Voltage Values Research Articles

A New Cascaded Multilevel Inverter for Modular Structure and Reduced Passive Components

In high-power applications, achieving adequate power quality in power converter design is accomplished by utilizing multilevel inverters instead of using two-level and three-level inverters. The device generates a sinusoidal output voltage, which results in reduced total harmonic distortion and lower voltage stress on the switches and leads to lower electromagnetic interference, making it suitable for use in renewable energy applications. However, to illustrate the advantages mentioned above, a significant number of switching devices and DC sources are necessary while raising the voltage levels. This article proposes an asymmetrical voltage generation method, which operates in a ratio of 1:5 and generates 25 levels using 11 power switches. The topology is modular in structure, and each module has a lower component count, which significantly reduces the overall cost. The proposed topology is capable of generating negative output voltage levels without the use of an H-bridge configuration, where only three switches are used to generate any voltage levels. The functionality of the developed module is amended by fixing different voltage values in DC sources. This article also presents a comprehensive examination of the circuit and the functioning of various voltage levels. The advantages of the proposed inverter have been demonstrated by comparative research with the currently existing MLI topologies. Ultimately, both the simulation and experimental findings validated the practical capabilities.

Evaluation of computed tomography anode voltage in clinical application: the influence of profiled filters

Monitoring of operational parameters of X-ray diagnostic equipment, including computer tomographs, is mandatory during acceptance and periodic tests in medical organizations. The importance of control of anode voltage of X-ray radiator is described (as one of the main technical parameters in diagnostic tests of patients, which can influence the quality of visualization and safe operation of the equipment). Anode voltage is evaluated by non-invasive methods using universal dosimeters in the user mode of equipment operation. The influence of profiled filters of Somatom Definition AS, SOMATOM go.All (Siemens, Germany) scanners on the accuracy of anode voltage measurement was investigated. The tests were conducted in clinic conditions without partial removal of the gantry (a structural element of the tomograph, inside which the system “X-ray emitter – detector” is located) and connection to the high-voltage circuit of the device. The distance between the sensitive elements of the measuring device and the displacement of the center of the sensing area relative to the position of the central axis of the X-ray beam of computed tomography scanner were taken into account. Normalized curves of kerma values, anode voltage values and their approximating analytical functions were obtained using a Piranha R&F/M 657 universal dosimeter (RTI Electronics AB, Sweden) at its displacement relative to the laser centralizer of computed tomography scanner. Based on the scheme for noninvasive estimation of anode voltage value, a formula of the relative deviation of the measured value of the anode voltage associated with the presence of a profiled filter at the output of the X-ray emitter of the tomograph and the displacement of the center point of the sensitive area of the measuring device relative to the central axis of the X-ray beam of the tomograph is obtained. The validity of the data based on the formula is confirmed experimentally. The results of the study will be helpful to technical specialists who maintain or control the X-ray computed tomography operating parameters.

Reliability analysis of output electrical response performance of multi-state flexoelectric structures under single and multiple failure modes

This paper proposes a reliability model of flexoelectric beams in the electrical open and short circuit states when different failure modes and the multiple failure modes of the output electrical response performances are considered, respectively. The reliability indices of the flexoelectric beams in the two circuit states can be defined based on the output electrical response models. Sequentially, the importance sampling (IS) and the mixed importance sampling (IS) methods are respectively used to calculate the reliability of the flexoelectric beams in single and multiple failure modes. The reliability results of the flexoelectric beams are verified by comparing them with the results of the Monte Carlo Simulation (MCS). The numerical results show that the flexoelectric beam is entered into a relatively safe and reliable state when the critical value of the open circuit voltage of 0.235 V and the thickness of the flexoelectric beams of 1 mm are considered as well as the length-thickness ratio of 20.

