Stability problems of PV inverter in weak grid: a review-Qianjin Zhang, Mingxuan Mao, Guo Ke, Lin Zhou, Bao Xie-State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044,People's Republic of China-IET POWER ELECTRONICS

 

Stability problems of PV inverter in weak grid:a review Qianjin Zhang1, Mingxuan Mao1,2, Guo Ke1, Lin Zhou1, Bao Xie11State Key 

Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044,People's Republic of China

2Postdoctoral Station of Electrical Engineering, Chongqing University, Chongqing 400044, People's Republic of China E-mail: mingxuan_mao@cqu.edu.cn

Abstract:

 Photovoltaic (PV) power generation, as one important part of renewable energy, has been greatly developed in recentyears. The stability of PV inverters is very important for the normal operation of PV systems. However, most PV systems,especially the large PV plants, locate in rural areas. The corresponding equivalent grid impedance is rather large and easy tolead to stability problems of grid-connected inverters and many researches have been done focusing on the stability problems.In this study, a survey of stability problems of PV inverters on weak grid condition is given. The stability problems are mainlydivided into two parts, i.e. the control loops instability and inverter output voltage instability. The control loops cover the currentloop and dc voltage loop. The output voltage instability refers to the voltage phasors relationship and the application of reactivepower compensation. The non-linear parts of inverter dead-time, digital control delay, and phase-locked loop are explored.Future trends and challenges are given

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Modelling and analysis of medium frequency transformers for power converters -Piotr Dworakowski-DOCTORAL DISSERTATION-Electric power.Gdansk University of Technology,2020.

 

Modelling and analysis of medium frequency transformers for power converters -Piotr Dworakowski-DOCTORAL DISSERTATION-Electric power.Gdansk University of Technology,2020. 

 ABSTRACT 

The evolutions in power systems and electric vehicles, related to the economic opportunities and the environmental issues, bring the need for high power galvanically isolated DC-DC converter. The medium frequency transformer (MFT) is one of its key components, enabled by the increasing switching frequency of modern power semiconductors like silicon carbide transistors or diodes. The increased operating frequency offers small converter size, leading to the decrease in raw material usage. Most likely this will result in the converter cost reduction which will further increase the demand for solid state transformer solutions. The modeling and analysis are essential in the development of the MFT technology which is attracting lots of research and industrial interest. In this dissertation the isolated DC-DC converter topologies are introduced with the particular focus on the dual active bridge (DAB). The key components of the isolated DC-DC converters, power semiconductors and medium frequency transformer are reviewed. A mathematical model of a 3-phase MFT in the isolated DC-DC power converter, suitable in electromagnetic transient and steady state simulation is developed. The transformer modeling methods are reviewed and the Lagrange energy method is used to derive a physically motivated model for circuit analysis. The model involves a matrix of nonlinear magnetizing inductances and a matrix of linear leakage inductances, both including self and mutual values. The macroscopic models of magnetic hysteresis are reviewed and the feedback Preisach model is developed. The design of a 3-phase 20 kHz transformer for a 100 kW 1.2 kV isolated DC-DC power converter is presented. The particular focus is put on the winding and core design, and power loss and thermal calculations which are the most critical aspects of the high-power density transformer. The design results in two 3-phase MFT prototypes, first of its kind worldwide. A finite element model of the transformer is developed allowing to determine the magnetic flux characteristic Φ(Θ) and the related inductances required in the circuit model. The finite element model is based on the measured equivalent B(H) and homogenized material properties. Other model parameters are calculated analytically and compared against the measurement on the prototype MFT. The dissertation is concluded showing the technical feasibility and benefits of the 3-phase MFT. The developed MFT prototype operating at 20 kHz is more than 10 times lighter than the equivalent 50 Hz transformer. The 3-phase 100 kW DC-DC converter efficiency is measured 99.2% which is an impressive result. The efficiency of the 3-phase DC-DC is higher than its equivalent single-phase variant. A challenge of high power MFT design related to the parasitic air gaps in the core is highlighted. The influence of the air gaps on core power loss is confirmed showing that the increase in the air gap size in a certain range causes a decrease in the core power loss. In the 3-phase MFT prototype the parasitic air gaps do not cause any measurable effect on winding power loss and temperature. It is shown that the relative magnetic permeability is nonlinearly decreasing with the increase of the number of parasitic air gaps. An exponential interpolation function is proposed allowing to estimate the equivalent magnetic permeability, average air gap length and magnetizing inductance for any high-power ferrite core MFT with a similar core assembly. The proposed MFT equivalent circuit model is proven accurate in steady state and transient analyses. The no-load inrush test confirms the importance of the magnetic cross saturation involved in the magnetizing inductance model. The influence of the mutual leakage inductance on the operation of the DAB converter is shown. The feedback Preisach model of hysteresis is proven accurate in the modeling of hysteresis loops in the multi air gap ferrite core MFT.

