Showing papers on "Voltage published in 2017"

State of Charge and State of Health Estimation for Lithium Batteries Using Recurrent Neural Networks

Abstract: This paper presents an application of dynamically driven recurrent networks (DDRNs) in online electric vehicle (EV) battery analysis. In this paper, a nonlinear autoregressive with exogenous inputs (NARX) architecture of the DDRN is designed for both state of charge (SOC) and state of health (SOH) estimation. Unlike other techniques, this estimation strategy is subject to the global feedback theorem (GFT) which increases both computational intelligence and robustness while maintaining reasonable simplicity. The proposed technique requires no model or knowledge of battery's internal parameters, but rather uses the battery's voltage, charge/discharge currents, and ambient temperature variations to accurately estimate battery's SOC and SOH simultaneously. The presented method is evaluated experimentally using two different batteries namely lithium iron phosphate ( $\text{LiFePO}_4$ ) and lithium titanate ( $\text{LTO}$ ) both subject to dynamic charge and discharge current profiles and change in ambient temperature. Results highlight the robustness of this method to battery's nonlinear dynamic nature, hysteresis, aging, dynamic current profile, and parametric uncertainties. The simplicity and robustness of this method make it suitable and effective for EVs’ battery management system (BMS).

Impact of Microcrack Generation and Surface Degradation on a Nickel-Rich Layered Li[Ni0.9Co0.05Mn0.05]O2 Cathode for Lithium-Ion Batteries

Abstract: To address the growing demand for energy density, the Ni-rich layered [Ni0.90Co0.05Mn0.05]O2 cathode has been synthesized and its electrochemical performance in lithium-ion cells has been benchmarked against a lower-Ni content Li[Ni0.6Co0.2Mn0.2]O2 cathode. Li[Ni0.90Co0.05Mn0.05]O2 delivers a high discharge capacity of 227 mA h g–1 compared to a capacity of 189 mA h g–1 for Li[Ni0.6Co0.2Mn0.2]O2 when cycled up to a lower cutoff voltage of 4.3 V, making it an appealing candidate for electric vehicles. With an increase in the charge cutoff voltage to 4.5 V, Li[Ni0.90Co0.05Mn0.05]O2 displays a capacity of 238 mA h g–1 compared to a capacity of 208 mA h g–1 for Li[Ni0.6Co0.2Mn0.2]O2. Although Li[Ni0.90Co0.05Mn0.05]O2 suffers during cycling from the usual rapid capacity fade in a manner similar to that of LiNiO2, 87 and 81% of the initial capacity could still be retained after 100 cycles even after cycling to higher cutoff voltages of 4.3 and 4.5 V, respectively. A comparison of Li[Ni0.90Co0.05Mn0.05]O2 and Li...

An Efficient Regenerative Braking System Based on Battery/Supercapacitor for Electric, Hybrid, and Plug-In Hybrid Electric Vehicles With BLDC Motor

Abstract: Complementary features of batteries and supercapacitors can be effectively used in a hybrid energy storage system (HESS). The utilization of the HESS in electric vehicles (EVs) offers many advantages, such as efficient regenerative braking, battery safety, and improved vehicle acceleration. In this paper, a new regenerative braking system (RBS) is proposed for EVs with HESS and driven by brushless DC (BLDC) motor. During regenerative braking, the BLDC acts as a generator. Hence, by using an appropriate switching algorithm, the dc-link voltage is boosted and the energy is transferred to the supercapacitor or the battery through the inverter. The harvested energy can be utilized to improve the vehicle acceleration and/or keep the battery pack from deep discharging while driving uphill. To provide a reliable and smooth brake, braking force distribution is realized through an artificial neural network. Simultaneously, the braking current is adjusted by a PI controller for constant torque braking. To evaluate the performance of the proposed RBS, different simulations and experiments are carried out. The results confirm high capability of the proposed RBS.