Sandwich-structured electrospun polyvinylidene difluoride sensor for structural health monitoring of glass fiber reinforced polymer composites

Stress monitoring and interlaminar failure detection attract much attention in glass fiber reinforced polymer (GFRP) structural health monitoring area. However, due to limitations of sensing or electrode materials, existing embedding sensors cannot be designed to have both of the abilities without sacrificing mechanical properties. This work fabricated a sandwich-structured sensor, which is composed of three layers of electrospun polyvinylidene difluoride membranes. The upper and lower electrodes are flexible membranes that ensure stable signal collection in the rigid GFRP material system. The sensor can quantitatively monitor the stress based on piezoelectric effect, and interlaminar crack propagation based on parallel plate capacitors. The voltage and capacitance values have a linear relationship with the stress level and crack length (R-square of the functions is 0.999 and 0.933), respectively. Due to the porous microstructure of electrospun membranes, polymer matric can well infiltrate the polyvinylidene difluoride nanofibers while preparing the sensor embedded GFRP. Thus, the perfect bonding of the sensor within GFRP ensures the effective sensing abilities until sample failure and negligible effect (< -7%) on the mechanical properties of GFRP.

Cu2+ ions implanted porous titania for efficient dye sensitized solar cells

In the quest to unlock the remarkable potential of nanotechnology, the sol-gel method was employed to craft a porous TiO2 nanostructured film, meticulously deposited onto FTO glass substrates. This endeavor marked a significant leap as a controlled bombardment of Cu ions, accelerated at 700 keV, at varying flux rates of 2x1013, 2x1014, and 2x1015 ions/cm² was introduced to these ingeniously engineered films. A comprehensive assessment of these nanocrystalline TiO2 structures, both before and after Cu+2 ion irradiation, revealed a fascinating array of results. he anatase tetragonal structure's permanence was validated by X-ray diffraction (XRD), which improved the material's stability and integrity. In the present study, an interesting observation was made that band edges show a dynamic behavior in Cuirradiated samples in UV-Vis spectroscopy. At 2x1014 ions/cm2, the phenomena peaked, revealing an intriguing redshift and an exceptionally low band gap value of 3.39 eV. In photoluminescence spectra, the peaks corresponding to the lattice defects show a significant reduction when the flux of the Cu ions on TiO2 is adjusted to 2 x 1014 ions/cm2. It is an indication that film quality and purity have improved. This arrangement for photoanode modification helps in the development of dye-sensitized solar cells with tremendous characteristics. The fabricated device with this novel approach results in high values of open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF), and maximum photoconversion efficiency of 5.10%. These findings indicate a new era of possibilities in the field of renewable energy, since these nanostructured materials have the ability to significantly alter the solar field.

Self-regulating heating and self-powered flexible fiber fabrics at low temperature

Self-regulating heating and self-powered flexibility are pivotal for future wearable devices. However, the low energy-conversion rate of wearable devices at low temperatures limits their application in plateaus and other environments. This study introduces an azopolymer with remarkable semicrystallinity and reversible photoinduced solid-liquid transition ability that is obtained through copolymerization of azobenzene (Azo) monomers and styrene. A composite of one such copolymer with an Azo: styrene molar ratio of 9:1 (copolymer is denoted as PAzo9:1-co-polystyrene (PS)) and nylon fabrics (NFs) is prepared (composite is denoted as PAzo9:1-co-PS@NF). PAzo9:1-co-PS@NF exhibits hydrophobicity and high wear resistance. Moreover, it shows good responsiveness (0.624 s−1) during isomerization under solid ultraviolet (UV) light (365 nm) with an energy density of 70.6 kJ kg−1. In addition, the open-circuit voltage, short-circuit current and quantity values of PAzo9:1-co-PS@NF exhibit small variations in a temperature range of -20 °C to 25 °C and remain at 170 V, 5 μA, and 62 nC, respectively. Notably, the involved NFs were cut and sewn into gloves to be worn on a human hand model. When the model was exposed to both UV radiation and friction, the temperature of the finger coated with PAzo9:1-co-PS was approximately 6.0°C higher than that of the other parts. Therefore, developing triboelectric nanogenerators based on the in situ photothermal cycles of Azo in wearable devices is important to develop low-temperature self-regulating heating and self-powered flexible devices for extreme environments.

