_emmteran.pdf
 

Design of Delta Primary - Transposed zigzag Secondary (DTz) Transformer to Minimize Harmonic Currents on the Three-phase Electric Power Distribution System Chairul Gagarin Irianto, Rudy Setiabudy, and Chairul Hudaya Department of Electrical Engineering, Universitas Trisakti, Jakarta, Indonesia

 

Design of Delta Primary - Transposed zigzag Secondary (DTz) Transformer to Minimize Harmonic Currents on the Three-phase Electric Power Distribution System Chairul Gagarin Irianto, Rudy Setiabudy, and Chairul Hudaya

Department of Electrical Engineering, Universitas Trisakti, Jakarta, Indonesia

Abstract: The delta primary - transposed zigzag secondary (DTz) transformer has been designed and used to reduce the bad impacts of the harmonic in the distribution power system. The DTz transformer is constructed with delta connection in primary winding and the three transposed windings at the different core legs of secondary winding. The harmonic reduction method of the DTz transformer applies two basic principles. The first principle is to inhibit electromagnetic energy of the harmonic currents by cancelling the phase polarity on the secondary winding. The second is to insulate the remaining of the mmf induction from harmonic current loads and minimize to circulate in the delta windings on the primary side. The triplen harmonics currents generated on the primary and secondary winding of DTz transformer are simulated in this paper. Both balanced and unbalanced loads of the three-phase distribution system are examined. The experiment shows that the total THD current in the secondary winding when balanced loads are applied is about 70.8 %, and in the primary side is 24.3 %. While for unbalanced loads, the average THD in secondary winding is 68.44 % and in delta winding is 26.4 %. It means the DTz transformer has a filter-ability to reduce about 42 - 46 % THD for both balanced and unbalanced loads. By comparing the computer simulation results and data measurements through experiment in the laboratory, it is proved that the use of the proposed DTz transformer is one of the methods to reduce harmonic currents and inhibit them to enter to the supply system.

Keywords: triplen harmonic currents, balanced and unbalanced loads, delta primary - transposed zigzag secondary winding (DTz) transformer, non-linear loads

LINK:https://www.researchgate.net/profile/Chairul_Hudaya/publication/267838702_Design_of_Delta_Primary_-Transposed_zigzag_Secondary_DTz_Transformer_to_Minimize_Harmonic_Currents_on_the_Three-phase_Electric_Power_Distribution_System/links/546d39d30cf26e95bc3caf85/Design-of-Delta-Primary-Transposed-zigzag-Secondary-DTz-Transformer-to-Minimize-Harmonic-Currents-on-the-Three-phase-Electric-Power-Distribution-System.pdf

Mitigation of DC Current Injection in Transformerless Grid-Connected Inverters By Weichi Zhang - School of Engineering Newcastle University United Kingdom

 Mitigation of DC Current Injection in Transformerless Grid-Connected Inverters Weichi Zhang B.Sc., M.Sc. A thesis submitted for the degree of Doctor of Philosophy April 2019 School of Engineering Newcastle University United Kingdom

Abstract With a large number of small-scale PV plants being connected to the utility grid, there is increasing interest in the use of transformerless systems for grid-connected inverter photovoltaic applications. Compared to transformer-coupled solutions, transformerless systems offer a typical efficiency increase of 1-2%, reduced system size and weight, and reductions in cost. However, the removal of the transformer has technical implications. In addition to the loss of galvanic isolation, DC current injection into the grid is a potential risk. Whilst desirable, the complete mitigation of DC current injection via conventional current control methods is known to be particularly challenging, and there are remaining implementation issues in previous studies. For this reason, this thesis aims to minimize DC current injection in grid-connected transformerless PV inverter systems. The first part of the thesis reviews the technical challenges and implementation issues in published DC measurement techniques and suppression methods. Given mathematical models, the performance of conventional current controllers in terms of DC and harmonics mitigation is analyzed and further confirmed in simulations and experiments under different operating conditions. As a result, the second part of the thesis introduces two DC suppression methods, a DC voltage mitigation approach and a DC link current sensing technique. The former method uses a combination of a passive attenuation circuit and a software filter stage to extract the DC voltage component, which allows for further digital control and DC component mitigation at the inverter output. It is proven to be a simple and highly effective solution, applicable for any grid-connected PV inverter systems. The DC link sensing study then investigates a control-based solution in which the dc injection is firstly accurately determined via extraction of the line frequency component from the DC link current and then mitigated with a closed loop. With an output current reconstruction process, this technique provides robust current control and effective DC suppression based on DC link current measurement, eliminating the need for the conventional output current sensor. Results from rated simulation models and a laboratory grid-connected inverter system are presented to demonstrate the accurate and robust performance of the proposed techniques. This thesis makes a positive contribution in the area of power quality control in grid-connected inverters, specifically mitigating the impact of DC injection into the grid which has influences on the network operating conditions and the design and manufacture of the PV power converter itself.

LINK: https://theses.ncl.ac.uk/jspui/bitstream/10443/4594/1/Zhang%20W%202019%20%28added%20to%20dspace%20on%20receipt%29.pdf