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Journal articles on the topic 'Medium-Frequency Transformer'

Author: Grafiati

Published: 4 June 2021

Last updated: 11 February 2022

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1

Changjiang, Zheng, Wang Qian, Wang Huai, Shen Zhan, and Claus Leth Bak. "Electrical Stress on the Medium Voltage Medium Frequency Transformer." Energies 14, no. 16 (August 19, 2021): 5136. http://dx.doi.org/10.3390/en14165136.

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This paper proposes an equivalent circuit model to obtain the transient electrical stress quantitatively in medium voltage medium frequency transformers in modern power electronics. To verify this model, transient simulation is performed on a 1.5 kV/1 kHz transformer, revealing voltage overshoot quantitatively between turns and layers of the transformer’s HV winding. Effects of rise time of the input pulse voltage, stray capacitance of the winding insulation, and their interactions on the voltage overshot magnitude are presented. With these results, we propose limiting the voltage overshoot and, thereafter, enhancing medium voltage medium frequency transformer’s insulation capability, which throws light on the transformer’s insulation design. Additionally, guidance on the future studies on aging and endurance lifetime of the medium voltage medium frequency transformer’s insulation could be given.

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2

Mogorovic, Marko, and Drazen Dujic. "Sensitivity Analysis of Medium-Frequency Transformer Designs for Solid-State Transformers." IEEE Transactions on Power Electronics 34, no. 9 (September 2019): 8356–67. http://dx.doi.org/10.1109/tpel.2018.2883390.

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3

ÖZÜPAK, Yıldırım. "Medium Frequency Electric Field Analysis of Power Transformers in High Voltage System." BEN Vol:2 Issue:3 2021 2, no. 3 (February 8, 2021): 1–5. http://dx.doi.org/10.36937/ben.2021.003.001.

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Electronic power transformers (EPT) are transformers that are smaller in size and volume compared to conventional 50 Hz frequency transformers. Medium frequency transformers (MFT) have begun to become important components in high voltage and high power energy conversion systems such as EPTs. In this study, the electric field distribution of these transformers is discussed. The electric field distributions in the transformer have been obtained using the two-dimensional finite element method (FEM). Besides, maximum electric field intensities were obtained in the study. ANSYS@Maxwell simulation program, which realizes a solution based on FEM, was used for these analyzes. Electromagnetic field analyzes of the same transformer under normal conditions were also performed to compare the analyzes. Besides, the values obtained from the high-frequency analysis, the values obtained from the study below 50 Hz frequency, and the values obtained experimentally were compared. In this way, the stress in the insulation material of the transformer and the weak parts of the insulation material were detected. It is expected that the method used will contribute to future studies to examine the results of the electric field distribution analysis of transformers.

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4

Himanshu, Harsimran Singh, Pandiyan Kumar, Muhammad Ali, Ho Lee, Muhammad Khan, Gwan Park, and Hee-Je Kim. "High Frequency Transformer’s Parasitic Capacitance Minimization for Photovoltaic (PV) High-Frequency Link-Based Medium Voltage (MV) Inverter." Electronics 7, no. 8 (August 8, 2018): 142. http://dx.doi.org/10.3390/electronics7080142.

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The high-frequency-based medium voltage (MV) inverter is used in renewable energy power sources for power transmission. However, power quality is compromised as a result of the increase in common mode noise currents by the high inter-winding parasitic capacitance in high-frequency link transformers. This fast voltage transient response leads to harmonic distortion and transformer overheating, which causes power supply failure or many other electrical hazards. This paper presents a comparative study between conventional and modified toroid transformer designs for isolated power supply. A half bridge high-frequency (10 kHz) MV DC–AC inverter was designed along with power source; a 680 W solar module renewable system was built. An FEM-simulation with Matlab-FFT analysis was used to determine the core flux distribution and to calculate the total harmonics distortion (THD). A GWInstek LCR meter and Fluke VT04A measured the inter-winding capacitance and temperature in all four transformer prototypes, respectively. The modified design of a toroid ferrite core transformer offers more resistance to temperature increase without the use of any cooling agent or external circuitry, while reducing the parasitic capacitance by 87%. Experiments were conducted along with a mathematical derivation of the inter-winding capacitance to confirm the validity of the approach.

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5

Pham, Khoi Dinh Anh, and Thai Thi Minh Pham. "Extending analyzed frequency range in interpretation of frequency responses measured on a distribution transformer." Science and Technology Development Journal 18, no. 3 (August 30, 2015): 39–46. http://dx.doi.org/10.32508/stdj.v18i3.883.