All-Printed Porous Carbon Film for Electricity Generation from Evaporation-Driven Water Flow

Abstract: Converting environmental “waste energies” into electricity via a natural process is an ideal strategy for environmental energy harvesting and supplying power for distributed energy-consuming devices. This paper reports that evaporation-driven water flow within an all-printed porous carbon film can reliably generate sustainable voltage up to 1 V with a power density of ≈8.1 µW cm−3 under ambient conditions. The output performance of the device can be easily scaled up and used to power low-power consumption electronic devices or for energy storage. Furthermore, the device is successfully used without electric storage as a direct power source for electrodeposition of silver microstructures. Because of the ubiquity of water evaporation in nature and the low cost of materials involved, the study presents a novel avenue to harvest ambient energy and has potential applications in low-cost, green, self-powered devices and systems.

Realizing Small Energy Loss of 0.55 eV, High Open-Circuit Voltage >1 V and High Efficiency >10% in Fullerene-Free Polymer Solar Cells via Energy Driver

Abstract: A new, easy, and efficient approach is reported to enhance the driving force for charge transfer, break tradeoff between open-circuit voltage and short-circuit current, and simultaneously achieve very small energy loss (0.55 eV), very high open-circuit voltage (>1 V), and very high efficiency (>10%) in fullerene-free organic solar cells via an energy driver.

A Dual-Carbon Battery Based on Potassium-Ion Electrolyte

Abstract: Although potassium-ion batteries (KIBs) have been considered to be promising alternatives to conventional lithium-ion batteries due to large abundance and low cost of potassium resources, their development still stays at the infancy stage due to the lack of appropriate cathode and anode materials with reversible potassium insertion/extraction as well as good rate and cycling performance. Herein, a novel dual-carbon battery based on a potassium-ion electrolyte (named as K-DCB), utilizing expanded graphite as cathode material and mesocarbon microbead as anode material is developed. The working mechanism of the K-DCB is investigated, which is further demonstrated to deliver a high reversible capacity of 61 mA h g-1 at a current density of 1C over a voltage window of 3.0–5.2 V, as well as good cycling performance with negligible capacity decay after 100 cycles. Moreover, the high working voltage with medium discharge voltage of 4.5 V also enables the K-DCB to meet the requirement of some high-voltage devices. With the merits of environmental friendliness, low cost and high energy density, the K-DCB shows attractive potential for future energy storage application.

Flexible display device

Abstract: A flexible display device including a substrate having an active region in which an input image is implemented and a bezel region outside the active region; a signal line (or an electrode) extending from the bezel region and transmitting a signal (or a voltage) to the active region; and a first bypass line provided above or below the signal line with one or more insulating layers interposed therebetween in the bezel region, wherein the first bypass line is connected to the signal line via a first bypass contact hole penetrating through the one or more insulating layers and receives the same signal as that of the signal line, and wherein the first bypass contact hole is provided as at least two bypass contact holes.

Optimal Charging of Li-Ion Batteries With Coupled Electro-Thermal-Aging Dynamics

Abstract: Fast and safe charging protocols are crucial for enhancing the practicality of batteries, especially for mobile applications, such as smartphones and electric vehicles. This paper proposes an innovative approach to devising optimally health-conscious fast-safe charge protocols. A multiobjective optimal control problem is mathematically formulated via a coupled electro-thermal-aging battery model, where electrical and aging submodels depend upon the core temperature captured by a two-state thermal submodel. The Legendre–Gauss–Radau pseudospectral method with adaptive multi-mesh-interval collocation is employed to solve the resulting highly nonlinear six-state optimal control problem. Charge time and health degradation are, therefore, optimally traded off, subject to both electrical and thermal constraints. Minimum-time, minimum-aging, and balanced charge scenarios are examined in detail. Sensitivities to the upper voltage bound, ambient temperature, and cooling convection resistance are investigated as well. Experimental results are provided to compare the tradeoffs between a balanced and traditional charge protocol.

