A Medium Frequency Transformer Design Tool with Methodologies Adapted to Various Structures
sábado, 18 de novembro de 2023
A Medium Frequency Transformer Design Tool with Methodologies Adapted to Various Structures Alexis Fouineau, Marie-Ange Raulet, Martin Guillet, Fabien Sixdenier, Bruno Lefebvre
A Medium Frequency Transformer Design Tool with Methodologies Adapted to Various Structures
Alexis Fouineau, Marie-Ange Raulet, Martin Guillet, Fabien Sixdenier, Bruno
Lefebvre
2020 Fifteenth International Conference on Ecological Vehicles and Renewable Energies (EVER)
Abstract—A comprehensive and generic medium
frequency transformer (MFT) design methodology is
presented in this paper, which can be applied to many
transformer structures. Models were found or developed
to cover all the necessary calculation, with emphasis on the
balance between computation time and accuracy, leading
to a fast and efficient design tool. Numerous MFT designs
are available at the end with the possibility to choose the
best candidate. A multi-megawatt offshore windfarm
converter application was chosen to show the optimization
procedure of the MFT design inside such a converter. The
best potential design was retained and validated by
numerous finite element simulations. This procedure was
repeated for various MFT structures in order to perform a
quantitative comparison of many different combinations of
technological choices. This study can give insights on the
best technological choices to be used for MFTs, and also
shows significant differences in performance between
structures.
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sexta-feira, 17 de novembro de 2023
CÓMO OBTENER LA MÁXIMA PUNTUACIÓN EN EL EXAMEN DE FÍSICA Resolver problemas de mayor y mayor nivel de complejidad. Moscú Khannanov, N.K-2021.
N.K. Khannanov CÓMO OBTENER LA MÁXIMA PUNTUACIÓN EN EXAMEN DE FÍSICA Resolver tareas de mayor y mayor nivel de complejidad. Moscú
Khannanov, N.K.
El manual propuesto proporciona características de los principales tipos de tareas de mayor y alto nivel de complejidad utilizadas en el Examen Estatal Unificado de Física. Se presta especial atención al análisis de las tareas que provocaron las mayores dificultades. Para la formación y la autopreparación para el Examen Estatal Unificado, se ofrecen tareas con respuestas detalladas de distintos niveles de dificultad para todos los bloques de contenido.
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terça-feira, 14 de novembro de 2023
Optimal Design Methodology for A High-Frequency Transformer Using Finite Element Analysis and Machine Learning by Eunchong Noh-University of Seoul-Electrical and Computer Engineering
Optimal Design Methodology for A High-Frequency Transformer Using Finite Element Analysis and Machine Learning
by
Eunchong Noh
A thesis submitted in partial fulfillment of
the requirements for the degree of
Master of Science
(Electrical and Computer Engineering)
December 2021
Thesis committee:
Gyu-Sik Kim, Professor, ECE, University of Seoul
Seung-Hwan Lee, Associate Professor, ECE. University of Seoul
Moon-Que Lee, Professor, ECE, University of Seoul
The demand for isolated DC-DC converters is increasing due to the spread of
electric vehicles (EV) and the expansion of renewable energy use. Accordingly, the
need for a high-frequency transformer, a key component of an isolated DC-DC
converter, is also increasing. This trend is also taking place in the field of railway
locomotive systems. Solid state transformer (SST) technology to improve the
performance and efficiency of railway locomotive propulsion systems is being
actively researched, and high-frequency transformer is the core of SST. Highfrequency
transformer design for railway locomotive systems has more complex
design elements that must be considered for volume-loss optimization and
insulation and thermal design.
This thesis investigates an optimization design methodology using machine
learning and NSGA-II for optimized high-frequency transformer design. For
machine learning, Finite-element analysis (FEA) simulation was used to obtain
high-frequency transformer parameter data. Conventional high-frequency
transformer optimization design methods used analytical models for parameter
calculation. However, this analytical model has a significant error when the shape
of the high-frequency transformer becomes complicated. In particular, the leakage
inductance of the high-frequency transformer is difficult to calculate with an
analytical model. So, it is difficult and cumbersome to apply it in the design. This
thesis obtained magnetizing inductance, leakage inductance, and copper loss of
shell-type transformer models in various shapes using FEA simulation. Then, using
the data obtained from the FEA simulation, a machine learning regression model
was created to minimize the parameter calculation error in complex shapes. In
addition, the NSGA-II algorithm, which is widely used in multi-variable
optimization design, is used to find the optimal transformer shape to perform
optimization that can satisfy multiple design elements at the same time.
Each parameter inferred by the machine learning regression model showed a
high correlation and sufficiently low inference error rate, used for parameter
calculation in the NSGA-II algorithm. The inferred parameters are used to calculate
transformer loss for optimization design or check whether constraints are satisfied.
