High Current Capability Research Articles

Single-flow multiphase flow batteries: Theory

Redox flow batteries are an emerging technology for stationary, grid-scale energy storage. Membraneless batteries in particular are explored as a means to reduce battery cost and complexity. Here, a mathematical model is presented for a membraneless electrochemical cell employing a single laminar flow between electrodes, consisting of a continuous, reactant-poor aqueous phase and a dispersed, reactant-rich nonaqueous phase, and in the absence of gravitational effects. Analytical approximations and numerical solutions for the concentration profile and current-voltage relation are derived via boundary layer analysis. Regimes of slow and fast reactant transport between phases are investigated, and the theory is applied to a membraneless zinc-bromine single-flow battery with multiphase flow. The regime of fast interphase reactant (bromine) transport is characterized by the negligible effect of advection within the cathode boundary layer, leading to a thin boundary layer whose size is largely independent of position, and by relatively high battery current capability. Increasing the nonaqueous (polybromide) phase volume fraction is shown to significantly improve battery performance, as has been observed in recent experiments. For the case of spherical polybromide droplets, the contribution of bromine release from the polybromide phase on the limiting current density becomes negligible for diameters above a critical droplet diameter, when the system can be characterized as having a slow interphase bromine transport. Overall, we show that our analytical approximations agree well with numerical solutions, and thus establish a useful theoretical framework for single-flow batteries with multiphase flow.

Crack growth threshold testing with flat-bottom hole specimens and artifact evaluation of electrothermal crack tip marking

A prior study [1] benchmarks a relatively new axisymmetric Flat Bottom Hole (FBH) specimen concept for use in crack growth threshold testing, with reduced crack initiation loads achieved by applying by an electrical pulse around the notch tip prior to testing.In this study, an improved electrothermal pulsing technology is used with higher current capability, and more precisely timed pulses. Electrical pulses were applied at high amplitude to initiate the crack at further reduced loads, and also at a lower amplitude to locally heat tint the crack tip during the test to leave visible marks on the fracture surface for post-test evaluation. For specimen, one of the marks was applied at near-threshold conditions before the completion of the threshold test to evaluate whether the marking method introduces artifact into the results. A small, but quantifiable artifact was observed immediately following marking at near threshold conditions, vanishing after 0.001-0.003 in. of crack growth. Test results include data for Ti 6-4 forging and Inconel 718 forging.

High-Speed Medium-Voltage SiC Thyristors for Pulsed Power Applications

The high peak current withstand capability of thyristors makes them extremely suitable for pulsed power applications. Silicon carbide (SiC) thyristors provide significant efficiency advantages compared with their silicon counterparts due to their very fast switching transitions. This article presents the development and characteristics of 3 kV SiC thyristors. A novel current-source gate driver is proposed to enhance their switching speed and, hence, maximize their benefits in pulsed power applications. The proposed driver provides a very high gate current slew rate while limiting the peak of the current pulse. The higher gate current slew rate achieves faster and, thus, more efficient device switching transition. Gate driver circuit description, variant topologies, and experimental results for a 3 kV SiC thyristor for a pulsed power application are presented to verify the proposed concepts.

Formation of highly vertical trenches with rounded corners via inductively coupled plasma reactive ion etching for vertical GaN power devices

A trench-gate metal-oxide-semiconductor field-effect transistor (T-MOSFET) has great potential for use in gallium nitride (GaN)-based vertical power switching devices owing to its high blocking voltage and high current capability. To form an optimal trench shape that has highly vertical sidewalls and rounded corners, we developed a dry-etching technique using inductively coupled plasma reactive ion etching (ICP-RIE). A highly vertical trench was obtained by including SiCl4 reactive gas mixed with Cl2 gas in the ICP-RIE process, where Si-related byproducts suppressed the etching of the sidewall and allowed selective etching in the vertical direction. We found that the optimization of the bias power was a key to suppress the formation of subtrenches and to avoid an isotropic etching mode. The optimal etching condition leads to natural formation of rounded corners at the trench bottom. In addition, a multistep-bias etching technique was applied to reduce etching-induced damage. Cross-sectional transmission electron microscopy images revealed that lattice distortion on the sidewall surface was eliminated by multistep-bias etching. Based on the rectification properties of the Schottky barrier diodes formed on the trench sidewalls, the Schottky barrier height was comparable to the not-etched surfaces. This indicates that the gap states caused by etching-induced damage can almost be eliminated in the multistep-bias process. The proposed technique is suitable for GaN-based vertical T-MOSFETs.

