Low Voltage Drop Research Articles

Airfoil cross flow field to enhance mass transfer capacity and performance for PEMFC

Proper design of the flow field in bipolar plates is important for improving proton exchange membrane fuel cells in water transport, gas distribution and net power density enhancement. Inspired by the fact that the streamlined design of an airplane airfoil makes the flow resistance reduced, a new airfoil cross flow field is proposed. Airfoil cross flow field is composed of a regular pattern of airfoil pins which are categorized in pin-type flow fields. The effects of different airfoil-pin shapes and arrangements on cell performance were explored. The results showed that airfoil cross flow field improved water management by finely modulating the airflow significantly increasing the gas flow rate in the channel. In addition, the airfoil cross flow field design achieves higher and more uniform oxygen distribution at the interface between the gas diffusion layer and the catalyst layer. The proper shape and arrangement of the airfoil-pins can effectively increase the net power density of the cell by 10.65 % and 2.49 % compared to the conventional parallel flow field and the square-pin flow field. Due to the streamlined design of the airfoil cross flow field, the voltage drop is approximately 60 % of that of the conventional parallel flow field and even slightly lower than that of the square-pin flow field, which demonstrates its high practicality. In summary, the airfoil cross flow field well coordinates the high current density and low voltage drop requirements of proton exchange membrane fuel cells, and some new points of view on flow field design are presented.

Nonlinear Enhanced Control for Wind Energy Generation System-Based Permanent Magnet Synchronous Generator

This paper proposes a Nonlinear Backstepping Approach (NBA) to improve the control performance of a Permanent Magnet Synchronous Generator (PMSG)-based Wind Energy Generation System (WEGS) under parameter uncertainties and short circuits with fluctuations in the grid voltage. Both the rectifier and the three-phase inverter are controlled using the NBA scheme; this method ensures Maximum Power Point Tracking (MPPT), which is a very appealing control objective with unpredictable scenarios of wind speed, and regulates the active and reactive power flows to the electrical network under varying wind speeds. Also, an inverter was employed to control voltage of the DC bus and the powers. The regulator’s stability is achieving using the Lyapunov approach. Simulation results with Matlab/Simulink confirm the efficiency of the presented scheme. The comparative analysis of the NBA with conventional Vector Controllers (VCs), under parameter deviations and for low voltage drop conditions, demonstrates the efficiency of the studied method.

Eliminating Harmonics and Voltage Ripples Using Optimal Constructive Recurrent Neural Network on Boost Rectifiers with Unbalanced Grid Sources

Various new methodologies and techniques have been proposed to improve power quality. One of the parameters that affect power quality is harmonics. Voltage and current unbalance is a frequent problem. Electronic devices such as rectifiers and power distribution networks are negatively affected by this imbalance. The current in the grid will be severely distorted. The DC bus voltage will fluctuate or ripple frequently, perhaps twice as often as the frequency. Direct power control (DPC) and voltage-oriented control (VOC) are two examples of control strategies developed for rectifiers. In classical VOC, the voltage and current in the synchronous frame of reference (dq) are controlled using a proportional-integral (PI) controller. However, the PI controller in controlling the VOC current has the disadvantage that when one variable changes, the other variables will also change. PI cannot control itself independently. it is difficult to achieve an accurate linear mathematical model of the system required for PI controllers. In addition, PI controllers often struggle to work satisfactorily on parameter variations, nonlinearities, and load disturbances. in transient conditions, the Optimal Constructive Recurrent Neural Network(OCRNN) controller takes faster time to reach a stable state. when there is a change in the reference dc voltage, PI has a higher overshot voltage and a lower voltage drop than OCRNN and takes longer than the OCRNN controller.

Novel SiC Trench MOSFET with Improved Third-Quadrant Performance and Switching Speed.

