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Keywords = unfolding circuit

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15 pages, 2269 KB  
Review
Redefining Endometrial Decidualization: The Central Role of the ER Stress–Immune–Metabolic Axis
by Özdem Karaoğlan, Özgül Tap and İbrahim Ferhat Ürünsak
Int. J. Mol. Sci. 2026, 27(10), 4382; https://doi.org/10.3390/ijms27104382 - 14 May 2026
Viewed by 274
Abstract
Decidualization in the human endometrium is not merely a hormone-dependent differentiation process; rather, it represents a multilayered adaptive program characterized by the tight integration of immune regulation, metabolic reprogramming, and cellular stress responses. In this review, endoplasmic reticulum (ER) stress and the associated [...] Read more.
Decidualization in the human endometrium is not merely a hormone-dependent differentiation process; rather, it represents a multilayered adaptive program characterized by the tight integration of immune regulation, metabolic reprogramming, and cellular stress responses. In this review, endoplasmic reticulum (ER) stress and the associated unfolded protein response (UPR) are proposed as central regulatory mechanisms governing this process. Triggered by increased protein synthesis and secretory demand, UPR activation under physiological conditions preserves proteostasis and supports the secretory capacity of stromal cells. In contrast, chronic or dysregulated activation leads to a maladaptive response characterized by apoptosis, inflammation, and metabolic dysfunction. UPR signaling pathways shape immune tolerance through their effects on macrophage polarization, uterine natural killer (uNK) cell function, and T cell balance. At the metabolic level, adenosine monophosphate-activated protein kinase (AMPK) regulates cellular adaptation through bidirectional interactions with mitochondrial function and redox homeostasis. Within this framework, the ER stress–immune–metabolic axis operates not as a linear pathway but as a dynamic network incorporating multiple feedback loops, thereby constituting a critical threshold mechanism that determines the success of decidualization. Disruption of this axis provides a shared mechanistic basis for pathologies such as recurrent implantation failure, pregnancy loss, and preeclampsia. From a therapeutic perspective, agents including chemical chaperones, UPR modulators, AMPK activators, and anti-inflammatory compounds hold translational potential by targeting these pathological feedback circuits. However, key knowledge gaps remain, particularly regarding the cell type-specific and temporal regulation of ER stress, the molecular boundaries defining the transition from adaptive to pathological states, and interspecies differences. Future studies employing single-cell omics approaches and functional in vivo models will be essential to elucidate the dynamic organization of this axis and to enable the development of targeted and personalized therapeutic strategies. Full article
(This article belongs to the Section Molecular Biology)
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18 pages, 4313 KB  
Article
Analysis of a Novel Three-Port Single-Stage Bidirectional DC–AC Converter for PV-ESS-V2G System
by Chunhui Liu, Yinfu Bao, Celiang Deng, Fan Zhang, Da Wang, Haoran Chen, Wentao Ma, Feng Jiang and Min Chen
Electronics 2026, 15(7), 1360; https://doi.org/10.3390/electronics15071360 - 25 Mar 2026
Viewed by 503
Abstract
Multiport DC–AC converters are widely used in photovoltaic-energy storage–charging systems, but traditional two-stage schemes face challenges in circuit cost and efficiency improvements. To address this issue, a novel three-port single-stage DC–AC converter is proposed for grid-connected applications. The proposed converter integrates two DC [...] Read more.
