Browse Topic: Capacitors

Items (248)
Find
Stretchable Material for Wearables Operates at Low PowerTBMG-373588/1/2020
A novel stretchable material, when used in light-emitting capacitor devices, enables highly visible illumination at low operating voltages, and it is also resilient to damage due to its self-healing properties.
Design of a Flexible Hybrid Powertrain Using a 48 V-Battery and a Supercapacitor for Ultra-Light Urban Vehicles2020-01-04454/14/2020
Global warming has put the transport sector, a major contributor of CO2 emissions, under high pressure to improve efficiency. In this context, ultra-light vehicles weighting less than 500 kg, as well as hybrid powertrains, are nowadays seen as promising development trends. The design process of the powertrain of a vehicle combining the advantages of the two concepts is presented in this paper. Through a performance study based on a simple MATLAB model, and mathematical simulation, a proposal is made. A powertrain using a battery and supercapacitor 48V dual power source network, two electric motors and clutches to switch between conventional, parallel, series and full electric modes proves to be an interesting system in terms of performance and costs. A simulation study conducted on a scenario with different outcome possibilities showed that high modularity of the system allows to achieve fuel efficiencies equivalent to approximately 3 l/100 km on the Artemis cycle. Finally, integration, packaging and cost are considered and some hints for further powertrain efficiency improvements are presented.
El Ganaoui-Mourlan, Ouafae, Miliani, El Hadj, Carlos Da Silva, Daniel, Couillandeau, Matthieu, Gonod, Charlie, Miller, Guillaume
Novel electrochemical capacitors with high-energy density using intercalated metal-organic framework electrodes2019-01-226012/19/2019
The energy-density improvement of capacitors while maintaining high power, long-term-cycle stability and safety is challenging. Asymmetric capacitors using non-faradaic and intercalation electrodes are proposed in order to achieve this. However the reported asymmetric capacitors with graphite-based negative electrode have a safety risk, which is an internal short circuit due to Li deposition when further high-energy density is performed. Here asymmetric capacitors consisting of intercalated metal-organic frameworks (iMOFs) negative operating potential range of 0.5-1.0 V vs. Li/Li+ that enable Li deposition reduction and activated carbon positive electrodes is proposed to construct a high volumetric energy (ca. 60 Wh L-1) and power densities with safety.
Ogihara, Nobuhiro
Downhill Safety Assistant Driving System for Battery Electric Vehicles on Mountain Roads2019-01-21299/15/2019
When driving in mountainous areas, vehicles often encounter downhill conditions. To ensure safe driving, it is necessary to control the speed of vehicles. For internal combustion engine vehicles, auxiliary brake such as engine brake can be used to alleviate the thermal load caused by the continuous braking of the friction brake. For battery electric vehicles (BEVs), regenerative braking can be used as auxiliary braking to improve brake safety. And through regenerative braking, energy can be partly converted into electrical energy and stored in accumulators (such as power batteries and supercapacitors), thus extending the mileage. However, the driver's line of sight in the mountains is limited, resulting in a certain degree of blindness in driving, so it is impossible to fully guarantee the safety and energy saving of downhill driving. Therefore, taking a pure electric light truck as an example, the system proposed in this paper first analyzes the driver's driving intention, proposes the system startup and exit strategy, and then combines the geographic information system (GIS) mountain road information, downslope speed limit and vehicle parameters, considering the motor and battery characteristics, establishes mathematical models such as the regenerative braking model and the brake temperature rise model based on vehicle dynamics and the conservation of energy, determines the appropriate braking mode(There are two braking modes)and the slope top safe speed by calculation, and reminds the driver when going uphill and downhill. The main goal is to use more regenerative braking, reduce the use or duration of the main brake, avoid overheating the main brake, improve the safety during continuous braking, and achieve smarter energy management. Finally, simulations are carried out under different conditions of vehicle speed, slope length, slope gradient and battery SOC. The results show that the system has a good energy-saving effect and can significantly improve the safety of BEVs running downhill.
Feng, Jia'ao, Tian, Zhongpeng, Cui, Jian, Zhou, Fangyu, Tan, Gangfeng
Using Monolithic Filters to Address EMI in Medical DevicesTBMG-351009/1/2019
Many factors are conspiring to increase the amount of “noise” or interference that can disturb the functionality and even damage electronic devices, starting with the sheer number used in our vicinity at any given time. Today’s Wi-Fi or Bluetooth-enabled medical instruments and even medical implants provide a prime example.