A SiC double-trench MOSFET embedded with a lower-barrier diode and an L-shaped gate-source in the gate trench, showing improved reverse conduction and an improved switching performance, was proposed and studied with 2-D simulations. Compared with a double-trench MOSFET (DT-MOS) and a DT-MOS with a channel-MOS diode (DTC-MOS), the proposed MOS showed a lower voltage drop (VF) at IS = 100 A/cm2, which can prevent bipolar degradation at the same blocking voltage (BV) and decrease the maximum oxide electric field (Emox). Additionally, the gate-drain capacitance (Cgd) and gate-drain charge (Qgd) of the proposed MOSFET decreased significantly because the source extended to the bottom of the gate, and the overlap between the gate electrode and drain electrode decreased. Although the proposed MOS had a greater Ron,sp than the DT-MOS and DTC-MOS, it had a lower switching loss and greater advantages for high-frequency applications.

Achieving CoAl2O4@Li1.2Ni0.13Co0.13Mn0.54O2 with Long Cyclic and High-Rate Performance via Citric Acid Combustion Method

Lithium-rich manganese-based cathode materials (LNCM) have high specific capacities and operating voltages. However, they also have intractable deficiencies such as low capacity retention and unsatisfactory rate capability. Herein, CoAl2O4 with spinel structure and chemically stable is adopted to decorate the surface of LNCM to modify the cyclic and high-rate performance of final product. 3CoAl2O4@LNCM synthesized by self combustion of citric acid shows the best electrochemical properties such as lower voltage drop (4.7 mV per cycle) and higher capacity retention of 81.33% (1 C) after 100 cycles, which is exceed to bare LNCM (7.7 mV per cycle, 47.65%). Besides, the charge transfer resistance R ct of the modified sample is lower, and its lithium ion diffusion coefficient D Li + is higher. Consequently, 3CoAl2O4@LNCM is able to demonstrate high rate performance, whereby a capacity retention of 65.84% (5 C) is achieved after 100 cycles. The improved electrochemical properties of 3CoAl2O4@LNCM because of the 3D diffusion channel of CoAl2O4 benefits lithium ion diffusion; and the chemical stability of CoAl2O4 enhances the corrosion resistance of LNCM bulk to the electrolyte. As such, this results in the suppression of TM ion dissolution, and the enhancement of cyclic stability and initial coulomb efficiency.

Noval carrier accumulation reverse-conducting lateral insulated gate bipolar transistor

Reverse-conducting lateral insulated gate bipolar transistor (RC-LIGBT) with freewheeling diode integrated in the body by introducing n<sup>+</sup> anode can realize the reverse conduction and optimize the turn-off characteristics of the device, which is a promising device in a power integrated circuit. In this work, a novel RC-LIGBT with electron-controlled gate (EG) and separated short-anode (SSA) is proposed and investigated by TCAD simulation, which can achieve low on-state voltage drop (<i>V</i><sub>on</sub>) and low turn-off loss (<i>E</i><sub>off</sub>) at the same time. The EG structure of p-n-n<sup>+</sup>-p (p<sup>+</sup> region/n-type silicon region/n-type barrier layer/p<sup>+</sup> region) is adopted, the gate electrode and anode electrode are connected by the EG structure. In the forward conduction state, a high-density electron accumulation layer is formed on the surface of the drift region by EG structure, which greatly reduces the <i>V</i><sub>on</sub> of the device. At the same time, the use of the SSA structure can also optimize the <i>E</i><sub>off</sub> of the device by forming an additional electron extraction channel. In addition, based on the EG structure, a low-doping p-drift can be combined with the SSA structure to simply achieve reverse-conduction and snapback-free characteristics. Furthermore, the EG structure and the SSA structure can complement each other. On the one hand, the high-density electron accumulation layer formed by EG structure compensates for the weakened conductance modulation effect caused by the SSA structure. On the other hand, the electron extraction channel of the SSA structure enables a large number of accumulated electrons to be removed quickly. The simulation results show that the proposed device has an excellent trade-off relationship between <i>V</i><sub>on</sub> and <i>E</i><sub>off</sub>, specifically, <i>V</i><sub>on</sub> is 1.16V, which is 55% lower than that of SSA LIGBT, and <i>E</i><sub>off</sub> is 0.099 mJ/cm<sup>2</sup>, which is 38.5% and 94.7% lower than that of SSA LIGBT and conventional LIGBT, respectively.