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In the field of diagnosis of mechanical failures in power transformer’s active part, i.e., windings, leads and the core, the technique of Frequency Response Analysis (FRA) has been recently approved as the main application tool. Mechanical failures in transformer windings reflect changes on measured terminal frequency responses normally in medium frequency range, from several to hundreds of kHz, which is in fact not easy to interpret for diagnosis. The authors proposed a new method based on simulation of a lumped three-phase equivalent circuit of power transformers to interpret frequency responses effectively, but only within low frequency range. This limitation is due to the fact that, the circuit cannot reflect well physical phenomena at medium and higher frequencies. To improve the FRA performance of the proposed method at medium frequencies for transformer failure diagnosis purpose, the paper introduces an investigation on a distributed three-phase equivalent circuit of a 200 kVA 10.4/0.46 kV Yy6 distribution transformer. Result of the investigation is a simplified procedure in determination of electrical parameters associated with the distributed circuit for better simulation based FRA interpretation at medium frequencies.

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6

Tian, Haonan, Zhongbao Wei, Sriram Vaisambhayana, Madasamy Thevar, Anshuman Tripathi, and Philip Kjær. "A Coupled, Semi-Numerical Model for Thermal Analysis of Medium Frequency Transformer." Energies 12, no. 2 (January 21, 2019): 328. http://dx.doi.org/10.3390/en12020328.

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Medium-frequency (MF) transformer has gained much popularity in power conversion systems. Temperature control is a paramount concern, as the unexpected high temperature declines the safety and life expectancy of transformer. The scrutiny of losses and thermal-fluid behavior are thereby critical for the design of MF transformers. This paper proposes a coupled, semi-numerical model for electromagnetic and thermal-fluid analysis of MF oil natural air natural (ONAN) transformer. An analytical model that is based on spatial distribution of flux density and AC factor is exploited to calculate the system losses, while the thermal-hydraulic behavior is modelled numerically leveraging the computational fluid dynamics (CFD) method. A close-loop iterative framework is formulated by coupling the analytical model-based electromagnetic analysis and CFD-based thermal-fluid analysis to address the temperature dependence. Experiments are performed on two transformer prototypes with different conductor types and physical geometries for validation purpose. Results suggest that the proposed model can accurately model the AC effects, losses, and the temperature rises at different system components. The proposed model is computationally more efficient than the full numerical method but it reserves accurate thermal-hydraulic characterization, thus it is promising for engineering utilization.

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7

Somkun, Sakda, Toshiro Sato, Viboon Chunkag, Akekachai Pannawan, Pornnipa Nunocha, and Tawat Suriwong. "Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter." Energies 14, no. 9 (April 23, 2021): 2407. http://dx.doi.org/10.3390/en14092407.

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This article reports an investigation into ferrite and nanocrystalline materials for the medium-frequency transformer of a dual active bridge DC-DC converter, which plays a key role in the converter’s efficiency and power density. E65 MnZn ferrite cores and toroidal and cut nanocrystalline cores are selected for the construction of 20-kHz transformers. Transformer performance is evaluated with a 1.1-kW (42–54 V)/400 V dual active bridge DC-DC converter with single-phase shift and extended phase shift modulations. The experimental results indicate that the toroidal nanocrystalline transformer had the best performance with an efficiency range of 98.5–99.2% and power density of 12 W/cm3, whereas the cut-core nanocrystalline transformer had an efficiency range of 98.4–99.1% with a power density of 9 W/cm3, and the ferrite transformer had an efficiency range of 97.6–98.8% with a power density of 6 W/cm3. A small mismatch in the circuit parameters is found to cause saturation in the nanocrystalline toroidal core, due to its high permeability. The analytical and experimental results suggest that cut nanocrystalline cores are suitable for the dual active bridge DC-DC converter transformers with switching frequencies up to 100 kHz.

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8

Anh Khoi Pham, Dinh. "Application of Frequency Response Analysis for in-service power transformers." Science and Technology Development Journal 20, K1 (March 31, 2017): 58–66. http://dx.doi.org/10.32508/stdj.v20ik1.415.

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CIGRE, IEC and IEEE have recently approved the technique of Frequency Response Analysis (FRA) as an application tool for diagnosis of mechanical failures in power transformer’s active part, i.e., windings, leads and the core. The diagnosis is based on the discrepancy between frequency responses measured on power transformers mainly at different time points. In Vietnam, utilities such as Power Transmission Companies and Power Corporations are investigating this technique for application on their power transformers. Mechanical failures in power transformers cause changes on measured frequency responses starting from a medium frequency range, from several hundreds of Hz or tens of kHz depending on transformer/winding type and power. For a reliable diagnosis, the understanding of transformer/winding structure on measured frequency responses is of importance; thus, the international standards suggested the simulation approach with physical distributed transformer circuits should be exploited. The development of physical distributed circuits of power transformers normally needs availability of internal transformer structure and material properties for an analytical approach. However, for in-service power transformers, this task is challenging since the required data are not available. For a feasible application of the simulation based FRA interpretation, this paper introduces an investigation on the development of a distributed equivalent circuit of an in-service 6.5 MVA 47/27.2 kV Yd5 power transformer. The result of this investigation is a feasible approach in determining electrical parameters in a physical distributed circuit, which supports analysis of frequency responses measured at transformer terminals for real application on in-service power transformers of utilities.

