Current Capacitance Research Articles

Strengths and Weaknesses of Elimination Voltammetry with Linear Scan

Electrochemical methods have undergone many important developments initiated by efforts to increase the sensitivity, selectivity, and stability (S&S&S) and to understand the underlying electrode processes. To meet these goals, there are hardware solutions with applications of new technologies and materials, and software solutions utilizing existing instrumentation. The article presents a viable, easy-to-implement software solution to the main shortcomings of linear sweep voltammetry (low sensitivity, high share of the capacitive component of the current, and the problem of overlapping signals) in the form of elimination voltammetry with a linear scan (EVLS). Based on the different dependences of the individual currents that make up the total voltammetric current (diffusion, charging, kinetics, and various irreversible components) on the scan rate, EVLS can eliminate or preserve particular current components. Increased sensitivity and selectivity can be expected especially in the case of a fully adsorbed electroactive particle subjected to an irreversible electrode process when the elimination of kinetic and capacitive current while preserving the diffusion current provides a theoretically confirmed peak-counter peak signal. EVLS is applicable for testing changes in the polarized electrode/electrolyte interface using EVLS functions eliminating the diffusion component of the current and preserving the kinetic and capacitive currents, which should ensure zero current conduction for a purely diffusion-controlled Nernstian-type reversible process. We point out the strengths, opportunities, and weaknesses of EVLS. Nevertheless, EVLS offers a new tool that contributes to a better understanding of electrochemical processes and their mechanisms.

Layer-by-layer WS2-Cr heterojunction as a positive working electrode material for high-performance supercapattery applications

This study investigates the impact on the electrochemical performance of pristine sputtered WS2 through the strategic integration of a highly conductive chromium interfacial layer. This study involves the fabrication of two different samples via magnetron sputtering: type I, WS2-sputtered and type II, WS2/Cr (sputtering of Cr as an interfacial layer between sputtered-WS2 and NF). Afterward, structural, topographic and elemental composition of as-synthesized samples were inspected via XRD, SEM, Raman, and EDX. Following this, the energy storage performance were evaluated by employing CV, GCD, and EIS in three and two electrode assembly sequentially. In three electrode testing WS2 and WS2/Cr exhibited the specific capacity (Qs) of 661.79C g−1 and 1600C g−1 at 3 mV/s along with the capacity retention of 61.37 % (WS2) and 83.04 % (WS2/Cr), respectively. Similarly, through GCD WS2 shows the Qs of 637.34C g−1 at 0.8 A/g conversely, WS2/Cr exhibited the Qs of 1220C g−1 at 1.3 A/g. Besides, the WS2/Cr demonstrated long-term longevity (capacity retention of 83.13 %) after 5000 GCD cycles. Based on exclusive electrochemical performance of type II of two samples, an asymmetric battery-type hybrid supercapacitor (WS2/Cr//AC) was fabricated by incorporating WS2/Cr and activated carbon (AC) as working and counter electrodes. WS2/Cr//AC revealed the Qs of 352C g−1 (785F g-1) at 0.7 A/g. Besides, it deliberately delivered 81 Wh kg−1 and 1750 W kg−1 energy and power. The device exhibits excellent cyclic stability by maintaining its capacity after 5000 GCD cycles and illustrated 87.30 % capacity retention. Following that, semi-empirical approach was applied to quantify the capacitive and diffusive currents’ contribution in overall device’s performance. The results highlight that WS2/Cr hold colossal potential to fill the proficiency gap between presently keep-going devices and stern demands of future energy storage applications.

Fault Line Selection of Small Current Grounding System Research Based on Zero Sequence Circuit Current Phase

Abstract This paper investigates fault line selection in small current grounding systems, focusing on the zero sequence current phase characteristics. Small current grounding systems, prevalent in medium voltage distribution networks, face challenges in fault detection due to minimal fault currents during single status phase grounding faults. Traditional methods relying on manual line switching and zero sequence voltage monitoring are inefficient and can induce overvoltage. This study categorizes fault line selection techniques into three approaches: steady-state fault information, transient information, and modern signal processing technology. The analysis of zero sequence currents in non-grounded systems reveals that fault line zero sequence currents equal the sum of system capacitive currents, flowing opposite to those in non-fault lines. Additionally, transient signal analysis shows that these signals provide more robust information for fault detection. MATLAB simulations validate the theoretical models, demonstrating that zero sequence current direction and amplitude effectively identify fault lines. The results confirm the efficacy of combining steady-state and transient signal analyses for accurate fault line selection, contributing to enhanced safety and reliability in power distribution networks. This research offers practical insights and tools for engineers, improving fault management and reducing potential economic losses in small current grounding systems.