Clean energy storage device derived from biopolymers with moderate charge-discharge cycles: Structural and electrochemical properties

This work explores a green biopolymer (GBP) energy storage system to address the growing problem of microplastics that can harm our health. A GBP was made using solution casting with chitosan (CHN) and starch from potato (SPC) as the polymer hosts. Sodium thiocyanate (NaSCN) as Na+ cation provider and glycerol as an environmentally friendly plasticizer were mixed with CHN:SPC host polymers to prepare GBP electrolytes. The electrochemical impedance spectroscopy (EIS) results confirm the boost in DC conductivity. From the AC conductivity spectra, regions ascribing to EP and DC contributions are demonstrated. X-ray diffraction (XRD) and FTIR characterization provide evidence of salt dissociation and amorphous phase improvement. The determination of the ion fraction was achieved by means of TNM. The electrochemical stability of the conducting film was observed to be maintained up to 2.75 V. Cyclic voltammetry (CV), revealing no sign of charge transfer occurring through Faradaic processes at the interface between the electrode and electrolyte. The galvanostatic charge–discharge (GCD) plot displayed a triangular pattern, indicating a low voltage drop and a notable specific capacitance of 70 F/g. Moreover, the EDLC (electrical double-layer capacitor) exhibited an average power density of 1120 W/kg and an energy density of 9.11 Wh/kg.

Simulation Design of Novel Non-Fluorine Polymers as Electron Transport Layer for Lead-Free Perovskite Solar Cells.

Significant progress has been made in the advancement of perovskite solar cells, but their commercialization remains hindered by their lead-based toxicity. Many non-toxic perovskite-based solar cells have demonstrated potential, such as Cs2AgBi0.75Sb0.25Br6, but their power conversion efficiency is inadequate. To address this issue, some researchers are focusing on emerging acceptor-donor-acceptor'-donor-acceptor (A-DA'D-A)-type non-fullerene acceptors (NFAs) for Cs2AgBi0.75Sb0.25Br6 to find effective electron transport layers for high-performance photovoltaic responses with low voltage drops. In this comparative study, four novel A-DA'D-A-type NFAs, BT-LIC, BT-BIC, BT-L4F, and BT-BO-L4F, were used as electron transport layers (ETLs) for the proposed devices, FTO/PEDOT:PSS/Cs2AgBi0.75Sb0.25Br6/ETL/Au. Comprehensive simulations were conducted to optimize the devices. The simulations showed that all optimized devices exhibit photovoltaic responses, with the BT-BIC device having the highest power conversion efficiency (13.2%) and the BT-LIC device having the lowest (6.8%). The BT-BIC as an ETL provides fewer interfacial traps and better band alignment, enabling greater open-circuit voltage for efficient photovoltaic responses.

Low voltage drop AlGaN UV-A laser structures with transparent tunnel junctions and optimized quantum wells

This paper presents the design, material growth and fabrication of AlGaN laser structures grown by plasma-assisted molecular beam epitaxy. Considering hole transport to be the major challenge, our ultraviolet-A diode laser structures have a compositionally graded transparent tunnel junction, resulting in superior hole injection and a low contact resistance. By optimizing active region thickness, a five-fold improvement in photoluminescence intensity is obtained compared to that of our own non-optimized test structures. The electrical and optical characteristics of processed devices demonstrate only spontaneous emission with a peak wavelength at 354 nm. The devices operate up to a continuous-wave current density of 11.1 kA cm−2 at room temperature, which is the highest reported for laser structures grown on AlGaN templates. Additionally, they exhibit a record-low voltage drop of 8.5 V to achieve this current density.