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Active Gate Drivers for High-Frequency Application of SiC MOSFETs-BY Alejandro Paredes Camacho-Thesis submitted in partial fulfilment of the requirement for the PhD degree issued by the Universitat Politècnica de Catalunya, in its Electronic Engineering Program.

Active Gate Drivers for High-Frequency Application of SiC MOSFETs-BY Alejandro Paredes Camacho-Thesis submitted in partial fulfilment of the requirement for the PhD degree issued by the Universitat Politècnica de Catalunya, in its Electronic Engineering Program. 

 Abstract 

The trend in the development of power converters is focused on efficient systems with high power density, reliability and low cost. The challenges to cover the new power converters requirements are mainly concentered on the use of new switching-device technologies such as silicon carbide MOSFETs (SiC). SiC MOSFETs have better characteristics than their silicon counterparts; they have low conduction resistance, can work at higher switching speeds and can operate at higher temperature and voltage levels. Despite the advantages of SiC transistors, operating at high switching frequencies, with these devices, reveal new challenges. The fast switching speeds of SiC MOSFETs can cause over-voltages and over-currents that lead to electromagnetic interference (EMI) problems. For this reason, gate drivers (GD) development is a fundamental stage in SiC MOSFETs circuitry design. The reduction of the problems at high switching frequencies, thus increasing their performance, will allow to take advantage of these devices and achieve more efficient and high power density systems. This Thesis consists of a study, design and development of active gate drivers (AGDs) aimed to improve the switching performance of SiC MOSFETs applied to high-frequency power converters. Every developed stage regarding the GDs is validated through tests and experimental studies. In addition, the developed GDs are applied to converters for wireless charging systems of electric vehicle batteries. The results show the effectiveness of the proposed GDs and their viability in power converters based on SiC MOSFET devices.

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13.56 MHz high power and high efficiency inverter for dynamic EV charging systems A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL OF ENGINEERING AND SCIENCE OF SHIBAURA INSTITUTE OF TECHNOLOGY by NGUYEN KIEN TRUNG IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY SEPTEMBER 2016

 

13.56 MHz high power and high efficiency inverter for dynamic EV charging systems

A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL OF ENGINEERING AND SCIENCE OF SHIBAURA INSTITUTE OF TECHNOLOGY by NGUYEN KIEN TRUNG IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY SEPTEMBER 2016