Synthesis and investigation of charge storage characteristics in Ni-MOF/PANI composite as an active electrode material for supercapacitor

This study aimed to develop a more stable and efficient energy storage device, synthesis of nickel-based pristine metal organic framework (MOF) and combined it with the emeraldine base phase of polyaniline (PANI) which is confirmed with XRD, SEM and TEM. Both Ni-MOF and PANI exhibit faradaic (battery-like) behaviour. However, when these two materials are combined, the stability of the resulting material is enhanced. The initial materials, MOF and PANI, exhibit specific capacities of 42 C/g and 72 C/g, respectively. However, when these two materials are combined, their composite exhibits an enhanced specific capacity of 122 C/g. The cyclic voltammetry (CV) analysis shows oxidation and reduction peaks, indicating faradaic behaviour. This behaviour is further confirmed by electrochemical impedance spectroscopy (EIS). Upon comparing it with prior results, the specific capacity appears to be slightly lower. However, it is anticipated to exhibit stronger stability, which is contradictory. The composite material (Ni-MOF/PANI) exhibits remarkable capacitive retention of 99.25 % even after undergoing 5000 cycles, as anticipated. In order to validate the aforementioned findings and determine the extent of the current contribution from capacitive and diffusive control, Dunn's model was employed. The data demonstrates the prevalence of diffusive-controlled (faradaic) current over capacitive current. The highest proportion of current resulting from diffusion is 96 %, achieved at a scan rate of 5 mV/s. The highest proportion of current resulting from capacitance is 24 %, achieved at a scan rate of 300 mV/s. At lower scan rates, the material exhibits a greater faradaic behaviour, whereas at higher scan rates, there is a progressive increase in non-faradaic processes. The insufficient time for diffusive process at higher scan rates is the cause. The Dunn's model with quadratic correction is also performed and comparative results were shown. Overall, the material exhibits more stability and dominance in the faradaic process, which paves the path for improved performance.

Stress grading system optimisation for an inverter‐fed rotating machine

AbstractStress grading systems using non‐linear resistive coatings are a key component to suppress surface corona in the end‐windings of rotating machine. Compared to a sinusoidal‐fed motor, the high slew rate of the voltage at the flanks of the repetitive square voltages from the inverter cause large capacitive currents to flow in the main wall insulation. These large currents, if not properly considered in the design phase, lead to severe electrothermal stress of the grading system. Experiments and simulations were conducted on a stress grading system whose structure arises from limitation posed by the motor structure. Measurements performed with different rise times show that the maximum potential along the conductive armour tape (CAT) increases non‐linearly with increasing axial distance, and the potential at the edge of the CAT reached nearly twice the peak‐to‐peak voltage at 500 ns rise time, leading to corona inception. As metal plates are used in the machine to dampen vibrations in the end‐winding, similar plates were also fastened to the stress grading system, worsening the already inadequate corona suppression performance. The stress grading system was therefore modified, avoiding the surface corona while, at the same time, reducing the temperature in the grading system to acceptable levels.

Simplified Ftacv Model to Quantify the Electrochemically Active Sitedensity in PGM-Free ORR Catalysts

