Improving voltage imbalance in inverter-based islanded microgrids during line-to-line short circuits- Miguel Castilla, Jaume Miret, Luis García de Vicuña, Ángel Borrell, Carlos AlfaroDepartment of Electronic Engineering, Universitat Politècnica de Catalunya, Vilanova i la Geltrú, Spain Department of Electric Engineering, Escola Universitària Salesiana de Sarrià, Barcelona, Spain-

 Abstract

 Line-to-line short circuits are the transient disturbances that cause the highest currents as well as the largest voltage imbalances in inverter-based microgrids. This paper presents a control scheme for grid-forming inverters in islanded microgrids that limits the current to a safe value during these types of short circuits while providing a lower voltage imbalance compared to state-of-the-art current limiting techniques. This control scheme is based on reducing both the amplitude of the reference voltage with the maximum amplitude of the reference current and the instantaneous reference voltage with only the inductive component of the virtual impedance. The combination of these two control actions provides low voltage imbalance, as the theoretical and experimental studies reveal. This voltage imbalance improvement is the main contribution of this paper and is maintained when the microgrid supplies linear and non-linear loads. In the theoretical study, the paper includes control design guidelines to satisfy static and dynamic specifications. The theoretical predictions are validated by means of experimental results measured in a laboratory microgrid. A practical performance comparison of current limiting techniques based on experimental tests is also reported

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https://upcommons.upc.edu/handle/2117/387136

“Active Gate Switching Control of IGBT to Improve Efficiency in High Power Density Converters” 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 Switching Control of IGBT to Improve Efficiency in High Power Density Converters” 

Thesis submitted in partial fulfilment of the requirement for the PhD degree issued by the Universitat Politècnica de Catalunya, in its Electronic Engineering Program 

by Hamidreza Ghorbani 

Director: Dr. Prof. Jose Luis Romeral Martinez Co-Director: Dr. Eng. Vicent Sala

Abstract 

Insulated gate bipolar transistor (IGBT) power semiconductors are widely employed in industrial applications. This power switch capability in high voltage blocking and high current-carrying has expanded its use in power electronics. However, efficiency improvement and reducing the size of products is one of main tasks of engineers in recent years. In order to achieve high-density power converters, attentions are focused on the use of fast IGBTs. Therefore, for achieving this desire the trend is designing more effective IGBT gate drivers. In gate drive (GD) controlling, the main issue is maintaining transient behavior of the MOS-channel switch in well condition; when it switches fast to reduce losses. It is well known that fast switching has a direct effect on the efficiency improvement; meanwhile, it is the major reason of appearing electromagnetic interference (EMI) problems in switched-mode power converters. Nowadays the most expectant of an active gate driver (AGD) is actively adjusting the switching transient through simple circuit implementation. Usually its performance is compared with the conventional gate driver (CGD) with fixed driving profile. As a result a proposed AGD has the capability of increasing the switching speed while minimizing the switching stress. Different novel active gate drivers (as feed-forward and closed-loop topologies) have been designed and analysed in this study. To improve the exist trade-off between switching losses and EMI problem, all effective factors on this trade-off are evaluated and considered in proposed solutions. Theoretical developments include proposed controlling methods and simulated efficiency of IGBTs switching control. The efficiency improvement has been pursued with considering EMI study in the proposed active gate controller. Experimental tests have been conducted to verify the design and validate the results. Beside technical aspects, cost study has also considered in the closed-loop GD. The proposed gate drivers are simple enough to allow its use in real industrial applications.

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https://upcommons.upc.edu/bitstream/handle/2117/168574/THG1de1.pdf

Návrh a realizace obousměrného DC/DC měniče Design and Realisation of Bidirectional DC/DC Converter By Bc. Antonín Tomšů -2016 VŠB – Technická univerzita Ostrava Fakulta elektrotechniky a informatiky Katedra elektroniky

Návrh a realizace obousměrného DC/DC měniče Design and Realisation of Bidirectional DC/DC Converter By Bc. Antonín Tomšů -2016 

VŠB – Technická univerzita Ostrava Fakulta elektrotechniky a informatiky Katedra elektroniky

 Abstract 

The diploma thesis deals with design and subsequent implementation of a bidirectional DC/DC converter. Theoretical part is an analysis of galvanic insulated inverters together with a description of the function of the peripheral circuit. Practical part deals with the dimensioning and selection of components for the implemented drive, which included a selection of IGBT transistors, exciters, design of medium-frequency transformer, capacitors, chokes, current and voltage sensors, calculation of the power dissipation and cooling. In the next part of the diploma thesis is verification of connection through simulation function in programming environment LTspice. The last part contains description of a laboratory model realized by the bidirectional DC / DC converter with a summary of the results.

