AC Applications Research Articles

Unobstructive and safe-to-wear watt-level wireless charger

A wearable microgrid that centralizes and distributes harvested energy across different body regions can optimize power utilization and reduce overall battery weight. This setup underscores the importance of developing cable-free wireless power transfer (WPT) systems for mobile and portable devices to eliminate the risks posed by wired connections, especially in dynamic and hazardous environments. We introduce a thin, stretchable, and safe hand band capable of watt-level wireless charging through the widely adopted Qi protocol operating at 130 kHz. The implementation of non-adhesive fabric encapsulation serves to protect the 50-μm-thin spiral copper antenna from mechanical strain, ensuring an overall hand band stretchability of 50%. We also create a stretchable “Ferrofabric”, characterized by a magnetic permeability of 11.3 and a tensile modulus of 75.3 kPa, that provides magnetic shielding for the antenna without compromising wearability. The “Ferrofabric” improves the coil inductance but induces core loss in AC application. By fully understanding and managing loss mechanisms such as the skin effect, proximity effect, core loss, and joule heating, we achieve a wireless charging efficiency of 71% and power delivery of 3.81 W in the kHz frequency range. Our WPT hand band is unobstructive to hand motion and can charge a handheld smartphone as fast as a desktop charger or power a battery-free chest-laminated e-tattoo sensor, with well-managed thermal and electromagnetic safety. Through a holistic electromagnetic, structural, and thermal design, our device culminates in a safe, rugged, and versatile solution for wearable WPT systems.

Comparative investigation on carbon dots and chloride fluxes modified ZnAl2O4:Cr3+ nanophosphors for temperature sensing, cutting-edge forensic, anti-counterfeiting and w-LEDs applications

A novel Cr3+ doped ZnAl2O4 is synthesized by grafting carbon dots (CDs) and chloride fluxes (NaCl, KCl, NH4Cl) through the solid-state reaction method. Upon excitation at 530 nm wavelength, the Cr3+ ions in the ZAO NPs emit red light due to the influence of a strong crystal field. This red emission arises from the electric dipole 2Eg→4A2g of the Cr3+ ions. Among the chloride fluxes examined, NH4Cl had a significant impact on the PL intensity. Notably, when CDs are incorporated into the ZAO:7Cr3+/NH4Cl NPs, a remarkable increase of 17.25-folds in photoluminescence (PL) intensity is observed. This enhancement is substantially higher than that of CDs alone (11.23-folds) and NH4Cl alone (3.82-folds). The increased PL intensity is attributed to the Förster resonance energy transfer (FRET) mechanism. Furthermore, the addition of CDs (5 wt.%) enhanced the colour purity (CP) of ZAO:7Cr3+/NH4Cl NCs to 99.8%, achieving a high Internal quantum efficiency (IQE) of 93.4 %. Notably, the CDs (5 wt.%)@ZAO:7Cr3+/NH4Cl NCs maintained 92.43 % of their emission intensity even at 420 K, demonstrating exceptional thermal stability compared to ZAO:7Cr3+ NPs. Moreover, the NPs holds promise for optical thermometry, boasting a high relative sensitivity (Sr) of 6.74 × 10–2 %K-1 across a temperature range spanning from 300 to 480 K. Moreover, the latent fingerprints (LFPs) developed using CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs demonstrate remarkable selectivity and high contrast. Under UV irradiation, the structural features of LFPs at levels I–III are clearly visible. In addition, the strong red fluorescence emitted by CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs makes them suitable for applications in AC. CDs(5 wt.%)@ZAO:7Cr3+ NCs exhibit significant potential for w-LED fabrication, achieving a correlated colour temperature (CCT) of 5517 K, a CIE coordinate of (0.332, 0.331), and a high colour rendering index (CRI) of Ra = 94, outperforming ZAO:7Cr3+/NH4Cl NPs. Overall results clearly demonstrates that, CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs are effective for applications in optical thermometry, dactyloscopy, w-LEDs, and AC.