Multiport DC–AC converters are widely used in photovoltaic-energy storage–charging systems, but traditional two-stage schemes face challenges in circuit cost and efficiency improvements. To address this issue, a novel three-port single-stage DC–AC converter is proposed for grid-connected applications. The proposed converter integrates two DC ports and one AC port through circuit multiplexing, eliminating the high-voltage DC bus and reducing system complexity. An unfolding bridge is employed at the AC port, and full bridge circuits are used at DC ports, reducing the number of high-frequency switches. The proposed single-stage topology inherently achieves galvanic isolation and bidirectional power conversion. To achieve accurate grid current regulation and wide-range zero-voltage-switching, a multiple-phase-shift modulation method is developed to ensure a sinusoidal current waveform. The effectiveness of the proposed converter and modulation method is verified through simulation results, demonstrating a peak efficiency of 97% and a total harmonic distortion of 2.91%. Full article
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14 pages, 850 KB  
Review
The Interplay Between Ca2+ Homeostasis, Endoplasmic Reticulum Stress, and the Unfolded Protein Response in Human Diseases
by Elia Ranzato and Simona Martinotti
Cells 2026, 15(4), 352; https://doi.org/10.3390/cells15040352 - 15 Feb 2026
Cited by 3 | Viewed by 2412
Abstract
The maintenance of endoplasmic reticulum (ER) Ca2+ homeostasis is intrinsically linked to the fidelity of protein folding, forming a functional tether that, when disrupted, triggers the Unfolded Protein Response (UPR). This bidirectional axis serves as a critical rheostat for cellular viability, yet [...] Read more.
The maintenance of endoplasmic reticulum (ER) Ca2+ homeostasis is intrinsically linked to the fidelity of protein folding, forming a functional tether that, when disrupted, triggers the Unfolded Protein Response (UPR). This bidirectional axis serves as a critical rheostat for cellular viability, yet its chronic dysregulation underpins the molecular etiology of numerous pathologies, including neurodegeneration, heart failure, and malignant transformation. This review provides a comprehensive interrogation of the Ca2+-ER Stress–UPR network, delineating how primary stress sensors—PERK, IRE1alpha, and ATF6—engage in complex feedback loops that either reinstate equilibrium or commit the cell to apoptosis. We specifically examine the PERK-CHOP-SERCA2b inhibitory circuit as a central driver of persistent Ca2+ depletion and discuss the role of Mitochondria-Associated Membranes (MAMs) in governing lethal Ca2+ transfer. Notably, we move beyond the classical paradigm of CHOP as a terminal apoptotic executioner, incorporating emerging evidence of its context-dependent adaptive functions. By synthesizing mechanistic insights across diverse disease models, this work highlights the transition from adaptive to maladaptive UPR as a universal pathological checkpoint. Ultimately, we evaluate the therapeutic potential of ‘axis-targeted’ interventions, such as SERCA activators and selective UPR modulators, aimed at resolving the underlying Ca2+ signaling defects in ER stress-related disorders. Full article
(This article belongs to the Special Issue Regulation of Ca2+ Signals in Human Disease)
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15 pages, 552 KB  
Review
Sleep, Emotion, and Sex-Specific Developmental Trajectories in Childhood and Adolescence
by Giuseppe Marano and Marianna Mazza
Children 2026, 13(2), 171; https://doi.org/10.3390/children13020171 - 26 Jan 2026
Cited by 2 | Viewed by 1326
Abstract
Sleep plays a central role in shaping emotional development during childhood and adolescence, yet increasing evidence indicates that these processes unfold differently in boys and girls. This narrative review synthesizes current findings on sex-specific associations between sleep patterns, neurodevelopmental trajectories, and emotional regulation [...] Read more.