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9

Leibl, Michael, Gabriel Ortiz, and Johann W. Kolar. "Design and Experimental Analysis of a Medium-Frequency Transformer for Solid-State Transformer Applications." IEEE Journal of Emerging and Selected Topics in Power Electronics 5, no. 1 (March 2017): 110–23. http://dx.doi.org/10.1109/jestpe.2016.2623679.

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10

Balci, Selami, Ibrahim Sefa, and Necmi Altin. "Thermal Behavior of a Medium-Frequency Ferrite-Core Power Transformer." Journal of Electronic Materials 45, no. 8 (May 5, 2016): 3978–88. http://dx.doi.org/10.1007/s11664-016-4567-5.

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11

Guillod, Thomas. "Medium-Frequency Transformer Scaling Laws: Derivation, Verif ication, and Critical Analysis." CPSS Transactions on Power Electronics and Applications 5, no. 1 (March 2020): 18–33. http://dx.doi.org/10.24295/cpsstpea.2020.00003.

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12

Huang, Pei, Chengxiong Mao, and Dan Wang. "Analysis of electromagnetic force for medium frequency transformer with interleaved windings." IET Generation, Transmission & Distribution 11, no. 8 (June 1, 2017): 2023–30. http://dx.doi.org/10.1049/iet-gtd.2016.1586.

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13

Pham, Khoi Dinh Anh. "Measurement-based electrical parameters of power transformers for Frequency Response Analysis interpretation-Part II: Winding Part II: Winding analysis." Science and Technology Development Journal 20, K3 (June 30, 2017): 11–17. http://dx.doi.org/10.32508/stdj.v20ik3.1077.

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For a practical Frequency Response Analysis (FRA) interpretation applicable to power transformers, frequency dependent electrical parameters of the core and windings in broad frequency range should be identified through non-destructive measurements. Since the core parameters are determined in Part I, electrical parameters of windings (resistances, capacitances) and leakage paths surrounding windings (leakage/zero-sequence impedances) of a distribution transformer will be discussed in this paper. Due to the fact that most parameters associated with the windings currently can only be measured at or around power frequency through diagnostic testing methods, the practical parameter-based FRA interpretation is not possible. To deal with this problem, the paper proposes a new approach based on the combination of different measured driving-point impedances and relevant analysis of the duality-based equivalent circuit in determining frequency dependent parameters associated with transformer windings. Results show that the physical FRA interpretation can be reasonable obtained for the test transformer in low and medium frequency range.

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14

Huang, Pei, Renjun Dian, Peng Wang, Dan Wang, Zhenxing Liu, and Qi Wang. "Comprehensive Analysis of Electric Field Characteristics for Multi-Winding Medium Frequency Transformer." Energies 14, no. 11 (June 4, 2021): 3285. http://dx.doi.org/10.3390/en14113285.

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The multi-winding medium frequency transformer (MMFT) has attracted widespread attention, since its application in power electronic transformers can simplify the system structure and reduce the volume and weight. However, the special working conditions of MMFT due to high voltage and high power density increase the difficulty of insulation design for MMFT. For this issue, this paper presents a comprehensive analysis of electric filed characteristics for MMFT. First, the electric field model of MMFT is established using the 2-D finite element method. Based on it, the influences of connection mode, core structure, and hollow winding on the electric field characteristics of MMFT are studied, including the overall electric field distribution, maximum electric field intensity, and the electric field intensity along a fixed path. The results show that there are differences in the maximum electric field intensity for different connection modes and different core structures, which provides references for MMFT insulation design. The proposed modeling method and analysis results in this paper are important for insulation improvement of MMFT.

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15

La Ganga, Alessandro, Roberto Re, and Paolo Guglielmi. "Input Parallel Output Series Structure of Planar Medium Frequency Transformers for 200 kW Power Converter: Model and Parameters Evaluation." Energies 14, no. 5 (March 7, 2021): 1450. http://dx.doi.org/10.3390/en14051450.

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Nowadays, the demand for high power converters for DC applications, such as renewable sources or ultra-fast chargers for electric vehicles, is constantly growing. Galvanic isolation is mandatory in most of these applications. In this context, the Solid State Transformer (SST) converter plays a fundamental role. The adoption of the Medium Frequency Transformers (MFT) guarantees galvanic isolation in addition to high performance in reduced size. In the present paper, a multi MFT structure is proposed as a solution to improve the power density and the modularity of the system. Starting from 20kW planar transformer model, experimentally validated, a multi-transformer structure is analyzed. After an analytical treatment of the Input Parallel Output Series (IPOS) structure, an equivalent electrical model of a 200kW IPOS (made by 10 MFTs) is introduced. The model is validated by experimental measurements and tests.

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16

Farnesi, Stefano, Mario Marchesoni, Massimiliano Passalacqua, and Luis Vaccaro. "Solid-State Transformers in Locomotives Fed through AC Lines: A Review and Future Developments." Energies 12, no. 24 (December 10, 2019): 4711. http://dx.doi.org/10.3390/en12244711.

