Voltage Requirements Research Articles

Origin of electrically induced defects in monolayer MoS2 grown by chemical vapor deposition

Defects in MoS2 play substantial role in determining the performance of MoS2-based field-effect transistors. Typically, growth/synthesis process conditions determine the type and concentration of defects. Here, we show that defects are also introduced by prolonged operation of single crystal chemical vapor deposition-grown monolayer MoS2 transistors which hinder the overall performance. Depending on the electrical stress conditions, these defects result in threshold voltage instabilities, enhanced channel conductance, improved screening of charged impurity scattering sites and possibly better thermal management in MoS2 transistors. It turns out that a piezoelectric response in MoS2 leads to permanent change in the material’s molecular configuration thereby causing other effects like suppressed hopping transport within the channel, increased free electron concentration, prominent metal-insulator transition and reduction in channel potential with or without increasing sulfur vacancy concentration. As these defects are progressively introduced in the channel, the thermal dissipation capability of our MoS2 transistors improved due to enhanced channel-dielectric coupling. Such variations in the device performance due to spontaneous response to high electric field trigger a need to reconsider supply voltage requirements of MoS2-based electronic circuits for low-power logic applications.

Dual hydrogen production from electrocatalytic water reduction coupled with formaldehyde oxidation via a copper-silver electrocatalyst

The broad employment of water electrolysis for hydrogen (H2) production is restricted by its large voltage requirement and low energy conversion efficiency because of the sluggish oxygen evolution reaction (OER). Herein, we report a strategy to replace OER with a thermodynamically more favorable reaction, the partial oxidation of formaldehyde to formate under alkaline conditions, using a Cu3Ag7 electrocatalyst. Such a strategy not only produces more valuable anodic product than O2 but also releases H2 at the anode with a small voltage input. Density functional theory studies indicate the H2C(OH)O intermediate from formaldehyde hydration can be better stabilized on Cu3Ag7 than on Cu or Ag, leading to a lower C-H cleavage barrier. A two-electrode electrolyzer employing an electrocatalyst of Cu3Ag7(+)||Ni3N/Ni(–) can produce H2 at both anode and cathode simultaneously with an apparent 200% Faradaic efficiency, reaching a current density of 500 mA/cm2 with a cell voltage of only 0.60 V.

Harnessing Soft Elasticity of Liquid Crystal Elastomers to Achieve Low Voltage Driven Actuation

AbstractDielectric elastomers (DE) are soft electromechanical transducers that can generate large, rapid, and reversible deformation under an electric field. Despite being one of the leading candidates for soft actuators, the widespread applications of dielectric elastomers are restricted by the high voltage requirement (1–10 kV) for thin film DEs, which increases the system complexity and pose a potential safety threat for humans. In this work, a new class of dielectric elastomer actuators using liquid crystal elastomers (DLCEs) is reported. Soft elasticity of DLCEs and the high dielectric constant are utilized to reduce the actuation voltage. Freestanding DLCE thin film actuators (≈20 µm) are fabricated, which can generate large actuation strains (≈88%) at 400 V, an input voltage almost one order of magnitude lower compared to typical dielectric elastomers actuators. This allows to develop a soft tunable bilayer DE lens, which can achieve a 21% focal length variation at 500 V.

Active Disturbance Rejection Control of an Interleaved High Gain DC-DC Boost Converter for Fuel Cell Applications

In this paper, a simplified and robust control strategy of an interleaved high gain DC/DC boost converter (IHGBC) is proposed in order to enhance DC bus voltage regulation in proton exchange membrane fuel cell (PEMFC) applications. The fluctuation of the energy source voltage and external load, and the change in system parameters lead to the instability of output voltage. Based on the creation of an average state space model of the DC/DC boost converter, the proposed controller is designed based on a linear active disturbance rejection control (LADRC), which has an external voltage loop and an internal current loop to meet the output voltage requirements under parameters uncertainties and disturbances. The effectiveness of the proposed approach strategy and its superiority were examined under different operating conditions and scenarios. Simulation and experiment results showed the efficiency and robustness of the suggested approach and the great effectiveness in the reference tracking and disturbance rejection.