Fault-Tolerant Multiport Converter for Hybrid Distribution Systems: Configuration, Control Principles and Fault Analysis

Multiport converters (MCs) are widely adopted in many applications, from renewable energy sources and storage integration to automotive applications and distribution systems. They are used in order to interface different energy sources, storage devices and loads with one single, simple converter topology in contrast to the traditional approach, which can require different solutions made by two-port converters. MCs allow for a reduction in the number of components and cascaded conversion stages with respect to an equivalent system of two-port converters, resulting in reduced complexity, dimensions and costs, as well as in improved reliability and enhanced efficiency. Nevertheless, some aspects related to the design of MCs are still worth further discussion when MCs are applied to hybrid AC/DC distribution systems. First, most converters are developed for one specific application and are not modular in structure. Furthermore, many of the proposed solutions are not equally suitable for AC and DC applications and they can introduce significant issues in hybrid distribution systems, with earthing management being particularly critical. Even though most available solutions offer satisfying steady-state and dynamic performances, fault behavior is often not considered and the possibility of maintaining controllability during faults is overlooked. Building on these three aspects, in this paper, a new MC for hybrid distribution systems is presented. An innovative circuit topology integrating three-phase AC ports and three-wire DC ports and characterized by a unique connection between the AC neutral wire and the DC midpoint neutral wire is presented. Its control principles and properties during external faults are highlighted, and extensive numerical simulations support the presented discussion.

DESIGNING OF DC GRID SOLAR-WIND HYBRID POWER GENERATION SYSTEM

Our project's main goal is to create a prototype hybrid renewable energy system that mixes solar and wind power. The system's goal is to directly feed energy from the turbine and solar panels into the DC grid. An inverter is also integrated to provide AC power. Our strategy emphasizes efficiency and simplicity by acquiring both AC and DC electricity from the project. Utilizing the complementing qualities of solar and wind energy, we want to develop a dependable and sustainable power generation system. We hope to show that combining renewable energy sources and maximizing energy output for both AC and DC applications is feasible with this creative design. Key Words: Dc grid, solar power generation, wind power generation, batteries, hybrid power generation

Оптимизация ВТСП кабелей постоянного и переменного тока с учетом эффекта продольного магнитного поля

It is known that in magnetic fields parallel to the transport current, an increase of the critical current is observed in most low-temperature and high-temperature superconductors — the effect of a longitudinal magnetic field (LMFE). LMFE has been theoretically predicted and experimentally confirmed in many studies. This article presents various methods for optimizing power coaxial cables based on high-temperature superconductors (HTS), considering LMFE. LMFE provides a higher current-carrying capacity of HTS DC cables and higher stability for HTS power AC cables, including lower AC losses. The results of optimization of HTS cables for both DC and AC applications with consideration of LMFE are presented and discussed. Two methods for calculating the magnetic field in coaxial HTS cables are presented: analytical and using the finite element method. The results of AC loss calculations and measurements for HTS cables are also presented.

Application of natural solar photocatalytic and DSSC's studies AC loaded on Ag–In2O3 nanoparticles by hydrothermal approach

Contaminants are repeatedly being released into the land, water and air about the world as a consequence of the high levels of human movement and development, which causes a fast an increase in the growing of pollution. In this assessment, activated charcoals supported on Ag–In2O3 nanomaterials were blended by hydrothermal system. The morphology constitution, surface assets and optical description of synthesized nanomaterials were characterized by XRD, UV-DRS, PL, HR-SEM and EDAX, HR-TEM, SAED pattern, FT-IR, XPS, BET, CV and VSM techniques. The optimized heterogeneous catalyst AC/Ag–In2O3 depicts high electro catalytic activity, fast-charge transport development, weak ferromagnetism, brilliant accessibility and stability for Rh6G dye degradation, which is endowed for application in the alkaline medium. The prepared photocatalytic activity towards AC/Ag–In2O3 have been revealed as the degradation of Rhodamine 6G (Rh6G) dye in the presence of aqueous solution directed to solar light irradiation. AC/Ag–In2O3 is initiated to maintain some more efficient than synthesized Ag–In2O3 and In2O3 by pH9 positively mineralizing of Rh6G dye under sun light irradiation. The mineralization of Rh6G dye has been confirmed by measuring COD analysis. It is suggested that Rh6G degrades in the presence of solar light via a particular mechanism, which was discovered that the catalyst remained more stable and reusable. It has been effectively determined that the AC/Ag–In2O3 nanomaterial achieves photocatalytic effects.

