Voltage Variations Research Articles

Research on surface energy and corrosion resistance by electrochemical processing of 304-Cu stainless steel

In this paper, activation (H7 series), over-passivation (H6 series), and passivation states were presented in the electrochemical processes. 304-Cu stainless steel was treated with two electrolytes (H6, H7), and then passivated by air oxidation, citric acid pickling, or ultraviolet irradiation. The variations of voltage and surface energy described the different stages of the process, corresponding to the changes in morphology, and the evolution of the passivation film. The H6 series with flat surfaces had higher corrosion potential and pitting corrosion potential, and the corrosion current was lower. The H7 series with rough surfaces had a thicker passivation film, poorer pitting corrosion resistance, and the best general corrosion resistance. The formula derived from the Arrhenius equation illustrates the functional relationship between the surface energy and the resistance of the passivation film, and the results validated the conclusions.

Simulation and optimization of EMI filter of conducted emission for high voltage gain DC-DC converter

In the continuity of the work on design of high voltage gain DC-DC converter, used for feeding the CubeSat electrospray thrusters with a variable output voltage according to the maneuver size, this paper introduces a simulation of the converter model with MATLAB/Simulink to determine its conducted emission level. By referring to the MIL-STD-461 standard, a required passive electromagnetic interference (EMI) filter parameters are calculated to reduce, under thresholds, the converter noise. With consideration of the available volume and power constraints in this kind of satellite, the design of common-mode (CM) choke is optimized with proposed procedure optimization, so as to reduce its volume and electrical losses. Also, this optimization procedure can be generalized and applied for any passive EMI filter design.

Encapsulation structure and in-situ embedding test and model study of a new type of road piezoelectric energy collector

In recent years, research on road piezoelectric energy harvesters (RPEH) has made great progress in the field of road vibration energy harvesting. However, the research on the packaging structure and embedding method of RPEH is not comprehensive. In this paper, a new type of transducer unit structure is developed, which can improve the electrical energy output compared with the drum piezoelectric transducer, and its waterproof performance of the transducer unit is tested under different water depth and duration. Then, a new RPEH package structure is made, and the output performance is compared with the three commonly used package structures in the current research, and the field construction of RPEH with different embedding methods is carried out on the actual road to evaluate the electrical energy output capacity of RPEH under different embedding methods, and the best construction method of RPEH is summarized through durability test. Finally, the three-dimensional simulation model of RPEH with different construction methods is established, and the stress and voltage are analyzed by finite element method to verify the best embedding method. The test results show that the piezoelectric output efficiency of the new transducer unit is increased by 38.9 %, and it still has good electrical energy output after 24 h immersion at a depth of 1.5 m, and its waterproof level reaches IPX8. Under larger excitation frequency and load, the indoor output of RPEH in the new package structure has better output performance in indoor test. The bolt-spring package is used to apply pre-pressure to RPEH, and the output efficiency of RPEH is improved. When the excitation conditions are 10 kN, 10 Hz, the output power is increased by 11.1 %, 127.3 % and 247.4 % compared with the other three package structures. The maximum power of RPEH is 3.41 W by placing concrete on the bottom surface of RPEH sponge washer and using asphalt as the pavement layer to ensure the durability of piezoelectric pavement. The finite element analysis illustrates the strain and voltage variation of piezoelectric pavement with different embedment modes, and the simulation results are consistent with the test results. The research results provide an important basis for the design of RPEH packaging structure and embedding method in road piezoelectric engineering.

Open-Circuit Voltage Variation in LiCoO2 Battery Cycled in Different States of Charge Regions

Open-Circuit Voltage Variation in LiCoO2 Battery Cycled in Different States of Charge Regions

Maximum span determination and optimal sizing of cable for improved performance of droop-controlled DC microgrid

