| 1. |
- Marin, Gustav, et al.
(författare)
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Stiffness and strength properties of five paperboards and their moisture dependency
- 2019
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Ingår i: Paper Conference and Trade Show, PaperCon 2019. - : TAPPI Press. - 9781510893948 ; , s. 1193-1208
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Konferensbidrag (refereegranskat)abstract
- Five folding box boards made on the same paperboard machine have been analyzed. The paperboards were from the same product series but had different grammage (235, 255, 270, 315, 340 g/m2) and different bending stiffness. The paperboards are normally used to make packages, and since the bending stiffness and grammage varies the packages performance will be different. Finite element simulations can be used to predict these differences. However, the stiffness and strength properties then need to be known. For efficient determination of the three-dimensional properties in MD, CD and ZD, it is proposed that the whole paperboard should be characterized with the following tests: in-plane tension, ZD tension, shear strength profiles and two-point bending. The stiffness and strength properties have with the proposed setups been determined at different relative humidity (20, 50, 70 and 90 % RH), and the mechanical properties have been evaluated as function of moisture ratio. The results showed a linear relation between mechanical properties and moisture ratio for each paperboard. The data was then normalized with data for the standard climate (50 % RH) and investigated as a function of moisture ratio. The results indicated that the normalized mechanical properties for all paperboards coincided along one single line and could therefore be expressed as a linear function of moisture ratio and two constants. Consequently, the study indicates that it is possible to obtain the mechanical properties of a paperboard, by knowing the structural properties for the preferred level of RH and the mechanical property for the standard climate (50 % RH and 23 °C).
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| 2. |
- Alahakoon, Sanath, et al.
(författare)
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Emerging Energy Storage Solutions for Transportation Electrification - A view
- 2019
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Ingår i: International Journal of Engineering and Technology Innovation. - : Taiwan Assoc Engineering & Technology Innovation. - 2223-5329 .- 2226-809X. ; 9:2, s. 75-90
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Forskningsöversikt (refereegranskat)abstract
- Energy storages have caught the attention of transportation community r the past several years. Rsecent developments in hybrid and plug-in ectric vehicles together with novel concepts in transportation such as ectric highways are the reasons for raising the role of energy orages in transportation to such a significant level. Performance mands for energy storage solutions vary significantly from one ansportation application to the other, making it difficult for the ientific community to converge to a single energy storage solution at caters all. This paper reviews the key performance demands of the jor transportation applications. It also investigates the aracteristics of emerging energy storage solutions and assess their itability for those reviewed transportation applications.
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| 3. |
- Bessegato, Luca, et al.
(författare)
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Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies
- 2019
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Ingår i: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107.
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Tidskriftsartikel (refereegranskat)abstract
- Modular multilevel converters (MMCs) can be configured to perform ac/ac conversion, which makes them suitable as railway power supplies. In this paper, a hierarchical control scheme for ac/ac MMCs for railway power supplies is devised and evaluated, considering the requirements and the operating conditions specific to this application. Furthermore, admittance models of the ac/ac MMC are developed, showing how the suggested hierarchical control scheme affects the three-phase and the single-phase side admittances of the converter. These models allow for analyzing the stability of the interconnected system using the impedance-based stability criterion and the passivity-based stability assessment. Finally, the findings presented in this paper are validated experimentally, using a down-scaled MMC.
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| 4. |
- Bessegato, Luca, et al.
(författare)
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Control of Direct AC/AC Modular Multilevel Converters Using Capacitor Voltage Estimation
- 2016
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Ingår i: 2016 18TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'16 ECCE EUROPE). - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- This paper applies a control method based on current control and sum-capacitor-voltage estimation to the direct ac/ac modular multilevel converter. As capacitor voltages are estimated, their measurements are not needed in the high-level control, which simplifies the communication between the main controller and the submodules of the converter. The stability of the internal dynamics of the converter, using the aforementioned control method, is studied using Lyapunov stability theory, proving that the system is globally asymptotically stable. The behavior of the converter is simulated focusing on three-phase 50 Hz to single-phase 16 (2)/(3) Hz conversion, which is typical for railway power supply systems of some European countries. Simulation results are in agreement with the expected behavior of the converter, both in steady-state and dynamic situations.
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| 5. |
- Bessegato, Luca, 1989-
(författare)
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Modeling of Modular Multilevel Converters for Stability Analysis
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modular multilevel converters (MMCs) have recently become the state-of-the-art solution for various grid-connected applications, such as high-voltage direct current (HVDC) systems and flexible alternating current transmission systems (FACTS). Modularity, scalability, low power losses, and low harmonic distortion are the outstanding properties that make MMCs a key technology for a sustainable future. The main objective of this thesis is the modeling of grid-connected MMCs for stability analysis. The stability of the interconnected system, formed by the converter and the ac grid, can be assessed by analyzing the converter ac-side admittance in relation to the grid impedance. Therefore, a method for the calculation of the ac-side admittance of MMCs is developed. This method overcomes the nonlinearities of the converter dynamics and it can be easily adapted to different applications. Moreover, the effects of different control schemes on the MMC ac-side admittance are studied, showing how the converter admittance can be reshaped. This is a useful tool for system design, because it shows how control parameters can be selected to avoid undesired grid-converter interactions. This thesis also studies ac/ac MMCs for railway power supplies, which are used in countries with a low-frequency railway grid, such as Germany (16.7 Hz) and Sweden (16 2/3 Hz). A hierarchical control scheme for these converters is devised and evaluated, considering the requirements and the operating conditions specific to this application. Furthermore, admittance models of the ac/ac MMC are developed, showing how the suggested hierarchical control scheme affects the three-phase and the single-phase side admittances of the converter. For computing the insertion indices, an open-loop scheme with sum capacitor voltage estimation is applied to the ac/ac MMC. Lyapunov stability theory is used to prove the asymptotic stability of the converter operated with the proposed control method. This specific open-loop scheme is also adapted to a modular multilevel matrix converter, which performs three-to-three phase direct conversion. Finally, this thesis presents the design of a down-scaled MMC prototype for experimental verification, rated at 10 kW with 30 full-bridge submodules. The hardware and the software are designed to be easily reconfigurable, which makes the converter suitable for different research projects focused on MMCs. Experiments on this down-scaled MMC are used to support and validate the key results presented throughout the thesis.
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