Graphene Lid Extends Photoemission Electron Microscopy to LiquidsTBMG-347537/1/2019
By capping liquids with graphene (an ultrathin sheet of pure carbon), researchers can easily image and analyze liquid interfaces and the surface of nanometer-scale objects immersed in liquids. In the imaging technique known as photoemission electron microscopy (PEEM), ultraviolet light or X-rays bombard a sample, stimulating the material to release electrons from a region at or just beneath its surface. Electric fields act as lenses, focusing the emitted electrons to create an image.
Stretchable Power Source for WearablesTBMG-347377/1/2019
Researchers have created highly stretchable supercapacitors for powering wearable electronics that consist of crumpled carbon nanotube (CNT) forests. The supercapacitors demonstrated solid performance and stability, even when stretched to 800% of their original size for thousands of stretching/relaxing cycles.
Power Electronic Noise-Simulation Measurement Comparison2019-01-14516/5/2019
A growing development of hybrid or fully electrical drives increases the demand for an accurate prediction of noise and vibration characteristics of electric and electronic components. This paper describes the numerical and experimental investigation of noise emissions from power electronics, as one of the new important noise sources in electric vehicles. The noise emitted from the printed circuit board (PCB) equipped with multi-layer ceramic capacitors (MLCC) is measured and used for the calibration and validation of numerical model. Material properties are tuned using results from experimental modal analysis, with special attention to the orthotropic characteristic of the PCB glass-reinforced epoxy laminate sheet (FR-4). Electroacoustic excitation is pre-calculated using an extension of schematic-based EMC simulation and applied to the structural model. Structural vibrations are calculated with a commercial FEM solver with the modal frequency response analysis. Sound radiation is simulated using the wave-based approach (WBT). Simulation and experimental results are compared in a frequency range up to 10 kHz. The developed simulation methodology can successfully identify the main noise sources from the equipped PCB. Critical peak noise responses are identified both in experiment and simulation.
Klarin, Borislav, Olbrich, Peter, Resch, Markus, Resch, Thomas, Brandl, Stephan, Reindl, Hartwig
Stretchable Interlaced-Nanowire Film for Ultraviolet Photodetectors with High Response SpeedTBMG-345886/1/2019
Stretchable electronics, which can be stretched, deformed and wrapped onto nonplanar curved surfaces, have attracted much attraction due to their potential applications in wearable electronics, implantable biomedical devices, and artificial electronic skin. So far, many types of stretchable electronic devices have been developed including stretchable transistors, light-emitting diodes (LEDs), supercapacitors, photodetectors and sensors. Ultraviolet (UV) photodetectors have wide applications in crime investigation, biological analysis, fire monitoring, UV irradiation detection and many other applications as well.
Self-Powered Wearable TechTBMG-345606/1/2019
Researchers have created highly stretchable supercapacitors for powering wearable electronics. The newly developed supercapacitor has demonstrated solid performance and stability, even when it is stretched to 800 percent of its original size for thousands of stretching/relaxing cycles.
The ‘Relativity’ of High Q CapacitorsTBMG-345576/1/2019
For many high-power RF applications, the “Q factor” of embedded capacitors is one of the most important characteristics in the design of circuits. This includes products such as cellular/telecom equipment, MRI coils, plasma generators, lasers, and other medical, military, and industrial electronics.