DC microgrids are seen as smart solutions to interface DC loads and distributed energy resources (DERs). However, in DC microgrids, the placement of sources and loads as well as the size of cable impact the system’s span, regulation of voltage, and losses. This paper proposes novel algorithms to determine the maximum span and optimal size of cable for the improved performance of a droop-controlled DC microgrid. The proposed algorithms utilize an improved power flow analysis (IPFA) method based on Newton-Raphson technique to determine the maximum span and the optimal size of cable, enhancing the voltage regulation and reducing the cost. Additionally, the impacts of power rating, droop constants, and size of cable on the DC microgrid’s maximum span are investigated and reported. Owing to the intricate nature of the problem concerning the ideal size of cable for the droop-controlled DC microgrid, a heuristic optimization approach is employed. Further to enhance the rate of convergence and computational performance, an improved particle swarm optimization (IPSO) is also proposed. The constraint of keeping the bus voltage variations below the allowable voltage regulation limits is applied to the objective function of the optimization problem. In the case of a droop-controlled, DC microgrid having a specified configuration, the suggested algorithm can determine the ideal size of cable, guaranteeing both the least cost and enhanced voltage regulation. Comprehensive numerical and modelling results have been presented for a droop-controlled DC microgrid with different loads and DERs to verify the effectiveness of the proposed methods. Furthermore, the analysis reveals that configuration III of the DC microgrid with an optimal cable size of 19 mm2 lowers the absolute voltage regulation to as low as 1.06 V. The results of the detailed analysis validate the enhanced performance of the proposed algorithms and are highly useful to both system designers and consumers of the DC microgrids, eventually paving the way for the widespread use of DC microgrids in the future.

Interleaved High Voltage Gain DC-DC Converter with Winding-Cross-Coupled Inductors and Voltage Multiplier Cells for Photovoltaic Systems

An interleaved high voltage gain DC-DC converter with winding-cross-coupled inductors (WCCIs) and voltage multiplier cells is proposed for photovoltaic systems. The converter configuration is based on the interleaved boost converter integrating the diode-capacitor clamp circuits, the winding-cross-coupled inductors, and voltage multiplier cells to increase the voltage gain and reduce the semiconductor voltage stresses. The equal current sharing of two phases is achieved with the help of the winding-cross-coupled inductors. The converter achieves high voltage gain while operating at a proper duty ratio. The low-voltage-rated MOSFETs with low on-resistance are available to reduce the conduction losses due to the low switch voltage stress. The leakage energy of the coupled inductors is recycled such that the voltage spikes on the power switches are avoided. The input current ripple is decreased due to the interleaved operation. The operating principle and steady-state analysis of the proposed converter are proposed in detail. The design guidelines of the proposed converter are given. In addition, the closed-loop controlled system of the proposed converter is designed to diminish the effect of the variations in input voltage and load on the output voltage. Finally, the experimental results of a 1000 W converter prototype with 36 V input and 400 V output are given to validate the theoretical analysis and the converter performance.

Short-voltage pulse generation for induction heating load detection on a multi-output inverter with shared power devices

Purpose The purpose of this paper is to develop a load detection method for domestic induction cooktops. The solution aims to minimize its impact in the converter power transmission while enabling the estimation of the equivalent electrical parameters of the load. This method is suitable for a multi-output resonant inverter topology with shared power devices. Design/methodology/approach The considered multi-output converter presents power devices that are shared between several loads. Thus, applying load detection methods in the literature requires a halt in the power transfer to ensuring safe operation. The proposed method uses a complementary short-voltage pulse to excite the induction heating (IH) coil without stopping the power transfer to the remaining IH loads. With the current through the coil and the analytical equations, the equivalent inductance and resistance of the load is estimated. The precision of the method has been evaluated by simulation, and experimental results are provided. Findings The measurement of the current through the induction coil as a response to a short-time single-pulse voltage variation provides enough information to estimate the load equivalent parameters, allowing to differentiate between no-load, non-suitable IH load and suitable IH load situations. Originality/value The proposed method provides a solution for load detection without requiring additional circuitry. It aims for low power transmission to the load and ensures zero-voltage switching and reduced peak current even in no-load cases. Moreover, the proposed solution is extensible to less complex converters, as the half bridge.