The development of platinum group metal-free catalysts is considered the most prominent path for reducing thecost of low-temperature fuel cells (LTFC). Despite the great advancement in the field, its further progress iscurrently limited by the ability to understand and mitigate the catalysts’ degradation mechanisms, which up torecent years was limited by the lack of activity descriptors. Recent work showed that this could be solved usingFourier-transformed alternating current voltammetry that enables to deconvolute Faradaic currents arising fromthe redox reaction of the active sites from the capacitive currents, and by that accurately measure the electrochemicallyactive site density of these catalysts in situ fuel cells. However, the analysis of the results can becomplex, requiring simulation software for accurate parameter extraction. Herein, a simplified analysis ofFourier-transformed alternating current voltammetry is presented. This was done by mapping the influence ofvarious variables, such as resistivity, capacitance, and thermodynamic and kinetic dispersion, on the accuracy ofelectrochemically active site density measurements. Under specific, yet realistic, operating conditions, a singleequation with the peak current of the 5th harmonic as the only variable can be used to quantify electrochemicallyactive site density with high accuracy. This approach was demonstrated using molecular catalysts, iron phthalocyanine,as a model molecule, and a commercial, heat-treated catalyst.

A method for measuring capacitive current in distribution networks based on injection signal method

Abstract In view of the problems that exist in the current distribution network, such as the narrow range of measurement capacitance to the ground and the difficulty of selecting the appropriate signal frequency. Based on the phasor method, this paper proposes a method for measuring capacitance current in a distribution network based on injected signal and analyzes and calculates the error of the method. The measurement technique involves inputting two constant-amplitude signals—one high-frequency and one low-frequency—into a zero-sequence PT (Potential Transformer) configured with an open delta connection. Based on the equivalent circuit models for both high and low-frequency signals, the high-frequency signal’s increased frequency allows the magnitude to be disregarded, simplifying the calculations. Using a simplified equation for the low-frequency signal component, this method enables rapid calculation of the capacitor current in the distribution network. Based on MATLAB software, the simulation calculation model is established, and the simulation results show that the measurement method is simple to calculate and has high accuracy, which can be used to measure the large-capacity grounding capacitance current test, so as to improve the measurement accuracy of the capacitance current of medium and low voltage distribution network.

Absolute Quantum Efficiency Measurements of Electrochemiluminescent Devices Through Electrical Impedance Spectroscopy

AbstractAC‐operating electrochemiluminescent devices (ECLDs) have recently shown a substantial increase in brightness, making them potentially relevant for applications in lighting and displays. To further improve the performance of these liquid‐state light‐emitting devices, it is essential to reliably assess the absolute quantum efficiency of electrochemiluminescence and the electrochemical reactions leading to exciton formation. However, significant non‐faradaic currents occurring under the AC operation schemes make it challenging to quantify the number of charges involved in the electrochemical reactions. Here, faradaic and non‐faradaic currents in sandwich‐type ECLDs are analysed by electric impedance spectroscopy and to assess the absolute quantum efficiency of the electrochemiluminescence (ΦECL). An equivalent circuit model enables analysis of the current at different voltage amplitudes and operating frequencies. The analysis reveals that non‐faradaic currents stem primarily from capacitive currents associated with the formation of electric double‐layers near liquid/electrode interfaces. Their contribution to the total current increases at high operating frequencies and low voltages. For ECLDs operating based on an exciplex‐formation and energy transfer pathway, the estimated ΦECL and resulting exciton formation efficiency are 0.53% and 27%, respectively. Reverse redox reactions are identified as a significant loss factor, thus indicating potential avenues for future improvements.

Analysis of nano sheet field effect transistor based on performance under different temperature and doping concentrations for 12 nm device

This paper presents a simulation study on a 12 nm Gate-all-around n-type Metal Oxide Semiconductor (GAA-nMOSFET), investigating the effects of temperature variations and doping concentrations. The structure of the device has three fins, and the channel is surrounded by gate material to reduce the short channel effect (SCE) and electrostatic capacitance. Various parameters such as threshold voltage (Vth), Ion/Ioff ratio, drain-induced barrier lowering (DIBL), and sub-threshold swing (SS) are evaluated at different temperatures 250 K, 300 K, and 350 K, doping concentrations of 1016cm−3, 1017cm−3, and 1018cm−3, with a high voltage of 0.65V. At a temperature of 250 K, in comparison to the 1016cm−3 doping concentration attention, the Vth is observed to be 0.31V, while the Ion/Ioff ratio is measured at 0.33e−14. Moreover, the DIBL experiences a reduction of 25 %, whereas the SS increases by 76 %. Furthermore, when the temperature is raised to 300 K relative to the 1017cm−3 doping concentration, the Vth increases to 0.32 V, and the Ion/Ioff current ratio rises to 0.45e−14. Meanwhile, the DIBL experiences a decrease of 20 %, and the SS increases by 71 %. Finally, at a temperature of 350 K concerning 1018cm−3 doping concentration, the Vth is measured at 0.34 V, and the Ion/Ioff current ratio reaches 0.47e−14 Concurrently, the DIBL shows a decrease of 28 %, While the SS increases to 79 %. To reduce electrostatic capacitance and leakage current, the use of a high-k dielectric material in a GAA-nMOSFET device is investigated. Improved performance traits such as decreased SCE, low DIBL, and strong SS are displayed. Additionally, the connection between threshold voltage and doping concentration is investigated. The effect of temperature variations and doping concentration on many essential characteristics of 12 nm GAA-nMOSFET shows the potential benefits of the device's unique architecture and material. The conclusions are supported through circuit schematics, simulations, and experimental data in this article.