Low-Cost HVdc Circuit Breaker With High Current Breaking Capability Based on IGCTs

DC circuit breaker plays an important role in the reliability of HVdc system, but the large number of expensive press-pack insulated-gate bipolar transistors (IGBTs) is used at present, which is a serious impediment to HVdc development. Thus, the low-price integrated gate commutated thyristor (IGCT) becomes a promising alternative device. This letter presents a low-cost HVdc circuit breaker with high current breaking capability based on IGCTs. The topology and principle of the proposed HVdc circuit breaker are introduced at first. Then, the parameter design is analyzed. A scaled-down test successfully demonstrates the high current breaking capability of 15 kA. In the end, the cost comparison shows that this scheme can achieve 61.8% cost reduction of the commutation branch.

Metal organic chemical vapour deposition regrown large area GaN‐on‐GaN current aperture vertical electron transistors with high current capability

Metal organic chemical vapour deposition regrown large area GaN‐on‐GaN current aperture vertical electron transistors with high current capability

Class-AB Flipped Voltage Follower Cell with High Current Driving Capability and Low Output Resistance for High Frequency Applications

In this paper, a class-AB flipped voltage follower cell with high current driving capability is proposed. The proposed flipped voltage follower (FVF) cell offers increased current sourcing capability and large input/output voltage swing due to the use of bulk-driven and level shifter techniques, respectively. Further, it uses an additional NMOS transistor connected between output and ground terminals to increase the current sinking capability and to reduce the output resistance. The stability analysis has been performed by using Routh–Hurwitz stability criteria which confirms that the proposed FVF cell is stable. The proposed FVF cell also offers a high symmetrical slew rate. The proposed FVF cell has been simulated in Cadence virtuoso analog design environment using BSIM3v3 180 nm CMOS technology and simulation results are presented to validate the effectiveness of the proposed circuit.

N, P co-doped porous carbon from cross-linking cyclophosphazene for high-performance supercapacitors

Abstract Nitrogen and phosphorus heteroatoms-doped carbon materials were prepared by carbonization of cross-linking cyclophosphazene from 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10- phosphaphenanthrene-10-oxide (DOPO-HQ) and Hexachlorocyclotriphosphazene (HCCP) as reactant, followed by activation with KOH as activator. The carbon materials possess a high specific surface area (up to 1342.328 m2 g−1), pore volume with a well-balanced microporosity (up to 0.7289 cm3 g−1), moderate heteroatom content and micrometer-sized morphology. Moreover, the heteroatom contents and porosity parameters (e.g. surface area and pore volume) can be easily controlled by the activation temperature in the range of 700–900 °C. When tested as a supercapacitor electrode in a three-electrode system using 6 M KOH solution as the electrolyte, the typical sample (DP-900) displays a high specific capacitance (265.8 F g−1 at 0.2 A g−1), excellent rate capability (155 F g−1 at 10 A g−1) and outstanding cycling stability (98% capacity retention after 10,000 charge/discharge cycles at 10 A g−1). Furthermore, high energy density of 14.912 Wh kg−1 at 1 A g−1 with a power density of 800 W kg−1 can be achieved in a two-electrode cell originating from the microporous structure as well as the excellent synergistic effect of N, P co-doping. These encouraging results demonstrate that the DPs electrode materials with high current charge and discharge capability show great potential for supercapacitor applications, where a fast charge/discharge is required.