Sleep plays a central role in shaping emotional development during childhood and adolescence, yet increasing evidence indicates that these processes unfold differently in boys and girls. This narrative review synthesizes current findings on sex-specific associations between sleep patterns, neurodevelopmental trajectories, and emotional regulation across pediatric populations. It examines how biological factors, including pubertal timing, sex hormones, circadian physiology, and maturation of fronto-limbic circuits, interact with environmental influences to generate distinct vulnerabilities to anxiety, depression, and behavioral dysregulation. Growing data suggest that girls exhibit greater sensitivity to sleep disturbances, particularly during the pubertal transition, with stronger links to internalizing symptoms such as anxiety and mood disorders. In contrast, boys appear more prone to externalizing behaviors and show differential responses to circadian misalignment and short sleep duration. Emerging evidence on sex-specific sleep architecture, REM-related emotional processing, and the bidirectional pathways through which sleep quality affects affective functioning are explored. Finally, clinical implications for early detection, personalized prevention, and targeted interventions tailored by sex and developmental stage are discussed. Understanding sex-based differences in sleep–emotion interactions offers a critical opportunity to refine pediatric mental health strategies and improve outcomes across developmental trajectories. Full article
(This article belongs to the Special Issue Advances in Mental Health and Well-Being in Children (Third Edition))
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29 pages, 1100 KB  
Review
Epigenetic Regulation of Erythropoiesis: From Developmental Programs to Therapeutic Targets
by Ninos Ioannis Vasiloudis, Kiriaki Paschoudi, Christina Beta, Grigorios Georgolopoulos and Nikoletta Psatha
Int. J. Mol. Sci. 2025, 26(13), 6342; https://doi.org/10.3390/ijms26136342 - 30 Jun 2025
Cited by 3 | Viewed by 4619
Abstract
Erythropoiesis, the process driving the differentiation of hematopoietic stem and progenitor cells to mature erythrocytes, unfolds through tightly orchestrated developmental stages, each defined by profound epigenetic remodeling. From the initial commitment of hematopoietic progenitors to the terminal enucleation of erythrocytes, dynamic changes in [...] Read more.
Erythropoiesis, the process driving the differentiation of hematopoietic stem and progenitor cells to mature erythrocytes, unfolds through tightly orchestrated developmental stages, each defined by profound epigenetic remodeling. From the initial commitment of hematopoietic progenitors to the terminal enucleation of erythrocytes, dynamic changes in chromatin accessibility, transcription factor occupancy, and three-dimensional genome architecture govern lineage specification and stage-specific gene expression. Advances in our understanding of the regulatory genome have uncovered how non-coding elements, including enhancers, silencers, and insulators, shape the transcriptional landscape of erythroid cells. These elements work in concert with lineage-determining transcription factors to establish and maintain erythroid identity. Disruption of these epigenetic programs—whether by inherited mutations, somatic alterations, or environmental stress—can lead to a wide range of hematologic disorders. Importantly, this growing knowledge base has opened new therapeutic avenues, enabling the development of precision tools that target regulatory circuits to correct gene expression. These include epigenetic drugs, enhancer-targeted genome editing, and lineage-restricted gene therapies that leverage endogenous regulatory logic. As our understanding of erythroid epigenomics deepens, so too does our ability to design rational, cell-type-specific interventions for red blood cell disorders. Full article
(This article belongs to the Special Issue New Advances in Erythrocyte Biology and Functions)
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22 pages, 3666 KB  
Article
Global Hotspots and Trends of Ecological Network Research (1991–2024): Insights from Bibliometric Analysis
by Jingxian Wang, Hui Tang, Wei Guo, Wendong Yu and Yunjian Luo
Sustainability 2025, 17(10), 4716; https://doi.org/10.3390/su17104716 - 21 May 2025
Cited by 1 | Viewed by 2211
Abstract
Ecological networks (ENs) offer a proactive, spatially explicit strategy for safeguarding the integrity, functionality, and sustainability of ecological spaces. With land and financial resources increasingly constrained, conventional approaches to expanding ecological spaces are often infeasible. ENs have emerged as a robust solution to [...] Read more.