Compensation of capacitive currents in high-throughput dielectrophoretic separators

Separation and classification are important operations in particle technology, but they are still limited in terms of suspended particles in the micrometer and nanometer size-range. Electrical fields can be beneficial for sorting such particles according to material properties. A mechanism based on strong and inhomogeneous fields is dielectrophoresis (DEP). It can be used to separate microparticles according to their material properties, such as conductivity and permittivity, by selectively trapping one particle type while the other can pass the separator. Conventional DEP-separators show either a limitation in throughput or frequency bandwidth. A low throughput limits the economical feasibility in many cases. A lower frequency bandwidth limits the variety of materials that can be sorted by DEP. To separate semiconducting particles from a mixture containing particles with higher conductivity according to their material, high frequencies are required. Possible applications are the separation of semiconducting and metallic carbon nanotubes or the separation of carbon-coated lithium iron phosphate particles from graphite in the recycling process of spent lithium-ion batteries. In this publication, we aim to display how to tune the electrical impedance of a high-throughput DEP separator based on custom-designed printed circuit boards to increase its frequency bandwidth. By adding inductors to the electrical circuit, we were able to increase the frequency bandwidth from 500 kHz to over 11 MHz. The experiments in this study act as proof-of-principle. Furthermore, a non-deterministic way to increase the impedance of the setup is shown, yielding a maximum frequency of 39.16 MHz.

Electronic properties of armchair & zigzag single-walled carbon nanotubes

This paper investigates the role of chirality and its impact on the electronic band structure in armchair and zigzag single-walled carbon nanotubes (SWCNTs). Simulating electronic band gaps for single-walled carbon nanotubes (SWCNTs) with various chiral indices has been done by using the tight-binding model. The increase in chirality results in an increase in the total number of bands in the electronic band structure. A study was conducted on the band gap at Fermi energy (E=0) and it was found that the electronic band structure in armchair and zigzag (SWCNTs) can be either metallic or semiconductor depending on chirality. The diameter of the tube and the band gap value are also provided. The effect of variations in the CNT channel length and oxide thickness on the gate capacitance and drain current of a single CNT have been analyzed. The results suggest that the simulated values are consistent with the theoretical values thus validating the results.

ВПЛИВ З’ЄДНУВАЛЬНОГО ВИСОКОВОЛЬТНОГО КАБЕЛЮ НА СТРУМИ І НАПРУГИ У ПРИСТРОЇ ІМПУЛЬСНОГО БАР’ЄРНОГО РОЗРЯДУ

The article is devoted to the study of the connecting cable influence, as an element with distributed parameters between the pulsed generator and discharge chamber in the electrical complex based on pulsed barrier discharge, to the values of currents and voltages in the system. Based on experimental studies and modeling, it has been established that the currents at different ends of the cable differ significantly from each other, which is due to the large value capacitive pulsed charging current of the cable. It has been established that during the barrier discharge, a correctly measured pulse current has significantly shorter duration than pulse of voltage. During the electrical discharge, a feature of the dependence of the current at the input to the cable is the appearance of an additional local maximum, of much smaller amplitude with a time shift equal to the time the electromagnetic wave movement along the cable. It has been shown that the use of the connecting cable of increased length makes it possible to increase the voltage between the electrodes of two times in comparison with the voltage at the cable input, without taking into account the voltage drop across the internal resistance of the generator when the cable length no less than twice the path length that the electromagnetic wave moves during the time from start of the pulse to maximum value generator pulse. References 16, figures 7.