Between Scylla and Charybdis: Balancing Among Structural Stability and Energy Density of Layered NCM Cathode Materials for Advanced Lithium-Ion Batteries

Abstract: Two major strategies are currently pursued to improve the energy density of lithium-ion batteries using LiNixCoyMnzO2 (NCM) cathode materials. One is to increase the fraction of redox active Ni (≥80%), which allows larger amounts of Li to be extracted at a given cutoff voltage (Umax). The other is to increase Umax, in particular for medium-Ni content NCM materials. However, the accompanying lattice changes ultimately lead to capacity fading in both cases. Here the structural changes occurring in Li1.02NixCoyMnzO2 (with x = 1/3, 0.5, 0.6, 0.7, 0.8 and 0.85) during cycling operation in the voltage range between 3.0 and 4.6 V vs Li are quantified by means of operando X-ray diffraction combined with detailed Rietveld analysis. All samples show a large decrease in unit cell volume upon charging, ranging from 2.4% for NCM111 (33% Ni) to 8.0% for NCM851005 (85% Ni). To make a fair comparison of the structural stability of the different NCM materials, energy densities as a function of Umax are estimated and corre...

Electrically and Sunlight-Driven Actuator with Versatile Biomimetic Motions Based on Rolled Carbon Nanotube Bilayer Composite

Abstract: Designing multistimuli responsive soft actuators which can mimic advanced and sophisticated biological movements through simple configuration is highly demanded for the biomimetic robotics application. Here, inspired by the human's flick finger behavior which can release large force output, a soft jumping robot mimicking the gymnast's somersault is designed based on the rolled carbon nanotube/polymer bilayer composite actuator. This new type of rolled bilayer actuator with tubular shape is fabricated and shows electrically and sunlight-induced actuation with remarkable performances including ultralarge deformation from tubular to flat (angel change >200° or curvature >2 cm−1), fast response (<5 s), and low actuation voltage (≤10 V). Besides jumping, the uniquely reversible rolling–unrolling actuation can lead to other smart soft robots with versatile complex biomimetic motions, including light-induced tumbler with cyclic wobbling, electrically/light-induced crawling-type walking robots and grippers, electrically induced mouth movement, and ambient-sunlight-induced blooming of a biomimetic flower. These results open the way for using one simple type of actuator structure for the construction of various soft robots and devices toward practical biomimetic applications.

Methodology for Wide Band-Gap Device Dynamic Characterization

Abstract: The double pulse test (DPT) is a widely accepted method to evaluate the dynamic behavior of power devices. Considering the high switching-speed capability of wide band-gap devices, the test results are very sensitive to the alignment of voltage and current (V-I) measurements. Also, because of the shoot-through current induced by Cdv/dt (i.e., cross-talk), the switching losses of the nonoperating switch device in a phase-leg must be considered in addition to the operating device. This paper summarizes the key issues of the DPT, including components and layout design, measurement considerations, grounding effects, and data processing. Additionally, a practical method is proposed for phase-leg switching loss evaluation by calculating the difference between the input energy supplied by a dc capacitor and the output energy stored in a load inductor. Based on a phase-leg power module built with 1200-V/50-A SiC MOSFETs, the test results show that this method can accurately evaluate the switching loss of both the upper and lower switches by detecting only one switching current and voltage, and it is immune to V-I timing misalignment errors.

Design of Maximum Efficiency Tracking Control Scheme for Closed-Loop Wireless Power Charging System Employing Series Resonant Tank

Abstract: This paper presents a maximum efficiency tracking control scheme for a closed-loop wireless power charging (WPC) system for wireless charging of mobile devices. Generally, wireless charging systems need a precise output voltage and current with the highest possible efficiency. In an open-loop system, output voltage and efficiency depend strongly on the coupling coefficient and load condition. Alternatively, a closed-loop WPC system has a constant output voltage against coupling and load variations. Many studies have been carried out regarding closed-loop systems. However, those previous studies have the drawback of efficiency degradation. In this paper, we propose a maximum efficiency tracking control scheme to achieve the highest possible efficiency. Therefore, the proposed WPC system satisfies both the requirements of a constant output voltage and high efficiency. The proposed control scheme determines the current of the transmitter based on the data received by the receiver via Bluetooth. For validation, the proposed WPC system was implemented at 6.78 MHz using loosely coupled series–series resonant coils, and we verified that the proposed system can track the maximum efficiency while maintaining a constant output voltage.