 Abstract 

Recently, Electric Vehicles (EVs) are a promising solution for reduc- ing CO2 emission and air pollution in the big cities. However, until now, the EVs have been not so attractive to consumers due to the short running distance, long charging time and high battery cost. The dynamic charging solution has been proposed to reduce the energy de- pendence and battery cost of EVs. As the demand of that systems, a 13.56 MHz high power inverter with the eciency of over 95% is re- quired. With the previous researches, there are three major research challenges have been recorded. At very high switching frequency such as 13.56 MHz, the in uence of the parasitic elements in the circuit is the rst challenge because it strongly aect both of power and drive circuit of the inverter. Consequently, the inverter may be damaged or unstable. Secondly, the switching and gate drive power loss in the inverter are also the challenge when it proportionally increase with the switching frequency. At 13.56 MHz, it is dicult to obtain the extremely high eciency such as 95%. Finally, the high output power required is another challenge due to the low rate-parameters and the challenges in the parallel connecting of the high speed switching de- vices. To overcome these challenges, a number of the analyses and proposed design are presented in this dissertation. Firstly, the eect of the parasitic elements in the high switch- ing frequency half-bridge inverter is analyzed and evaluated in detail based on the perspective of the ringing loop in the circuit. Based on these, an optimized PCB design is proposed to minimize the parasitic inductance in the ringing loop of the inverter. With the improved PCB, the experiment results show that, the peak voltage and the am- plitude of the ringing current in the circuit is reduced. However, the ZVS condition and the stability of the inverter at high input voltage condition are not achieved due to the high frequency ringing in the circuit. Therefore, a ringing damping circuit is proposed. The high stability and the low power loss on the proposed damping circuit is the advantage to obtain high eciency of the inverter. In the ex- periment results, the ringing current in the circuit is damped. A 1.2 kW output power is obtained with the eciency of 93.1%. This is an improvement in the 13.56 MHz inverter. However, it does not meet the required eciency of the inverter for the dynamic EV charging systems due to limited switching speed of the silicon-MOSFET. Secondly, to improve the eciency of the inverter, the GaN HEMT device is used. In an experiment, the inverter using GaN HEMT obtains the eciency of 97.5% which shows the potential to meet the required eciency of the inverter for the dynamic EV charging systems. However, the output power of the inverter is limited due to the low rate current of the GaN HEMT. And the parallel connection of GaN HEMT devices at 13.56 MHz is very dicult because of the strong unbalance dynamic current distribution. Therefore, a design using multiphase resonant inverter is proposed. The proposed module design, the proposed power loss analysis method to obtain highest eciency and the proposed drive circuit design have been addressed in detail. In experiment, a 3 kW inverter with the eciency of 96.1% is achieved that signicantly improves the eciency of 13.56 MHz inverter. A 10 kW inverter with the eciency of over 95% will be developed by following this proposed design in near future. Finally, the 13.56 MHz high power inverter with the eciency of over 95% can be realizable. However, the Class DE operation mode which is used in multiphase resonant inverter requires exact parameter of load, resonant circuit and several turning in the experiment process. Therefore, it is still dicult to apply in the dynamic charging systems where the parameters of the coupling system will always change in the operation. The inverter behavior analysis and the further researches to keep the soft switching condition in the operation with the dynamic coupling system are necessary in the future work.

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ISLANDING DETECTION AND POWER QUALITY ANALYSIS IN MICROGRID a Dissertation Submitted to the GRADUATE SCHOOL OF ENGINEERING AND SCIENCE OF SHIBAURA INSTITUTE OF TECHNOLOGY by TRAN THANH SON

 ISLANDING DETECTION AND POWER QUALITY ANALYSIS IN MICROGRID 

a Dissertation Submitted to the GRADUATE SCHOOL OF ENGINEERING AND SCIENCE OF SHIBAURA INSTITUTE OF TECHNOLOGY 

by TRAN THANH SON 

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY SEPTEMBER 2019

Abstract

The microgrid (MG) has been developed based on the important con- cept of distributed generation (DG) with high penetration of renew- able energy integrated with energy storage systems (ESSs). MGs can operate in both grid-connected and islanding mode. Therefore, this thesis focuses on autonomous multi-islanded entities and the seamless reconnection to the main grid as the self-healing ability of the fu- ture power system. The minimization of power quality issues (mainly that of voltage, frequency, and harmonics) in such entities based on controllers, with or without intercommunication, is also an important part of this thesis. The future power system, with the signicant pen- etration of distributed generations (DGs), can rapidly respond to any problem occurring within it by separating into autonomous islanded entities to prevent the disconnection of DGs. As a result, high-quality and continuous power is supplied to consumers. The future research that is necessary for the realization of the future power system is discussed.

Besides, the emergence of Distributed Generation (DG) in the elec- tric system has brought about the appearance of the islanding phe- nomenon. In AC networks, there are a lot of Islanding Detection Methods (IDMs) have been studied. However, not too much IDMs in DC networks have been published because of the absence of frequency and reactive power. The active IDM based on injected perturbation signal and rate of change of power output is proposed. This IDM can detect islanding condition not only in the worst case (the power of the load and PV are equal) but also in another case (the power of load is greater than the power of PV). It can be applied to both single

and multi-PV operation scenarios. Also, the cancellation problem is analyzed and the solution is proposed to solve this problem. Besides, the eectiveness of the proposed method, the cancellation problem, and the solution are verified by simulation in Matlab/Simulink.