Characterization of the Operation of a BESS with a Photovoltaic System as a Regular Source for the Auxiliary Systems of a High-Voltage Substation in Brazil

Substation (SS) auxiliary systems (SAux) are facilities responsible for hosting the alternating (AC) and direct current (DC) busbar to serve the equipment and systems that perform the substation’s protection, control, and supervision. External and internal power supplies typically ensure the continuity of such a facility. The electricity support will be restricted to diesel emergency generators (DG) if the external power supply is unavailable due to a contingency. The DG present a slower response time and are susceptible to starting failures. Microgrids with Battery Energy Storage Systems (BESS) paired with photovoltaic systems (PV) are presented as an innovative and reliable solution for powering the SAux. In this article, tests were carried out on the microgrid of the Edson Mororó Moura Institute of Technology (ITEMM) in Brazil to support the use of microgrids BESS/PV in the SAux of a transmission SS of the São Francisco Hydroelectric Company (Chesf). Without an external power supply, BESS commands the action of islanded operation, maintaining both voltage and frequency requirements of the microgrid without load shedding. It was possible to observe all operations of the microgrid. The experimental results showed that the solution proposed in the paper implements a dependable self-dispatchable autonomous power supply.

Multi-port DC circuit breaker based on dual capacitor current limiting and energy sink

The coupling relationship between the removal of the fault current and the dissipation of the residual energy of the fault line during the fault isolation process of the multi-port capacitive current-limiting DC circuit breaker prolongs the breaking time of the fault to a certain extent. In order to solve the above problems, this paper proposes a multi-port DC circuit breaker based on dual-capacitor current limiting and energy sinking on the premise of decoupling the fault current attenuation and removal process and the fault line residual energy discharge process. Further reduce the fault breaking time and equipment withstand voltage requirements of the DC circuit breaker. Firstly, the topology and working principle of the proposed circuit breaker are analyzed, and then the parameters in the topology are designed. Then a simulation model is built in the PSCAD/EMTDC simulation platform to verify the fault breaking performance and breaking time. The effect of decoupling the fault current clearing process and the fault line residual energy discharge process on the effectiveness of shortening the fault breaking time is verified.

Age Estimation of a Hybrid Energy Storage System for Vehicular Start–Stop

Ultracapacitors are energy storage devices that have shown outstanding capability in a vast spectrum of applications, mainly in energy storage systems required to deliver short bursts of electrical energy. Ultracapacitors possess high power density while batteries possess high energy density. In this paper, a hybrid energy storage device comprising a lithium-ion ultracapacitor module and a lead acid battery was modeled, built, and tested for vehicular start–stop application, which requires a much larger number of engine cranking events than conventional vehicles. The combination of a lead acid battery with Li-ion ultracapacitors was chosen due to the fact that the vast majority of vehicles utilize lead acid batteries to crank the internal combustion engine. This allows retrofitting this hybrid setup in conventional vehicles along with the start–stop feature without inflicting damage to the already installed lead acid battery. The start–stop feature puts high stress on the lead acid battery, contributing to its faster aging. This feature is commonly found in hybrid vehicles to save the unnecessarily burned fuel during idling. This paper discusses aging of the lead acid battery as a result of being used in hybrid vehicles equipped with start–stop when used alone versus when used in the hybrid setup. The paper shows cranking tests performed on a number of cars to obtain voltage, current, power, and energy requirements for combustion engine cranking. Mathematical derivation, analysis, and an energy storage age estimation method are also presented. A set of cranking events followed by capacity checks performed on two automobile energy storage systems, one being a lead acid battery alone and the other being the proposed hybrid module, show the advantage of integrating the ultracapacitor module with the lead acid battery to extend its life span almost fivefold in a hybrid automobile.

Application of Nonlinear Differential Equation in Electric Automation Control System

Abstract This article uses fifth-order nonlinear differential equations to describe the dynamic process of electrical automation control systems. This method first derives the equivalent system of the nonlinear fuzzy global system and then uses the orthogonal polynomial series expansion technique and its integral operation matrix. The local manifold at the dominant unstable equilibrium point of a single-machine infinite-bus system after a failure described by a two-dimensional quadratic nonlinear differential equation is calculated, and the stability boundary of the power system is obtained. The research results show that the output frequency fluctuation of the electrical automation control system is small after the algorithm is adopted, and the intelligent control system can accurately diagnose and warn the electrical faults. The system can meet the requirements of online voltage coordinated control.

Microfabricated acoustofluidic membrane acoustic waveguide actuator for highly localized in-droplet dynamic particle manipulation.

Precision manipulation techniques in microfluidics often rely on ultrasonic actuators to generate displacement and pressure fields in a liquid. However, strategies to enhance and confine the acoustofluidic forces often work against miniaturization and reproducibility in fabrication. This study presents microfabricated piezoelectric thin film membranes made via silicon diffusion for guided flexural wave generation as promising acoustofluidic actuators with low frequency, voltage, and power requirements. The guided wave propagation can be dynamically controlled to tune and confine the induced acoustofluidic radiation force and streaming. This provides for highly localized dynamic particle manipulation functionalities such as multidirectional transport, patterning, and trapping. The device combines the advantages of microfabrication and advanced acoustofluidic capabilities into a miniature "drop-and-actuate" chip that is mechanically robust and features a high degree of reproducibility for large-scale production. The membrane acoustic waveguide actuators offer a promising pathway for acoustofluidic applications such as biosensing, organoid production, and in situ analyte transport.