Inductive Power Transfer for Massive Electric Bicycles Charging Based on Hybrid Topology Switching With a Single Inverter

Abstract: It is more convenient and safer to employ inductive power transfer (IPT) systems to charge the battery pack of electric bicycles (EBs) than conventional plug-in systems. An IPT charging method suitable for charging massive EBs is proposed to achieve constant current (CC) and constant voltage (CV) output without feedback control strategies or communication link between transmitter side and receiver side. Two ac switches (ACSs) and an auxiliary capacitor utilized at receiver side are employed to be operated once to change the charging modes from CC mode to CV mode. The characteristics of the load-independent current output in the CC mode and load-independent voltage output in the CV mode are achieved by properly selecting the passive parameters of inductances and capacitors, so that no sophisticated control strategies are required to regulate the output as per the charging profile. The feasibility of proposed method has been verified with an experimental prototype in form of efficiency, stability of output current and voltage in CC/CV mode. The simple and economical approach is suitable for the massive EBs charging system with only one inverter, especially in China.

Carbon nanotube transistors scaled to a 40-nanometer footprint

Abstract: The International Technology Roadmap for Semiconductors challenges the device research community to reduce the transistor footprint containing all components to 40 nanometers within the next decade. We report on a p-channel transistor scaled to such an extremely small dimension. Built on one semiconducting carbon nanotube, it occupies less than half the space of leading silicon technologies, while delivering a significantly higher pitch-normalized current density—above 0.9 milliampere per micrometer at a low supply voltage of 0.5 volts with a subthreshold swing of 85 millivolts per decade. Furthermore, we show transistors with the same small footprint built on actual high-density arrays of such nanotubes that deliver higher current than that of the best-competing silicon devices under the same overdrive, without any normalization. We achieve this using low-resistance end-bonded contacts, a high-purity semiconducting carbon nanotube source, and self-assembly to pack nanotubes into full surface-coverage aligned arrays.

A High-Voltage Aqueous Electrolyte for Sodium-Ion Batteries

Abstract: Sodium bis(fluorosulfonyl)imide based aqueous electrolytes exhibit a wide electrochemical stability window of up to 2.6 V when the water-to-salt molar ratio falls below 2:1, enabling the fabrication of high-voltage rechargeable aqueous sodium-ion batteries.

Tunable SnSe2 /WSe2 Heterostructure Tunneling Field Effect Transistor.

Abstract: The burgeoning 2D semiconductors can maintain excellent device electrostatics with an ultranarrow channel length and can realize tunneling by electrostatic gating to avoid deprivation of band-edge sharpness resulting from chemical doping, which make them perfect candidates for tunneling field effect transistors. Here this study presents SnSe2 /WSe2 van der Waals heterostructures with SnSe2 as the p-layer and WSe2 as the n-layer. The energy band alignment changes from a staggered gap band offset (type-II) to a broken gap (type-III) when changing the negative back-gate voltage to positive, resulting in the device operating as a rectifier diode (rectification ratio ~104 ) or an n-type tunneling field effect transistor, respectively. A steep average subthreshold swing of 80 mV dec-1 for exceeding two decades of drain current with a minimum of 37 mV dec-1 at room temperature is observed, and an evident trend toward negative differential resistance is also accomplished for the tunneling field effect transistor due to the high gate efficiency of 0.36 for single gate devices. The ION /IOFF ratio of the transfer characteristics is >106 , accompanying a high ON current >10-5 A. This work presents original phenomena of multilayer 2D van der Waals heterostructures which can be applied to low-power consumption devices.

Variable Frequency Controller for Inductive Power Transfer in Dynamic Conditions

Abstract: Inductive power transfer is a highly attractive option for powering unmanned aerial or underwater vehicles, in harsh environments and while in continuous motion. This study presents a variable frequency controller for series–series compensated contactless chargers operating in dynamic conditions. The controller tracks, in real time, the frequency for which the output voltage is load independent. The criterion for that is the zeroing of the phase difference between the secondary current and the primary-side inverter output voltage. Control is performed by a phase-locked loop with optical communication between the two sides. Experimental results on a 1-kW prototype, for power transfer while in motion, show fast frequency response, along with steady output voltage, despite load variations. Comparison is performed with two other fixed frequencies of operation; the natural frequency of the primary resonant circuit and the maximum output power frequency at nominal gap. The proposed control is proven superior in terms of output power level and stability, as well as safety to highly misaligned conditions.