A novel heap-based optimizer for allocation of shunt capacitors in radial distribution network

Due to power losses, a sizeable portion of the electrical power produced is lost, which causes voltage deviation and instability as a result of rising load demand at the radial distribution network (RDN). Shunt capacitor penetration will enhance the RDN’s efficiency by reducing power losses, improving the voltage profile and stability. For the best sizing and allocation of shunt capacitors (SCs) in RDN, a novel human-based metaheuristic heap-based optimizer (HBO) influenced by the ideas of corporate rank hierarchy (CRH) of standard organization is presented. The real power loss, voltage variation, and voltage stability index are all minimized while equality and inequality criteria are met by the HBO optimal allocation of SCs. One, two, and three numbers of SCs were investigated when installing the reactive compensating devices. Using typical IEEE 33-bus and 69-bus RDNs, covering a range of scenarios in the form of single- and multi-objective functions, the effectiveness of the HBO technique was examined. The real power loss for the conventional IEEE 33-bus and 69-bus RDN was reduced by 34.46% and 35.50%, respectively compared to their respective base cases. By contrasting the outcomes of the power loss with well-established and new optimization approaches, the efficacy and superiority of the suggested HBO were demonstrated.

A coordinated voltage control scheme based on linearized power flow functions for non-optimal and optimal problems

This paper proposes a coordinated voltage control scheme for transmission systems based on linearized power flow functions to determine the set points of local control voltage devices. The scheme considers models and interactions between different devices to attain the appropriate performance (non-optimal or optimal) of the whole power system. The sensitivity analysis is used to formulate a partly linearized model that relates the voltage variations of buses to the reactive power variation of synchronous machines, settings of static VAr compensators (SVCs), shunt capacitors susceptance, and tap position of load tap changers (LTCs) to determine the set of the settings of the voltage control devices. Two formulations are proposed by considering the susceptance of SVCs or the slope and reference voltage of characteristics of SVCs as control variables. The developed formulation based on the linearized power flow functions provides the possibility of the practical implementation of the coordinated voltage control scheme, especially the optimal one, by reducing the model complexity and solving time. The performance of the proposed formulations is investigated by some studies of voltage control and an optimally coordinated problem on the IEEE 30-bus and IEEE 118-bus test systems.

Revolutionizing load management: A novel technique to diminish the impact of electric vehicle charging stations on the electricity grid

The proliferation of Electric Vehicle Charging Stations (EVCSs) raises challenges for power grids, resulting in increased losses and variations in voltage. The study describes a novel technique for reducing the impact of EVCSs on the electricity grid. Distributed Generators (DGs) are strategically deployed at susceptible nodes. To identify nodes vulnerable to EV charging-induced overloading, the weak bus placement approach is used. DGs are placed at these nodes to increase capacity and maintain grid stability. Contingency analysis is used to simulate the grid's response to various disruptions in order to assess the strategy's efficacy. The study includes 13 EVCSs, each with a 25 MW capacity, located at predetermined load buses. This integration increases the demand from 2,850 MW to 3,175 MW, resulting in 55.65 MW of system losses. Three more DGs, each with a different capacity, contribute to the system losses being effectively reduced to 51.016 MW, which is higher than the base losses of 51.025 MW. This study's main objectives were to: (1) thoroughly evaluate the impact of EVCSs using the Newton-Raphson (NR) load flow; and (2) provide a systematic strategy for addressing the power losses and voltage fluctuations brought on by EVCSs. This approach involves integrating DGs strategically.

Probing single electrons across 300-mm spin qubit wafers

Building a fault-tolerant quantum computer will require vast numbers of physical qubits. For qubit technologies based on solid-state electronic devices1–3, integrating millions of qubits in a single processor will require device fabrication to reach a scale comparable to that of the modern complementary metal–oxide–semiconductor (CMOS) industry. Equally important, the scale of cryogenic device testing must keep pace to enable efficient device screening and to improve statistical metrics such as qubit yield and voltage variation. Spin qubits1,4,5 based on electrons in Si have shown impressive control fidelities6–9 but have historically been challenged by yield and process variation10–12. Here we present a testing process using a cryogenic 300-mm wafer prober13 to collect high-volume data on the performance of hundreds of industry-manufactured spin qubit devices at 1.6 K. This testing method provides fast feedback to enable optimization of the CMOS-compatible fabrication process, leading to high yield and low process variation. Using this system, we automate measurements of the operating point of spin qubits and investigate the transitions of single electrons across full wafers. We analyse the random variation in single-electron operating voltages and find that the optimized fabrication process leads to low levels of disorder at the 300-mm scale. Together, these results demonstrate the advances that can be achieved through the application of CMOS-industry techniques to the fabrication and measurement of spin qubit devices.