Experimental DTC of an Induction Motor Applied to Optimize a Tracking System

In recent years, the areas of industrial application of high performance AC drives, especially the induction motor (IM), based on Direct Torque Controller (DTC) technique has gradually increased due to its advantages over the other techniques of control. Among these applications are cited, propulsion and tracking systems. This work presents the experimental part of a research project conducted by the authors where they have implemented an algorithm for a DTC in order to achieve a tracking system designed for a series of solar panels to maximize its overall efficiency. In this paper, three different switching tables are presented for choosing the best between them for a less fluctuation in torque. This study is justified by reduced cost of implementation compared to other methods that require the use of expensive hardware and complicated control techniques. The tests were carried out under the same conditions with the same equipment of the testbed, to get a good comparative study. Three variants were tested: simple switching table, table of sectors shifted by 30 ° and a table with 12 sectors. The results show an improvement, but a dilemma between the torque ripple and those of the stator flux.

Technology Optimisation of Hybrid PV Systems for Covering Energy Needs of Emergency Shelters for Ukrainian War Refugees

Hybrid photovoltaic systems have become a common solution for decreasing energy consumption for specific objects and customers at present time. The efficiency of the entire system depends strongly also on the technology of the used battery inverter. In general, DC-coupled inverters are recognized to be more energy efficient. Surprisingly, in some specific cases, AC-coupled systems can offer better results. Ukraine escalates the problem with internal migration, that can be solved just through constructing new communities of emergency shelters. Integrating these units into Ukrainian overloaded and damaged distribution grids must be projected very precisely to limit not just power consumption but also power injection. Particular savings can be reached with the proper application of AC or DCcoupled systems. This article describes that phenomenon presented on specific real cases defined through own consumption profile, battery storage system management, climate conditions, and PV system design. The presented results show that the proper choice of battery inverter technology can save interesting amount of energy produced from the installed PV system. The AC coupled system can offer not just higher flexibility and modularity, but also higher energy efficiency of the hybrid system, lower grid feed-in.

Design of H5 Transformerless Inverter for Photovoltaic System

There are two distinct categories of sources for generating electrical power: conventional and non-conventional. At now, traditional sources such as coal, gas, and nuclear power are widely employed for the purpose of electricity generation; nevertheless, they are associated with detrimental environmental consequences. Therefore, it is crucial to utilize renewable energy sources like sun and wind to provide some of the necessary electrical power. The driving force behind this transition is the imperative for clean energy, the mitigation of greenhouse gas emissions, and the capacity to create electricity in geographically isolated regions. A proposed solution for using solar energy in single-phase AC applications involves the implementation of an H5 converter topology. The proposed architecture employs twin input DC-DC boost converters, which incorporate solar panels and batteries, to manage the desired output DC voltage. The H5 topology has notable suitability for single-phase transformerless inverters in AC applications encompassing low and high-power demands, owing to its capacity to effectively mitigate leakage current. In order to evaluate the viability of the suggested methodology, a MATLAB simulation is performed to simulate the complete procedure. Furthermore, the development of a prototype is underway in order to assess and verify the performance and outcomes of the converter. The simulation will be conducted with either the MATLAB.