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One of the most important innovation expectation in railway electrical equipment is the replacement of the on-board transformer with a high power converter. Since the transformer operates at line-frequency (i.e., 50 Hz or 16 2/3 Hz), it represents a critical component from weight point of view and, moreover, it is characterized by quite poor efficiency. High power converters for this application are characterized by a medium frequency inductive coupling and are commonly referred as Power Electronic Transformers (PET), Medium Frequency Topologies or Solid-State Transformers (SST). Many studies were carried out and various prototypes were realized until now, however, the realization of such a system has some difficulties, mainly related to the high input voltage (i.e., 25 kV for 50 Hz lines and 15 kV for 16 2/3 Hz lines) and the limited performance of available power electronic switches. The aim of this study is to present a survey on the main solutions proposed in the technical literature and, analyzing pros and cons of these studies, to introduce new possible circuit topologies for this application.

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17

Arslan, Serdal, İlhan Tarimer, M. E. Güven, and Sibel Akkaya Oy. "A medium frequency transformer design for spot welding machine using sizing equation and finite element analysis." Engineering review 40, no. 3 (May 21, 2020): 42–51. http://dx.doi.org/10.30765/er.40.3.05.

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In this study, a medium frequency power transformer has been designed analytically and its sizes have been obtained. The transformer’s analyses were made numerically by 2D AnsysMaxwell Solver software package. The Solver has also helped to study suitable transformer core and winding samples. Unlike medium frequency transformer, which is generally driven by unipolar PWM method, the designed transformer is driven by bipolar PWM method in the study. The core losses were obtained for different core materials (Trafoperm N3 and Amorfous 2605SA1) by AnsysMaxwell numerical and analytical calculations. The calculated losses for no-load working conditions were compared with each other. The designed transformer has been analyzed for its noload and loaded working conditions magnetically. Finally, the radial and axial forces created in the windings have also been examined for loaded working condition.

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18

Drabek, Pavel, Zdeněk Peroutka, Martin Pittermann, and Marek Cedl. "New Configuration of Traction Converter With Medium-Frequency Transformer Using Matrix Converters." IEEE Transactions on Industrial Electronics 58, no. 11 (November 2011): 5041–48. http://dx.doi.org/10.1109/tie.2011.2138114.

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19

Sandoval, Jose Juan, Harish Sarma Krishnamoorthy, Prasad N. Enjeti, and Sewan Choi. "Reduced Active Switch Front-End Multipulse Rectifier With Medium-Frequency Transformer Isolation." IEEE Transactions on Power Electronics 32, no. 10 (October 2017): 7458–68. http://dx.doi.org/10.1109/tpel.2016.2632717.

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20

Mogorovic, Marko, and Drazen Dujic. "100 kW, 10 kHz Medium-Frequency Transformer Design Optimization and Experimental Verification." IEEE Transactions on Power Electronics 34, no. 2 (February 2019): 1696–708. http://dx.doi.org/10.1109/tpel.2018.2835564.

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21

Guo, Zhicheng, Ruiyang Yu, Wei Xu, Xianyong Feng, and Alex Q. Huang. "Design and Optimization of a 200-kW Medium-Frequency Transformer for Medium-Voltage SiC PV Inverters." IEEE Transactions on Power Electronics 36, no. 9 (September 2021): 10548–60. http://dx.doi.org/10.1109/tpel.2021.3059879.

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22

Huang, Pei, Chengxiong Mao, and Dan Wang. "Electric Field Simulations and Analysis for High Voltage High Power Medium Frequency Transformer." Energies 10, no. 3 (March 16, 2017): 371. http://dx.doi.org/10.3390/en10030371.

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23

Kauder, T., T. Belgrand, R. Lemaître, A. Thul, and K. Hameyer. "Medium-frequency power transformer using GOES for a three-phase dual active bridge." Journal of Magnetism and Magnetic Materials 504 (June 2020): 166672. http://dx.doi.org/10.1016/j.jmmm.2020.166672.

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24

Xu, Yun, Lixia Chen, Wenzhang Guo, Chengjiang Shangguan, Jinxin Zuo, and Kaiwen He. "Optimal Design of Medium-Frequency Fe-Based Amorphous Transformer Based on Genetic Algorithm." IEEE Transactions on Plasma Science 46, no. 10 (October 2018): 3240–48. http://dx.doi.org/10.1109/tps.2018.2835151.

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25

Islam, Md Rabiul, Youguang Guo, and Jianguo Zhu. "A medium frequency transformer with multiple secondary windings for medium voltage converter based wind turbine power generating systems." Journal of Applied Physics 113, no. 17 (May 7, 2013): 17A324. http://dx.doi.org/10.1063/1.4795850.

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26

Stojadinović, Miloš, and Jürgen Biela. "Modeling and Design of a Medium-Frequency Transformer for High-Power DC-DC Converters." IEEJ Journal of Industry Applications 8, no. 4 (July 1, 2019): 685–93. http://dx.doi.org/10.1541/ieejjia.8.685.