Current Oscillation Phenomenon of MMC Based on IGCT and Fast Recovery Diode With High Surge Current Capability for HVDC Application

Integrated gate commutated thyristor (IGCT) has low loss, low cost, and high reliability in the application of modular multilevel converter (MMC). However, due to the special turn-off process of IGCT, the commutation transient is very different for IGCT in MMC. This letter reveals a current oscillation phenomenon of MMC based on IGCT and fast recovery diode (FRD). Especially, this oscillation effect becomes apparent when the FRD with high surge current capability is employed in MMC because of high junction capacitance and high stray inductance, which will threaten the safe operation of the system. This letter analyzes the current oscillation mechanism and gives the current oscillation modeling. In addition, through detailed tests under various stray inductances, the specific stray inductance range that can cause large current oscillation is obtained and an optimized inductance parameter of IGCT-MMC is proposed. The experiments show that the safe operation area of IGCT in MMC can be guaranteed maximally with the optimized parameter.

Smart protection system for identification and localisation of faults in multi‐terminal DC microgrid

DC microgrid provides the horizontal infrastructures to integrate distributed generation (DG) and loads. Unlike traditional AC systems, DC systems cannot survive or sustain high magnitude fault currents. It makes locating faults very difficult. The conventional protection techniques completely de-energies the DC link in the DC microgrid. A new protection scheme for multi-terminal DC microgrid against line-to-line fault and the low resistance earth fault is presented in this study. The scheme isolates the faulted section from the DC microgrid. Healthy sections are operated without any disturbance and supply continuity is maintained in a ring main DC bus system. The current sensors are mounted at DC bus segments to monitor the entering and outgoing current at different nodes. Further, the current sensors are also mounted at both ends of service mains to monitor their current difference at both ends of the service mains. The controller detects this current difference and opens circuit breakers. To meet the requirement of fast interrupting time and high short-circuit current withstanding capability, insulated-gate bipolar transistors used as circuit breakers. The fault location scheme gives the fault location in various sections (service mains) and faults resistance in the microgrid. The proposed concepts have been verified by computer simulation.

Low-Leakage and Variable V HOLD Power Clamp for Wide Stress Time Range From ESD to Surge Test

In recent years, on-chip clamp designs for enhancing destructive immunity of ICs mounted on systems against residual currents of system level immunity tests have been proposed. To cope with a long duration pulse (several tens μs) such as a surge immunity test is one of the issues of the system level on-chip clamp. A clamp combined RC-trigger and static trigger is one approach to achieve both a low voltage clamping against component level ESD events and system level surge protection. However, the combined clamp using the conventional static trigger is difficult to achieve both a high current capability against the long pulse event and a low standby leakage current. This work presents a combined clamp that overcome the trade-off between the long pulse current capability and the standby leakage current using a variable holding voltage technique. The proposed clamp achieves the higher current capability against the long pulse event without increasing the standby leakage by holding voltage lowering while keeping a higher trigger voltage. It can contribute to increase PCB design freedom and to protect ICs efficiently from wider time range immunity tests.

Effective microgrid restructuring in the presence of high DG proliferation

Distributed generators bring in promising benefits as well as question the efficacious relaying operation of the conventional radial distribution systems on the penetration. Among different types of interface machines, synchronous generators upon increased penetration create major disruptions to the existing operation of relays and circuit breakers due to their high fault current capability. Hence, this work employs reconfiguration as a strategy to mitigate the protection issues imposed by a highly proliferated DG network. As restructuring also has the capability to create relay miscoordinations, a vigilant identification of optimal structure is carried out. 22.9% loss reduction, 24.3% reduction in the sustained interruption hours faced by an average consumer and 35.8% decrease in the maximum electricity price paid by the consumer at a load point are achieved for the practical 52-bus microgrid while attempting to reconfigure in view of addressing the protection challenges. 21.84% drop is observed in total size of fault current limiters as well. 33 and 69 bus benchmark systems transformed to a microgrid are also employed to validate the proposed reconfiguration strategy. New tie-line combinations are searched for each test system in a view to look for a superior structure giving out best results in the context of study.