Ecological networks (ENs) offer a proactive, spatially explicit strategy for safeguarding the integrity, functionality, and sustainability of ecological spaces. With land and financial resources increasingly constrained, conventional approaches to expanding ecological spaces are often infeasible. ENs have emerged as a robust solution to address challenges effectively. This study combined bibliometric analysis with a traditional literature review to examine keyword co-occurrence in EN-related publications from the Web of Science Core Collection (1991–2024). The results showed a significant increase in publication volume and identified three main research themes: (i) theoretical foundations of ENs, focusing on conceptual frameworks and principles; (ii) construction methodologies of ENs, emphasizing the design and optimization through tools such as graph theory, circuit theory, the Minimum Cumulative Resistance model, and the Patch-generating Land Use Simulation model; and (iii) EN and ecosystem services, highlighting contributions to green infrastructure and forest management. The evolution of research frontiers unfolds across three distinct stages: establishing theoretical foundations (1991–2009), advancing methodologies (2010–2021), and integrating interdisciplinary approaches (2022–2024). Four future priorities guiding EN studies include advancing ecosystem service quantification and integration, enhancing climate change adaptation and resilience, strengthening socioeconomic integration for sustainable development, and leveraging interdisciplinary collaboration and technological innovation. Full article
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22 pages, 2021 KB  
Article
Online Pulse Compensation for Energy Spectrum Determination: A Pole-Zero Cancellation and Unfolding Approach
by Tiago Motta Quirino, Thiago Campos Acácio Paschoalin, Guilherme Inácio Gonçalves, Pedro Henrique Braga Lisboa, Luciano Manhães de Andrade Filho and Bernardo Sotto-Maior Peralva
Electronics 2025, 14(3), 493; https://doi.org/10.3390/electronics14030493 - 25 Jan 2025
Cited by 5 | Viewed by 2784
Abstract
Signal conditioning circuits, in particle energy spectrum determination systems, introduce shaping characteristics that affect pulse integrity. This study explores algorithms to compensate for these effects, focusing on digital signal processing for pole-zero cancellation (PZC) and unfolding techniques. The PZC algorithm successfully corrects baseline [...] Read more.
Signal conditioning circuits, in particle energy spectrum determination systems, introduce shaping characteristics that affect pulse integrity. This study explores algorithms to compensate for these effects, focusing on digital signal processing for pole-zero cancellation (PZC) and unfolding techniques. The PZC algorithm successfully corrects baseline shift and pulse amplitude loss, providing significant improvements in signal fidelity. Although a digital PZC applied in streaming for high event rates was previously not feasible, this work proposes its implementation on FPGA, combining it with the unfolding method to enable online compensation and enhanced performance under various experimental conditions. Full article
(This article belongs to the Special Issue New Advances of FPGAs in Signal Processing)
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24 pages, 444 KB  
Article
A Distributed and Parallel (k, n) QSS Scheme with Verification Capability
by Theodore Andronikos
Mathematics 2024, 12(23), 3782; https://doi.org/10.3390/math12233782 - 29 Nov 2024
Cited by 3 | Viewed by 1641
Abstract
This paper presents a new quantum secret sharing scheme featuring a (k, n) threshold and built-in verification. This innovative protocol takes advantage of entanglement and unfolds in three distinct phases. In anticipation of the coming of the distributed quantum [...] Read more.
This paper presents a new quantum secret sharing scheme featuring a (k, n) threshold and built-in verification. This innovative protocol takes advantage of entanglement and unfolds in three distinct phases. In anticipation of the coming of the distributed quantum computing era, this protocol is designed to function entirely in parallel within a fully distributed environment, where the spymaster and her agents are located in different places. This is a significant shift from most similar protocols that assume that all information recipients are in one location. The spymaster can send all necessary information to her agents at once, streamlining the process. Each phase runs simultaneously, which helps to reduce the overall execution cost. Given its complexity, we offer a thorough analysis to ensure its information-theoretic security, protecting against both external eavesdroppers and internal rogue agents. The protocol does away with the need for quantum signatures or pre-shared keys, making it simpler and less complex. Lastly, its potential for implementation on current quantum computers looks promising since it relies only on CNOT and Hadamard gates, with all participants using similar or identical quantum circuits. Full article
(This article belongs to the Special Issue Quantum Cryptography and Applications)
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6 pages, 820 KB  
Hypothesis
Syndrome Sinistre: Left Brachiocephalic Vein Compression and its Neurological Manifestations
by Karthikeyan M. Arcot and Vincent S. DeOrchis
Neurol. Int. 2024, 16(5), 1158-1163; https://doi.org/10.3390/neurolint16050087 - 17 Oct 2024
Cited by 2 | Viewed by 5130
Abstract
Embryologically, the left brachiocephalic vein (LBV) originates as an anastomotic channel between the right and left anterior cardinal veins. This positions the LBV between the manubrium sterni anteriorly and the innominate artery posteriorly. This pattern of adjacency of the aorta to the LBV [...] Read more.