Dynamic Analysis, Stability and Design of Grid Forming Converters With PI-Based Voltage Control in DC and 3-Phase AC Microgrids

This paper analyzes the dynamic behavior of the voltage control loop based on proportional-integral regulators, commonly used for grid-forming converters in 3-phase AC and DC Microgrids and applications that involve a DC-link voltage control. The paper proposes a simple and accurate generalized analysis useful both for the system characterization and design. Two different control schemes, based on linear (Direct Voltage Control, DVC) and quadratic voltage feedback (Quadratic Voltage Control, QVC), are analytically studied, simulated and experimentally tested, demonstrating a superior performance of the QVC under the presence of constant power loads. The operation limits, the system stability and the disturbance rejection capability are analyzed considering the effect of control and plant parameters and the effect of the different types of disturbances and the operating point, taking into account the non-linearities of the system. The analysis is mainly focused on the effect of constant power loads given their negative impact on the system performance. The study provides a generic procedure for the analysis and design of proportional-integral voltage controllers, including the selection of the system capacitance for meeting specific dynamic specifications while considering system characteristics as the load level, the stability margins and the maximum voltage deviation under disturbances.

Application of AC superimposed DC waveforms to bismuth electrorefining

Electrorefining in molten salts is used for purifying actinides. Optimizing electrorefining is key to minimizing processing time and radiological waste. One possible way of improving electrorefining efficiency is using an AC superimposed DC waveform. This waveform has demonstrated potential benefits in aqueous solutions but has never been utilized in a molten metal, molten salt application. This work investigates the effects of using an AC superimposed DC waveform on molten bismuth electrorefining in a molten LiCl–KCl–CaCl2 eutectic. Bismuth has been identified as a potential surrogate for plutonium electrorefining and a potential cathode in electrorefining used nuclear fuel (UNF). All electrorefining runs resulted in a high purity cathode ring and high yield with exception of the run using a low-frequency, high-amplitude superimposed AC waveform, which experienced some contamination and a lower yield. The other three AC superimposed DC runs experienced an average yield 6.7 % higher than the average yield of the DC runs. The electrorefining run using the high-frequency, high-amplitude superimposed AC signal had the highest yield. It is recommended in future studies to investigate the statistical variability of electrorefining yield and current efficiency and the impact of AC superimposed DC waveforms on solidified bismuth anodes.

Modulation of pore structure in a microporous carbon for enhanced adsorption of perfluorinated electron specialty gases with efficient separation

Physical adsorption-based separation and recovery of perfluorinated electron specialty gases from N2 contribute to reducing the greenhouse effect and increasing economic value in the electronics industry. Commercial activated carbon materials are promising adsorbents for the practical application due to the industrial-scale production, while they usually characterize an unsatisfactory micropore structures, and the rational modulation to meet the requirement of fluorinated gas adsorption is in demand. In this work, a series of KOH-treated commercial activated carbon (ACK) with KOH/carbon mass ratios of 1 ∼ 4 were systematically characterized and evaluated for adsorptive separation of SF6, NF3, and CF4. Characterization results reveal that KOH treatment largely promotes the modulation of pore structure and results in the extremely narrow pore size distribution at 0.5 ∼ 0.9 nm, highest microporosity of 97.6 % in the optimal ACK1, which are ascribed to etching effect of KOH on carbon framework. Static adsorption results indicate that a simultaneous enhancement in gas uptake and separation selectivity is found in ACK1 compared to the parent AC for all the studied fluorinated gases. Importantly, ACK1 performs a high SF6 uptake of 3.10 mmol·g−1 and the record SF6/N2 selectivity of 683.9 (298 K, 100 kPa) among the reported carbon adsorbents, which is comparable to the top-performing MOFs material. The kinetic adsorption and dynamic breakthrough experiments further verify the fast adsorption rate, excellent separation performance of SF6/N2, and recyclability of ACK1 adsorbent. These findings expand the promising application of commercial AC in the adsorption-based separation of perfluorinated electron specialty gases including SF6, NF3, and CF4.

A Comparative Review of Three Different Power Inverters for DC–AC Applications

This paper presents a comparative review of three different widely used power inverters, namely the conventional six-switch inverter; the reduced switch count four-switch inverter; and the eight-switch inverter. The later inverter can be reconfigured as a neutral-point diode-clamped inverter at the failure of one inverter leg. The three power inverters are compared and discussed with respect to cost, complexity, losses, common mode voltage, and control techniques. The paper is intended to serve as a guide regarding selecting the appropriate inverter for each specific application. Simulation results are presented to demonstrate the performance of the three power inverters, followed by a comprehensive comparison between the three power inverters.