A Multi-Loop Slew-Rate-Enhanced NMOS LDO Handling 1-A-Load-Current Step With Fast Transient for 5G Applications

Compact low dropout (LDO) with high current handling capability and superior transient response is gaining increasing attention for the battery-powered 5G mobile applications. In this article, a new multiple-loop design technique for fast-transient response LDO regulator design has been proposed and successfully implemented in a 0.13- $\mu \text{m}$ SOI CMOS process for portable smartphone and tablet PC applications. Its supply current capacity is more than 1 A, and its output voltage is from 1.2 to 1.8 V. The proposed LDO features a 10-mV undershoot and overshoot with 1-A/100-ns load current on a 1- $\mu \text{F}$ output capacitor. This superior transient performance is achieved by embodying a novel frequency compensation scheme without penalty of dc loop gain drop in large load current conditions. The dc loop gain is 60 dB and constant regardless of the fact that the load current varies from 0 to 1 A. This contributes to a small load regulation and line regulation of 0.6 $\mu \text{V}$ /A and 0.23 mV/V, respectively. The LDO consumes 35- $\mu \text{A}$ quiescent current in the mission mode and 5 $\mu \text{A}$ in the standby mode. The LDO silicon size is 325 $\mu \text{m}\,\,\times $ 106 $\mu \text{m}$ .

The Research on Characteristics of Li-NiMnCo Lithium-Ion Batteries in Electric Vehicles

The energy density of canode materials for lithium-ion batteries has a major impact on the driving range of electric vehicles. In order to study the charge-discharge characteristics and application feasibility of Li-NiMnCo lithium-ion batteries for vehicles, a series of charge and discharge experiments were carried out with different rates of Li-NiMnCo lithium-ion batteries (the ratio of nickel, cobalt, and manganese was 5 : 2 : 3) in constant-current-constant-voltage mode. Firstly, a set of charge-discharge experiments were performed on different types of single-cell lithium-ion batteries. The results show that, under temperature conditions, the charge and discharge voltage-capacity curves of the four different types of Li-NiMnCo lithium batteries mentioned in the paper are not much different, and the charge-discharge characteristic curves are similar, indicating that different types of batteries with the same material composition have similar charge and discharge characteristics. Subsequently, a series of charge and discharge tests with different rates were conducted on such ternary lithium batteries. The characteristic curves with different charge-discharge rates indicate that this new type of ternary lithium battery has high current charge and discharge capability and is suitable for use in new energy electric vehicles. In addition, by analyzing the voltage-SOC curve under different magnification conditions, it is known that there is an approximate linear relationship between the battery voltage value and the SOC within a certain SOC range. The SOC value can be evaluated by the battery voltage, which should be controlled within a reasonable range to avoid overcharge or overdischarge of battery, thereby, causing permanent damage to the battery.

Supercapacitor-Based Long Time-Constant Circuits: A Unique Design Opportunity for New Power Electronic Circuit Topologies

Supercapacitor (SC), or electric double-layer capacitor (EDLC), technology has matured well during the past two decades into three commercial variations with capacitance values ranging between 1 and 50,000 F. Compared to electrolytic or film-type capacitors with the same canister size, they offer capacitance that is more than 1 million times larger, with a one to two order smaller equivalent series resistance (ESR). A smaller ESR means a very high current charge or discharge capability without excessive heating of the device. One major limitation is the lower dc voltage ratings of less than 5 V.

A class‐AB flipped voltage follower cell with high symmetrical slew rate and high current sourcing/sinking capability

SummaryThe paper presents a class‐AB flipped voltage follower (FVF) cell based on quasi‐floating gate and bulk‐driven techniques. The quasi‐floating gate technique is used to increase the current sinking capability, whereas the bulk‐driven technique is used to enhance the current sourcing capability by reducing the threshold voltage. Using these two techniques, the proposed class‐ AB FVF cell offers high current sinking and sourcing capabilities. Also, it provides high symmetrical slew rate without any additional circuitry. The physical layout of the proposed class‐ AB FVF cell has been designed in Cadence Virtuoso Layout XL editor using BSIM3v3 180‐nm CMOS technology, and post‐layout simulation results have been presented to validate its performance. The corner analysis of the proposed class‐ AB FVF cell has also been performed with temperature and supply voltage as design variables to show its performance under extreme conditions.