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Development of High-Step-Up IsolatedDCDC Converter based on Super-High Frequency Switching to Physical Limit in Circuit Devices-Department of Electrical Engineering, Kobe City College of Technology Masataka Minami

Development of High-Step-Up IsolatedDCDC Converter based on Super-High Frequency Switching to Physical Limit in Circuit Devices-Department of Electrical Engineering, Kobe City College of Technology Masataka Minami

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Shibaura Institute of Technology doctoral degree thesis High frequency inverter for plasma generation equipment, and research on high frequency matching devices.-芝 浦 工 業 大 学 博 士 学 位 論 文 プラズマ生成装置の高周波インバータ、 および高周波整合器に関する研究 平成 29 年3 月

 

Shibaura Institute of Technology doctoral degree thesis High frequency inverter for plasma generation equipment, and research on high frequency matching devices. March 2017 

 芝 浦 工 業 大 学 博 士 学 位 論 文 プラズマ生成装置の高周波インバータ、 および高周波整合器に関する研究 平成 29 年3 月

Overview 

This paper is concerned with high-frequency plasma generation equipment for functional devices, semiconductor and liquid crystal manufacturing equipment, and aims to reduce power loss in high-frequency inverters, improve power conversion efficiency, and wide-range impedance matching of high-frequency matching boxes using high-frequency transformers. This is a summary of research results regarding. Thin film formation using high-frequency plasma, such as plasma chemical vapor deposition (Plasma CVD), is widely used in the production of semiconductors, liquid crystals, and solar cells. In recent years, the range of applications has expanded to include thin film coatings for industrial purposes. Furthermore, as a pretreatment for a physical vapor deposition (PVD) process, high-frequency plasma treatment using high-frequency waves is widely used to remove a natural oxide film (pre-clean). Conventionally, the mainstream of photoresist stripping treatments has been treatments that do not involve physical reactions, such as liquid etching treatment (wet etching) using acidic or alkaline solutions. In recent years, dry etching, which uses high-frequency plasma to etch materials with reactive gases, etching gases, ions, and radicals, has become mainstream in semiconductors, liquid crystals, and manufacturing equipment. High-frequency plasma technology is becoming increasingly important in the research and development of functional devices. Conventionally, high-frequency inverters with a frequency of 13.56 MHz and a high-frequency output of 1 kW, which are often used in semiconductor manufacturing equipment, have a low high-frequency power conversion efficiency of about 50%, and about 1 kW of power loss is converted into heat. To dissipate 1 kW of heat, a water-cooled heat exchanger and auxiliary equipment were required, which required 200 liters of cooling water per hour. There were also problems from the environmental standpoint of cooling water and ancillary equipment, energy consumption, and economics. In this study, we focused on high-frequency output transformers with the aim of reducing high-frequency power loss and improving power conversion efficiency. Conventionally, a high-frequency output of 1 kW was obtained using four output transformers, but in this research, we investigated a high-efficiency, high-frequency output transformer, and a circuit configuration that achieves a high-frequency output of 1 kW. By using a single high-frequency inverter with a high-frequency output of 1 kW, it is possible to The high frequency output synthesizer used in the frequency inverter is no longer required. Therefore, we investigated ways to reduce power loss in high-frequency output combiners. To create a single high-frequency output transformer, four MOS-FETs must be connected in parallel. We investigated a push-pull type high-frequency inverter with four MOS-FETs connected in parallel using an axial printed circuit board (PCB). We also investigated power loss and temperature at high frequencies in high-frequency output transformers and high-frequency output combiners, which are important in realizing high-efficiency, high-frequency inverters. Furthermore, we evaluated and investigated the power loss and temperature at high frequencies of the high frequency ferrite core that constitutes the high frequency output transformer. Conventionally, in an ICP dry etching system using an L-type high-frequency matching box used in inductively coupled plasma (ICP), the chamber pressure used for high-frequency plasma generation is a low pressure of about 0.1 to 13 Pa, and a pressure of 1011 cm-3 or more is used for generating high-frequency plasma. High density plasma can be obtained. ICP high-frequency plasma is currently the mainstream etching method in semiconductor etching processes because high-density plasma can be obtained without using an electromagnetic coil. In the production of functional devices, photocurable resin (photoresist) is used.