Review of Fault Diagnosis and Fault-Tolerant Control Methods of the Modular Multilevel Converter Under Submodule Failure

Modular multilevel converters (MMCs) have attracted extensive research interests in various ac and dc conversion applications due to their modular structure and excellent harmonic performance. However, the large number of power switches increases the potential risk of submodule (SM) failure, which greatly challenges the safe and reliable operation of the MMC. This paper presents a detailed review of fault diagnosis and fault-tolerant control methods of the MMC under SM failures. On this basis, comprehensive comparisons are conducted among different fault diagnosis methods, and verification results are provided to analyze the advantages and disadvantages of the popular fault-tolerant control methods. Finally, the review is concluded, and future trends and research opportunities are discussed.

Multifilament HTS Cables to Reduce AC Loss: Proof-of-Concept Experiments and Simulation

Reducing AC losses of HTS is essential for AC application since it can lower the constraint on the cryogenic cooling demand. Several studies have reported that the manufacturing of multi-filament HTS cables can reduce AC loss. However, large coupling losses were identified in the existing cables, due to the existence of coupled copper or soldering layers. We report in this paper a novel way to develop multi-filament HTS cables, mainly focusing on suppressing the coupling losses by reducing the contact resistivity within the HTS cables. Heat shrink tubes are used to directly insulate narrow HTS filaments into a cable structure. Sample cables were made with 4 mm and 2 mm wide HTS strips. Both transport losses and total AC losses in a rotational magnetic field were measured to quantify the AC loss reduction for the multi-filament HTS cables. The measurements were used to validate the modelling results, and to predict AC loss reduction for 1 mm wide HTS cable. The results showed loss reduction up to around 90% in the 1mm wide HTS cable compared with 4 mm cable. As a result, the proposed multi-filament HTS cables will have promising applications in reducing AC loss.

A Measuring System for HTS Wires and Coils Properties at Low Temperatures

The use of high temperature superconducting materials (HTS) in various applications, requires knowledge of their critical parameters like critical current, critical magnetic field and critical temperature, in DC applications like high magnetic field generators, superconducting magnetic energy storage system (SMES), magnetic resonance imaging (MRI), magnets for particle accelerators, SC Maglev trains and other applications. Also, these parameters are important for specific properties in alternating current applications like fault current limiters, transformers, generators, motors, and power transmission lines. An important characteristic that needs to be tucked into consideration for AC applications is the power losses that occur in the HTS superconducting materials, which limits the maximum performance that the superconducting materials can attain for these applications. In order to measure these characteristics, which depend on the type of material used, but also on the temperature and other parameters, it is necessary to use an appropriate setup device that allows both obtaining the working temperature range (4.2 K to 300 K and other necessary parameters like high vacuum 10-6 mbar, high current supply (500 A), high magnetic field measurement system (1-10 T), etc. For the cryogenic cooling of the entire system, a closed cycle Gifford-McMahon type cryocooler is used, with two cooling stages, stage I at 50 K and second stage at 4.2 K (liquid Helium temperature). The set-up system used for measurement of the parameters of HTS superconducting materials (YBCO, BSCCO or MgB2) and the various coils made with them, is described in this article together with its functional parameters and some experimental results obtained by testing an YBCO coils system. The maximum generated magnetic flux density was 5 T in the centre of the coils system.