Achievement of low turn-on voltage in Ga2O3 Schottky and heterojunction hybrid rectifiers using W/Au anode contact

The use of the low work function (4.5 eV) tungsten (W) as a rectifying contact was studied to obtain low on-voltages in W/Ga2O3 Schottky rectifiers and NiO/Ga2O3 heterojunction rectifiers that were simultaneously fabricated on a single wafer. The devices were produced with varying proportions of relative areas and diameters, encompassing a spectrum from pure Schottky Barrier Diode (SBD) to pure Heterojunction Diode (HJD) configurations. The turn-on voltages with W contacts ranged from 0.22 V for pure Schottky rectifiers to 1.50 V for pure HJDs, compared to 0.66 and 1.77 V, respectively, for Ni/Au contacts. The reverse recovery times ranged from 31.2 to 33.5 ns for pure Schottky and heterojunction rectifiers. Switching energy losses for the SBD with W contacts were ∼20% of those for HJDs. The reverse breakdown voltages ranged from 600 V for SBDs to 2400 V for HJDs. These are the lowest reported turn-on voltage values for 600/1200 V-class Ga2O3 rectifiers that extend the range of applications of these devices down to the voltages of interest for electric vehicle charging applications.

Ripple of a DC/DC converter based on SEPIC topology

Mathematical models serve as the basis for unified methods for the calculation and designing of radio-electronic devices. The developed limiting continuous mathematical model of a DC/DC converter, built using SEPIC topology, allows to determine the range of changes in currents flowing through the inductor windings and voltages on the capacitor plates, as well as to determine their maximum and minimum values for various converter parameters, such as switching frequency of the power switch, fill factor, element ratings, etc. The research results have shown that the phase coordinates of the mathematical model tend to the real values of currents and voltages of the converter when the switching frequency of the power switch is more than 200 kHz. Correspondence is established between the calculated values of the pulsation ranges and the results obtained during modelling (with changes in the filling factor and switching frequency of the power switch).

Influence of Applied Discharge Voltage and Gas Flow Rate on Nickel Plasma Jet Parameters Diagnosed by Optical Emission Spectroscopic Technique

Abstract: In this work, we measure the plasma parameters by using an AC high-voltage power supply that generates a non-thermal plasma jet system at atmospheric pressure. A nickel (Ni) metal strip, with dimensions of 1.5 × 10 cm2, was connected to the anode electrode of the AC power supply. This nickel strip was immersed in a flask with a small amount of distilled water positioned below the plasma plume nozzle. Optical emission spectroscopy (OES) was used to diagnose the plasma system at different argon gas flow rates (1-5 L/min) and varying applied voltage values (11-15 kV). It is significant to know the processes accompanying plasma generation to measure their parameters which include the electron temperature (Te), electron number density (ne) of the plasma, Debye length (λD), and plasma frequency (fp). Our results showed an increase in the intensity of spectral lines with the increase in applied discharge voltage (11-15 kV). The maximum peak for ArI was observed at a wavelength of 811.531 nm, and the maximum peaks for nickel (Ni) were observed at wavelengths of 285.21 and 519.70 nm. Also, the results indicated a gradual increase in electron temperature (Te) and electron density (ne) values at the applied voltage of 0.403-0.468 eV. Likewise, the electron density (ne) was in the range of (11.486-13.851) × 1017 cm-3. Keywords: Atmospheric plasma jet, Nickel (Ni) plasma parameters, Electron temperature, Spectroscopic optical emission (OES).

Implementation of Solar Panels as an Alternative to Electric Power Used in WiFi-based Freezer Box Temperature Monitoring System (Case Study of NN Frozen Food Wajak)

A freezer box temperature monitoring system using solar panels as alternative power is an important technology to ensure the quality of stored products. This research develops a WiFi-based temperature monitoring system that uses a DS18B20 temperature sensor, a PZEM-004T digital sensor, and an ESP8266 module to read and send real-time data to a website platform. Data is collected through a temperature sensor connected to the ESP8266 microcontroller, then displayed on the LCD screen and uploaded to the server for further monitoring via WiFi connection. The results show that this system successfully maintains the freezer box temperature at optimal conditions with an average temperature value of -24.82°C and a temperature range ranging from -28.81°C to -19.63°C. The voltage values are in the range of 197.10 V - 218.70 V, current between 0.02 A - 1.03 A, and power between 158 W - 186.80 W.

