5,806 research outputs found

    1. Helgoland Power and Energy Conference - 24. Dresdener Kreis 2023

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    Der Sammelband "1. Helgoland Power and Energy Conference" beinhaltet neben einem kurzen Bericht zum 24. Treffen des Dresdener Kreises 2023 wissenschaftliche Beiträge von Doktoranden der beteiligten Hochschulinstitute zum Thema Elektroenergieversorgung. Der Dresdener Kreis setzt sich aus der Professur für Elektroenergieversorgung der Technischen Universität Dresden, dem Fachgebiet Elektrische Anlagen und Netze der Universität Duisburg-Essen, dem Fachgebiet Elektrische Energieversorgung der Leibniz Universität Hannover und dem Lehrstuhl Elektrische Netze und Erneuerbare Energie der Otto-von-Guericke Universität Magdeburg zusammen und trifft sich einmal im Jahr zum fachlichen Austausch an einer der beteiligten Universitäten

    Enhancing grid-forming converters control in hybrid AC/DC microgrids using bidirectional virtual inertia support

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    This paper presents a new grid-forming strategy for hybrid AC/DC microgrids using bidirectional virtual inertia support designed to address weak grid conditions. The stability of hybrid AC/DC microgrids heavily relies on the AC mains frequency and the DC-link voltage, and deviations in these factors can lead to undesirable outcomes such as load curtailments and power system congestions and blackouts. This paper introduces a unique approach that leverages bidirectional virtual inertia support to enhance the stability and reliability of hybrid AC/DC microgrids under weak grid conditions. The proposed strategy employs virtual inertia as a buffer to mitigate rapid changes in DC-link voltage and AC frequency, thereby enhancing system stability margins. This strategy significantly contributes to a more stable and reliable grid operation by reducing voltage and frequency fluctuations. A standard hybrid AC/DC microgrid configuration is used to implement the bidirectional virtual inertia support, where a bidirectional interlinking converter control is adjusted to deliver inertia support to both the AC and DC subgrids. This converter utilizes the DC grid voltage and AC grid frequency as inputs, effectively managing active power balance and implementing auxiliary functions. Extensive simulations are conducted under weak grid conditions and standalone mode to validate the effectiveness of the proposed strategy. The simulation results demonstrate a remarkable improvement in frequency nadir, rate-of-change-of-frequency (RoCoF), and DC bus voltage deviation in the hybrid AC/DC microgrids. The bidirectional virtual inertia support substantially reduces voltage and frequency fluctuations, enhancing the microgrid stability and resilience. There is an improvement of over 45% and 25% in the frequency deviation and voltage deviation, respectively, achieved through implementing the proposed control strategy

    RF Energy Harvesting Techniques for Battery-less Wireless Sensing, Industry 4.0 and Internet of Things: A Review

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    As the Internet of Things (IoT) continues to expand, the demand for the use of energy-efficient circuits and battery-less devices has grown rapidly. Battery-less operation, zero maintenance and sustainability are the desired features of IoT devices in fifth generation (5G) networks and green Industry 4.0 wireless systems. The integration of energy harvesting systems, IoT devices and 5G networks has the potential impact to digitalize and revolutionize various industries such as Industry 4.0, agriculture, food, and healthcare, by enabling real-time data collection and analysis, mitigating maintenance costs, and improving efficiency. Energy harvesting plays a crucial role in envisioning a low-carbon Net Zero future and holds significant political importance. This survey aims at providing a comprehensive review on various energy harvesting techniques including radio frequency (RF), multi-source hybrid and energy harvesting using additive manufacturing technologies. However, special emphasis is given to RF-based energy harvesting methodologies tailored for battery-free wireless sensing, and powering autonomous low-power electronic circuits and IoT devices. The key design challenges and applications of energy harvesting techniques, as well as the future perspective of System on Chip (SoC) implementation, data digitization in Industry 4.0, next-generation IoT devices, and 5G communications are discussed