Higher Order Compensation for Inductive-Power-Transfer Converters With Constant-Voltage or Constant-Current Output Combating Transformer Parameter Constraints

Abstract: Compensation is crucial for improving performance of inductive-power-transfer (IPT) converters. With proper compensation at some specific frequencies, an IPT converter can achieve load-independent constant output voltage or current, near zero reactive power, and soft switching of power switches simultaneously, resulting in simplified control circuitry, reduced component ratings, and improved power conversion efficiency. However, constant output voltage or current depends significantly on parameters of the transformer, which is often space constrained, making the converter design hard to optimize. To free the design from the constraints imposed by the transformer parameters, this paper proposes a family of higher order compensation circuits for IPT converters that achieves any desired constant-voltage or constant-current (CC) output with near zero reactive power and soft switching. Detailed derivation of the compensation method is given for the desired transfer function not constrained by transformer parameters. Prototypes of CC IPT configurations based on a single transformer are constructed to verify the analysis with three different output specifications.

Methods and apparatus for increasing a transfer of energy in an inductive power supply

Abstract: Aspects of the subject disclosure may include, generating, by a waveform generator, an alternating waveform by selectively enabling one or more switches coupled to a storage device, and supplying, by the waveform generator, the alternating voltage waveform to a winding coupled to a magnetic core of an inductive power supply to modify an alternating magnetic flux in the magnetic core from current alone flowing through a transmission medium coupled to the inductive power supply. Other embodiments are disclosed.

A Novel Nine-Level Inverter Employing One Voltage Source and Reduced Components as High-Frequency AC Power Source

Abstract: Increasing demands for power supplies have contributed to the population of high-frequency ac (HFAC) power distribution system (PDS), and in order to increase the power capacity, multilevel inverters (MLIs) frequently serving as the high-frequency (HF) source-stage have obtained a prominent development. Existing MLIs commonly use more than one voltage source or a great number of power devices to enlarge the level numbers, and HF modulation (HFM) methods are usually adopted to decrease the total harmonic distortion (THD). All of these have increased the complexity and decreased the efficiency for the conversion from dc to HF ac. In this paper, a nine-level inverter employing only one input source and fewer components is proposed for HFAC PDS. It makes full use of the conversion of series and parallel connections of one voltage source and two capacitors to realize nine output levels, thus lower THD can be obtained without HFM methods. The voltage stress on power devices is relatively relieved, which has broadened its range of applications as well. Moreover, the proposed nine-level inverter is equipped with the inherent self-voltage balancing ability, thus the modulation algorithm gets simplified. The circuit structure, modulation method, capacitor calculation, loss analysis, and performance comparisons are presented in this paper, and all the superior performances of the proposed nine-level inverter are verified by simulation and experimental prototypes with rated output power of 200 W. The accordance of theoretical analysis, simulation, and experimental results confirms the feasibility of proposed nine-level inverter.

Flexible and Wearable All-Solid-State Supercapacitors with Ultrahigh Energy Density Based on a Carbon Fiber Fabric Electrode

Abstract: Wearable textile energy storage systems are rapidly growing, but obtaining carbon fiber fabric electrodes with both high capacitances to provide a high energy density and mechanical strength to allow the material to be weaved or knitted into desired devices remains challenging. In this work, N/O-enriched carbon cloth with a large surface area and the desired pore volume is fabricated. An electrochemical oxidation method is used to modify the surface chemistry through incorporation of electrochemical active functional groups to the carbon surface and to further increase the specific surface area and the pore volume of the carbon cloth. The resulting carbon cloth electrode presents excellent electrochemical properties, including ultrahigh areal capacitance with good rate ability and cycling stability. Furthermore, the fabricated symmetric supercapacitors with a 2 V stable voltage window deliver ultrahigh energy densities (6.8 mW h cm−3 for fiber-shaped samples and 9.4 mW h cm−3 for fabric samples) and exhibit excellent flexibility. The fabric supercapacitors are further tested in a belt-shaped device as a watchband to power an electronic watch for ≈9 h, in a heart-shaped logo to supply power for ≈1 h and in a safety light that functions for ≈1 h, indicating various promising applications of these supercapacitors.