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27

Wang, Ruitian, Fei Xiao, Zhihua Zhao, Yang Shen, and Guorun Yang. "Effects of Asymmetric Coupling on Winding AC Resistance in Medium-Frequency High-Power Transformer." IEEE Transactions on Magnetics 50, no. 11 (November 2014): 1–4. http://dx.doi.org/10.1109/tmag.2014.2320370.

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28

Lade, Robert K., Joo Hwa Lee, and Dikshitulu K. Kalluri. "Frequency Transformer: Appropriate and Different Models for a Building-up and Collapsing Magnetoplasma Medium." Journal of Infrared, Millimeter, and Terahertz Waves 32, no. 7 (June 28, 2011): 960–72. http://dx.doi.org/10.1007/s10762-011-9804-7.

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29

Ruiz-Robles, Dante, Vicente Venegas-Rebollar, Adolfo Anaya-Ruiz, Edgar Moreno-Goytia, and Juan Rodríguez-Rodríguez. "Design and Prototyping Medium-Frequency Transformers Featuring a Nanocrystalline Core for DC–DC Converters." Energies 11, no. 8 (August 10, 2018): 2081. http://dx.doi.org/10.3390/en11082081.

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Medium frequency transformers (MFTs) are a key component of DC–DC dual active bridge (DAB)-type converters. These technologies are becoming a quintessential part of renewable energy solutions, such as photovoltaic systems and wind energy power plants, as well as in modern power grid interfaces functioning as solid-state transformers in smart-grid environments. The weight and physical dimensions of an MFT are key data for the design of these devices. The size of an MFT is reduced by increasing its operating frequency. This reduction implicates higher power density through the transformer windings, as well as other design requirements distinct to those used for conventional 60/50 Hz transformers; therefore, new MFT design procedures are needed. This paper introduces a novel methodology for designing MFTs, using nanocrystalline cores, and tests it using an MFT–DAB lab prototype. Different to other MFT design procedures, this new design approach uses a modified version of the area-product technique, which consists of smartly modifying the core losses computation, and includes nanocrystalline cores. The core losses computation is supported by a full analysis of the dispersion inductance. For purposes of validation, a model MFT connected to a DAB converter is simulated in Matlab-Simulink (The MathWorks, v2014a, Mexico City, Mexico). In addition, a MFT–DAB lab prototype (1 kVA at 5 kHz) is implemented to experimentally probe further the validity of the methodology just proposed. These results demonstrate that the analytic calculations results match those obtained from simulations and lab experiments. In all cases, the efficiency of the MFT is greater than 99%.

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30

D.Srinivasa Rao & Dr. Anupama A. Deshpande. "DAB Based DC-DC High Frequency Link PET for Interconnecting MVDC-LVDC Grids." International Journal for Modern Trends in Science and Technology 7, no. 05 (May 27, 2021): 165–71. http://dx.doi.org/10.46501/ijmtst0705028.

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This paper proposes dual active bridge (DAB) based high frequency power electronic transformer (PET) for interconnecting medium voltage dc (MVDC) and low voltage dc (LVDC) grids for dc power distribution. The above proposed concept works on dual active phase shift principle and square wave HF modulation technique for bidirectional power transfer. Compared to the traditional dc transformer scheme, The proposed power electronic transformer (PET) can disconnect from LVDC distribution grid effectively as a dc breaker when a short circuit fault occurs in the distribution grid. The isolated DC-DC PET topology with a wide range of voltage conversion ratio is useful for High Voltage DC tapping. The DAB based on switched capacitor is connected to the medium voltage DC side and acts as an inverter. The proposed topology has the ability to transfer higher power, and lower circulating power, lower high frequency link voltage, and RMS current and peak values with the same transmission power in the MVDC side. This paper analyzes the topology, voltage and power characterization, control strategy in detail. Increase in the intermediate AC frequency will reduce the size of the transformer and other passive elements significantly in the circuit. The theoretical analysis is supported by MATLAB simulation.

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31

Espinosa, Eduardo, José Espinoza, Pedro Melín, Jaime Rohten, Carlos Baier, and Marcelo Reyes. "Finite Control Set—Model Predictive Control with Non-Spread Spectrum and Reduced Switching Frequency Applied to Multi-Cell Rectifiers." Energies 14, no. 19 (September 23, 2021): 6045. http://dx.doi.org/10.3390/en14196045.

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Multi-cell converters are widely used in medium-voltage AC drives. This equipment is based on power cells that operate with low-voltage-rating semiconductors and require an input multipulse transformer. This transformer cancels the low-frequency current harmonics generated by the three-phase diode-based rectifier. Unfortunately, this transformer is bulky, heavy, expensive, and does not extend the existing power cell (three-phase rectifier—Direct Current (DC) voltage-link—single-phase inverter) to the transformer. In this study, a harmonic cancelation method based on finite control set-model predictive control (FCS–MPC), extending the power cell’s modularity to the input transformer. On the other hand, it considers treating the two disadvantages of the FCS–MPC: High switching frequency and spread spectrum. The details were developed in theory and practice to obtain satisfactory experimental results.