A Seven-Level Inverter With Natural Balance and Boosting Capability

This paper introduces a new active-neutral-point clamped (ANPC) seven-level inverter with a switched-capacitor technique. The introduced inverter generates a seven-level ac output voltage with a maximum voltage-boosting gain of 1.5. The higher output voltage does not imply high voltage across the switches, as the maximum blocking voltage of the switches does not exceed the input voltage. The dc-link capacitor voltages are naturally balanced, and the flying capacitor achieves self-balancing through the series-parallel connection of the input voltage source, without the need for auxiliary control methods. Additionally, compared to major traditional seven-level inverters such as NPC, FC, and hybrid topologies, the proposed topology reduces the dc voltage requirement by 33.3%, eliminating the need for an intermediate dc-boosting stage and making the introduced inverter a good candidate for applications such as photovoltaic panels and full-cells systems, both characterized by a low input voltage. The operation and performance of the proposed topology are validated through simulation and experimental results.

Differential Single-Phase Inverters With Active Power Decoupling: A Survey

This paper provides an overview of differential single-phase inverter topologies with active power decoupling (APD) and their main control techniques. Owing to the advantage of achieving APD without additional semiconductor devices, thus boosting inverter reliability at a minimum cost, these topologies have gained increasing interest, especially for small-scale photovoltaic applications. Therefore, in this study, we consider it essential to synthesize the main differential single-phase inverters, their operating principles, and provide a unified mathematical description for each topology. The study identified and analyzed three main structures: buck, boost, buck–boost, and derived topologies. First, a comparative analysis, including a hardware assessment in terms of the DC-link voltage requirements, voltage and current stresses on the switches, and losses, shows the performance of various inverter topologies under different operating parameters (e.g., input voltage and decoupling capacitance). Second, this paper discusses the main control strategies applied to this class of inverters to achieve both primary control (autonomous or grid-connected operation) and APD functions, while highlighting the development of control algorithms that are less dependent on parameter variations and more robust to external disturbances. Finally, the need for further research on reliability improvement in single-phase differential inverters, particularly in the context of emerging technologies, such as high-speed switches (e.g., wide-bandgap semiconductors) and advanced control techniques, is emphasized.

Graphene oxide electrode for unusual water softening in capacitive deionization

With the depleting freshwater resources and increasing demand for potable water, brackish water sources are potential sources for obtaining potable water due to their availability and low salt concentration. Various technologies are employed to treat the brackish water among which the Capacitive deionization (CDI) is an energy-efficient technique to achieve this due to its high regeneration and reuse capability, low voltage requirement, no pressure requirement, and scalability. The major bottlenecks in this pursuit involve limited desalination capacities and high costs. Here, we demonstrate the use of graphene oxide (GO) as an efficient and inexpensive electrode material for CDI. The hydrophilic nature of GO enables the interaction of hydrolyzed ions in water with the GO surface and reduces electrode-water resistance. The oxygen-containing groups in GO store pseudo charge making it useful for CDI. GO electrodes show a desalination capacity of ∼ 230 mg/g, which is the highest among all carbon-based materials at a high flow rate of ∼ 720 ml/min for 1000 ppm sodium chloride feed solution operating at a cell potential of 1 V. The salt adsorption capacity of GO increases with increasing ionic charges as Na+ < Mg2+ < Fe3+. Excellent recyclability and complete regeneration of electrodes along with high salt adsorption capacity underline the potential of GO electrodes to achieve high capacity, high rate, and efficient CDI.

Computationally Examining the Effect of Plate Thickness on Hole-Emitter-Type Electrospray Thrusters

A new method for determining the onset voltage of electrospray thrusters is proposed, which specifically focuses on electrospray thrusters manufactured by laser drilling through flat plates. The novelty of this method is that it accounts for the effect of the thickness of the plate on the electrospray onset voltage requirements, while traditional methods do not. Key results from this study indicate that for certain materials a change in thickness results in a notable change in the onset voltage, which implies that the plate thickness needs to be considered when planning the design of the thruster emitters. This methodology allows for a robust method of observing the influence of key parameters on the onset voltage. These developments can potentially facilitate and improve the design of these thrusters, enabling an accurate understanding of the power requirements before manufacture.