Evaluation Approach and Controller Design Guidelines for Subsequent Commutation Failure in Hybrid Multi-Infeed HVDC System

Due to the difference in output characteristics between the line-commutated converter-based high-voltage direct current (LCC-HVDC) and voltage-source converter-based high-voltage direct current (VSC-HVDC), the hybrid multi-infeed high-voltage direct current (HMIDC) presents complex coupling characteristics. As the AC side is disturbed, the commutation failure (CF) occurring on the LCC side is the main factor threatening the safe operation of the system. In this paper, the simplified equivalent network model of HMIDC is established by analyzing the output characteristics of VSC and LCC. Hereafter, based on the derived model and the control system of LCC-HVDC, the dynamic equations of the extinction angle are deduced. Consequently, by applying the phase portrait method, the causes of CF occurring in the HMIDC system as well as the impacts of control parameters on the transient stability are revealed. Furthermore, the stabilization boundaries for the reference value of the DC voltage are obtained via the above analysis. Finally, the theoretical analysis is verified by the simulations in the PSCAD/EMTDC.

Design and Analysis of MEMS-Based Capacitive Power Inverter Using Electrostatic Transduction

In this study, a capacitive microelectromechanical system (MEMS) based DC/AC power inverter design for renewable energy applications is proposed, modeled, and analyzed. In the proposed approach, electrostatic actuation is preferred to develop a DC/AC power inverter with varying phase overlap lengths for solar energy systems. The operating voltage required during the analysis is applied to the active part as the tensile stress. Thus, the maximum displacement is achieved with less instability. The developed inverter is based on MEMS to achieve miniaturized performances, producing smooth sine wave output, efficiently obtaining the signal frequency, and low power consumption. The proposed inverter has a thickness of 325 μm, an active settlement area of 45x45x0.585 mm3, and an initial capacitance value of 2.9 pF. In addition, a 50 Hz mechanical resonance frequency was used to be compatible with the frequency of the city network. It can convert voltage values between 0.5V and 24V DC with a MEMS power inverter. Since the inverter is based on a capacitive structure, it provides near-zero power consumption. The frequency and waveform of the converted DC/AC signal match the AC signal of a power grid with an efficiency of 5%.

Using the proportional dual integral strategy to improve the characteristics of the indirect field-oriented control of DFIG-based wind turbine systems

In this work, a new indirect field-oriented command (IFOC) for wind systems based on a doubly-fed induction generator (DFIG) is designed to get better energy and stream quality. Also, overcoming the problems of IFOC. It is proposed to use proportional dual integral (PDI) controllers in order to replace traditional controllers and augment the robustness of the studied wind turbine system. The proposed IFOC-PDI is a modification of the IFOC, where the basic idea behind the designed technique is to combine a proportional-integral (PI) regulator with an integral term. This technique has been applied to the machine inverter, where the IFOC-PDI aims to calculate reference voltage values. The pulse width modulation (PWM) is used to translate voltage reference values ​​into pulses to run the machine inverter. The main objective of this article is to compare the competence of the IFOC-PDI to that of the IFOC-PI in different tests, including two different wind speed profiles and DFIG parameters variation. The major benefit of this command is a decrease in harmonic distortion of the currents, and active and reactive power (Ps and Qs) fluctuations. The results using MATLAB demonstrated that the IFOC-PDI improved the IFOC-PI in the minimization of stream harmonic distortion (6.63%, 10.42%, and 17.86%) and notable minimization of fluctuations in both Ps (32.08%, 46.24%, and 12.10%) and Qs (45.95%, 66.88%, and 14.49%). Also, the overshoot value of Ps was minimized compared to the IFOC-PI in all tests by ratios estimated at 57.79%, 12.41%, and 33.96%. The steady-state error of Ps was minimized compared to the IFOC-PI in all tests by ratios estimated at 29.43%, 85.88%, and 76.36%. The IFOC-PDI is also very resistant in the case of DFIG parameters variation.