Through the optimization design using NSGA-II, a Pareto front curve for volume
and loss that satisfies all design conditions was obtained. The designer can select
and use the designs according to the situation.
The methodology can be designed for more complex shapes to achieve higherperformance
high-frequency transformer design. In addition, the complexity of the
design is reduced because numerous consideration factors can be easily considered
through constraint setting in the NSGA-II. Finally, unlike the conventional design
methodology, which has a significant influence on the skill and intuition of the
designer, once the environment is set up, the design proceeds only by inputting
target parameters and executing the code so that the design time can be reduced.
Therefore, it is possible to design a high-frequency transformer with constantly
high performance regardless of the designer's skill level.
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sexta-feira, 10 de novembro de 2023
The Discussion of Characteristic of Ferrite Core for High Frequency Transfomers
Abstract
For the time being, high-freqency switching technique is widely
used in various applications. Therefore, the techniques of switching
method of devices and designing of high-frequency transformers have
become one of the main research subjects in power eletronic area.
The main objective of this thesis is discussing the characteristics of
core materials which are used for high-frequency transformers. In
experimental, an integrator has been used to obtain the waveforms of
magnetic flux. In cooperating with excitating current, these waveforms
are transformed into hysteresis curves. The relationships between length
of airgap and performance of transformer are also investigated
VIEW FULL TEXT: http://u.dianyuan.com/bbs/u/66/1441761213875165.pdf
sábado, 4 de novembro de 2023
Ph.D. Thesis Modular Multiport Power Converter Topologies for Electric Vehicle Charging Stations by Ngoc Dat Dao-Graduate School of Yeungnam University Department of Electrical Engineering-
Ph.D. Thesis Modular Multiport Power Converter Topologies for
Electric Vehicle Charging Stations
Graduate School of Yeungnam University
Department of Electrical Engineering
Major in Control and Electric Machinery Power Conversion
by Ngoc Dat Dao
Advisor: Professor Dong-Choon Lee
August 2021
Abstract The main objective of this thesis is to develop converter topologies with high efficiency
and low cost for fast charging stations. Based on the investigation of different power
conversion structures for fast charging stations, new topologies have been derived, which
can offer additional benefits to EV fast charging stations.
Firstly, a novel isolated three-port DC/DC converter is proposed, which is based on a
series resonant converter (SRC) and a dual active bridge (DAB) converter for electricvehicle
(EV) charging stations with fast and slow charging functions. With this three-port
structure, the proposed converter has fewer components, which results in lower system cost
and volume compared with separate charger systems. A simple control method using phase
shift and frequency modulations was developed to control the output power of the fast and
slow charging ports simultaneously. An optimal phase shift angle was also derived to
minimize the transformer current for when only the DAB converter is operated for slow
charging. To verify the converter operation, a 5-kW SiC-based prototype with a power
density of 2.74-kW/dm3 was built and tested with an input voltage of 600-V. A high
efficiency performance over a wide output voltage range has been achieved, and the peak
efficiency is 98.2% at the rated conditions
Secondly, a half-bridge bidirectional isolated matrix-based AC/DC converter is
proposed for compact AC/DC power stages in fast charging stations. The converter can
control not only the DC voltage or current, but also the power factor of the AC current with
a single conversion stage, which helps to achieve a higher power density with a lower
complexity. The converter operates with zero-voltage switching (ZVS) or zero-current
switching (ZCS) in all switches. Hence, the switching frequency of the converter can be
increased higher, leading to smaller passive components. Besides the simple circuit, the
modulation scheme derived from time domain analyses is also easy to implement. The
proposed topology has been verified by experimental results for a 2-kW SiC-based
prototype. A high efficiency of 96.8 % was achieved at a full load condition. The current
THD is lower than 4 % and the power density is 1.8-kW/dm3. Furthermore, an experiment
for two modules has been carried out to demonstrate the feasible of the proposed converter
for modular SST-based charging stations.
Finally, a novel semi-modular three-phase AC/DC structure is proposed for SST-based
fast charging stations. The proposed system employs single-stage indirect matrix-based
AC/DC converters. A single full-bridge rectifier is used for each phase of the medium
voltage (MV) grid so that each AC/DC module does not need a voltage rectifier. As a result,
the number of semiconductor devices in the proposed system is reduced significantly
compared with other existing SST-based systems. A decentralized control scheme without
high-speed communication has been developed to regulate the input and output currents
while keeping the voltages of each module balance. A design of a 360-kW system has been
carried out to evaluate the efficiency of the proposed system, which is 97.7 % at rated
power. With delta connection in three-phase system, a third harmonic current can be
injected to the phase currents to increase the output current and power by 15 %. Simulation
results for a 360-kW 3.3-kV system are provided to verify the performance of the proposed
system. Finally, a 3-kW hardware prototype has been built and tested to demonstrate the
feasibility of the proposed system.
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