Simulation and experimental study of parameters in multiple-nozzle electrospinning: Effects of voltage and nozzle configuration on the electric field and electrospun jet attributes

Multiple-jet electrospinning techniques are devised to increase productivity and deposition area for large scale production of nanofibers. The electrospun jets in multiple-nozzle electrospinning behave differently than jets in the conventional single-nozzle setup, and the electric field and fiber non-uniformity becomes a main concern to address. The effects of different nozzle arrangements and voltages on the process and jet characteristics from each nozzle were examined for multiple-nozzle setups with up to five nozzles. Results show that the cone angle of the whipping jets and the length and deflection angle of the straight jets were influenced by the voltage and nozzle setup. From the electric field simulation, it shows that the electric field strength was reduced with the addition of nozzles, which also tend to lead to higher voltage requirement in order to initiate and sustain jets from all nozzles. The strength and distribution of electric field also varied with difference nozzle arrangements. Increasing the internozzle distance tends to increase the mean electric field strength. With four and five nozzles, unequal spacings with larger inner to outer distance ratio resulted in more uniform electric field distributions.

Battery Charging Control Using Photovoltaic with Sepic Converter

This article presents a battery charging design using photovoltaic with a septic converter. The use of batteries as energy storage is one way to ensure the availability of energy to the load and overcome the weaknesses of photovoltaic systems which depend on solar irradiation and temperature. when the solar irradiation is low, the battery can supply energy to the load. SEPIC converter is used to adjust the battery charging voltage requirements. The output voltage of the SEPIC converter is maintained constant by setting the duty cycle using a microcontroller. Based on the results of experimental testing, this PV system with a SEPIC converter can work well. Battery charging can be done optimally. This system is also equipped with automatic disconnection of the battery if the battery is fully charged so that the lifetime of the battery is maintained

Performance Evaluation of Novel Piezoelectric Cantilever Beam Structure for Energy Harvesting

This study proposes an elastic compact Piezoelectric energy harvester (PEH) in multiple configurations, including a single cantilever beam, a single cantilever beam with a hole, two cantilever beams with a hole contributing towards a wider operating bandwidth. The cantilever beams are designed in multiple structural forms and section shapes, including symmetrical uniform section rectangle frames. Natural frequencies, vibration modes, and output voltages of PEH are estimated using Finite element software, with the frame acting as a rigid body and the cantilever plate acting as a deformed structure. A PEH with a rectangular cantilever plate surrounded by a rigid frame is designed and attached to the vibration platform with a customized fixture in the simulation software. The design meets the requirements of natural frequency and high output voltage in the low-frequency band. The PEH structure is simulated using a variety of piezoelectric materials, primarily PZT4 and PZT5H, barium titanate, lithium niobate, zinc oxide, and polyvinylidene difluoride (PVDF) using the finite element method. In the structural configuration of two cantilever beams with holes, PEH exhibited the maximum output voltage of 32.832 V for Zinc oxide compared to other materials. So, it can be concluded that insertion of hole and variation in the geometry of cantilever structure along with frame plays a vital role in achieving a large voltage from the vibrations in PEH. HIGHLIGHTS The finite element approach was used to develop and simulate the cantilever-based piezoelectric energy harvesting structure Multiple elastic compact Piezoelectric energy harvester (PEH) designs, including a single cantilever plate, a single cantilever plate with a hole, and two cantilever plates with a hole, are simulated using different materials The frame, hole insertion, and geometry modification of the cantilever structure all play important roles in generating a substantial voltage from the vibrations in PEH This study presents an Eigen frequency analysis of different PEH structures GRAPHICAL ABSTRACT

Influence of environmental conditions and voltage application on the electromechanical performance of Nafion-Pt IPMC actuators

Ionic polymer–metal composites (IPMCs) are a class of ionic-type electroactive polymers which can be configured as capacitor actuators with very low voltage requirements (⩽5 V AC or DC). Their compact, portable, and lightweight properties, coupled with a biomimetic bending actuation response, makes them ideal for human–machine integrated technologies such as medical implants, active skins, and artificial muscles. Unfortunately, IPMC actuator’s hydration-related sensitivity inhibits practical application in industry and makes experimental research difficult. Therefore, this research sought to quantify the hydration-related parameters of IPMC actuators by applying a wide range of experimental tests to characterize the material’s hydration-dependent features. This included saturation, dielectric, and bending actuation measurements. The IPMC’s degree of saturation properties were classified to establish sample rehydration, preparation, and preservation techniques. IPMC electrical-solvent properties were measured to estimate IPMC actuation performance based on capacitance and dissipation measurements. Maximized actuation was identified for samples tested in 95% RH (i.e. percentage relative humidity). This condition produced an optimized displacement range and retained quality. Through statistical analysis, the work showed large electroactive performance variability (up to 50% deviation), which is a primary obstacle inhibiting this technology from practical application. Finally, an array of electrical field bias applications (i.e. cycled, constant, and post voltage removal monitoring) at intensities ranging from 0.75 to 1.2 V (direct current voltage) were used to quantify actuation rate, maximum displacement, as well as voltage application and removal back-relaxation behavior.