Synthesis, Crystal Structure, and Theoretical Screening of Solvatochromism and Light-Harvesting Performance of Hexamine V-Substituted Lindqvist-Based Photosensitizer for Photovoltaic Solar Cells.

In this paper, we employ density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches to predict the solvatochromism and light-harvesting properties of a newly synthesized hybrid hexamine (HMTA) vanadium-substituted Lindqvist-type (V 2 W 4 ) polyoxometalate (POM), (C7H15N4O)2(C6H13N4)2[V2W4O19]·6H2O, (HMTA-V 2 W 4 ) for application in dye-sensitized solar cells (DSSCs). Single crystal X-ray diffraction (XRD) and noncovalent interaction (NCI) analyses show a 3D-supramolecular packing stabilized by means of hydrogen bonds and van der Waals (vdW) and ionic interactions between highly nucleophilic cage-like HMTA surfactant, lattice water, and electrophilic V 2 W 4 polyanions. Experimental and theoretical UV/vis absorption spectra show large absorption in the visible region, which is strongly solvent polarity dependent. This solvatochromic behavior can be attributed to hydrogen bonding interactions between the V 2 W 4 polyanion and protic solvents. Furthermore, the energy level of semiconductor-like nature of HMTA-V 2 W 4 with high LUMO level matches well with the conduction band (CB) of TiO2, which is beneficial for the photovoltaic device performance. The photovoltaic empirical parameters are theoretically predicted to demonstrate a remarkably high open-circuit voltage (Voc) value (1.805 eV) and a photoelectric conversion efficiency (PCE) value up to 8.7% (FF = 0.88) along with superior light-harvesting efficiency (LHE) (0.7921), and therefore, the studied compound is expected to be a potential candidate as a photosensitizer dye for applications in DSSCs. The aim of this work was to broaden the range of applications of POMs, owing to their low-cost fabrication, leveraging and flourishing optoelectronic properties, and ever-improving efficiency and stability for use in future technology pointed to the development of clean and green renewable energy sources to solve the current energy crisis.

Implementation of Regenerative Brake System Controller by Using Mini Controller Arduino

The key requirement for electric vehicles is efficient braking. The objective of this study is to provide a detailed description of the regenerative braking system utilizing various power flow regulators. This study utilizes a buck-boost type Boost Converter. There are two methods employed to modify the voltage derived from the fluctuating input produced during regenerative braking: one to decrease it and the other to boost it. Subsequently, a voltage sensor detects the resulting output voltage, which is then regulated using an Arduino microcontroller. The examination findings indicate that the buck-boost converter performs well, maintaining an output voltage within the range of 39-40 volts. This allows it to function well even when there are fluctuations in the input voltage. The voltage value can be utilized for the purpose of charging a battery for a 36 Volt electric motor. The findings demonstrate the efficacy of utilizing a Buck-Boost Converter regulator. Furthermore, it could charge the battery within a span of 8 seconds, making it a viable option for electric vehicles as an alternative to regenerative braking for battery recharging.

Measurements and TCAD simulations of guard-ring structures of thin silicon sensors before and after irradiation

The developing of high performing silicon detectors for particle tracking in the next generation of high-energy physics experiments at future colliders (e.g., HL-LHC, FCC) able to operate efficiently up to very high fluence (∼1⋅10171MeVneq/cm2) is of the utmost importance. In order to sustain high voltage values with minimum leakage current injection into the core region of the sensor, the design and optimisation of the Guard-Ring (GR) protection structure is crucial, especially when small substrate thicknesses are used. In a recent R&D batch produced at Fondazione Bruno Kessler (FBK) in the framework of the “eXFlu” project - INFN CSN5 grant for Young Researchers, different optimisation studies of GR structures for thin substrates (45, 30, 20 and 15μm) up to high fluence (2.5⋅10151MeVneq/cm2) have been addressed. These have been enabled thanks to ad-hoc advanced Technology CAD (TCAD) modelling of different GR design strategies, accounting for the comprehensive bulk and surface radiation-induced damage effects, and an extensive test campaign on such GR structures, both before and after irradiation. In this paper the validation of the development framework of the various GR design options before and after irradiation is presented.