Magnetization Loss Measurement of Twisted Stacked Tape Cable and Comparison With CORC

High Temperature Superconducting (HTS) cables for large current capacity are being studied in several forms for power device applications. Currently, the cables are being developed for DC applications rather than AC applications. However, if a technology for reducing AC loss is developed, it will be possible to apply HTS cables to various AC devices. Twisted Stacked-Tape Cable (TSTC) is one of the large current HTS cables. It is made by stacking and twisting multiple HTS tapes for large current capacity. The HTS tapes in TSTC should be twisted for the uniformity of current distribution in each tape. Since the HTS tape has a wide thin film shape, it is very difficult to twist itself. In this paper, we measured the magnetization losses of TSTC samples without the striations under AC magnetic fields that had peak values below 0.1 T. Several molds for the TSTC samples were made by using a 3D printer. TSTC samples had several numbers of stacked tapes and two kinds of the tape width. The magnetization losses of the samples in the molds were measured under uniform AC magnetic fields. The experimental results were compared to those of the straight HTS stacked cables and conductor on round core (CORC) cables.

Comparing Electrodynamic Losses During Transport Current Cycles in Insulated and Non-Insulated HTS Coils

So far, the No-insulation (NI) technology using High Temperature Superconducting (HTS) materials has been limited to magnetic and power devices involving slow charging rates, generally avoiding AC applications, due to the onset of transverse currents. However, the limits of applicability are not well defined and few quantitative comparisons between insulated and NI coils under time-varying regimes have been presented. A proper analysis of the AC losses under these conditions is important to assess the possible use of NI windings for fast-charging or AC devices. This paper focuses on the layer-wound configuration of NI coils, less studied in the literature than the pancake-wound configuration. The investigation aims at comparing the behavior of two coils wound from the same tape, with or without electrical insulation between turns. The two coils are characterized by a very similar geometry, with the same number of turns and layers. The AC losses are assessed by adopting appropriate experimental setups in two different laboratories. Charge-discharge tests are performed with different ramp-rates up to a peak current with a triangular or trapezoidal waveform, determining the electrodynamic losses during these current cycles. Furthermore, the windings are supplied with sinusoidal currents of different amplitude and frequency, pointing out the differences in terms of AC losses between the two coil configurations.

Activated Carbon for Sepsis Prevention and Intervention: A Modern Way of Utilizing Old Therapies

(1) Background: Uncontrolled inflammation often contributes to life-threatening sepsis sequela such as multi-organ dysfunction syndrome (MODS), and is accompanied by abnormal levels of pathological and damage-associated molecular patterns (PAMPs & DAMPs) in biological fluids. Activated carbon or charcoal (AC) of new generation with ameliorated biocompatibility has spurred renewed interest in the regulation of these toxins’ levels in inflammation states. (2) Methods: We searched PubMed, Google Scholar, ScienceDirect, Researchgate, and other sources for the relevant literature from 1550 B.C. till 2022 A.C. (3) Results: Laboratory and clinical investigations demonstrate that activated carbon or charcoal (AC) mitigates inflammation in different pathological states when applied orally, per rectum, or in a hemoperfusion system. AC protects the microbiome and bone marrow, acts as an anti-inflammatory and anti-oxidant remedy, and recovers the plasmatic albumin structure. The mechanism of AC action is related to a non-selective (broad-range) or/and selective adsorption of PAMPs & DAMPs from biological fluids. A high-adsorptive capacity towards noxious substances and application of AC as early as possible seems paramount in inflammation treatment for preventing sepsis and/or multi-organ failure. (4) Conclusion: AC could be considered an adjunctive treatment for preventing sepsis and/or multi-organ failure.

Electromagnetic and Thermal Analysis of HTS AC Cable using T-A Formulation

High temperature superconducting (HTS) cables have been developed into various products and attracted wide attention in industrial applications due to their high critical temperature, current density, zero resistance and overcurrent strength. Recently the triaxial YBCO cables are used in AC applications with the consideration of the flexibility and economy of materials. In this paper, the transient electromagnetic thermal characteristics of a triaxial HTS cable are analysed by the T-A formulation and the Thermal-Fluid Coupling Module of the COMSOL software under the condition of alternating current flow. Firstly, the electromagnetic T-A formulation and the basic theory of heat transfer are introduced. Transient magnetic fields, critical current distribution, and magnetization losses are discussed under T-A modelling. To evaluate the thermal behaviour of the cable under normal current conditions, liquid nitrogen laminar flow is coupled with the heat transfer module, while the heat source data are obtained from the previous T-A results.