    EXTENDABLE HIGH-GAIN DC-DC CONVERTER FOR STORAGE BATTERY AND PHOTOVOLTAIC CELL

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    DC-DC converters with significant gain, ripple-free input current, and shared ground are required to elevate the output voltages of batteries, fuel cells, and Photovoltaic sources. The proposed topology utilizes a solitary switch to control the circuit and it has additional inculpation of a voltage doubler cell at the load side, a switch capacitor cell in the middle, and a quadratic cell at the output side. These cascaded configurations lead to significant voltage gains at moderate duty cycle rates. Additionally, the voltage stress over the power components is negligible, coming in under one-third of the resultant voltage. Moreover, the number of cells at the input and output side can be extended to obtain high voltage according to the requirements of the load. The gain in voltage, efficiency, and normalized voltage stress of the semiconductor elements in the circuit are examined concerning other solutions found in the literature. Eventually, photovoltaic and battery sources were included to analyze the proposed topology to confirm the circuit’s multifaceted functionality. The circuit was developed for 270 W, 440 V output from 36 V input, and a 40 kHz switching pulse was used to drive the switch. The theoretical and simulation analysis states that incorporating photovoltaic and other sources did not deteriorate the transformation efficiency. Simulink and PSIM analysis found that the circuit successfully transferred  power from source to load. ABSTRAK: Penukar DC-DC yang mempunyai gandaan ketara, input arus bebas riak dan pembumi berkongsi penting bagi meningkatkan voltan keluar bateri, sel bahan api dan sumber fotovolta. Topologi yang dicadangkan ini menggunakan suis tersendiri bagi mengawal litar dan ia mengandungi sel pendua voltan tambahan bagi menghentikan arus di bahagian beban, sel suis kapasitor di tengah dan sel kuadratik di bahagian voltan keluar. Konfigurasi berturutan ini membawa kepada gandaan voltan ketara pada kadar kitar tugas sederhana. Tambahan, tekanan voltan ke atas komponen kuasa boleh diabaikan, iaitu satu pertiga daripada voltan terhasil. Selain itu, bilangan sel di bahagian kemasukan dan keluaran arus boleh dilanjutkan bagi mendapatkan voltan tinggi mengikut keperluan beban. Gandaan voltan, kecekapan dan tekanan voltan ternormal pada bahan dalam litar semikonduktor diperiksa dengan menyamai penyelesaian lain yang ditemui dalam kajian terdahulu. Akhirnya, sumber fotovolta dan bateri dimasukkan bagi menganalisis topologi yang dicadangkan bagi mengesahkan fungsi pelbagai rupa litar. Litar yang dibangunkan ini digunakan pada kuasa 270 W, pada aras voltan 440 V dengan kemasukan voltan 36 V dan suis operasi berfrekuensi 40 kHz. Analisis teori dan simulasi menyatakan bahawa gabungan fotovolta dan sumber lain tidak mengurangkan kecekapan transformasi. Analisis Simulink dan PSIM mendapati litar ini berjaya memindahkan 95% kuasa dari sumber kepada beban

    Hybrid fuel cell-supercapacitor system: modeling and energy management using Proteus

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    The increasing adoption of electric vehicles (EVs) presents a promising solution for achieving sustainable transportation and reducing carbon emissions. To keep pace with technological advancements in the vehicular industry, this paper proposes the development of a hybrid energy storage system (HESS) and an energy management strategy (EMS) for EVs, implemented using Proteus Spice Ver 8. The HESS consists of a proton exchange membrane fuel cell (PEMFC) as the primary source and a supercapacitor (SC) as the secondary source. The EMS, integrated into an electronic board based on the STM32, utilizes a low-pass filter algorithm to distribute energy between the sources. The accuracy of the proposed PEMFC and SC models is validated by comparing Proteus simulation results with experimental tests conducted on the Bahia didactic bench and Maxwell SC bench, respectively. To optimize energy efficiency, simulations of the HESS system involve adjusting the hybridization rate through changes in the cutoff frequency. The analysis compares the state-of-charge (SOC) of the SC and the voltage efficiency of the fuel cell (FC), across different frequencies to optimize overall system performance. The results highlight that the chosen strategy satisfies the energy demand while preserving the FC’s dynamic performance and optimizing its utilization to the maximum

    Modeling the battery parameters that effect the fault current of a feeding BESS in LV grids