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磁気結合インダクタを応用した 高電力密度コンバータの実現へ向けた研究 A Study on Realization of High Power Density Converters using Coupled Inductors-Shimane University Graduate School Graduate School of Integrated Science and Engineering Interdisciplinary Graduate School of Science and Engineering, Shimane University

 磁気結合インダクタを応用した 高電力密度コンバータの実現へ向けた研究 A Study on Realization of High Power Density Converters using Coupled Inductors 木村 翔太 島根大学大学院 総合理工学研究科 

Interdisciplinary Graduate School of Science and Engineering, Shimane University 2018年 3月

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Design method of current resonant converter October 31, 2014 Sanken Electric Co., Ltd. Technical Headquarters Chief Engineer Masashi Ochiai-電流共振形コンバータの設計法 2014年10月31日 サンケン電気(株) 技術本部 技師長 落合政司

 

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Research on performance improvement and industrial application of static electromagnetic equipment using iron-based amorphous alloys-Doctoral Dissertation (Thesis(doctor)----Tohoku University-2019-JAPAN

 

Research on performance improvement and industrial application of static electromagnetic equipment using iron-based amorphous alloys-Doctoral Dissertation (Thesis(doctor)----Tohoku University-2019-JAPAN

ABSTRACT：Iron-based amorphous alloy has the advantages of lower iron loss and higher permeability compared with conventional grain-oriented silicon steel due to disappearance of magnetocrystalline anisotropy derived from randomly aligned magnetic atoms. One can expect for considerable improvementinpower efficiency of presently commercialized staticelectromagnetic machinessuch as distribution transformer and filtering reactor for inverter system by replacing the core material from silicon steel to iron-based amorphous alloy. Moreover, the material’s satisfactory performance at higher frequency enables application to the fieldof next generationin power distribution system. However, the commercially available iron-based amorphous alloy produced with meltquenching method has a shape of 20 to 30 m-thick thin foil; the coremade from the stacked and wound several hundred to thousand foils isfragile. This form of amorphous core causes difficulty in mass-production of the low cost and larger power capacity electromagnetic machines. Consequently, the range of industryapplication of amorphous alloy has been limited at present. Hence, this study aims at contribution to the savings of energy and CO2emission by theproposalsof low cost structures and design methodologies of three typesof amorphous electromagnetic machinethoseenable extensions of power capacity and excitation frequency. Additionally,the effect of improvement inpower efficiencies of them isdemonstrated by way of prototype tests. This thesis consists of six chapters;the research results are shown in accordance with the following organization. The chapter 1 describes the background and the objective of this study. The chapter 2 describes conventional technology and problems of amorphous electromagnetic machines. First, the advantages and disadvantages of presently mass-produced iron-based amorphous alloy were organizedcomparing the magnetic and physical properties of it with those of conventional grain-oriented silicon steel. Then, this chapter reviewed production methods of presently commercialized amorphous electromagnetic machinesandclarified the problems to be solved for extension of range of industryapplication. The chapter 3 describes the development of larger capacity distribution transformer with amorphous wound cores as the first case. This study considered a 30 MVA classed three phase amorphous core transformer that was not implementedup to nowbecause of structural problems, and proposed a structure that supports the fragile core while suppressing increase of iron loss. In advance of design, an estimation method of iron loss taking thecompressive stressin the core into account was established, which enabled the quantification of relationship between support method of larger wound core and its iron loss. The cores were divided into inner and outer components suspended independently; thedesign buffered the compressive stress affected in the cores and reduced the iron loss by 32% compared with that with a conventional support structure. In addition, providing the shielding components where the leakage field is concentrated resulted in 66% decrease in strayloss by utilizing the electromagnetic analysis. Then, a proposed support structure including 10 MVA single phase three legs amorphous core and windings were manufactured separately, and loss performancesof them were evaluated. This study determined totalloss at a load factor of 50% using measured values of iron loss and copper loss and analytical values of stray loss assuming an averaged load operating condition of transformer; as a result, the totalloss in a 30 MVA three phase amorphous core transformer could be reduced by 35% against a conventional silicon steel core transformer of same power capacity. The chapter 4 describes the development of amorphous core reactor for filtering component in uninterruptible power system (UPS) as the second case. This study invented two types of core structure for low cost and larger capacity three phase AC reactors formed from the toroidally wound amorphous yoke cores and the magnetic leg cores cut from solidified toroidal amorphous cores. Calculation models of iron loss in the cores and gap loss induced from the fringing flux between core components were established on the basis of a technique for extracting the coordinate components of the magnetic flux density in accordance with the anisotropic magnetization curvesin plane and laminated directionsof the amorphous foils. It was confirmed that the calculated iron losses at utility and carrier frequencies agree with measured losses within a 10% error. The prototyped amorphous reactors had approximately half the total losses of that of a conventional silicon steel core reactor and increased the power efficiency of the 400 kVA UPS by up to 0.55%. Furthermore, this study demonstrated the practicalityof aminiaturized amorphous reactor designed with a magnetic flux density of 1.2 T increased from standard oneof 0.8 T. It was verified that total loss and unit volume of the prototyped miniaturized reactor could be reduced by 35% and 43% respectivelycompared with those of a silicon steel core reactor. The chapter 5 describes the development of high frequency amorphous transformer for isolated DC-DC converter in DC-interconnected offshore wind farm system as the third case. This study designed and prototyped a core-type 3 kHz-excited 500 kVA transformer consisting of a single phase lap-joint amorphous wound core and windings with primary and secondary copper (Cu)sheets wound alternately in turns. The alternately wound winding structure suppressed the proximity effect between Cu sheets and the in-plane eddy current due to the fringing flux crossing the edge of sheets and fixtures, and the copper loss at 3 kHz was 61% lower than that of conventionally designed winding with primary and secondary sheets wound continuously. The rated total loss of the transformer with alternately wound windings was 21% lower than that of a conventional one. Furthermore, this study proposed a guideline for iron loss-reducing design of the lap-joint part in the amorphous core based onthe measured iron loss at high frequencies and the results of electromagnetic analysis. The chapter 6 concludes the loss reduction effect of three types of amorphous electromagnetic machinedeveloped in this study and describes the remaining issues.