Batch-to-Batch Variation in Laser-Inscribed Graphene (LIG) Electrodes for Electrochemical Sensing.

Laser-inscribed graphene (LIG) is an emerging material for micro-electronic applications and is being used to develop supercapacitors, soft actuators, triboelectric generators, and sensors. The fabrication technique is simple, yet the batch-to-batch variation of LIG quality is not well documented in the literature. In this study, we conduct experiments to characterize batch-to-batch variation in the manufacturing of LIG electrodes for applications in electrochemical sensing. Numerous batches of 36 LIG electrodes were synthesized using a CO2 laser system on polyimide film. The LIG material was characterized using goniometry, stereomicroscopy, open circuit potentiometry, and cyclic voltammetry. Hydrophobicity and electrochemical screening (cyclic voltammetry) indicate that LIG electrode batch-to-batch variation is less than 5% when using a commercial reference and counter electrode. Metallization of LIG led to a significant increase in peak current and specific capacitance (area between anodic/cathodic curve). However, batch-to-batch variation increased to approximately 30%. Two different platinum electrodeposition techniques were studied, including galvanostatic and frequency-modulated electrodeposition. The study shows that formation of metallized LIG electrodes with high specific capacitance and peak current may come at the expense of high batch variability. This design tradeoff has not been discussed in the literature and is an important consideration if scaling sensor designs for mass use is desired. This study provides important insight into the variation of LIG material properties for scalable development of LIG sensors. Additional studies are needed to understand the underlying mechanism(s) of this variability so that strategies to improve the repeatability may be developed for improving quality control. The dataset from this study is available via an open access repository.

Mesoporous pineapple crown-derived activated carbon modified matrix for the detection of carbendazim in the presence of anionic surfactant

Carbon paste electrodes (CPEs) are commonly employed in electroanalysis because of their chemical stability, broad electrochemical window, low capacitive current, ease of fabrication, and surface renewability. Electrocatalysts can easily be embedded into CPEs to make them suitable for a variety of applications. Poor biowaste management presents a significant challenge in the agro-industry and agriculture due to the rapid decomposition of biowaste, driven by its high water content and limited biological stability, which leads to pest attraction and greenhouse gas emissions. Consequently, this green waste can be utilized for the development of electrocatalysts. Activated carbon (AC) has been utilized in progressive electrochemical applications as it exhibits high conductivity and porosity that help to enhance electrocatalytic activity. Herein, pineapple fruit crown (PC) peel-derived AC (PCAC) is utilized as the sensing material for the determination of fungicide, carbendazim (CBM). The synthesized material was characterized using SEM, FT-IR, XRD, EDX, AFM, CV and EIS. Besides, to enhance the surface properties, Sodium dodecyl sulfate (SDS) surfactant is used as a mediator in detecting CBM. The CV and SWV approaches were employed to assess the electrochemical response of the developed electrodes for the CBM determination. Under optimum experimental conditions, the SDS/PCAC/CPE exhibits low DLim and QLim values of 32.0 nM and 128.0 nM with considerable selectivity. Furthermore, the SDS/PCAC/CPE was employed in real-time analysis of CBM in spiked environmental samples, which showed satisfying recovery results. Moreover, the electrode showed good stability over multiple measurements, and these results demonstrate that SDS/PCAC/CPE is a promising sensor for CBM detection.

A novel high-sensitivity time-domain current differential protection scheme for renewable power transmission system

Integrating large-scale renewable energy sources in modern power systems has altered fault characteristics, resulting in the performance degradation of conventional current differential protection. This paper proposes a novel high-sensitivity time-domain current differential protection scheme. The proposed scheme utilizes the Bergeron model to eliminate the impact of the distributed capacitive current. Furthermore, the Bergeron model error is analyzed theoretically during normal operation, and an algorithm is designed to identify and adjust the α- and β-mode line parameters. Additionally, novel internal fault criteria are presented to mitigate the negative impact of the 0-mode line parameter error. Compared to traditional frequency-domain approaches, the proposed method can more accurately and rapidly distinguish internal and external faults, while reducing the dependency on precise line parameters. Eventually, a VSC-HVDC sending-end grid model consisting of 100% renewable power generations is established using PSCAD/EMTDC software. Simulation results confirm that the proposed protection scheme exhibits exceptional performance in terms of operating speed, sensitivity, and tolerance to fault resistance and noise.