A Mutual Boosting Self-Excitation Hybrid Cell for Harvesting High Entropy Energy at 32% Efficiency.

Triboelectric nanogenerators (TENGs) and dielectric elastomer generators (DEGs) are potentially promising energy conversion technologies, but they still have limitations due to their own intrinsic characteristics, including the low energy output of TENGs caused by the air breakdown effect, and external polarization voltage requirement for DEGs, which severely limit their practical applications. Herein, coupling TENG with DEG is proposed to build a mutual beneficial self-excitation hybrid generator (named TDHG) for harvesting distributed and low-quality mechanical energy (high entropy energy). Experimental results demonstrate that the output charges of this TDHG are enhanced by fivefold of that of the conventional charge-excitation TENG, and continuous operation of DEG is also realized by simple mechanical triggering. More importantly, owing to the high peak power contributed by TENG and the long output pulse duration guaranteed by DEG, the TDHG realizes a much higher energy conversion efficiency of 32% in comparison to either the TENG (3.6%) or DEG (13.2%). This work proposes a new design concept for hybridized energy harvester toward highly efficient mechanical energy harvesting.

Temperature Characteristic Analysis of the Output Intrinsically Safe Buck Converter and Its Design Consideration

Aiming at the unreliability resulting from ignoring the temperature effect and randomness of switching frequency in the traditional design method of an intrinsically safe Buck converter, a reliable design method based on the minimum frequency and considering the temperature characteristic is proposed. The theoretical design range of capacitance is deduced according to the maximum output ripple voltage and output intrinsic safety performance requirements. Considering the temperature characteristics of the capacitor, the actual maximum and minimum capacitances are obtained corresponding to the theoretical design capacitance within a given temperature range. It is pointed out that the actual minimum capacitance increases with the decrease of switching frequency, while the actual maximum capacitance is independent of frequency. Therefore, it can be deduced that there exists a minimum frequency which can meet the requirements of both output ripple voltage and intrinsically safe performance. When the actual maximum capacitance equals the actual minimum capacitance, the analytic expression of the minimum frequency is obtained. Assuming a capacitance adjustment, the actual working frequency of the converter corresponding to the minimum frequency is deduced. The design flow of an intrinsically safe Buck converter based on the minimum switching frequency considering the temperature characteristic is presented. The correctness of the theoretical analysis and the feasibility of the proposed design method are verified by experimental results. This design method can also be applied to other types of intrinsically safe converters.

Design and Analysis of Front Side Modular Multilevel Converter for Smart Transformer in 15 kV Arba Minch Distribution Network Using Diverse Controllers and Multicarrier Modulation

This paper presents design and analysis of a bidirectional medium voltage (MV) front-side converter of smart transformer (ST) for Arba Minch Town distribution system. A modular multilevel converter (MMC) configuration is used in the MV side of the ST. The grid side MV is 15 kV RMS line value and the desired MVDC voltage is 24.5 kV for ensuring bidirectional operation of the converter in the time of grid outage. A half bridge semiconductor power module is used to model the front-side MMC. Based on the MV DC voltage requirement, the number of submodules per phase leg is designed to be four (four in the upper arm and four in the lower arm). Multicarrier modulation techniques such as phase-shifted PWM and level-shifted PWM are used to generate gate signals. The model is developed in MATLAB/Simulink, and its performance with respect to input side voltage harmonics, current harmonics, and output DC voltage value has been tested by carrying out several case studies under different controllers such as proportional integrator(PI), fuzzy inference system (FIS), and adaptive neuro fuzzy inference system (ANFIS) for obtaining reference signal for modulation. Level-shifted PWM is used with PI, FIS, and ANFIS, whereas phase-shifted PWM with a technique of introducing DC bias is used with PI controller alone. From the simulation results, it has been observed that better power system current quality of FS-MMC is obtained for PS-PWM (2.16%) than level-shifted PWM (5.22%). Use of FIS and ANFIS with level shift PWM method slightly brings down the current THD values to 2.98% and 2.72%, respectively (decrease by 2.5%). Also, a maximum output DC voltage of 24650 V is obtained for ANFIS with level shift PWM as compared to values obtained by PI with level shift PWM and PI with phase shift PWM.