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© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. ; This work presents a methodology for the time-frequency characterization of the switching losses in Gallium Nitride Field Effect Transistors used in power electronics applications, particularly in DC-DC converters. Typically, switching losses are measured in the time-domain through the integration of the instantaneous power, that is, the product of the voltage multiplied by the current, during the turn-on and turn-off transients. Nonetheless, as novel power transistors allow for switching times in the nanosecond range, the accuracy of such measurements is compromised by the limitations of the probe-oscilloscope systems in terms of bandwidth and dynamic range. Here, we analyze the time-domain switching loss measurement method, and then, through a complementary setup it is demonstrated how to validate the results in the frequency domain. A DC-DC half-bridge buck converter circuit based in the EPC2001C was used as representative test sample. Less than 1% of difference in critical parameters such as rise-time, pulse width, state-levels and, switching frequency, is encountered between the time and frequency domain approaches. Moreover, the measurement uncertainty is analyzed and estimated to be between 1% and 8%. This work allows for highly confident switching loss measurements, a better understanding of the switching phenomena and of the measurement system performance. ; This research work is carried in the framework of the 16ENG06 ADVENT project. This project, 16ENG06 ADVENT, has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. ...

This dissertation embraces the development and the realization of a 1-MW Multi-PhysicsPower Hardware in the Loop setup for the testing of wind energy converter nacelles at RWTH Aachen University. Moreover, results from the commissioning and the first testphase of the installation are depicted. The background of wind energy in general, the current conditions of legislative regulations, and the state of the art technologies in use forwind energy converters are included in this research study. In addition, the change of theelectrical power grid due to the increasing share of renewable power generation is illustrated and suggestions which currently are discussed for addressing the resultingproblems in grid operation are presented.This study characterizes the advantages and technical aspects of Hardware in the Loopi nvestigation with focus on Multi-Physics Power Hardware in the Loop. Furthermore, its use for the certification and testing of wind turbine nacelles with emphasis on test-benchbasedexamination of nacelles is delineated. Examples of interfaces for power-level Hardware in the Loop testing are given. Firstly, a flexible interface solution for the testing of components at household power levels is introduced that has been developed at the Institute ACS. Secondly, the challenges of power-level interfaces for high power test benches are depicted. Moreover, the 1-MW system-level nacelle test bench is outlined including an exposition of the involved technologies regarding the electrical as well as the mechanical and signal level domain. The test bench setup is compared to other ground-level wind turbine testing installations and the characteristics of the different approaches are evaluated. An experimental verification of the test bench completes the description of the setup. The results are analyzed and discussed. Based on the outcomes of this dissertation the method of investigating nacelles of wind energy converters on system-level test benches has been proven advantageous. In particular, the use of ...

Note: This is a preprint of paper #2074 presented at the 14th European Wave & Tidal Energy Conference (EWTEC) 2021 in Plymouth, UK. The final version of paper with the same title can be found in the EWTEC 2021 proceedings. Abstract: The majority of devices designed to extract energy from ocean waves operate through exploitation of the buoyancy (Froude-Krylov) and/or diffraction force regimes. Such devices extract energy through interaction with the displacement and/or acceleration of fluid particle motions respectively. By comparison, very little consideration has been given to systems which extract wave energy through coupling with fluid particle velocities. This paper performs a preliminary investigation into the hydrodynamics of a Wave Energy Converter (WEC) that is driven through interaction with the wave-induced fluid particle velocity. In particular, the work focuses on lift-based WECs consisting of a number of wave-driven, rotating hydrofoils. The paper develops a mathematical framework for such a system operating in regular, linear waves in 2D. It is noted that despite the unique nature of the device, it is possible to represent its operation using mathematics which are already familiar to the wave energy sector. The mathematical framework is subsequently used to investigate the performance of a pair of wave-driven, rotating hydrofoils. Results show that power capture efficiencies up to approximately 80% are potentially possible for the particular system considered under the constraints assumed. It is also found that the system is relatively insensitive to variations in design and control conditions. This suggests that further investigation is warranted to determine if lift-based WECs might represent a reasonable means of wave energy extraction. ; This work was produced as part of the LiftWEC Project. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 851885. This output reflects the views only of the author(s), and the ...

Patents on ocean wave energy dates back to 1799, however no wave energy converter (WEC) concept have a commercialised device. The cost of energy produced with wave energy converters is very high compared to traditional energy sources. Even when compared to energy from wind turbines wave energy needs cost reductions. Hence, next to political will, the main obstacle for a commercial break through of wave energy technology is the high cost of energy. Initiatives to lower costs are made in areas of minimising structural costs and increasing the energy production per device. Wave Star A/S has recently focused research on improving the power take off (PTO) system converting the mechanical motion of the floats into electricity. This has brought attention to discrete fluid power (DFP) technology, especially secondary controlled common pressure rail systems. A novel discrete PTO-system has been proposed and found feasible for the Wavestar WEC. However, with a technology shift from a continuous to a discrete fluid power PTO-system, new challenges emerge. The current project investigates and optimises the novel discrete fluid power PTO-system proposed for the Wavestar WEC. Initiating from an investigation of energy extraction by WECs utilising a discrete PTO force, an investigation of the system configuration is conducted. Hence, the configuration of the multi-chamber cylinder and the common pressure rails are investigated for the discrete fluid power force system. A method for choosing the system configuration for a given wave climate is demonstrated. From the energy extraction by WECs employing a discrete PTO force it is seen that a discrete system with relative few applicable forces may yield energy extraction levels close to that of a continuous PTO force system. The system configuration investigation show how the wave climate naturally influence the optimal system configuration yielding maximal energy output, and how one may choose the system configuration based on the installation site. The switching manifold is the control element of the secondary controlled force system. The force is controlled by connecting each of the cylinder chambers to one of the common pressure lines. Bidirectional check valves are proposed as a possible improvement of the energy conversion efficiency, since these enable passive valve shifts at a favourable low pressure difference across the switching valves. A model based feasibility study shows promising energy results for the bidirectional check valves, however, a minor increase in the force steps applied may be induced. Due to the lack of cheap and commercial large fast on/off valves and especially bidirectional check valves, the current project further includes a conceptual design of a multi-poppet on/off valve and a multi-poppet bidirectional check valve. The conceptual design is based on a theoretical investigation of valve switching time dependency on various design parameters. Finally a set of parameters are given based on dynamical simulations of the designed valves. The valves are designed with a rated flow of 1000 L/min@5 bar and the active switching time for the designed valves is seen to be less than 10 ms. A combination of on/off and bidirectional check valve are proposed for the switching manifold when designed for use in wave energy converters. Involvement in designing, installation and control of a full scale PTO test-bench has been under-taken parallel to the theoretical work. Preliminary force switching tests have been conducted to investigate the influence of valve switching time on the dynamic behaviour of the PTO-system. The results of these tests show that the pressure dynamic in the cylinder chambers and the transmission lines connecting the switching manifold and the cylinder chambers are highly influenced by the valve switching time.