Total Ionizing Dose (TID) Effects on the 1.2 kV SiC MOSFETs under Proton Irradiation

In this paper, the effects of various proton irradiation energies and doses on the electrical characteristics of SiC MOSFETs have been evaluated and characterized using a proton accelerator. The devices under test were designed, fabricated and packaged using 1.2 kV/0.6 µm-tech SiC MOSFET processes. The results demonstrate that the threshold voltage (Vth) of the irradiated devices shifted towards negative values due to the radiation-induced positive oxide trapped charges. Moreover, this negative shift in Vth and positive trapped charges of field limiting ring (FLR) oxide led to an increase in output currents and a reduction in the breakdown voltage values.

Motion speed control of magnetic microsphere robot under alternating signals

Gradient magnetic field driving method does not have strict structural requirements for micro robots, making processing convenient. However, the speed control parameter of micro robots under gradient magnetic fields is single, which limits the practical application of this type of robots. Therefore, this article proposes to use alternating signals to control the motion speed of magnetic microsphere robots. Here, a motion analysis model of a magnetic microsphere robot driven by alternating signals is established, and a formula for calculating the movement speed of the magnetic microsphere robot is provided. The special motion mode of the magnetic microsphere robot driven by alternating signals is considered, and the correctness of the theoretical calculation is verified by experiments. The mechanisms and conditions for the different motion modes of magnetic microsphere robots are revealed. The movement speed of the magnetic microsphere robot under the alternating voltage signals is determined as a function of signal frequency, signal duty cycle, and bias voltage value. The results show that under the alternating voltage signals, the magnetic microsphere robot has three different motion states, namely rotation -movement alternation, swing-movement alternation, and pure movement. There are three control parameters of the speed, which are signal change frequency, duty cycle, and bias voltage.

Mechanical and electric friction properties of Poly(methyl methacrylate) – Nitrocellulose blend polymer for triboelectric nanogenerators

In this study, nitrocellulose - polymethyl methacrylate (NC/PMMA) blend film as a positive triboelectric material for triboelectric nanogenerator (TENG) with controlled flexibility was successfully synthesized by varying the PMMA content in the polymer blend. The combination of NC and PMMA reduced the limitations of the individual component materials with improved mechanical properties such as tensile strength, elastic modulus and elongation at breaking point. The TENG fabricated from NC/PMMA as a positive friction layer paired with fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE) as a negative friction layer demonstrates a high peak to peak voltage output of 234 V at low frequency and with an actuation force of 10~N. The open circuit triboelectric voltage value maintains 91% durability after 26200 click-release cycles. This work provides a potential approach to simultaneously improve the electrical and mechanical properties of triboelectric materials, promoting the possibility of practical applications of TENG.

Gate-Switchable Molecular Diffusion on a Graphene Field-Effect Transistor.

Controlling the surface diffusion of particles on 2D devices creates opportunities for advancing microscopic processes such as nanoassembly, thin-film growth, and catalysis. Here, we demonstrate the ability to control the diffusion of F4TCNQ molecules at the surface of clean graphene field-effect transistors (FETs) via electrostatic gating. Tuning the back-gate voltage (VG) of a graphene FET switches molecular adsorbates between negative and neutral charge states, leading to dramatic changes in their diffusion properties. Scanning tunneling microscopy measurements reveal that the diffusivity of neutral molecules decreases rapidly with a decreasing VG and involves rotational diffusion processes. The molecular diffusivity of negatively charged molecules, on the other hand, remains nearly constant over a wide range of applied VG values and is dominated by purely translational processes. First-principles density functional theory calculations confirm that the energy landscapes experienced by neutral vs charged molecules lead to diffusion behavior consistent with experiment. Gate-tunability of the diffusion barrier for F4TCNQ molecules on graphene enables graphene FETs to act as diffusion switches.