Current dependence of output voltage and discharge capacity of a tertiary battery

Tertiary batteries (TBs), which can be charged by a temperature change (ΔT), are prospective energy-harvesting devices. In this work, we investigated the variations in the output voltage (VTB) and discharge capacity (QTB) with current (I) of NaxCo[Fe(CN)6]0.87/NaxNi[Fe(CN)6]0.94 TBs (ΔT of 30 K) per unit weight of total active materials at 45 °C. Reflecting the battery resistance R, VTB(I) decreases with increasing I as VTBIRI=VTB0−MRI, where M is the total weight of the active material. We found that QTB(I) had values that were slightly smaller than those obtained by incorporating only the voltage-drop effect, QTBIRI=QTB(0)×VTBIR(I)VTB(0). The deviation between the observed QTB(I) and QTBIR(I) can be accurately explained in terms of the I-induced deformation of the discharge curve.

Investigating the impact of applied magnetic field and current on anode power deposition in AF-MPDT

The high temperature superconductors enhanced magnetoplasmadynamic thruster is a promising device for various space mission scenarios. However, a critical issue hindering the enhancement of the thruster’s performance is the problem of anode power deposition. Previous studies have identified the anode fall voltage as a major contributor to this power deposition. This paper introduces an approximate analytical formula for calculating anode power deposition resulting from anode fall voltage. The paper further analyzes and calculates the variation of anode fall voltage with an applied magnetic field and discharge current. The findings reveal a direct correlation between applied magnetic field and both anode fall voltage and power, indicating an increase with higher magnetic field values. In contrast, while the anode fall voltage experiences a slight decline with increased discharge current, the anode power deposition remains elevated due to the transition from field ionization to thermal ionization. To gain a comprehensive understanding of anode power deposition, an experiment was conducted to obtain measurements under different operating conditions, involving varying levels of applied magnetic field and discharge current. The experimental results align with the theoretical predictions. These insights have the potential to serve as a valuable reference for enhancing the efficiency of magnetoplasmadynamic thrusters, bringing us closer to unlocking the full potential of these remarkable propulsion systems in the realm of space exploration.

High Mobility Amorphous Polymer‐Based 3D Stacked Pseudo Logic Circuits through Precision Printing

AbstractDirect printing of conjugated polymer thin‐film transistors enables the fabrication of deformable devices with low cost, high throughput, and large area. However, a relatively poor device performance of printed devices remains a major obstacle to their application in high‐end display backplanes and integrated circuits. In this study, high‐performance and highly stackable printed organic transistors is developed, arrays, and circuits using a near‐amorphous polymer, indacenodithiophene‐co‐benzothiadiazole (IDT‐BT). The printed devices exhibited high saturation mobility (>1 cm2 V−1 s−1), high on/off ratio (>107), and low subthreshold slope (245 mV dec−1). In addition, 16 × 16 printed IDT‐BT arrays achieved 100% fabrication yield, with excellent device‐to‐device uniformity and low variations of mobility (9.55%) and threshold voltage (4.51%), and good operational and environmental stability (>365 days). Furthermore, five stacked 3D transistors are demonstrated with an excellent 3D uniformity without compromising device performance due to a low required thermal budget for processing amorphous IDT‐BT. Finally, a new concept of 3D universal logic gate with high voltage gain (33.91 V/V) and record density (100 printed transistors per cm2) is proposed and fabricated, which is relevant for the commercialization of low‐cost printed display backplanes and high‐density integrated circuits based on highly processable polymeric semiconductors.