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    The popularity of renewable energy makes the use of battery energy storage systems (BESS) in the grid very attractive. BESS can support the intermittent power output of renewable energy sources. BESS can also provide a support during and after grid failure and even provide black-start capability in case of a blackout. Li-ion batteries are mainly used for these BESS because of their high energy density. In this thesis, the parameters affecting on the fault current of the battery in a BESS are modeled. In most studies around BESS, the inverter has gotten more attention than the battery part. However, the battery part behaves different than a simple DC voltage source. It is evaluated to what extent the behaviour of the battery affects the fault current fed by a BESS. The focus is on the open-circuit voltage (OCV) and internal resistance (Rint) of the battery. The state of charge (SoC), operating temperature, C-rate and state of health (SoH) of the battery affect this voltage and resistance. The behavior of the inverter is also taken into account to get a realistic BESS model. The developed model uses only data available in the manufacturer’s datasheets and information from existing studies. Today, a general fault model already exists for conventional generators, e.g., synchronous generators, but for inverter-based distributed energy resources (IBDER), e.g. BESS, there is not yet a generally accepted model for fault current calculations. There is a great need for simplified fault current models in the industry. These fault models are needed to get the overall dynamic fault response. One possible application is the sizing of overcurrent protection devices. If a BESS feeds in island mode, the available fault current will often be smaller due to the sensitive components that can handle less fault current than robust synchronous or asynchronous machines. These robust generators can provide high short-circuit currents for a short amount of time. The BESS model is incorporated into a simulation software program, here Matlab Simulink, to perform simulation

    Design and Implementation of a single switch high gain boost topology : Structure, Ripple Control and ZCS

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    The need for high gain DC-DC converters has lately increased in tandem with the utilization of renewable energy supplies. Particularly appealing are high gain converters that do not require the inclusion of extra power switches and/or other passive elements to the system. As a result, this study proposes a non-isolated single switch converter with ultra-high voltage gain (UHG) that is appropriate for most renewable energy conversion systems, like solar installations. With only a single MOSFET working within a suitable duty cycle region, the proposed converter provides significant voltage gain and around 95% efficiency. Moreover, the MOSFET in this UHG converter is turned on in zero current switching (ZCS) mode, resolving the diode recovery issue. The recommended UHG converter’s working modes, steady-state parametric study, circuit variables like voltage stress on switching devices, and converter gain are all thoroughly explained. Comparisons have been done with comparable topologies presented in the literature, and lastly, experimental results depending on 200W (20V input, 320V output voltage) are given to validate the operation of the proposed UHG design.publishedVersionPeer reviewe