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博士論文 Doctoral Dissertation 電気自動車の走行中ワイヤレス給電における 制御設計とシステム構築に関する研究 Study on Control Design and System Implementation for In-motion Wireless Charging of Electric Vehicles-------東京大学大学院 工学系研究科 電気系工学専攻 Department of Electrical Engineering, Graduate School of Engineering, The University of Tokyo

 

OVERVIEW

This paper is about wireless power transfer technology that charges electric vehicles while they are running. The system is now stuck with the stationary wireless power supply system, which previously stopped and slowly charged the vehicle. Concerning control design and system construction based on a new perspective that focuses on very different dynamic characteristics. The aim is to establish technology that will The practical application of wireless power transfer technology while driving will accelerate the spread of electric vehicles. It could become a ground-breaking technology that will give a strong boost and bring about a paradigm shift in the current automobile society. This paper In this section, we will discuss the issues required for wireless power transfer technology while driving, and provide clear solutions for these issues. We will present our approach and clarify the effectiveness of these approaches through demonstration experiments. In addition, control design By presenting the knowledge obtained in the form of system construction, we cover a wide range of topics from theory to application. We hope that this paper will make a major contribution to society or be a step toward popularization. The content and structure of this paper are shown below. Chapter 1 deals with the electrification of cars towards a decarbonized society, and discusses current high-performance batteries and Rather than research and development with fast charging as the key technology, we are developing a new vehicle based on motors, capacitors, and wireless technology. Show about Ma society. Here, cars of the future will be powered by highly responsive electric motors rather than engines. Fast charging, using long-life, high-power capacitors instead of lithium-ion batteries. Instead, wireless power supply, which charges slowly while running, plays a major role. wireless power transfer If infrastructure and cars are connected by technology, the cruising range on a single charge, which is tied to battery performance, will lose meaning. The convenience of electric cars will improve dramatically. On the other hand, energy storage devices that require frequent charging and discharging The chair has the advantage of using physical battery capacitors rather than chemical batteries, which have a short lifespan. However, all Since it is difficult to electrify roads, it is not possible to save enough energy to get from the main road to your home. Large capacity capacitors such as electric double layer capacitors are suitable. Finally, the electric motor Advanced motion control realizes safe and eco-friendly driving, and this technology has produced many results in our laboratory. It is proven. Therefore, in order to create this new car society, wireless power transfer technology is essential. It is essential to establish wireless charging while stationary, and what is particularly important here is wireless charging while stationary, which replaces quick charging. This technology is not a wireless power transfer technology that connects a moving vehicle to infrastructure. Na Oh, you can only receive power from one power transmitter for a few seconds to a few tens of seconds at most while driving on a highway. When driving at high speeds, power cannot be received for even a few seconds, so control on the order of milliseconds must be achieved. stomach. The essence of the technology for wireless power transfer while driving is to realize this instantaneous power transfer. It also makes clear that there are many issues that need to be resolved. In this paper, we will address the issues presented in Chapter 1. Each chapter presents a clear approach. ​

