| 1. |
- Tran, Minh Quan, et al.
(författare)
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MPC-Based Coordinated Voltage Control in LV Distribution Systems: A Case Study in Chalmers Campus Network
- 2023
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Ingår i: Conference Proceedings - 2023 IEEE Asia Meeting on Environment and Electrical Engineering, EEE-AM 2023.
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Konferensbidrag (refereegranskat)abstract
- This paper presents detailed analysis results of a model predictive control (MPC)-based coordinated voltage control demonstrated in a real low voltage network, the Chalmers campus in Sweden. First, the modeling of the MPC is presented, and the state space mode is obtained by linearization of the power flow equation around the operation point. Thus, an updated voltage vector in the grid is calculated through the sensitivity gain corresponding to reactive power deviation in the grid. Second, the developed MPC model is integrated into an Internet of Things (IoT) platform developed under the European FlexiGrid project. The state measurements in the Chalmers campus network are collected through the IoT platform as the input for the MPC model. Then, the optimal setpoints for distributed energy resources (DERs) are calculated and sent to DERs via the IoT platform. Lastly, onsite demonstration results are analyzed, showing the performance of the MPC-based voltage control in low-voltage distribution systems.
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| 2. |
- Tran, Trung Thai, et al.
(författare)
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Virtual Oscillator based Hierarchical Control Strategy for Multi-mode Operation of Microgrids
- 2022
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Ingår i: IEEE PES Innovative Smart Grid Technologies Conference Europe. ; 2022-October
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Konferensbidrag (refereegranskat)abstract
- One of the most important challenges in controlling a Microgrid is to enable a multi-mode operation with a smooth change from different modes. Recently, hierarchical control is considered as an effective approach to control and manage a Microgrid. This paper proposes a compatible hierarchical control strategy, leveraging the superior characteristics of Andronov-Hopf Oscillator, that enables both grid-connected and islanded operation, as well as seamless, reliable transition between operation modes. The proposed control strategy includes a PI-based Power Tracking Control loop, a Power Sharing Control loop using average consensus approach, a PR-based Synchronization Control, and a Fault Initiated Islanding Detection based on wideband, online impedance estimation. The results in MATLAB/Simulink are provided to validate the effectiveness of the proposed strategy.
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| 3. |
- Dittrich, Laura, et al.
(författare)
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Retention of noble and rare isotope gases in plasma-facing components-Experience from the JET tokamak with the ITER-like wall
- 2023
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Ingår i: Fusion engineering and design. - : Elsevier BV. - 0920-3796 .- 1873-7196. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- Plasma edge cooling, ion cyclotron wall conditioning and disruption mitigation techniques involve massive gas injection (by puffs or pellets) to the torus. A certain fraction remains in plasma-facing components (PFC) due to co-deposition and implantation. An uncontrolled release/desorption of such retained species affects the stability of plasma operation. The aim of this work was to determine the lateral and depth distribution of noble (3He, 4He, Ne, Ar), seeded (N2, Ne, Ar) and tracer gases (15N, 18O) in PFC retrieved from the JET tokamak with the ITER-Like Wall (JET-ILW) after three experimental campaigns (ILW-1, ILW-2, ILW-3). Results regarding the retention of those gases are shown as well as a comparison to the deuterium retention in the studied areas. Heavy ion elastic recoil detection analysis was used, being the only technique capable of detection and quantitative assessment of all elements, especially low-Z isotopes. Helium was found on the divertor Tile 5, locally up to 44.1015 3He cm-2 and 12.1015 4He cm-2, and on the limiters as well. Neon was found in two positions on the limiters, with up to 10.1015 Ne cm-2 and the 15N tracer on Be limiters exposed to ILW-3. A correlation of N retention with the N seeding rates for each campaign has also been found.
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| 4. |
- Kaur, Rajdeep, et al.
(författare)
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Ion Track Formation and Nanopore Etching in Polyimide : Possibilities in the MeV Ion Energy Regime
- 2023
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Ingår i: Macromolecular materials and engineering. - : Wiley-VCH Verlagsgesellschaft. - 1438-7492 .- 1439-2054.
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Tidskriftsartikel (refereegranskat)abstract
- Polyimide films of thickness 7.5 µm are irradiated by a wide range of ions (1H to 197Au) with energies between 1.05 and 48 MeV. Irradiated samples are then chemically etched in sodium hypochlorite solution to investigate nanopore formation due to ion track etching. A threshold in terms of electronic stopping power, Set, needs to be surpassed to preferentially etch the ion tracks. Close to Set, intermittent tracks are formed where only part of the track is etchable. The fraction of these etchable parts increases as we move away from Set, toward higher stopping powers, eventually yielding continuous etchable tracks. Both intermittent and continuous track formation thresholds are observed to be velocity-dependent, yielding a decrease of the thresholds in the present work compared to previously reported thresholds for swift heavy ions. This finding leads the authors to suggest that electrostatic ion accelerators with terminal voltages of several MV are applicable for the production of ion track membranes up to ≈10–20 µm in thickness. Suitable ions for nanopores in 7.5 µm polyimide films include 42 MeV 59Co and 48 MeV 197Au. The growth mechanism for the pores during etching is discussed, relating it to the properties of the original ion track.