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32

Kornilov, Gennady Petrovich, Ildar Ravil’evich Abdulveleev, and Timur Rifkatovich Khramshin. "Research of Non-Sinusoidal Voltage in Frequency Converter of Medium Power Operation." Applied Mechanics and Materials 792 (September 2015): 8–14. http://dx.doi.org/10.4028/www.scientific.net/amm.792.8.

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The article presents the comparative analysis of influence frequency regulated electric drive and current electric drive to harmonic structure of voltage of power grid. There was obtained the dependence of total harmonic distortion (THD) of curve on loading power for 2 types of valve converters. The effectiveness is shown in use of filter compensating device, connected at low side of converting transformer. There were defined the ranges of filter adjusting for improving THD of voltage curve. The described solutions are performed by the structural modeling method of Simulink packet in Matlab environment.

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33

Lian, Chengjian, and Daming Zhang. "Electromagnetic Field and Lumped Circuit Analysis of Planar Transformer at Medium Frequency for Converter Application." Advances in Science, Technology and Engineering Systems Journal 2, no. 3 (June 2017): 878–83. http://dx.doi.org/10.25046/aj0203109.

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34

Bahmani, M. Amin, Torbjorn Thiringer, and Mohammad Kharezy. "Design Methodology and Optimization of a Medium-Frequency Transformer for High-Power DC–DC Applications." IEEE Transactions on Industry Applications 52, no. 5 (September 2016): 4225–33. http://dx.doi.org/10.1109/tia.2016.2582825.

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35

Huang, Pei, Chengxiong Mao, Dan Wang, Libing Wang, Yuping Duan, Jun Qiu, Guang Xu, and Huihong Cai. "Optimal Design and Implementation of High-Voltage High-Power Silicon Steel Core Medium-Frequency Transformer." IEEE Transactions on Industrial Electronics 64, no. 6 (June 2017): 4391–401. http://dx.doi.org/10.1109/tie.2017.2674591.

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36

Krishnamoorthy, Harish S., Dibyendu Rana, Pawan Garg, Prasad N. Enjeti, and Ira J. Pitel. "Wind Turbine Generator–Battery Energy Storage Utility Interface Converter Topology With Medium-Frequency Transformer Link." IEEE Transactions on Power Electronics 29, no. 8 (August 2014): 4146–55. http://dx.doi.org/10.1109/tpel.2013.2295419.

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37

Soltau, Nils, Daniel Eggers, Kay Hameyer, and Rik W. De Doncker. "Iron Losses in a Medium-Frequency Transformer Operated in a High-Power DC–DC Converter." IEEE Transactions on Magnetics 50, no. 2 (February 2014): 953–56. http://dx.doi.org/10.1109/tmag.2013.2283733.

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38

Zhao, Shishuo, Qiang Li, Fred C. Lee, and Bin Li. "High-Frequency Transformer Design for Modular Power Conversion From Medium-Voltage AC to 400 VDC." IEEE Transactions on Power Electronics 33, no. 9 (September 2018): 7545–57. http://dx.doi.org/10.1109/tpel.2017.2774440.

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39

Barrios, Manuel A., Víctor Cárdenas, Jose M. Sandoval, Josep M. Guerrero, and Juan C. Vasquez. "A Cascaded DC-AC-AC Grid-Tied Converter for PV Plants with AC-Link." Electronics 10, no. 4 (February 8, 2021): 409. http://dx.doi.org/10.3390/electronics10040409.

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Cascaded multilevel converters based on medium-frequency (MF) AC-links have been proposed as alternatives to the traditional low-voltage inverter, which uses a bulky low-frequency transformer step-up voltage to medium voltage (MV) levels. In this paper, a three-phase cascaded DC-AC-AC converter with AC-link for medium-voltage applications is proposed. Three stages integrate each DC-AC-AC converter (cell): a MF square voltage generator; a MF transformer with four windings; and an AC-AC converter. Then, k DC-AC-AC converters are cascaded to generate the multilevel topology. This converter’s topological structure avoids the per-phase imbalance; this simplifies the control and reduces the problem only to solve the per-cell unbalance. Two sets of simulations were performed to verify the converter’s operation (off-grid and grid-connected modes). Finally, the papers present two reduced preliminary laboratory prototypes, one validating the cascaded configuration and the other validating the three-phase configuration.

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Florkowski, Marek, Jakub Furgał, Maciej Kuniewski, and Piotr Pająk. "Overvoltage Impact on Internal Insulation Systems of Transformers in Electrical Networks with Vacuum Circuit Breakers." Energies 13, no. 23 (December 2, 2020): 6380. http://dx.doi.org/10.3390/en13236380.