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Mémoire de Master en Electrotechnique Présenté par : TOUHAMI Sarah Asma Intitulé Modélisation des transformateurs : Etude de l’hystérésis et de la saturation magnétique

 

Mémoire de Master en Electrotechnique Présenté par : TOUHAMI Sarah Asma 

Intitulé Modélisation des transformateurs : Etude de l’hystérésis et de la saturation magnétique Président du jury : S. MEKHTOUB Professeur Ecole Nationale Polytechnique

 Examinateurs : A.BOUBAKEUR Professeur Ecole Nationale Polytechnique

 H.SAHRAOUI Maitre de conférences Ecole Nationale Polytechnique 

 Abstract— The objectif of this work is the modeling and analysis of transformers. In this study the hysteresis, the saturation and the modeling have been widely discussed. Experimental tests and numerical simulations on models adjusted Software EMTP (Electromagnetic Transients Program) were conducted and the comparison of obtained results confirmed the validity of what we have made as a correction of this software specially designed for large electrical networks.

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Méthodologies de Conception de Transformateurs Moyenne Fréquence pour application aux réseaux haute tension et réseaux ferroviaires Alexis Fouineau--THESE de DOCTORAT DE L’UNIVERSITE DE LYON opérée au sein de l’Université Claude Bernard Lyon 1 Ecole Doctorale N° 160 ECOLE DOCTORALE ELECTRONIQUE, ELECTROTECHNIQUE, AUTOMATIQUE DE LYON Spécialité de doctorat : Génie Électrique Soutenue publiquement le 13/11/2019, par : Alexis FOUINEAU

 

Méthodologies de Conception de Transformateurs Moyenne Fréquence pour application aux réseaux haute tension et réseaux ferroviaires

THESE de DOCTORAT DE L’UNIVERSITE DE LYON opérée au sein de l’Université Claude Bernard Lyon 1 Ecole Doctorale N° 160 ECOLE DOCTORALE ELECTRONIQUE, ELECTROTECHNIQUE, AUTOMATIQUE DE LYON Spécialité de doctorat : Génie Électrique Soutenue publiquement le 13/11/2019, par : Alexis FOUINEAU opérée au sein de l’Université Claude Bernard Lyon 1 Ecole Doctorale N° 160 