Radiation dose reduction and image quality improvement with ultra-high resolution temporal bone CT using deep learning-based reconstruction: An anatomical study

PurposeThe purpose of this study was to evaluate the achievable radiation dose reduction of an ultra-high resolution computed tomography (UHR-CT) scanner using deep learning reconstruction (DLR) while maintaining temporal bone image quality equal to or better than high-resolution CT (HR-CT). Materials and methodsUHR-CT acquisitions were performed with variable tube voltages and currents at eight different dose levels (volumic CT dose index [CTDIvol] range: 4.6–79 mGy), 10242 matrix, and 0.25 mm slice thickness and reconstructed using DLR and hybrid iterative reconstruction (HIR) algorithms. HR-CT images were acquired using a standard protocol (120 kV/220 mAs; CTDI vol, 54.2 mGy, 5122 matrix, and 0.5 mm slice thickness). Two radiologists rated the image quality of seven structures using a five point confidence scale on six cadaveric temporal bone CTs. A global image quality score was obtained for each CT protocol by summing the image quality scores of all structures. ResultsWith DLR, UHR-CT at 120 kV/220 mAs (CTDIvol, 50.9 mGy) and 140 kV/220 mAs (CTDIvol, 79 mGy) received the highest global image quality scores (4.88 ± 0.32 [standard deviation (SD)] [range: 4–5] and 4.85 ± 0.35 [range: 4–5], respectively; P = 0.31), while HR-CT at 120 kV/220 mAs and UHR-CT at 120 kV/20 mAs received the lowest (i.e., 3.14 ± 0.75 [SD] [range: 2–5] and 2.97 ± 0.86 [SD] [range: 1–5], respectively; P = 0.14). All the DLR protocols had better image quality scores than HR-CT with HIR. ConclusionUHR-CT with DLR can be performed with up to a tenfold reduction in radiation dose compared to HR-CT with HIR while maintaining or improving image quality.

Development of a dose-rate dosimeter using a silicon photodiode for a medical linear accelerator in a 10 MV flattening filter-free mode.

This study was aimed at developing a dose-rate dosimeter to measure the instantaneous dose rate of a commercially available medical linear accelerator. A dose-rate dosimeter composed of a silicon photodiode (Si-PD), a complementary metal-oxide semiconductor single operational amplifier, a resistor of 20 MΩ, a capacitor of 100 pF, and a mini-substrate measuring 16 × 16mm2 was evaluated. Voltage outputs from the proposed dosimeter were measured using an analog-to-digital converter on a microcomputer. A custom-made x-ray tube generator at an energy of 120kV with a tube current ranging from 0.1 to 2.0 mA was used for the dose-rate calibration. Dose-rate calibration was performed 83.3mm from an x-ray source using a commercially available semiconductor dosimeter. The developed Si-PD dosimeter could measure up to 0.6 Gy/s at a distance of 19.3mm from the x-ray source. Measurements were also performed using a medical linear accelerator in a 10 MV flattening filter-free mode at depths of 0, 25, 50, and 100mm with an irradiation field of 100 × 100mm2 at a constant distance of 1000mm from the source to the dosimeter. A peak voltage variation corresponding to the instantaneous dose rate was observed using a sampling period of 1.0ms, and the peak voltages decreased with the depth. The detected pulse numbers were 512, 484, 491, and 511 at depths of 0, 25, 50, and 100mm, respectively.

Gate-controlled spin injection polarity in 2D transistors with Schottky barrier

In 2D semiconductors, the Schottky barrier formed at the metal–semiconductor interface plays a crucial role in controlling electron and spin injection. To explore the spin injection mechanism under gate control, we study MoS2 coupled to ferromagnetic metals. We introduce a spin drift diffusion model which is applicable to the Schottky contact. In this system, the current passing through the Schottky barrier can be larger for the minority spin than for the majority spin due to the tunnel effect. We observe a polarity switching in spin injection with gate voltage variation when the conduction band bottom of the minority spin ferromagnetic metal is closely aligned with the Fermi level. Our results also suggest the spin injection efficiency can be tuned by gate control for half-metals.