An ultra-deep TSV technique enabled by the dual catalysis-based electroless plating of combined barrier and seed layers

Silicon interposers embedded with ultra-deep through-silicon vias (TSVs) are in great demand for the heterogeneous integration and packaging of opto-electronic chiplets and microelectromechanical systems (MEMS) devices. Considering the cost-effective and reliable manufacturing of ultra-deep TSVs, the formation of continuous barrier and seed layers remains a crucial challenge to solve. Herein, we present a novel dual catalysis-based electroless plating (ELP) technique by tailoring polyimide (PI) liner surfaces to fabricate dense combined Ni barrier/seed layers in ultra-deep TSVs. In additional to the conventional acid catalysis procedure, a prior catalytic step in an alkaline environment is proposed to hydrolyze the PI surface into a polyamide acid (PAA) interfacial layer, resulting in additional catalysts and the formation of a dense Ni layer that can function as both a barrier layer and a seed layer, particularly at the bottom of the deep TSV. TSVs with depths larger than 500 μm and no voids are successfully fabricated in this study. The fabrication process involves low costs and temperatures. For a fabricated 530-μm-deep TSV with a diameter of 70 μm, the measured depletion capacitance and leakage current are approximately 1.3 pF and 1.7 pA at 20 V, respectively, indicating good electrical properties. The proposed fabrication strategy can provide a cost-effective and feasible solution to the challenge of manufacturing ultra-deep TSVs for modern 3D heterogeneous integration and packaging applications.

Failure behavior of tantalum electrolytic capacitors under extreme dynamic impact: Mechanical–electrical model and microscale characterization

Tantalum electrolytic capacitors have performance advantages of long life, high temperature stability, and high energy storage capacity and are essential micro-energy storage devices in many pieces of military mechatronic equipment, including penetration weapons. The latter are high-value ammunition used to strike strategic targets, and precision in their blast point is ensured through the use of penetration fuzes as control systems. However, the extreme dynamic impact that occurs during penetration causes a surge in the leakage current of tantalum capacitors, resulting in a loss of ignition energy, which can lead to ammunition half-burst or even sometimes misfire. To address the urgent need for a reliable design of tantalum capacitor for penetration fuzes, in this study, the maximum acceptable leakage current of a tantalum capacitor during impact is calculated, and two different types of tantalum capacitors are tested using a machete hammer. It is found that the leakage current of tantalum capacitors increases sharply under extreme impact, causing functional failure. Considering the piezoresistive effect of the tantalum capacitor dielectric and the changes in the contact area between the dielectric and the negative electrode under pressure, a force–electric simulation model at the microscale is established in COMSOL software. The simulation results align favorably with the experimental results, and it is anticipated that the leakage current of a tantalum capacitor will experience exponential growth with increasing pressure, ultimately culminating in complete failure according to this model. Finally, the morphological changes in tantalum capacitor sintered cells both without pressure and under pressure are characterized by electron microscopy. Broken particles of Ta–Ta2O5 sintered molecular clusters are observed under pressure, together with cracks in the MnO2 negative base, proving that large stresses and strains are generated at the micrometer scale.

Sputter Deposited Crystalline MoO2 Films as a High-Capacity and Stable Electrode Material for Supercapacitors: Mechanistic/Electrochemical Insights