8 A, 200 V normally-off cascode GaN-on-Si HEMT: From epitaxy to double pulse testing

In this paper, we provide a comprehensive study on all aspects of development of normally-off multi-finger III-nitride HEMT on Silicon in cascode configuration. AlGaN/GaN HEMT epi-stack with in situ SiN cap was grown on 2-in. Silicon (111) using MOCVD, utilizing a 2-step AlN nucleation, step-graded AlGaN transition layer and C-doped GaN buffer. Depletion-mode HEMTs in winding gate geometry with a gate width of 30 mm were fabricated with thick electroplated metal contacts and an optimized bilayer SiN passivation. Devices were diced and packaged in TO254 with conducting epoxy and Au-coated ceramic substrate. These packaged D-mode HEMTs exhibited a threshold voltage (Vth) of −12 V, maximum ON current of 10 A, and a 3-terminal hard breakdown in excess of 400 V. Bare dies of D-mode HEMTs were then integrated with commercially procured silicon MOSFET in a TO254 package in cascode configuration to achieve Vth > 2 V, ON current of 8 A, and breakdown >200 V. The normally-off cascaded GaN HEMTs were subjected to various gate and drain stress measurements and were found to exhibit a Vth shift of 10 mV after 1000 s of positive gate (+5 V) stress. The input and output capacitances of the cascode devices were measured to be 1 nF and 0.8 nF, respectively. The 3rd quadrant operation was checked at 8 A on-state current level to reveal a lower voltage drop of 0.7 V. Finally, cascode HEMTs were subjected to double pulsed testing (DPT) using a half-bridge evaluation board. On and off rise times of 52 ns and 59 ns were obtained along with energy loss of 25 μJ and 20 μJ, respectively, for devices switched at 8 A, 100 V.

Suppressing the self-discharge of MXene-based supercapacitors by liquid crystal additive

MXenes are widely used as electrodes for supercapacitors (SCs) due to their excellent conductivity and abundant redox active sites. However, the severe self-discharge of MXene-based SCs results in significant energy loss, limiting their integration with various energy-harvesting devices. Here we introduced the nematic liquid crystal 4-n-pentyl-4′-cyanobiphenyl (5CB) molecules into Ti3C2Tx films and LiCl aqueous electrolytes to suppress the self-discharge rate. The nematic liquid crystal molecules would arrange parallel to each other when the Ti3C2Tx films were charged, while the electrolyte viscosity would increase due to the electrorheological effect, causing the slow cross-diffusion of active ions and reducing the self-discharge. As a result, the MXene-based SCs had a low voltage drop of 35% after 4600 s and a low leakage current of 3.0 µA, respectively. The MXene-based SCs could store energy more effectively, improving their practical application potential in integrated energy harvesting devices, for example, storing the electrical energy harvested by the triboelectric nanogenerators. This work proposed a simple strategy to suppress the self-discharge of Ti3C2Tx-based SCs by liquid crystal additive, which can be extended to other MXenes, promoting the applications of MXenes in energy storage devices and integrated electronics.

Constructed multifunctional CuOx core and electrodeposited nickel‑cobalt sulfide for high areal energy-power density supercapacitor

Construction of heterostructure is regarded as an effective strategy for enhancing the electrochemical performance of electrode materials for supercapacitor. Moreover, the relatively poor conductivity and commonly structural design severely decrease the electron transfer ability and surface utilization of nickel cobalt sulfides during charge-discharge process. In this work, three unique core structures of Cu, CuO, and CuOx (Cu-Cu2O-CuO) were successfully constructed on copper foam via an in-situ redox strategy. Among them, the CuOx cores exhibit higher capacity and lower voltage drop because of the high conductivity of Cu, the generation of built-in electric field between Cu2O and CuO, as well as rich active areas. Three-dimensional interconnected NiCoS nanosheets grown on the surface of CuOx cores with high areal-loading and robust interfacial adhesion. Benefited from the unique structural advantages and synergistic effect of multi-metallic active centers, the CuOx/NiCoS composite exhibits high specific capacitance of 3305 mF cm−2 at 5 mA cm−2, outstanding rate capability of 68.3% when the current density increases to 60 mA cm−2, and long-term lifespan. Notably, the assembled CuOx/NiCoS//PAC asymmetric supercapacitor delivers a high areal energy density and power density (263.3 μWh cm−2 at 2.4 mW cm−2), which can drive some small electronic devices. This study offers a novel pathway for further design of a core-shell structured electrode materials with an enhanced capacity and rate capability for advanced energy storage devices.