    Laser Technologies for Applications in Quantum Information Science

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    Scientific progress in experimental physics is inevitably dependent on continuing advances in the underlying technologies. Laser technologies enable controlled coherent and dissipative atom-light interactions and micro-optical technologies allow for the implementation of versatile optical systems not accessible with standard optics. This thesis reports on important advances in both technologies with targeted applications ranging from Rydberg-state mediated quantum simulation and computation with individual atoms in arrays of optical tweezers to high-resolution spectroscopy of highly-charged ions. A wide range of advances in laser technologies are reported: The long-term stability and maintainability of external-cavity diode laser systems is improved significantly by introducing a mechanically adjustable lens mount. Tapered-amplifier modules based on a similar lens mount are developed. The diode laser systems are complemented by digital controllers for laser frequency and intensity stabilisation. The controllers offer a bandwidth of up to 1.25 MHz and a noise performance set by the commercial STEMlab platform. In addition, shot-noise limited photodetectors optimised for intensity stabilisation and Pound-Drever-Hall frequency stabilisation as well as a fiber based detector for beat notes in the MHz-regime are developed. The capabilities of the presented techniques are demonstrated by analysing the performance of a laser system used for laser cooling of Rb85 at a wavelength of 780 nm. A reference laser system is stabilised to a spectroscopic reference provided by modulation transfer spectroscopy. This spectroscopy scheme is analysed finding optimal operation at high modulation indices. A suitable signal is generated with a compact and cost-efficient module. A scheme for laser offset-frequency stabilisation based on an optical phase-locked loop is realised. All frequency locks derived from the reference laser system offer a Lorentzian linewidth of 60 kHz (FWHM) in combination with a long-term stability of 130 kHz peak-to-peak within 10 days. Intensity stabilisation based on acousto-optic modulators in combination with the digital controller allows for real-time intensity control on microsecond time scales complemented by a sample and hold feature with a response time of 150 ns. High demands on the spectral properties of the laser systems are put forward for the coherent excitation of quantum states. In this thesis, the performance of active frequency stabilisation is enhanced by introducing a novel current modulation technique for diode lasers. A flat response from DC to 100 MHz and a phase lag below 90° up to 25 MHz are achieved extending the bandwidth available for laserfrequency stabilisation. Applying this technique in combination with a fast proportional-derivative controller, two laser fields with a relative phase noise of 42 mrad for driving rubidium ground state transitions are realised. A laser system for coherent Rydberg excitation via a two-photon scheme provides light at 780 nm and at 480 nm via frequency-doubling from 960 nm. An output power of 0.6 W at 480 nm from a single-mode optical fiber is obtained . The frequencies of both laser systems are stabilised to a high-finesse reference cavity resulting in a linewidth of 1.02 kHz (FWHM) at 960 nm. Numerical simulations quantify the effect of the finite linewidth on the coherence of Rydberg Rabi-oscillations. A laser system similar to the 480 nm Rydberg system is developed for spectroscopy on highly charged bismuth. Advanced optical technologies are also at the heart of the micro-optical generation of tweezer arrays that offer unprecedented scalability of the system size. By using an optimised lens system in combination with an automatic evaluation routine, a tweezer array with several thousand sites and trap waists below 1 μm is demonstrated. A similar performance is achieved with a microlens array produced in an additive manufacturing process. The microlens design is optimised for the manufacturing process. Furthermore, scattering rates in dipole traps due to suppressed resonant light are analysed proving the feasibility of dipole trap generation using tapered amplifier systems

    Experimental and Theoretical Studies of Unstable Dynamics of Caltech’s Plasma Jet: X-Rays, Ultraviolet, and Visible Light

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    The Caltech plasma jet experiment launches a laboratory plasma jet that is analogous to an astrophysical jet. Even though the temperature of the plasma jet is around 2 eV, 6 keV X-rays and 20--60 eV extreme ultraviolet (EUV) radiation were detected when the plasma jet was perturbed by magnetohydrodynamic instabilities. How charged particles in a plasma are accelerated to suprathermal energy has been a key question in plasma physics, solar physics, and astrophysics. Studying these surprisingly energetic radiations from Caltech’s plasma jet can help answer this question. Toward this goal, this thesis contains an experimental study of the X-rays and a theoretical study of the EUV radiation. In the experimental study, a PIN-diode-based 1D X-ray camera has been developed to spatially, temporally, and spectrally resolve the transient, low-intensity, and suprathermal X-rays detected to be simultaneous with magnetohydrodynamic instabilities that disrupt the plasma jet. This X-ray camera has high detection efficiency over the 5–10 keV X-ray band, an over 20-degree field of view (FOV), and the capability to produce more than 50 time-resolved frames with a submicrosecond time resolution. The X-ray images are formed by a pinhole or by a coded aperture placed outside the vacuum chamber in which the plasma jet is launched. The 1D imaging shows that the location of the X-ray source is either a few centimeters away from an inner disk electrode or near a spatially translatable metal frame that is 30–40 cm away from the electrode. In the theoretical study, we propose a collisional two-fluid model which involves a novel two-stream instability that is indifferent to collisions, even though collisions have been traditionally presumed to damp the two-stream instability. This model is used to explain previously observed localized dimming of visible light and a simultaneous, localized burst of EUV radiation from a plasma jet the cross section of which is constricted by a kink-instigated Rayleigh-Taylor instability. On being triggered by the constriction of the plasma cross section, the proposed two-stream instability produces a region of low density where an electric double layer leads to localized electron heating. The low-density region is consistent with and so likely explains the visible light dimming, and the localized electron heating is consistent with and likely explains the EUV radiation. The numerical solution of the collisional two-fluid model demonstrates good agreement with the apparent electron velocity and density profiles in the plasma jet.</p
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