Single phase transformerless inverter topologies for grid-tied photovoltaic system: A review - Monirul Islam a,Saad Mekhilef ,Mahamudul Hasan

Single phase transformerless inverter topologies for grid-tied photovoltaic system: A review Monirul Islam a,Saad Mekhilef ,Mahamudul Hasan 

 Power Electronics and Renewable Energy Research Laboratory (PEARL), Department of Electrical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia 
Department of Mechanical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

 Abstract :
Grid-tied inverters are the key components of distributed generation system because of their function as an effective interface between renewable energy sources and utility. Recently, there has been an increasing interest in the use of transformerless inverter for low-voltage single-phase grid-tied photovoltaic (PV) system due to higher efficiency, lower cost, smaller size and weight when compared to the ones with transformer. However, the leakage current issues of transformerless inverter, which depends on the topology structure and modulation scheme, have to be addressed very carefully. This review focuses on the transformerless topologies, which are classified into three basic groups based on the decoupling method and leakage current characteristics. Different topologies under the three classes are presented, compared and evaluated based on leakage current, component ratings, advantages, and disadvantages. An examination of demand for the inverter, the utility grid, and the PV module are presented. A performance comparison in MATLAB/Simulink environment is done among different topologies. Also an analysis has been presented to select a better topology. Finally, based on the analysis and simulation results, a comparison table has been presented. Furthermore, some important experimental parameters have been summarized.
LINK
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.702.4372&rep=rep1&type=pdf

H6-type transformerless single-phase inverter for grid-tied photovoltaic system -Monirul Islam, Saad Mekhilef ✉ Power Electronics and Renewable Energy Research Laboratory (PEARL), Department of Electrical Engineering, University of Malaya.

H6-type transformerless single-phase inverter for grid-tied photovoltaic system ISSN 1755-4535
Received on 20th April 2014 Accepted on 7th October 2014 doi: 10.1049/iet-pel.2014.0251
 www.ietdl.org
Monirul Islam, Saad Mekhilef ✉ Power Electronics and Renewable Energy Research Laboratory (PEARL), Department of Electrical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia ✉ E-mail: saad@um.edu.my

 Abstract:
There has been an increasing interest in transformerless inverter for grid-tied photovoltaic (PV) system because of the benefits of lower cost, smaller volume as well as higher efficiency compared with the ones with transformer. However, one of the technical challenges of the transformerless inverter is the safety issue of leakage current which needs to be addressed carefully. In addition, according to the international regulations, transformerless inverter should be capable of handling a certain amount of reactive power. In this study, a new H6-type transformerless inverter for grid-tied PV system is proposed that can eliminate the threat of leakage current. The proposed topology has also the capability to inject reactive power into the utility grid. Three-level output voltage employing unipolar sinusoidal pulsewidth modulation can be achieved with the proposed topology. The proposed topology structure and detail operation principle with reactive power control are investigated. The relationship among the existing topologies and their reactive power control capability are also discussed. The proposed topology is simulated in MATLAB/Simulink software to initially verify the accuracy of theoretical explanations. Finally, a universal prototype rated 1 kW has been built and tested. The experimental results validate the theoretical analysis and simulation results.
VIEW COMPLETE TEXT:
https://pdfs.semanticscholar.org/43da/3251d204cbce6582f68347422b84d95e4a1f.pdf

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