A Single-Phase Transformerless Inverter With Charge Pump Circuit Concept for Grid-Tied PV Applications

Abstract: This paper proposes a new single-phase transformerless photovoltaic (PV) inverter for grid-tied PV systems. The topology is derived from the concept of a charge pump circuit in order to eliminate the leakage current. It is composed of four power switches, two diodes, two capacitors, and an LCL output filter. The neutral of the grid is directly connected to the negative polarity of the PV panel that creates a constant common mode voltage and zero leakage current. The charge pump circuit generates the negative output voltage of the proposed inverter during the negative cycle. A proportional resonant control strategy is used to control the injected current. The main benefits of the proposed inverter are: 1) the neutral of the grid is directly connected to the negative terminal of the PV panel, so the leakage current is eliminated; 2) its compact size; 3) low cost; 4) the used dc voltage of the proposed inverter is the same as the full-bridge inverter (unlike neutral point clamped (NPC), active NPC, and half-bridge inverters); 5) flexible grounding configuration; 6) capability of reactive power flow; and 7) high efficiency. A complete description of the operating principle and analysis of the proposed inverter are presented. Experimental results are presented to confirm both the theoretical analysis and the concept of the proposed inverter. The obtained results clearly validate the performance of the proposed inverter and its practical application in grid-tied PV systems.

Al-Doped Black Phosphorus p–n Homojunction Diode for High Performance Photovoltaic

Abstract: 2D layered materials based p–n junctions are fundamental building block for enabling new functional device applications with high efficiency. However, due to the lack of controllable doping technique, state-of-the-art 2D p–n junctions are predominantly made of van der Waals heterostructures or electrostatic gated junctions. Here, the authors report the demonstration of a spatially controlled aluminum doping technique that enables a p–n homojunction diode to be realized within a single 2D black phosphorus nanosheet for high performance photovoltaic application. The diode achieves a near-unity ideality factor of 1.001 along with an on/off ratio of ≈5.6 × 103 at a low bias of 2 V, allowing for low-power dynamic current rectification without signal decay or overshoot. When operated under a photovoltaic regime, the diode's dark current can be significantly suppressed. The presence of a built-in electric field additionally gives rise to temporal short-circuit current and open-circuit voltage under zero external bias, indicative of its enriched functionalities for self-powered photovoltaic and high signal-to-noise photodetection applications.

Optimal placement of TCSC and SVC for reactive power planning using Whale optimization algorithm

Abstract: In the present work, Whale optimization algorithm (WOA), Differential evolution (DE), Grey wolf optimization (GWO), Quasi-opposition based Differential Evolution (QODE) and Quasi-opposition based Grey wolf optimization (QOGWO) algorithm has been applied for the solution of reactive power planning with FACTS devices i.e., Thyristor controlled series compensator (TCSC) and Static Var compensator (SVC). WOA is a recently developed nature-inspired meta-heuristic algorithm based on hunting behaviour of Humpback Whales; DE is a stochastic real-parameter optimization technique comprising of genetic parameters namely - mutation & cross-over; and GWO is a nature-inspired meta-heuristic algorithm based on hunting behaviour of Grey wolf. Standard IEEE 30 and IEEE 57 bus test system has been adopted for the testing purposes. Location of TCSC has been determined by the power flow analysis method and location of SVC has been determined by the voltage collapse proximity indication (VCPI) method. Further, WOA, GWO, DE, QODE and QOGWO algorithms have been applied to find the optimal setting of all control variables including TCSC, the series type and SVC, the shunt kind of FACTS device in the test system which minimizes active power loss and system operating cost while maintaining voltage profile within permissible limit. The superiority of the proposed WOA technique has been illustrated by comparing the results obtained with all other techniques discussed in the present problem. ANOVA test has also been conducted to show the statistical analysis between different techniques. The proposed approach shows lesser number of iterations which does not gets trapped in the local minima and offers promising convergence characteristics.