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| 5. |
- Pham, Ngan Hoang, et al.
(författare)
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Self-Limited Formation of Bowl-Shaped Nanopores for Directional DNA Translocation
- 2021
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:11, s. 17938-17946
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Tidskriftsartikel (refereegranskat)abstract
- Solid-state nanopores of on-demand dimensions and shapes can facilitate desired sensor functions. However, reproducible fabrication of arrayed nanopores of predefined dimensions remains challenging despite numerous techniques explored. Here, bowl-shaped nanopores combining properties of ultrathin membrane and tapering geometry are manufactured using a self-limiting process developed on the basis of standard silicon technology. The upper opening of the bowl-nanopores is 60–120 nm in diameter, and the bottom orifice reaches sub-5 nm. Current-voltage characteristics of the fabricated bowl-nanopores display insignificant rectification indicating weak ionic selectivity, in accordance to numerical simulations showing minor differences in electric field and ionic velocity upon the reversal of bias voltages. Simulations reveal, concomitantly, high-momentum electroosmotic flow downward along the concave nanopore sidewall. Collisions between the left and right tributaries over the bottom orifice drive the electroosmotic flow both up into the nanopore and down out of the nanopore through the orifice. The resultant asymmetry in electrophoretic–electroosmotic force is considered the cause responsible for the experimentally observed strong directionality in λ-DNA translocation with larger amplitude, longer duration, and higher frequencies for the downward movements from the upper opening than the upward ones from the orifice. Thus, the resourceful silicon nanofabrication technology is shown to enable nanopore designs toward enriching sensor applications.
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| 6. |
- Tran, Tuan Thien, et al.
(författare)
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In-situ characterization of ultrathin nickel silicides using 3D medium-energy ion scattering
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial ultrathin films are of utmost importance for state-of-the-art nanoelectronic devices, such as MOSFET transistors and non-volatile memories. At the same time, as the film thickness is reduced to a few nanometers, characterization of the materials is becoming challenging for commonly used methods. In this report, we demonstrate an approach for in-situ characterization of phase transitions of ultrathin nickel silicides using 3D medium-energy ion scattering. The technique provides simultaneously depth-resolved composition and real-space crystallography of the silicide films using a single sample and with a non-invasive probe. We show, for 10 nm Ni films on Si, that their composition follows a normal transition sequence, such as Ni-Ni2Si-NiSi. However, the transition process is significantly different for samples with initial Ni thickness of 3 nm. Depth-resolved crystallography shows that the Ni films transform from an as-deposited disordered layer to an epitaxial silicide layer at the temperature of ~290 °C, significantly lower than previously reported. The high depth resolution of the technique permits us to determine the composition of the ultrathin films to be 38% Ni and 62% Si.
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| 7. |
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| 8. |
- Wolf, Philipp Mika, 1994-
(författare)
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Synthesis and In Situ ToF-LEIS Analysis of Ultrathin Silicides and Ti-based Films
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thin films and coatings play a significant role in today’s society, with applications in electronics, optics, mechanics, and biomedicine. Further advancement in the field of surface coatings requires a good understanding of the unique features of ultrathin films and surfaces, which can only be reached with analysis techniques capable of resolving composition and morphology on a sub-nm scale.Time-of-flight low-energy ion scattering (ToF-LEIS), is such a method, with the surplus of non-destructive analysis. This thesis is devoted to demonstrating the use of in situ ToF-LEIS in the study of ultrathin film synthesis and surface modification. To showcase the possibilities offered by ToF-LEIS, two studies are presented: (1) The study of the phase transition of ultrathin nickel silicides and (2) the study of Ti-based coatings exposed to oxygen at elevated temperatures.In the first study, the growth and the phase transition sequence of Ni on Si(100) are investigated for initial film thicknesses below 4 nm. A partially ordered film with composition equivalent to Ni2Si is found for room-temperature deposition. Further, an unprecedented direct phase transition from orthorhombic δ-Ni2Si to epitaxial NiSi2-x, skipping the NiSi phase present in thicker films, is observed at 290 °C. This direct phase transition is explained by an enhanced interfacial effect between the substrate and the silicide for ultrathin films.The second study contains the in situ investigation of effects of low amounts of oxygen and high temperature on four coatings, in situ grown Ti as well as ex situ grown Ti, TiN, and (Ti,Al)N. On the ex situ samples, a persistent surface oxide layer is found, not removable by ion sputtering, limiting the effects of further oxygen exposure compared to the in situ sample. The nitride samples show a high stability towards further oxidation even at elevated temperatures. Additionally, the formation of an Al-rich surface layer is observed on (Ti,Al)N above 750 °C.
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