High-Frequency Transformer Design for Solid- State Transformers in Electric Power Distribution Systems Roderick Javier Garcia Montoya University of Arkansas, Fayetteville

High-Frequency Transformer Design for Solid-State Transformers in Electric Power Distribution Systems
ABSTRACT
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering by Roderick Javier Garcia Montoya Universidad Tecnológica de Panamá Bachelor of Science in Electromechanical Engineering, 2011
December 2015 University of Arkansas This thesis is approved for recommendation to the Graduate Council. ABSTRACT The objective of this thesis is to present a high- or medium-frequency transformer design methodology for Solid-State Transformer (SST) applications. SSTs have been proposed as a replacement of the traditional 50/60 Hz transformer in applications demanding high-power density. Moreover, due to the high penetration of distributed generation, DC grids, energy storage systems, and sensitive loads, SSTs have been considered as an enabling technology for envisioned future energy systems. These applications demand additional functionalities that may not be achieved with traditional transformers. For example, active power flow control, harmonic suppression, voltage regulation, voltage sag compensation, and reduced size and volume. In this thesis, SST topologies are evaluated in order to determine their impact upon the transformer design. In addition, design considerations for core and wire selections, isolation requirements, and different transformer structures are investigated. As a result, the proposed transformer design methodology accounts for leakage inductance requirements for optimal power transfer, high-frequency effects in the transformer core and windings, and a flux density optimization to maximize transformer’s efficiency. The design procedure has been implemented in MATLAB® as an interactive tool for designing high-frequency transformers.
LINK
http://scholarworks.uark.edu/cgi/viewcontent.cgi?article=2381&context=etd

Design and Development of High-voltage and High-frequency Transformer for Solid-state Transformer* Park Siho - Kyungpook National University Daegu, Korea

Design and Development of High-voltage and High-frequency Transformer for Solid-state Transformer* Park Siho School of Architectural, Civil, Environmental, and Energy Engineering 

Graduate School, Kyungpook National University Daegu, Korea
 (Supervised by Professor Cha Honnyong)

 (Abstract)
In this paper, design guide of high-voltage isolated high-frequency transformer is proposed. Since a potential difference of up to 20 kV occurs at both ends of a transformer constituting a 3-port 3-level NPC based dual half-bridge DAB converter of solid-state transformer, it is necessary to design a transformer capable of 30 kV insulation considering margin. In order to insulate a voltage of 30 kV with air only, a very long distance between the primary and secondary wire of the transformer must be used. Therefore, bobbins made of Teflon resin and Polycarbonate were fabricated and insulation was obtained. To reduce the insulation parameter, core was connected to output neutral point terminal. The bobbin consists of an inner bobbin, an outer bobbin, a guard, and is designed to have sufficient dielectric strength. Through the simulation verification, only the primary wire portion was molded to remove the dielectric breakdown element generated at the portion where the outer bobbin and the guard contact with each other. A prototype transformer was built, completed operation verification and passed 30kV withstand voltage test. In the case of temperature test, there is no enough air layer to allow heat to escape from the secondary wire. Therefore, a high number of temperatures are measured, but this can be solved by turning the fan on.

Seminário Científico de Sistemas de Eletrônica de Potência – SCSEP 2017 – nos dias 13 e 14 de dezembro, no Auditório de Engenharia Elétrica no Centro Tecnológico (CTC) da UFSC.