In this work, we have optimized and fabricated pristine molybdenum dioxide (MoO2) electrodes over the Silicon (Si) substrate and examined the impact of various ion-loaded aqueous electrolytes on their electrochemical behavior. The sputtered electrodes exhibited a high crystalline structure and a very low resistivity. These highly conductive electrodes were tested in three different aqueous electrolytes (acidic, neutral, and alkaline) to establish a relation between the electrode and the nature of the electrolyte to achieve optimal electrochemical performance and cyclability. The electrochemical kinetics showed that the charge storage mechanism was unique for all the electrolytes. The capacitive current was dominant in the neutral electrolyte, whereas it was diffusive dominant in alkaline and 70% capacitive in the acidic electrolyte. Our findings indicated that the MoO2@Si electrode exhibited superior electrochemical activity in an acidic electrolyte. The electrode showed a voltage window of 0.6 V with an areal capacity of 24 mF/cm2 at 0.1 V/s scan rate. Moreover, the electrode also demonstrated excellent cyclability and capacitance retention (∼145%) till 5000 cycles. These results highlighted that the binder-free MoO2@Si electrode showed outstanding electrochemical activity and stability, which makes it suitable for sulfuric acid electrolyte-based energy storage systems.

Comprehensive Analysis of DC Link Capacitors Used in Cascaded H-Bridge Motor Driver

An essential part of inverter design is selecting direct current-Link Capacitors (DCLC) for Medium-Voltage Cascaded H-bridge motor Drivers (MV-CHBMD). This article analyzes capacitor configuration for MV-CHBMD to improve the quality of driver output and input current depending on an analysis of DCLC current effects. The techniques were employed with two-level converters to find the harmonics, and the root mean square (RMS) value of the capacitor current has been expanded to seven-level MV-CHBMD. Additionally, a novel mathematical technique has been recommended for determining the RMS current and voltage ripple of the DCLC. The proposed MATLAB simulation technique provides a comprehensive analysis of the outcome results. This allows for easy customization to other modulation methods and application to higher-level MV-CHBMD. Specifically, it calculates the worst-case scenario for the DC-link voltage in a 1000-horsepower and 3.3-kV system. The study also presents empirical evidence that specific system components endure excessive stress. This information is valuable for accurately specifying system components and ensuring optimal system design in the MV-CHBMD system. This article examines the potential impact of standard mode voltage on the bearings of medium-voltage motors. In addition, an optimal approach for selecting DCLCs in a multilevel cascaded H-bridge (CHB) motor driver strategy is proposed, effectively eliminating voltage stress on switching devices. The effectiveness of these systems is demonstrated by presenting simulation results. A comprehensive study analyzed the performance of various inverter levels, including total harmonic distortion (THD) and efficiency. The DC link was constructed using the MATLAB platform to conduct a thorough analysis. The proposed approach exhibits superior performance and lower costs compared to traditional methods. The experimental work and test confirm the simulation results. The test result showed that selecting DCLCs in a CHB provides a higher-quality output waveform into CHB, which supports the controlling structure and reduces the probability of malfunctions.

Rational Design of Enzymatic Electrodes: Impact of Carbon Nanomaterial Types on the Electrode Performance

This research focuses on the rational design of porous enzymatic electrodes, using horseradish peroxidase (HRP) as a model biocatalyst. Our goal was to identify the main obstacles to maximizing biocatalyst utilization within complex porous structures and to assess the impact of various carbon nanomaterials on electrode performance. We evaluated as-synthesized carbon nanomaterials, such as Carbon Aerogel, Coral Carbon, and Carbon Hollow Spheres, against the commercially available Vulcan XC72 carbon nanomaterial. The 3D electrodes were constructed using gelatin as a binder, which was cross-linked with glutaraldehyde. The bioelectrodes were characterized electrochemically in the absence and presence of 3 mM of hydrogen peroxide. The capacitive behavior observed was in accordance with the BET surface area of the materials under study. The catalytic activity towards hydrogen peroxide reduction was partially linked to the capacitive behavior trend in the absence of hydrogen peroxide. Notably, the Coral Carbon electrode demonstrated large capacitive currents but low catalytic currents, an exception to the observed trend. Microscopic analysis of the electrodes indicated suboptimal gelatin distribution in the Coral Carbon electrode. This study also highlighted the challenges in transferring the preparation procedure from one carbon nanomaterial to another, emphasizing the importance of binder quantity, which appears to depend on particle size and quantity and warrants further studies. Under conditions of the present study, Vulcan XC72 with a catalytic current of ca. 300 µA cm−2 in the presence of 3 mM of hydrogen peroxide was found to be the most optimal biocatalyst support.