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A hybrid control approach for LLC resonant converter
, Article 12th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2021, 2 February 2021 through 4 February 2021 ; 2021 ; 9780738111971 (ISBN) ; Tahami, F ; Barzkar, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this paper, a novel hybrid control approach is proposed to control the LLC resonant converter. Since the converter consists of both continuous variables and logical variables, it is intrinsically hybrid. Apart from that, because of fast dynamics of the converter and the fact that there is no closed form solution for discontinuous conduction modes (DCM), modeling and control of the LLC resonant converter is still a challenge. In the authors' previous work, a systematic model was proposed for the converter, the direct piecewise affine model. In this paper, an appropriate controller based on the proposed model is represented and the design procedure is discussed in details; the block diagram...
Modeling and Control of LLC Resonant Converter Based on Theories of Hybrid Systems
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
In comparison to pulse width modulation (PWM) converters, the ability of soft switch-ing enables resonant converters to operate at high frequencies, as the result of which these converters enjoy high efficiency, high power density, and low electromagnetic interference (EMI). Among resonant tank topologies, the LLC resonant tank is a very desirable structure, as the LLC resonant converter can operate in boost mode and properly regulate the output voltage under light loads and despite large variations in the input voltage and/or the load. However, there are major modeling issues with resonant converters, since conventional modeling approaches cannot properly model fast dynamics of these...
The direct piece-wise affine modeling of llc resonant converter
, Article 45th Annual Conference of the IEEE Industrial Electronics Society, IECON 2019, 14 October 2019 through 17 October 2019 ; Volume 2019-October , 2019 , Pages 2062-2067 ; 9781728148786 (ISBN) ; Tahami, F ; Molla Ahmadian, H ; Sharif University of Technology
IEEE Computer Society
2019
Abstract
Resonant converters are hard nonlinear systems which are comprised of both continuous and discontinuous nonlinearities. Many nonlinear modeling approaches lead to a very awkward, unsystematic stability analysis and controller design. Hence, stability analysis and stabilizing controller design of the popular LLC resonant converter still remain challenging as direct consequences of the absence of a "systematic modeling". In this paper, the LLC resonant converter is modeled in the form of Piece-Wise Affine (PWA) systems and a Direct Piece-Wise Affine (DPWA) model of the DC-DC LLC resonant converter is proposed. No dynamic is omitted in the modeling approach, and accordingly, the proposed...
Introduction and Literature review of power system challenges and issues
, Article Power Systems ; 2021 , Pages 19-43 ; 16121287 (ISSN) ; Lotfi, A ; Behkam, R ; Moradzadeh, A ; Barzkar, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Over many decades, the electric power industry has evolved from a single low-power generator serving a small area to highly interconnected networks serving a large number of countries, or even continents. Nowadays, an electric power system is one of the largest man-made systems ever created, consisting of an enormous number of components ranging from small electric appliances to very large turbo-generators. Running such a large system is a significant challenge. It has necessitated the resolution of numerous issues by educational and industrial institutions. The main issues of the power system can be categorized into planning, operation, and control issues which are analyzed in this chapter,...
Sustainable-Resilient Supplier Selection Through Fuzzy Multi-Criteria Decision Making Approaches
, M.Sc. Thesis Sharif University of Technology ; Akbari Jokar, Mohammad Resa (Supervisor) ; Memari, Ashkan (Co-Supervisor)
Abstract
Today, with the expansion of business relations at international levels, there are many organizations that operate in global supply chains. Activities at such levels face new types of challenges in various fields of "supply chain management" pillars, of which "supplier selection" is one of them. The possibility of unexpected events, the need to comply with environmental protection laws, as well as the need to take into account social considerations, are among the things that have increased by being in larger supply chains, making it challenging to provide the basic resources needed in such chains and forcing their managers to considering considerations other than what they have always...
Design of a Sustainable Supply Chain Network for Urban Spent Batteries
, M.Sc. Thesis Sharif University of Technology ; Akbari Jokar, Mohammad Reza (Supervisor) ; Memari, Ashkan (Supervisor)
Abstract
This research addresses the design and optimization of a sustainable supply chain for an environmental startup, with a focus on the collection and recycling of urban alkaline batteries in Tehran. This problem is motivated by the lack of proper management of this type of waste, its environmental pollution, and the resulting loss of natural resources. The main concern is the optimal selection of metro stations to be equipped with collection boxes and the determination of the transportation and recycling network structure in such a way that the economic performance of the network (total profit/cost) is optimized while environmental impacts (carbon emissions) are controlled simultaneously. To...
Artificial intelligence for detection of external cervical resorption using label-efficient self-supervised learning method
, Article Journal of Endodontics ; Volume 50, Issue 2 , 2024 , Pages 144-153.e2 ; 00992399 (ISSN) ; Dianat, O ; Abbasi, R ; Zahedrozegar, S ; Ashkan, A ; Motamedian, S. R ; Rohban, M. H ; Nosrat, A ; Sharif University of Technology
Elsevier
2024
Abstract
Introduction: The aim of this study was to leverage label-efficient self-supervised learning (SSL) to train a model that can detect ECR and differentiate it from caries. Methods: Periapical (PA) radiographs of teeth with ECR defects were collected. Two board-certified endodontists reviewed PA radiographs and cone beam computed tomographic (CBCT) images independently to determine presence of ECR (ground truth). Radiographic data were divided into 3 regions of interest (ROIs): healthy teeth, teeth with ECR, and teeth with caries. Nine contrastive SSL models (SimCLR v2, MoCo v2, BYOL, DINO, NNCLR, SwAV, MSN, Barlow Twins, and SimSiam) were implemented in the assessment alongside 7 baseline deep...