O Instituto de Eletrônica de Potência (INEP) promoverá o terceiro Seminário Científico de Sistemas de Eletrônica de Potência – SCSEP 2017, evento que ocorrerá nos dias 13 e 14 de dezembro de 2017 no Auditório Luiz Antonio Teixeira, localizado no prédio da Engenharia Elétrica da UFSC, Florianópolis e será organizado por comissão local. O seminário está programado para receber aproximadamente 100 pessoas, entre alunos e professores da instituição e de outras, assim como profissionais da área que atuam nos setores público e privado. O evento tem como objetivo apresentar e divulgar os últimos avanços da área por meio da ação de alunos e pesquisadores do Instituto, incluindo pós-doutorandos, doutorandos, mestrandos, alunos de iniciação científica e tecnológica e em conclusão de curso de graduação. Tais trabalhos estão sendo desenvolvidos no INEP e se encontram em estágio avançado, representando possíveis soluções para a indústria e possibilitando, assim, a interação entre as partes. No evento serão realizadas também palestras e debates com convidados especialistas da área, com a finalidade de discutir as tendências e demandas atuais para a área de Eletrônica de Potência, bem como suas perspectivas futuras.
WEBSITE: http://scsep.inep.ufsc.br/

 LINK DA REVISTA SCSEP2017
http://scsep.inep.ufsc.br/wp-content/uploads/2015/09/Revista_SCSEP_2017.pdf

Inversor Dual-Buck Monofásico Sem Transformador para Injeção de Energia na Rede Lucas Munaretto- Marcelo L. Heldwein-Universidade Federal de Santa Catarina — UFSC Departamento de Engenharia Elétrica e Eletrônica / Instituto de Eletrônica de Potência — INEP, Florianópolis – SC, Brasil

Doctoral Thesis A Study on High Efficiency Bidirectional Grid-tied Converters -Sung-Ho Lee (이 성 호) Department of Electrical Engineering Pohang University of Science and Technology

Doctoral Thesis 
A Study on High Efficiency Bidirectional Grid-tied Converters Sung-Ho Lee (이 성 호) 
Department of Electrical Engineering Pohang University of Science and Technology 2016 

This thesis presents three high efficiency grid-tied converter topologies and their respective control algorithms. These converters are applicable to various industrial fields such as energy storage systems (ESS), renewable energy systems, uninterruptible power supply (UPS) systems, and electric vehicles (EV). First, a high efficiency bidirectional grid-tied flyback converter that uses a single power conversion technique and a control system for it are introduced. The proposed converter consists of a bidirectional flyback dc-dc converter and an unfolding circuit. Due to its switching control strategy, the proposed converter performs bidirectional power conversion between the energy storage device and the grid through only single step. From the model analysis, the inherent dynamic characteristics are figured out. Based on the analysis, a control system is developed, which consists of a linear feedback controller with a low pass filter, a repetitive controller, and a feed-forward controller; this overcomes the constrains caused by a right-half-plane zero and a filter resonance and makes the proposed converter achieve the desired control performances and stability. In conclusion, the proposed converter can obtain high efficiency using a single power conversion technique, and the developed control system makes the proposed converter feasible. Second, a high efficiency single-phase bidirectional inverter for a PV energy system integrated with an energy storage system. The proposed single-phase inverter is developed using the transformerless system configuration so that it provides high power conversion efficiency, excellent power density, and low production cost. Using its circuit structure and switching operation, the proposed inverter can suppress the ground leakage current which is considered to be one of the most important design parameters in a transformerless PV system. Therefore, the proposed inverter gives the feasibility for the transforemrless system configuration in a PV energy system integrated with an energy storage system and enhances the overall performance of the bidirectional power converter system. The third is a novel high efficiency three-phase bidirectional grid-tied converter with high power density for high power applications. The proposed converter is composed of the threelevel dc-dc converter and the modified three-phase T-type three-level inverter. The threelevel converter circuit configuration gives smaller passive component size and lower switch voltage stress compared to other two-level grid-tied converters. In addition, due to its novel circuit structure, the proposed converter can use the active and passive components for only two phases of the grid in the inverter stage and eliminate the leakage current problem. Thus, because the proposed converter enables to not only decrease the number of components but also make the transformerless configuration feasible, it provides higher efficiency and higher power density compared to other high power grid-tied converters. All proposed converters are analyzed theoretically, and implemented practically. to evaluate their performance. Finally, the experimental results show that the proposed converters improve overall performance such as high power conversion efficiency, power density, and production cost with satisfying the standards for the grid regulations.