Monolithic integration of display driver circuits and displays manufactured by screen printing

Here, we report all-screen printed display driver circuits, based on organic electrochemical transistors (OECTs), and their monolithic integration with organic electrochromic displays (OECDs). Both OECTs and OECDs operate at low voltages and have similar device architectures, and, notably, they rely on the very same electroactive material as well as on the same electrochemical switching mechanism. This then allows us to manufacture OECT-OECD circuits in a concurrent manufacturing process entirely based on screen printing methods. By taking advantage of the high current throughput capability of OECTs, we further demonstrate their ability to control the light emission in traditional light-emitting diodes (LEDs), where the actual LED addressing is achieved by an OECT-based decoder circuit. The possibility to monolithically integrate all-screen printed OECTs and OECDs on flexible plastic foils paves the way for distributed smart sensor labels and similar Internet of Things applications.

Operation mechanism and performance optimization for a novel ultralow loss SOI LIGBT with high current capability

In this paper, a novel ultralow on-state voltage-drop (VON) and high current capability SOI lateral insulated gate bipolar transistor (LIGBT) is proposed and investigated by simulation. The proposed device features a folded trench gate (FTG) and a step thickness (ST) drift region filled with insulator, named FTS LIGBT. The FTG is employed to increase the channel density and modulate the current distribution, achieving high current capability and reducing the VON. The stepped insulator in drift region acts as the barrier to suppresses holes from being extracted by cathode and enhances the conductivity modulation, thus further contributes to an ultralow VON in the on-state. Meanwhile, the drift region with varied thickness approximates the effect of variation of lateral doping (VLD) technique to optimize the electric-field distribution, and then maintains high breakdown voltage (BV). Additionally, the T-shaped P+ cathode region improves hole collection efficiency and vertical channels provide a low-resistance for hole current, and thus improves the latch-up immunity and short-circuit capability. Compared with the conventional LIGBT at the same turn-off loss (EOFF), the VON of the FTS LIGBT is reduced by 23% and 38% at the current density of 100 A cm−2 and 200 A cm−2, respectively; The EOFF is reduced by 53% at the current density of 100 A cm−2 at the same VON. The FTS exhibits high saturation current capability (751 A cm−2), which is 2.5 times as that of the conventional LIGBT.

Self-driven power management system for triboelectric nanogenerators

This paper presents a fully functional power management system for triboelectric nanogenerators (TENGs) with the TENG as the only power source. TENG was developed for the objective to provide power to electronic devices and sensors without the need for a battery (the so-called self-powered systems). A unique feature of the TENG's electrical output is high pulsed voltage but low current capability, making TENGs unsuitable for direct use as a power source. To provide continuous and steady electrical voltage for conventional electronics, a power management system (PMS) is required. Existing PMS′ based on power electronic converters do not provide a complete solution due to the use of additional power sources for the logic circuit and switch drivers. The PMS to be reported in this work provides a complete solution for a self-powered system with the TENG as the only power source. This goal is accomplished with a novel approach of employing discrete semiconductor devices, including a silicon-controlled rectifier (SCR) and zener diodes, for controlling the power flow paths, without using any integrated circuit. The effectiveness of the newly developed PMS has been experimentally validated with a prototype and a contact and separation mode TENG device.

Biomimic Vein-Like Transparent Conducting Electrodes with Low Sheet Resistance and Metal Consumption

HighlightsThe electrical transport of the metallized vein networks is mimicked from the material transport function of the leaf vein networks.The vein-like transparent conducting electrodes show ultralow sheet resistance < 0.1 Ω □−1, broadband optical transparency > 80%, and high current density transport capability > 6000 A cm−2.The metal consumption for the metallization of the leaf veins can be as low as 4 g m−2.