Embryologically, the left brachiocephalic vein (LBV) originates as an anastomotic channel between the right and left anterior cardinal veins. This positions the LBV between the manubrium sterni anteriorly and the innominate artery posteriorly. This pattern of adjacency of the aorta to the LBV is unique to mammals and results from a quirk of evolution. With age, the ascending aorta unfolds, elongates and dilates. Simultaneously, there is a change in the thoracic geometry that reduces the thoracic volume primarily from disc height loss and kyphosis. These transitions progressively compress the LBV. Normally, this compression is circumvented via collateral pathways and “Blood finds a way”. However, traversing these circuitous pathways comes at a cost and can result in delayed transit times and venous congestion. While it is possible that compression of the LBV in the setting of adequate collateral channels may fail to provoke any pathologic sequelae, we propose a phenomenon in which such compression in the setting of inadequate collateral circulation may lead to a state of pathologic venous congestion. This anatomic anomaly and its associated clinical features, if identified, can offer a new avenue for treatment options for some of the hitherto unexplained neurologic disorders. Full article
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34 pages, 37835 KB  
Article
Design and Development of Miniature Measuring Instrument for Parachute Cords Dynamic Load for Stepless Parachute Opening
by Wei Liang, Xin Zhao, Pengpeng Wu, Yuxin Li and Shuai Lv
Sensors 2024, 24(19), 6232; https://doi.org/10.3390/s24196232 - 26 Sep 2024
Viewed by 1946
Abstract
Spacecraft recovery technology is crucial in the field of aerospace, in which the parachute plays a key role in slowing down the descent speed of the spacecraft and realizing a smooth landing. In order to construct a dynamically adjustable parachute deployment strategy, it [...] Read more.
Spacecraft recovery technology is crucial in the field of aerospace, in which the parachute plays a key role in slowing down the descent speed of the spacecraft and realizing a smooth landing. In order to construct a dynamically adjustable parachute deployment strategy, it is necessary to measure the parachute dynamic load accurately in real-time. However, the existing sensor measurement scheme makes it difficult to meet the measurement requirements due to its large structure and complex wiring. In order to meet the current demand for real-time measurement of parachute cords dynamic load, a miniature measuring instrument is designed. According to the function and technical requirements of the miniature measuring instrument, the hardware modules of the acquisition system are selected and designed, and the integration debugging and performance optimization of the microcontroller module, A/D sampling module, signal acquisition circuit, and power supply module are carried out. The software of the parachute cords tension acquisition system based on the miniature measuring instrument is developed. The Load Cell is modeled by using SolidWorks 2022 and statically analyzed by using Ansys 2022 R1 Workbench finite element analysis software. Then the final structure of the Load Cell and the pasting position of the strain gauge are determined through the results analysis as well as experimental verification. The hardware module of the signal acquisition system for the miniature measuring instrument is then encapsulated. The force value of the miniature measuring instrument is calibrated and tested many times by using the microcomputer-controlled electronic universal testing machine. The experimental results show that the designed miniature measuring instrument has accurate data, strong stability, and good real-time performance, which meets the demand for real-time accurate measurement of miniature measuring instruments, and can provide reliable data for parachute cords parameter validation and stepless unfolding design. Full article
(This article belongs to the Section Physical Sensors)
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24 pages, 6988 KB  
Article
Considerations on Combining Unfolding Inverters with Partial Power Regulators in Battery–Grid Interface Converters
by Ilya A. Galkin, Rodions Saltanovs, Alexander Bubovich, Andrei Blinov and Dimosthenis Peftitsis
Energies 2024, 17(4), 893; https://doi.org/10.3390/en17040893 - 14 Feb 2024
Cited by 2 | Viewed by 2372
Abstract
The application of electrochemical cells as a source unit of electrical energy is rapidly growing—used in electric vehicles and other electric mobility devices, as well as in energy supply systems—as energy storage, often together with renewable energy sources. The key element of such [...] Read more.