IEEE Energy Conversion Congress and Exposition (ECCE) (10th, 2018, Portland, USA) ; The present work has been partially supported by the predoctoral grants program FPU for the formation in university teaching of Spain MECD under the grant IDs FPU16/06829 and FPU16/05313. This work also was supported in part by the Research, Technological Development and Innovation Program Oriented to the Society Challenges of the Spanish Ministry of Economy and Competitiveness under grant ENE2016-77919-R; by the European Union through ERFD Structural Funds (FEDER); and by the government of Principality of Asturias, under IDEPA grant 2017 Thyssen SV-PA-17-RIS3-3

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMCdc-dc) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency. However, the new requirements related to the communication, especially the high bandwidth that the LED driver must achieve, converts the design of the SMCdc-dc into a very challenging task. In this work, three different methods for achieving such a high bandwidth with an SMCdc-dc are presented: increasing the order of the SMCdc-dc output filter, increasing the number of voltage inputs, and increasing the number of phases. These three strategies are combinable and the optimum design depends on the particular VLC application, which determines the requirements of the VLC transmitter. As an example, an experimental VLC transmitter based on a two-phase buck converter with a fourth-order output filter will demonstrate that a bandwidth of several hundred kilohertz (kHz) can be achieved with output power levels close to 10Wand power efficiencies between 85% and 90%. In conclusion, the design strategy presented allows us to incorporate VLC into SSL, achieving high bit rates without damaging the power efficiency of LED lighting ; This work has been supported by the Spanish Government under Project MINECO-15-DPI2014-56358-JIN, the scholarship FPU14/03268 and the Principality of Asturias under the Project SV-PA-17-RIS3-4 and by European Regional Development Fund (ERDF) grants

This study presents a fully differential dynamic comparator with low kickback noise, an effect caused by voltage variations in the regeneration nodes of these types of circuit. Given their low power dissipation, dynamic comparators are key circuits in analog-to-digital converters (ADCs), especially in pipelined ADCs. The proposed comparator has been simulated and compared with three other comparator topologies. The value of the kickback noise generated by the proposed circuit is lower than that generated by other conventional dynamic comparators over a wide input range, while simultaneously showing a low offset voltage error. The dynamic comparator has been implemented in a low-resolution ADC with a resolution of 2.5 effective bits, which has been prototyped in a 0.35-𝜇m CMOS AMS C35B4 process. Its size is 34 𝜇m × 38 𝜇m. ; This work has been partially funded by Spanish government projects TEC2015‐66878‐C3‐2‐R (MINECO/FEDER, UE) and RTI2018‐097088‐B‐C33 (MINECO/FEDER, UE).

2019 Energy Conversion Conference and Exposition (ECCE 2019) (2019. Baltimore) ; The present work has been partially supported by the predoctoral grants program FPU for the formation in university teaching of Spain MECD underthe grant IDs FPU16/06829 and FPU16/05313. This work also was supported in part by the Research, Technological Development and Innovation Program Oriented to the Society Challenges of the Spanish Ministry of Economy and Competitiveness under grant ENE2016-77919-R; by the European Union through ERFD Structural Funds (FEDER); and by the government of Princi-pality of Asturias, under IDEPA grant 2017 Thyssen SV-PA-17-RIS3-3

High-Brightness Light Emitting Diodes (HB-LEDs) are considered the future trend in lighting not only due to their high efficiency and high reliability, but also due to their other outstanding characteristics: chromatic variety, shock and vibration resistance, etc. Nevertheless, they need the development of new power supplies especially designed for boosting and taking advantage of their aforementioned characteristics. Besides, their behaviour is completely different from the rest of lighting devices and, consequently, it should be also taken into account in the design of the converters used to drive them. As a result, many well-known topologies have been optimized or redesigned in order to be used in LED–lighting applications and many new topologies have come up in the recent years with the same purpose. In this paper, the main HB-LED characteristics will be explained, highlighting how they influence the design of their power supplies. After, the main topologies will be presented from the simplest to the most complex ones, analysing their advantages and disadvantages ; This work has been supported by Spanish Government under projects RUE-10-CSD2009-00046 FEDER Funds, MICINN10-DPI2010-21110-C02-01 and student grant FPI BES-2011-044114

ENERGIES 2019 journal paper published as part of the EnFAIT and OPERA projects funded by European Union (EU) Horizon 2020 funding.