Study of Distribution Transformer Voltage Drops in Feeder 5 Out Going Districts 4 and 6 at PT. PLN (Persero) Tarakan City, North Kalimantan

This research aims to determine the low-voltage drop that occurs at the substation and on the customer side. The voltage drop is affected by many factors, including line resistance, line current, power factor, and line length. The need for electric power is increasing every year, causing power losses and voltage drops in the network to be a major concern. This research was conducted at Feeder 5, outgoing villages 4 and 6, one of the areas of PT. PLN in Tarakan City. The research data is voltage measurement data. This research applies analytical calculations with a quantitative descriptive method compared to calculations based on ETAP software. The allowable voltage drop by SPLN is 5% of the nominal voltage. The results of the analysis show that the average voltage drop that occurs is still within the limits permitted by the SPLN, namely below 5% of the nominal voltage.

An improved resistance model of positive subsonic plasma channels in water

The subsonic plasma channel and water can be regarded as series resistors in the pre-breakdown stage of sub-millisecond pulsed discharge in conductive water. An improved resistance model of the positive subsonic plasma channel is proposed. The gap resistance and the morphology of the bubble cluster and the plasma channel inside it are obtained from the electrical measurement and optical observation, respectively. The resistance of the plasma channel in the strong-ionization stage is calculated using the small-current arc resistance model. The improved model of the water resistance is established by analyzing the relationship between its equivalent cross-sectional area and its length in an uneven electric field. The resistance of the plasma channel in the weak-ionization stage is calculated. The resistance, voltage, and energy in the gap are analyzed based on the improved resistance model. The plasma channel's resistance is far less than the water resistance. The low voltage drop in the plasma channel leads to a high electric potential in the plasma channel's head, which is conducive to the plasma channel's development. 97% of the total energy in the pre-breakdown stage is consumed by the water resistor. The improved resistance model is helpful to supplement the development mechanism of the sub-millisecond pulsed discharge in water.

Design and demonstration of efficient transparent 30% Al-content AlGaN interband tunnel junctions

Ultra-violet (UV) light emitting diodes operating at 339 nm using transparent interband tunnel junctions are reported. Tunneling-based ultraviolet light emitting diodes were grown by plasma-assisted molecular beam epitaxy on 30% Al-content AlGaN layers. A low tunnel junction voltage drop is obtained through the use of compositionally graded n and p-type layers in the tunnel junction, which enhance hole density and tunneling rates. The transparent tunnel junction-based UV LED reported here show a low voltage drop of 5.55 V at 20 A/cm2 and an on-wafer external quantum efficiency of 1.02% at 80 A/cm2.

Разработка и верификация поведенческих моделей линейных стабилизаторов напряжения с защитой от короткого замыкания и перегрузки в рабочем цикле

The object of development are behavioral models of a linear negative voltage regulator in two modifications. Linear voltage regulators manufactured by KREMNIY EL GROUP JSC were chosen as prototypes for the models. IC 5348EM035 with a fixed output negative voltage value of 5 V, IC 5348EP035 with an adjustable output negative voltage value of 1.25V to 14.5V and their functional analogue IC UCC284DP manufactured by Texas Instruments were used. These are low voltage drop with duty cycle short circuit and overload protection regulators. Behavioral models are implemented in SPICE language through converting netlists of prototype equivalent circuits. Equivalent circuits on the regulators IC functional circuits were made, taking into account a typical switching circuit. Equivalent circuits of regulators are implemented on the standard mathematical blocks, limiters, dependent sources, controlled switches and passive elements. Parameter limits are written inside controlled sources by mathematical relations. When verifying behavioral models, it was established that the results of modeling the regulators operation correspond to the data in the technical descriptions of manufacturers. The verification was carried in typical switching circuits with given input electrical parameters. In present study the results of modeling the main characteristics of microcircuits are described: input and output voltages, voltage drop across the regulator and timing diagrams of the main modes of operation of the IC, including the mode of duty cycle short circuit and overload protection regulators. The developed and verified behavioral models of linear voltage regulators 5348EM035 and 5348EP035 and their functional analogue UCC284DP will be useful in the engineering, design and study of the characteristics of power supply devices for electronic and industrial equipment. These SPICE models are applicable in modern specialized CAD systems for circuit design and simulation.