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Vacuum circuit breakers are increasingly used as switching apparatus in electric power systems. The vacuum circuit breakers (VCBs) have very good operating properties. VCBs are characterized by specific physical phenomena that affect overvoltage exposure of the insulation systems of other devices. The most important phenomena are the ability to chop the current before the natural zero crossing, the ability to switch off high-frequency currents, and the rapid increase in dielectric strength recovery. One of the devices connected directly to vacuum circuit breakers is the distribution transformer. Overvoltages generated in electrical systems during switching off the transformers are a source of internal overvoltages in the windings. The analysis of the exposure of transformers operating in electrical networks equipped with vacuum circuit breakers is of great importance because of the impact on the insulation systems of switching overvoltages (SO). These types of overvoltages can be characterized by high maximum values and atypical waveforms, depending on the phenomena in the circuit breaker chambers, system configuration, parameters of electrical devices, and overvoltage protection. Overvoltages that stress the internal insulation systems are the result of the windings response to overvoltages at transformer terminals. This article presents an analysis of overvoltages that stress the transformer insulation systems, which occur while switching off transformers in systems with vacuum circuit breakers. The analysis was based on the results of laboratory measurements of switching overvoltages at transformer terminals and inside the winding, in a model medium-voltage electrical network with a vacuum circuit breaker.

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Guo, Yunxiang, Cheng Lu, Liang Hua, and Xinsong Zhang. "Optimal Design of High-Power Medium-Frequency Transformer Using Hollow Conductors with Consideration of Multi-Objective Parameters." Energies 13, no. 14 (July 15, 2020): 3654. http://dx.doi.org/10.3390/en13143654.

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A power electronic transformer (PET) is applied to the high-speed train for lightweight demand. A 300 kW/5 kHz high-power medium-frequency transformer (HPMFT) using hollow conductors in a power unit of the PET is optimally designed in this paper. The target of the design is to balance the loss, leakage inductance, and weight of the HPMFT. For this purpose, the design parameters of the HPMFT are firstly confirmed according to the system structure and parameters of the PET. Secondly, the design process of HPMFT is developed. Finally, the results of 48 design schemes of core-type and shell-type structures are compared by the comprehensive evaluation standard, which equilibrates the three above objective parameters of the HPMFT. According to the optimal scheme, a prototype is manufactured, whose test results verify the correctness of the optimal design method.

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Liu, Chen Yao, Kuo Bin Liu, and Din Goa Huang. "Design of a Power Transformer for a LLC Resonant Power Converter." Advanced Materials Research 740 (August 2013): 823–29. http://dx.doi.org/10.4028/www.scientific.net/amr.740.823.

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We designed and implemented a power converter to provide a dc power bus for the MCOR 12 correction supply. The characteristics of the dc power bus are variable frequency at both heavy and medium or light loads. These characteristics match the working requirement of the correction supply. The dc power bus has a relaxation oscillator that generates a symmetric triangular waveform, to which MOSFET switching is locked. The frequency of this waveform is related to a voltage to be modulated with feedback circuitry. As a result, the circuit and complex transformer are driven with a half-bridge. We designed the complex resonant transformer and describe in this paper a simulation model that is highly important, thus to exploit its frequency-dependent transfer characteristics. We obtained a power bus with small ripple to provide the correction power. The high-performance characteristics of the resonant dc power bus are illustrated in this paper.

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Dworakowski, Piotr, Andrzej Wilk, Michal Michna, Bruno Lefebvre, Fabien Sixdenier, and Michel Mermet-Guyennet. "Effective Permeability of Multi Air Gap Ferrite Core 3-Phase Medium Frequency Transformer in Isolated DC-DC Converters." Energies 13, no. 6 (March 14, 2020): 1352. http://dx.doi.org/10.3390/en13061352.

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The magnetizing inductance of the medium frequency transformer (MFT) impacts the performance of the isolated dc-dc power converters. The ferrite material is considered for high power transformers but it requires an assembly of type “I” cores resulting in a multi air gap structure of the magnetic core. The authors claim that the multiple air gaps are randomly distributed and that the average air gap length is unpredictable at the industrial design stage. As a consequence, the required effective magnetic permeability and the magnetizing inductance are difficult to achieve within reasonable error margins. This article presents the measurements of the equivalent B(H) and the equivalent magnetic permeability of two three-phase MFT prototypes. The measured equivalent B(H) is used in an FEM simulation and compared against a no load test of a 100 kW isolated dc-dc converter showing a good fit within a 10% error. Further analysis leads to the demonstration that the equivalent magnetic permeability and the average air gap length are nonlinear functions of the number of air gaps. The proposed exponential scaling function enables rapid estimation of the magnetizing inductance based on the ferrite material datasheet only.

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Mingotti, Alessandro, Federica Costa, Gaetano Pasini, Lorenzo Peretto, and Roberto Tinarelli. "Modeling Capacitive Low-Power Voltage Transformer Behavior over Temperature and Frequency." Sensors 21, no. 5 (March 2, 2021): 1719. http://dx.doi.org/10.3390/s21051719.