In-silico research on the effects of variable voltage pulse protocols on the cell survival and permeabilization fractions in electroporated cancerous tissues

Reversible electroporation is used to increase the cell membrane permeability by the application of short duration, high voltage electric pulses with electrodes strategically positioned to induce localized drug concentration in the tumor tissue. However, inadequate selection of pulses’ characteristics can lead to relevant loss of cell viability or lack of cell permeabilization, affecting aversively the results of the therapy. Accordingly, the balance between cell membrane electro-permeabilization and cell death is crucial, and the recursive modification of electroporation parameters can favor this balance to increase the drug uptake into viable cells. Particularly, the controlled diminution of the voltage level as the number of pulses increases can reduce the cell damage without compromising the membrane electro-permeabilization. In this work, a previously developed in-silico tool, based on the Global Method of Approximate Particular Solutions (GMAPS), is calibrated, validated, and used to study the differences between constant voltage and variable voltage pulse protocols (CVP and VVP) in terms of the magnitude and distribution of cell survival and permeabilization fractions along the tissue domain, and the internalization efficiency of the therapy. In VVP protocols, the reduction of the applied voltage with the number of pulses is numerically estimated to reach a target volume-averaged survival fraction in the most sensitive zone of the tissue. Numerical results indicate that differences between the pulse protocol types (CVP and VVP) depend on the initial voltage level ∅0 and number of pulses K, with the VVP protocol bringing about superior results for the larger values of ∅0 and K considered here.

Early-Stage ISC Fault Detection for Ship Lithium Batteries Based on Voltage Variance Analysis

With the progressive development of new energy technologies, high-power lithium batteries have been widely used in ship power systems due to their high-power density and low environmental pollution, and they have gradually become one of their main propulsion energy sources. However, the large-scale deployment of lithium batteries has also brought a series of safety problems to ship operations, especially the battery internal short circuit (ISC). Battery ISC faults are very hidden and unpredictable at the initial stage and often fail to be detected in time, ultimately leading to overheating, fire or even an explosion of the ship’s power system. Based on this, this paper proposes a fast and accurate method for early-stage ISC fault location and detection of lithium batteries. Initially, voltage variations across the lithium battery packs are quantified using curvilinear Manhattan distances to pinpoint faulty battery units. Subsequently, the localized characteristics of voltage variance among adjacent batteries are leveraged to detect an early-stage ISC fault. Simulation results indicate that the proposed method can quickly and accurately locate the position of 5 Ω, 10 Ω and 15 Ω ISC faulty batteries within the battery pack, as well as detect the abnormal batteries in a timely manner with considerable sensitivity and reliability.

Single-Phase Robust Charger with High Power Quality for Electric Vehicle Application

The widespread use of electric vehicles (EVs) necessitates the development of a robust charging infrastructure. The goal of this research paper is to create a high-quality, single-phase charger for electric cars. The purpose of this design is to provide a charger that is both fast and efficient but also protects against power quality problems including harmonics, power factor correction, and voltage variations. A single-phase–single-stage improved power quality EV charger for small and medium power applications has been designed and simulated. A single DC-DC converter is utilized for constant charging and improved power quality operation. The charger presented exhibits improved power quality as sinusoidal current is drawn from the utility grid supply with the total harmonic distortion (THD) in compliance with the IEEE 519 and IEC 61000-3-2 standards. In order to charge the battery of an electric vehicle, most two-stage converters first use a boost converter for power factor correction (PFC), and then they use a DC-DC converter that can accept any input voltage. These two-stage conversions are inefficient and use more parts than necessary. This work proposes a PFC converter based on a single-stage switching inductor Cuk converter, which has the advantages of high step-down gain, low current stress, high efficiency, and a small number of components. The suggested converter’s operational analysis and design equations are performed in continuous current mode. The proposed converter is the subject of extensive mathematical modelling, analysis, simulation, and experimentation presented in this study. With both constant voltage (CV) and constant current (CC) loads, the proposed converter’s performance is analysed with regard to power quality indices like voltage total harmonic distortion (THD), current THD, and total power factor. Additionally, in CV mode and CC mode, the suggested converter’s dynamic performance with battery charging is evaluated in relation to the extensive supply changes. The developed charger presents a reliable and efficient solution for EV charging, fostering the transition to a cleaner and more sustainable transportation system.