In Situ Surface Coating and Oxygen Vacancy Dual Strategy Endowing a Li-Rich Li1.2Mn0.55Ni0.11Co0.14O2 Cathode with Superior Lithium Storage Performance

Lithium-rich Mn-based cathode materials are widely regarded as the next-generation cathode materials for high-energy-density lithium-ion batteries owing to their low cost and high specific capacity. Nonetheless, their commercial application is seriously hindered by low initial Coulombic efficiency, capacity loss, and voltage drop during long-term cycling. Herein, surface phosphorus doping and a mixture protective layer with oxygen vacancies (OVs) which consists of Li3PO4 and LiMnPO4 as a surface-coating layer on the Li1.2Mn0.55Ni0.11Co0.14O2 cathode material through a facile solid–gas reaction treatment, which can simultaneously optimize the surface chemical structure and deplete lithium impurity, is proposed. What is more, the dual strategy of surface engineering and OVs can improve electronic conductivity and regulate the ion diffusion rate. The dual-modified sample expresses a discharge capacity of 180.9 mA h g–1 with a capacity retention of 89.2% at 0.5 C after 250 cycles, which is better than that of the pristine sample (63.7%). This work provides a facile and effective method for surface coating design to improve other Li-rich manganese-based cathodes for rechargeable batteries.

A logic level matching circuit in a communication circuit

Aiming at the problems of using optocouplers to achieve logic level matching in the current communication circuit, there are many components, high cost, and high requirements for component parameters. Based on the basic requirements of circuit logic level matching, this paper combines The research on the basic principle of triode switch, using the Schottky diode’s unidirectional conduction and low conduction voltage drop characteristics, introduces a logic level matching circuit for inter-module communication with switch isolation function in communication circuits. Through the verification of relevant experiments such as functionality, stability and reliability, the circuit has a simple structure and stable performance, and is very suitable for use in communication circuits between modules of different voltage levels.

A transformer‐less high‐boosting common‐grounded multi‐phase DC–DC converter with continuous input‐current favourable for low‐power applications

AbstractThe traditional dc–dc converters have limited boosting ability. Significant voltage gains can be accomplished only at extreme duty ratios, where the high voltage/current stress and losses occur on semiconductors. This work proposes a common‐ground multi‐phase boost dc–dc converter that benefits from high boosting factor at low duty ratios, continuous input‐current and minimum operational modes (only two at CCM) regardless of number of phases. Due to the presence of common‐ground point, the proposed converter can efficiently remove the leakage current while using the PV as the input source. Also, because of multi‐phase nature, the proposed converter has low current stress on its input devices, which leads to lower voltage drops and better efficiencies. The number of phases can freely be selected based on required boosting factor or converter efficiency. To assure of proper performance of proposed converter, the three‐phase (n = 3) version has been investigated in detail and its steady‐state analysis as well as real‐gain and loss calculations have been presented. The competitiveness of the suggested converter has been verified by performing comprehensive comparative analysis. The experimental results (for n = 3) have also been provided to certify the correct performance of suggested converter.

Freestanding Bipolar Membranes with an Electrospun Junction for High Current Density Water Splitting.

Freestanding bipolar membranes (BPMs) with an extended-area water splitting junction were fabricated utilizing electrospinning. The junction layer was composed of a mixed fiber mat that was made by concurrently electrospinning sulfonated poly(ether ether ketone) (SPEEK) and quaternized poly(phenylene oxide) (QPPO), with water splitting catalyst nanoparticles intermittently deposited between the fibers. The mat was sandwiched between solution cast SPEEK and QPPO films and hot-pressed to form a dense trilayer BPM with an extended-area junction of finite thickness, composed of QPPO nanofibers embedded in a SPEEK matrix with the catalyst nanoparticles interspaced between the two polymers. The composition, ion-exchange capacity, and catalyst type/loading in the junction were varied, and the water splitting characteristics of the membranes were assessed. The best BPMs fabricated in this work employed a graphene oxide catalyst and exhibited a low trans-membrane voltage drop of about 0.82 V at 1000 mA/cm2 in water splitting experiments with 0.5 M Na2SO4 and stable water splitting operation for 60 h at 800 mA/cm2.