The application of electrochemical cells as a source unit of electrical energy is rapidly growing—used in electric vehicles and other electric mobility devices, as well as in energy supply systems—as energy storage, often together with renewable energy sources. The key element of such systems is the power electronic converter used for DC energy storage and AC grid interfacing. It should be bidirectional to charge and discharge the battery when it is necessary. Two-stage battery interface converters are the most common; their DC-DC stage controls the battery current and adjusts voltage, but the DC-AC stage (inverter or frontend) controls the current in the grid. The use of unfolding inverters in two-stage battery interfaces can have some advantages. In this case, the DC-DC converter produces half-sinewave pulsating voltages and currents, but the unfolding circuit changes the polarity of the voltages and currents and produces no switching losses. Another trend of modern power electronics is the principle of partial power processing. In this case, power electronic converters deal only with a part of the total power; therefore, losses in such converters are reduced. This paper considers combining unfolding frontends with partial power DC-DC converters that enable the further reduction in losses. In this paper, it is shown that such implementation of the partial power conversion principle in semi-DC-AC systems is really possible based on the real-time matching of the voltage of the partial-power DC-DC converter, battery voltage (which depends on its state of charge) and the rectified instantaneous voltage of the AC grid. Full article
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31 pages, 89613 KB  
Article
An Automatic Defect Detection System for Petrochemical Pipeline Based on Cycle-GAN and YOLO v5
by Kun Chen, Hongtao Li, Chunshu Li, Xinyue Zhao, Shujie Wu, Yuxiao Duan and Jinshen Wang
Sensors 2022, 22(20), 7907; https://doi.org/10.3390/s22207907 - 17 Oct 2022
Cited by 69 | Viewed by 8743
Abstract
Defect detection of petrochemical pipelines is an important task for industrial production safety. At present, pipeline defect detection mainly relies on closed circuit television method (CCTV) to take video of the pipeline inner wall and then detect the defective area manually, so the [...] Read more.
Defect detection of petrochemical pipelines is an important task for industrial production safety. At present, pipeline defect detection mainly relies on closed circuit television method (CCTV) to take video of the pipeline inner wall and then detect the defective area manually, so the detection is very time-consuming and has a high rate of false and missed detections. To solve the above issues, we proposed an automatic defect detection system for petrochemical pipeline based on Cycle-GAN and improved YOLO v5. Firstly, in order to create the pipeline defect dataset, the original pipeline videos need pre-processing, which includes frame extraction, unfolding, illumination balancing, and image stitching to create coherent and tiled pipeline inner wall images. Secondly, aiming at the problems of small amount of samples and the imbalance of defect and non-defect classes, a sample enhancement strategy based on Cycle-GAN is proposed to generate defect images and expand the data set. Finally, in order to detect defective areas on the pipeline and improve the detection accuracy, a robust defect detection model based on improved YOLO v5 and Transformer attention mechanism is proposed, with the average precision and recall as 93.10% and 90.96%, and the F1-score as 0.920 on the test set. The proposed system can provide reference for operators in pipeline health inspection, improving the efficiency and accuracy of detection. Full article
(This article belongs to the Section Fault Diagnosis & Sensors)
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16 pages, 6012 KB  
Article
A High-Gain and High-Efficiency Photovoltaic Grid-Connected Inverter with Magnetic Coupling
by Chien-Hsuan Chang, Chun-An Cheng, Hung-Liang Cheng and En-Chih Chang
Micromachines 2022, 13(10), 1568; https://doi.org/10.3390/mi13101568 - 21 Sep 2022
Viewed by 2506
Abstract
Conventional photovoltaic (PV) grid-connected systems consist of a boost converter cascaded with an inverter, resulting in poor efficiency due to performing energy processing twice. Many pseudo DC-link inverters with single energy processing have been proposed to improve system efficiency and simplify circuits. However, [...] Read more.