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The use of capacitive dividers (CDs) in medium-voltage (MV) networks started as simple voltage detectors and as rough voltage measurement instruments for protective purposes. Now, with the spread of intelligent electronic devices and renewable energy sources at the distribution level, capacitive dividers are designed and installed to perform accurate voltage measurements. Such a requirement is mandatory when the power quality has to be assessed. Therefore, CDs are currently being used either for power frequency or for high-frequency (supraharmonic- or partial-discharge-level) measurements. In this paper, typical off-the-shelf CDs are studied and modeled to understand how they behave in a wide range of frequencies and when the temperature varies. To this purpose, specific setups and tests have been developed and performed. From the results, it is clear that with proper modeling of CDs, it is possible to exploit them for measuring phenomena in a wide range of frequencies, including the effects due to temperature variations and self-resonances.

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Agarwal, Rachit, Sandro Martin, and Hui Li. "Influence of Phase-Shifted Square Wave Modulation on Medium Frequency Transformer in a MMC Based SST." IEEE Access 8 (2020): 221093–102. http://dx.doi.org/10.1109/access.2020.3042935.

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Krishnamoorthy, Harish, Michael Daniel, Jorge Ramos-Ruiz, Prasad Enjeti, Liming Liu, and Eddy Aeloiza. "Isolated AC–DC Converter Using Medium Frequency Transformer for Off-Shore Wind Turbine DC Collection Grid." IEEE Transactions on Industrial Electronics 64, no. 11 (November 2017): 8939–47. http://dx.doi.org/10.1109/tie.2017.2652405.

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47

Dong, Dong, Mohammed Agamy, Jovan Z. Bebic, Qin Chen, and Gary Mandrusiak. "A Modular SiC High-Frequency Solid-State Transformer for Medium-Voltage Applications: Design, Implementation, and Testing." IEEE Journal of Emerging and Selected Topics in Power Electronics 7, no. 2 (June 2019): 768–78. http://dx.doi.org/10.1109/jestpe.2019.2896046.

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48

Balci, Selami, Ibrahim Sefa, and Necmi Altin. "Design and analysis of a 35 kVA medium frequency power transformer with the nanocrystalline core material." International Journal of Hydrogen Energy 42, no. 28 (July 2017): 17895–909. http://dx.doi.org/10.1016/j.ijhydene.2017.03.158.

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Adamowicz, Marek, Zbigniew Krzemiński, and Paweł Stec. "Dual Active Bridge (DAB) DC-DC converter for multilevel propulsion converters for electrical multiple units (EMU)." MATEC Web of Conferences 180 (2018): 04002. http://dx.doi.org/10.1051/matecconf/201818004002.

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Semiconductor power devices made from silicon carbide (SiC) reached a level of technology enabling their widespread use in power converters. Two different approaches to implementation of modern traction converters in electric multiple units (EMU) have been presented in recent years: (i) 3.3-kV SiC MOSFET-based three-level PWM inverter with regenerative braking and (ii) 6.5-kV IGBT-based fourquadrant power electronic traction transformer (PETT). The former has successfully reached optimized dimensions and efficiency but still requires a bulky line frequency transformer for multisystem applications. The latter characterizes inherent galvanic isolation from AC traction, which is realized by cascaded system of power electronic cells containing medium frequency transformers (MFT). The downsizing of the 6.5-kV IGBT-based cells is, however, problematic. The present paper proposes a different approach, that involves the use of a fast switching 1.2-kV SiC MOSFETS. The SiC-based PETT proposed in the paper is dedicated first for the DC traction. For multi-system application the input voltage of the proposed PETT can be adjusted using weight-optimized adjusting autotransformer. Thanks to utilization of fast-switching SiCbased power modules the weight and size of the power electronic cells can be optimized in a convenient way.

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50

Si, Wenrong, Weiqiang Yao, Hong Guan, Chenzhao Fu, Yiting Yu, Shiwei Su, and Jian Yang. "Numerical Study of Vibration Characteristics for Sensor Membrane in Transformer Oil." Energies 14, no. 6 (March 17, 2021): 1662. http://dx.doi.org/10.3390/en14061662.

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Membrane is the most important element of extrinsic Fabry-Perot interferometer sensors. Studying the relationship between working medium viscosity and membrane vibration characteristics are critical to the sensor design because the transformer oil viscosity will cause viscous loss during membrane vibration. The numerical investigation of membrane vibration characteristics in transformer oil is performed based on the finite element method. Besides, the effect of energy loss caused by viscosity is examined. It is firstly showed that the membrane has the highest sensitivity for the first-order vibration mode, and the transformer oil reduces the fundamental frequency by 60%. Subsequently, when viscosity and heat loss are considered, the amplitude is less than one-fifth of that without energy loss. The viscosity has a more significant effect on the velocity and temperature fields when the vibration frequency is close to the natural frequency. Finally, viscosity has a remarkable impact on the time domain response. Mechanical energy is converted into thermal energy during the vibration and the amplitude will gradually decrease with time. The effect of energy loss caused by viscosity on the membrane vibration characteristics is revealed, which would be important for an oil-immersed membrane design.

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