ECOLE DOCTORALE ELECTRONIQUE, ELECTROTECHNIQUE, AUTOMATIQUE DE LYON

Spécialité de doctorat : Génie Électrique Soutenue publiquement le 13/11/2019, 

par : Alexis FOUINEAU

Abstract

 Medium Frequency Transformers (MFT) are an innovative technology compared to low frequency transformers, with the promise of reduced volume and increased efficiency. This PhD thesis focuses in particular on their design for high voltage, high power applications, such as high voltage and medium voltage DC networks, as well as railway networks. In these applications, MFTs are used in converters that can generate specific constraints to be taken into account during their design: non-sinusoidal signals, polarization voltage, target inductance values. Moreover, the technological choices currently available for the realization of MFTs are numerous, and there is currently no consensus on any technology for any given application. Trends could be identified using a tool to classify MFT designs from the literature. Thus, the most promising technologies were selected and retained for the future. Based on these technologies, a design methodology was developed to quickly and semi-automatically design and compare MFTs with different technological choices. It consists of three steps: pre-design, analytical design, and validation. The complete analytical design of the MFT with different technological choices is carried out using an automated design tool developed during this thesis, named SUITED (SUpergrid Institute TransformEr Design). This methodology requires models and data for each of the components and phenomena of the MFT. Concerning the magnetic core, a review and selection of models from the literature were carried out for the evaluation of the magnetizing inductance and magnetic losses. In addition, magnetic characterizations have made it possible to highlight the impact of certain technological processes on the levels of loss of magnetic cores made of nanocrystalline material, which is an excellent candidate for MFTs. Concerning the windings, analytical models to calculate the magnetic field, leakage inductance and skin and proximity effects were developed and compared with those in the literature and simulations. These models are proving to be more accurate on the MFT geometries considered. On top of that, a new method for evaluating the parasitic capacitances of windings with rectangular turns has been successfully implemented and validated. Thermal networks have been identified for the different MFT geometries. The thermal resistances of conduction, convection and radiation are calculated from detailed models. In particular, the anisotropy of materials is taken into account for thermal conduction, and the convection coefficients are evaluated via different correlations for each face of the MFT. The thermal networks are then solved iteratively and analytically to take into account the non-linearity of the thermal resistances while optimizing the required computation time. Finally, this entire design methodology was applied to three case studies corresponding to the target applications: high voltage, medium voltage and rail. The results obtained do show the performance and necessity of this approach.

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Medium Frequency Transformer Leakage Inductance Modeling and Experimental Verification M. Mogorovic and D. Dujic--POWER ELECTRONICS LABORATORY ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE--

2017 IEEE Energy Conversion Congress and Exposition (ECCE) 

Medium Frequency Transformer Leakage Inductance Modeling and Experimental Verification 

M. Mogorovic and D. Dujic 

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 Abstract—This paper provides detailed analytical modeling and finite elements method (FEM) analysis of the medium frequency transformer (MFT) leakage inductance, as one of the key design factors governing the operation of galvanically isolated power electronics converters. Precise leakage inductance modeling in design stage is especially important for converter topologies based on resonant conversion where MFT is a part of a resonant circuit. A comprehensive analytical model that takes into account both the geometric and frequency effects on the given MFT leakage inductance is generated based on the transformer physical structure, thus allowing for optimization of the MFT design with targeted equivalent circuit leakage inductance reference. The derived models are benchmarked to the measurement results on the developed MFT prototype.

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State Of Art survey for design of Medium Frequency High Power Transformer Sriram Vaisambhayana1 , Catalin Dincan2 , Cao Shuyu1 , Anshuman Tripathi1 , Tian Haonan1 , Karthikeya BR1 Energy Research Institute @ NTU Singapore1 Aalborg University Denmark

AA

Abstract

 Medium and high frequency, high power transformers play an important role in footprint reduction along with their functions of galvanic isolation, and voltage transformation in all high power converters typically used in traction power systems, offshore wind plant power converters, and solid state transformer based distribution system grids. This state of art report analysis the various materials and design tradeoffs that govern the electromagnetic behavior and loss mechanisms of the medium frequency transformer applications. Typical winding and core geometries that have been reported extensively in the literature are described, and some design procedures and flow charts are analyzed including specific optimization routines. Estimation of core loss at high frequency using Steinmetz method and other modified methods are shown in detail. Thermal modelling including static and dynamic methods available in literature are put forward with references to thermal management methods. FEM analysis for electromagnetic behavior is described and couple of commercially available tools and their limitations are analyzed. Different challenges of relevance are included in different sections and brief comparisons are drawn. Design tools which are available is given a preview and limitations are drawn. A comprehensive literature survey was done and included in the paper in the reference section

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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https://hal.science/hal-03023154/file/Fouineau_full_paper_Medium_Frequency_Transformer_Design_Tool.pdf

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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:https://www.mediafire.com/file/fbm93uowzz5hdim/Khannanov-CÓMO+OBTENER+LA+MÁXIMA+PUNTUACIÓN+EN+EL+EXAMEN+FISICA.pdf/file

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

Abstract 

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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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

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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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