Conventional photovoltaic (PV) grid-connected systems consist of a boost converter cascaded with an inverter, resulting in poor efficiency due to performing energy processing twice. Many pseudo DC-link inverters with single energy processing have been proposed to improve system efficiency and simplify circuits. However, their output voltage gain is limited by the non-ideal characteristics of the power diode, making them difficult to apply in high-output voltage applications. This paper proposes combining a boost converter with magnetic coupling and a full-bridge unfolding circuit to develop an inverter featuring high voltage-gain and high efficiency. According to the desired instantaneous output voltage, the high-gain boost converter and the full-bridge unfolding circuit are sequentially and respectively controlled by SPWM. A sinusoidal output voltage can be generated by performing energy processing only once, effectively improving the conversion efficiency. Magnetic coupling is adopted to increase the voltage gain of step-up, and the step-down function is realized by the full-bridge unfolding circuit to reduce conduction loss. Finally, a 500 W prototype was fabricated for the proposed high-gain inverter. The experimental results were used to verify the correctness of the theoretical analysis and the feasibility of the circuit structure. Full article
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17 pages, 11660 KB  
Article
Design and Experimental Validation of a Single-Stage PV String Inverter with Optimal Number of Interleaved Buck-Boost Cells
by Artem Fesenko, Oleksandr Matiushkin, Oleksandr Husev, Dmitri Vinnikov, Ryszard Strzelecki and Piotr Kołodziejek
Energies 2021, 14(9), 2448; https://doi.org/10.3390/en14092448 - 25 Apr 2021
Cited by 11 | Viewed by 2982
Abstract
Increasing converter power density is a problem of topical interest. This paper discusses an interleaved approach of the efficiency increase in the buck-boost stage of an inverter with unfolding circuit in terms of losses in semiconductors, output voltage ripples and power density. Main [...] Read more.
Increasing converter power density is a problem of topical interest. This paper discusses an interleaved approach of the efficiency increase in the buck-boost stage of an inverter with unfolding circuit in terms of losses in semiconductors, output voltage ripples and power density. Main trends in the power converter development are reviewed. A losses model was designed and used for the proposed solution to find an optimal number of interleaved cells. It describes static and dynamic losses in semiconductor switches for buck and boost mode. The presented calculation results demonstrate the efficiency of the interleaved approach for photovoltaic system. 1 kW power converter prototype was designed with two parallel dc-dc cells for experimental verification of obtained theoretical results. The experimental results confirm theoretical statements. Full article
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19 pages, 8914 KB  
Article
A Transformer-Less Buck-Boost Grid-Tied Inverter with Low Leakage-Current and High Voltage-Gain
by Chien-Hsuan Chang and Yi-Fan Chen
Appl. Sci. 2021, 11(8), 3625; https://doi.org/10.3390/app11083625 - 17 Apr 2021
Cited by 6 | Viewed by 3139
Abstract
To improve the efficiency of photovoltaic (PV) grid-tied systems and simplify the circuit structure, many pseudo DC-link inverters have been proposed by combining a sinusoidal pulse-width modulation (SPWM) controlled buck-boost converter and a low-frequency polarity unfolder. However, due to the non-ideal characteristics of [...] Read more.
To improve the efficiency of photovoltaic (PV) grid-tied systems and simplify the circuit structure, many pseudo DC-link inverters have been proposed by combining a sinusoidal pulse-width modulation (SPWM) controlled buck-boost converter and a low-frequency polarity unfolder. However, due to the non-ideal characteristics of power diodes, the voltage-gain of a buck-boost converter is limited. To meet the needs of grid-connected systems with low input voltage and 220 Vrms utility, this paper uses two two-switch buck-boost converters with coupled inductors to develop a transformer-less buck-boost grid-tied inverter with low leakage-current and high voltage-gain. The proposed inverter is charging on the primary side of the coupled inductor and discharging in series on the primary side and the secondary side so that the voltage-gain can be greatly increased. Furthermore, the utility line can be connected to the negative end of the PV array to suppress leakage current, and the unfolding circuit can be simplified to reduce the conduction losses. High-frequency switching is only performed in one metal-oxide-semiconductor field-effect transistor (MOSFET) in each mode, which can effectively improve conversion efficiency. A prototype was implemented to obtain experimental results and to prove the validity of the proposed circuit structure. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
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