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https://dspace.vsb.cz/bitstream/handle/10084/115788/TOM0106_FEI_N2649_2612T015_2016.pdf?sequence=1&isAllowed=y

Řídicí jednotka reverzibilního DC/DC měniče-Control Unit of Reversible DC/DC Converter-Bc. Michal Chudárek-VŠB- TECHNICKÁ UNIVERZITA OSTRAVA Fakulta elektroniky a informatiky Katedra elektroniky

 

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https://dspace.vsb.cz/bitstream/handle/10084/108550/CHU0009_FEI_N2649_2612T015_2015.pdf?sequence=1&isAllowed=y

THÈSE Pour obtenir le grade de DOCTEUR DE L’UNIVERSITÉ JEAN MONNET DE SAINT-ÉTIENNE Ecole Doctorale Sciences, Ingénierie, Santé : ED SIS 488 Discipline : Optique Photonique Hyperfréquence Présentée et soutenue publiquement le 26 Mars 2014 Par Khamis YOUSSOUF KHAMIS Modélisation des Transformateurs Planaires Intégrés

Summary 

The use of passive components has experienced significant growth in recent decades, particularly in the field of mobile telephony and embedded electronics. The work presented in this thesis is part of a project between the LT2C laboratories of UJM and Ampère of INSA LYON. The objective of this thesis is the modeling of signal micro-transformers used to isolate the power (Driver IC) and control (JFET or MOSFET) parts. The points addressed in this thesis are the choice of transformer structures which meet the project requirements, the development of a transformer model which takes into account in particular the losses and the evolution of the permeability of the magnetic material and the different capacitive couplings. . Simulations using HFSS were carried out in order to design the selected structures and validate the developed model. Manufacturing steps compatible with those of microelectronics were used to fabricate one-layer and two-layer prototypes of magnetic material with different configurations. A high frequency characterization (2MHz-200MHz) using the vector network analyzer was carried out and finally a comparative study between the simulation results and the measurement results is the subject of a presentation. 

 VIEW FULL TEXT:https://core.ac.uk/download/pdf/52639727.pdf

Farias Martins, Lais (2019) Modelling and Analysis of DC-DC Converters for Bidirectional EV Charging Applications. PhD thesis, University of Sheffield.

Farias Martins, Lais (2019) Modelling and Analysis of DC-DC Converters for Bidirectional EV Charging Applications. 

PhD thesis, University of Sheffield. 

 Abstract This thesis is focused on the modelling and analysis of DC-DC converter topologies used for bidirectional charging of electric vehicles. Bidirectional converters are used in vehicle-to-grid (V2G) systems to allow bidirectional power transfer between the vehicle and the grid. Following the investigation in the literature review of potential converter topologies used in V2G applications and modelling techniques, this research proposes the application of the cyclic-averaging method for analysis of the Dual Active Bridge, 4th order resonant CLLC converter, and series compensated Inductive Power Transfer (IPT) converter. First, the cyclic-averaging method is applied for analysis of a phase-shift modulated Dual Active Bridge converter (DAB). For implementation of the cyclic analysis, the operation of the converter is first analysed using a Spice simulation to determine the system’s operation modes and duty cycles. The cyclic-averaging model is validated against a Spice simulation and employed to predict the converter’s output and to perform harmonic analysis of the inductor current. Following the analysis of the DAB, a 4th order CLLC converter is evaluated considering frequency and phase-shift modulations. The cyclic-averaging model is derived to model the behaviour of the converter’s output and state-variables in steady state. Additionally, a Fundamental Mode Approximation (FMA) model and a novel piecewise-linear state-variable model are also implemented for comparison. The models obtained are validated using Spice and, for the phase-shift modulated converter, experimental results. Finally, the series compensated IPT converter is analysed considering operation under phase-shift modulation. A FMA model is derived and, using circuit transformation, the state-variable and cyclic-averaging models previously defined for the CLLC converter are adapted for the analysis of the IPT converter. A prototype is built for validation of the cyclic model. Overall, for all converters analysed in this research, the cyclic-averaging method showed good performance with considerably fast execution and accuracy similar to Spice simulations.

VIEW FULL TEXT: https://etheses.whiterose.ac.uk/26746/1/Thesis_final.pdf

이중 변환 UPS의 병렬 운전 시 외란 저감 성능 향상을 위한 정지 좌표계 상의 전향 보상 기법 류효준1 , 윤영두✝, 모재성1 , 최승철1 , 우태겸1 Feed-Forward Compensation Technique in Stationary Reference Frame for the Enhanced Disturbance Rejection Performance in Parallel Operation of Double-Conversion UPSs

 이중 변환 UPS의 병렬 운전 시 외란 저감 성능 향상을 위한 정지 좌표계 상의 전향 보상 기법 류효준1 , 윤영두✝, 모재성1 , 최승철1 , 우태겸1

 Feed-Forward Compensation Technique in Stationary Reference Frame for the Enhanced Disturbance Rejection Performance in Parallel Operation of Double-Conversion UPSs 

By Hyo-Jun Ryu1 , Young-Doo Yoon✝, Jae-Sung Mo1 , Seung-Cheol Choi1 , and Tae-Gyeom Woo1 

Abstract 

Generally, a proportional-resonant controller is used to eliminate steady-state errors during the voltage– current control of a double-conversion uninterruptible power supply (UPS) in a stationary reference frame. Additionally, the feed-forward control compensating for the load current, which can be considered a disturbance of the voltage controller, can be used to improve the disturbance rejection performance. However, during the parallel operation of UPSs, circulating current can occur between UPS modules when performing both feed-forward control and droop control because feed-forward control reduces the circulating current impedance. This study proposes a feed-forward compensation technique that considers the impedance of circulating current. An additional feed-forward compensation technique is developed to enhance the disturbance rejection performance. The validity of the proposed feed-forward compensation technique is verified by the experiment results of the parallel operation of a 500 W double-conversion UPS module.

VIEW FULL TEXT:https://www.kstudy.com/fbook/KIPE/27-5/1.pdf

A Comparative Review of Three Different Power Inverters for DC–AC Applications Ali Abdel-Aziz 1 , Mohamed A. Elgenedy 2,* and Barry Williams 1-25 October 2023

 A comparative review of three different power inverters for DC–AC applications

 Ali AbdelAziziMohamed ElgenedyBarry Williams25 October 2023DOI: 10.3390/EN16217254

 Abstract 

This paper presents a comparative review of three different widely used power inverters, namely the conventional six-switch inverter; the reduced switch count four-switch inverter; and the eight-switch inverter. The later inverter can be reconfigured as a neutral-point diode-clamped inverter at the failure of one inverter leg. The three power inverters are compared and discussed with respect to cost, complexity, losses, common mode voltage, and control techniques. The paper is intended to serve as a guide regarding selecting the appropriate inverter for each specific application. Simulation results are presented to demonstrate the performance of the three power inverters, followed by a comprehensive comparison between the three power inverters .

VIEW FULL TEXT: https://core.ac.uk/download/590007582.pdf

不平衡负载下三相 UPS 逆变器的研究 Research on Three-phase UPS with Unbalanced Load-Ye Bincheng1 , Meng Chao1,2, Wei Wen1 1.PROTEK Electronic Technology Corporation（Xiamen, 361028. China）；2.School of Energy, Xiamen University（Xiamen, 361002, China）

 不平衡负载下三相 UPS 逆变器的研究 Research on Three-phase UPS with Unbalanced Load 要：三相电压的对称输出是衡量交流电源性能的一个重要指标。提出了一种新型的三相 UPS 逆变器系统，利用 Δ/Z0 型变 压器为三相不平衡负载造成的零序电流分量提供通路，再通过设计正、负序双 PI 控制器抑制不平衡负载中负序电压分量。从而 解决零序电压和负序电压造成的三相电压不平衡问题，使该三相 UPS 逆变电源系统可带三相不平衡负载。试制一台 60kVA 的三 相 UPS 样机，并给出实验结果。 关键词：三相 UPS 三相逆变器 不平衡负载 电压对称性 

Abstract: The balanced output of three-phase voltage is an important index to measure the function of alternating current .In order to obtain high-grade output voltage in the case where the load is out-off-balance, this paper analyzed the mechanism and result of threephase voltage caused by unbalanced load, and some existing solutions to solve this problem. A new three-phase UPS inverter system is also raised which use △ /ZO transformer to provide a current path for zero-sequence current that caused by three-phase unbalanced load. What’s more, it controlled the component of negative sequence voltage in the unbalanced load by designing the doubled PI controller (of positive and negative sequence). In these ways it could solve the imbalance of three-phase voltage caused by Zero-sequence voltage and， making the three-phase UPS inverter system able to load the three-phase unbalanced load. A 60kVA three-phase UPS prototypes was built and the results were given based on the experiments.

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https://core.ac.uk/download/323950531.pdf

“Performance Evaluation of a Proportional Integral with Proportional Derivative Feedforward Voltage Control for UPSs”-Tiago J. C. Sousa, Vítor Monteiro, Júlio S. Martins, J. C. Aparício Fernandes, João L. Afonso----ALGORITMI Research Centre – University of Minho Guimarães – Portugal

 Performance Evaluation of a Proportional-Integral with Proportional-Derivative Feedforward Voltage Control for UPSs 

Tiago J. C. Sousa, Vítor Monteiro, Júlio S. Martins, J. C. Aparício Fernandes, João L. Afonso ALGORITMI Research Centre – University of Minho Guimarães – Portugal 

 Abstract—This paper presents a performance evaluation of a proportional-integral (PI) with proportional-derivative (PD) feedforward control for the output voltage of a single-phase off-line uninterruptible power supply (UPS) without using additional sensors. The control system is explained and simulation results are presented to analyze the steady state and transient response of the implemented voltage control. A laboratorial prototype was developed, and acquired experimental results considering linear and nonlinear loads are presented and discussed, corroborating the obtained simulation results.

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https://core.ac.uk/download/185627388.pdf