Impedance Modeling and Aging Research of the Lithium-Ion Batteries Using the EIS Technique2019-01-05964/2/2019
As the core component of electric vehicles (EVs), batteries attach increasingly general attention along with the rapid expansion of electric vehicle market. Battery performance effect directly the safety and reliability of the EVs, so its managing technologies are more and more crucial. Among them, the methods of estimating the state of health (SoH) and predicting remaining useful life become the focuses, which are essential to ensure their dependability and optimum performance over time. This paper mainly focuses on impedance modeling and aging research (aging diagnosis and life prediction) of lithium-ion batteries. Electrochemical impedance spectroscopy (EIS) technique is used to obtain impedance characteristic of batteries. On the one hand, equivalent circuit modeling (ECM) can be motivated by EIS, with the goal to fit measured impedance data using circuit elements. On the other hand, the aging research of batteries can be analyzed using the resistance information provided by EIS due to the correlation between battery resistance and lifetime. The possible causes of battery aging are analyzed based on changes in the impedance spectrum, which are obtained under different life conditions through an accelerated life experiment. According to the result and the corresponding electrode process, an improved Randels model is then established. Furthermore, a method to predict the battery life based on EIS is proposed. The battery life characterization parameters and calculation methods are defined according to related test manuals and standards. Then, the impedance amplitude of a certain frequency is selected as an estimation parameter. Finally, the first-order polynomial is selected as the fitting function comparing with the fitting results of various functions.
Gao, Qian, Dai, Haifeng, Wei, Xuezhe, Jiang, Bo
Fabric Alternative to Batteries for Wearable DevicesTBMG-341484/1/2019
Wearable biosensors for health monitoring lack a lightweight, long-lasting power supply. A new method was developed for making a charge-storing system that is easily integrated into clothing for embroidering a charge-storing pattern onto any garment.
Compact, High-Resolution Rotary Position SensorTBMG-3310610/1/2018
It is often desirable to sense the angular position of a rotating part. Numerous kinds of rotation sensors have been developed over the years; one type is a capacitive sensor, where a capacitance varies according to angular position. Rotary sensors known in the art are lacking in resolution and generally have an oversized form factor, making them impractical for applications requiring maximum signal production for a limited sensing area, in addition to having differential cancellation of offset bias and gain terms to reject noise caused by motion not in the direction of rotation of the sensor. What is needed is a rotary position sensor with high resolution and a reduced form factor that is able to operate for long periods of time, while having a reduced cost of fabrication.
Electric double layer capacitors prepared with polyvinyl alcohol and multi-walled carbon nanotubes2018-36-03139/3/2018
Portable electronics, wearables, electric vehicles and solar cells are sectors in increasingly development which include innovation and miniaturization of the devices. In this scenario, the development of smaller and lightweight energy storage devices, which store more energy, is required. Besides, it is desirable for these devices to be environmentally friendly to minimize pollution. In an attempt to meet these requirements, this work purposes the development and the characterization of nanofibers-based electrode composed of Polyvinyl alcohol (PVA) and multi-walled carbon nanotubes (MWCNT) for electric double layer capacitors (ELCDs) devices with aqueous electrolyte. This composite has been prepared by electrospinning technique and consolidate an electrical conductive and high-surface material electrode. After that, the PVA/MWCNT electrode was assembled in coin cell device with Sodium Sulfate (Na2SO4) electrolyte for electrochemical characterization. The characterization results showed that EDLCs devices present specific capacitance of ∼4.8 Fg-1, energy density of ∼0.1 Wh kg-1, power density of ∼600W kg-, fast charge transfer at electrode/electrolyte interface and high lifetime All these results encourage further development on PVA/MWCNT materials as electrode for EDLCs and Li-Air batteries devices. This new generation of devices are opening niches of applications on multi billionaire markets from communication to transport.
Real, Carla Giselle Martins, Vicentini, Rafael, Nunes, Willian Gonçalves, Boas, Otávio Vilas, Costa, Lenon Henrique, Soares, Davi Marcelo, Zanin, Hudson
Polyacrylonitrile and activated carbon composite for electric double layer capacitors2018-36-03109/3/2018
Electrospinning of polymers blends solutions offers the potential to produce nanofibers for using in a variety of applications. Here, we report the synthesis of nanofibers with polyacrylonitrile (PAN) and activated carbon (AC) composite by employing this technique. As-produced material is an electrical conductive and high-surface material electrode with outstanding electrochemical properties, which we explore electric double layer capacitors (EDLCs) coin cell devices. Our results show that EDLCs manufactured with PAN/AC composite have fairly high specific capacitance, low internal impedance and high lifetime. All these results encourage further development of PAN/AC materials as electrode for EDLCs and Li- Air batteries devices. This new generation of devices are opening niches of applications on multi-millionaire markets such as electric vehicles & solar and wind power systems. Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The authors solely responsible for the content of the paper.
Real, Carla Giselle Martins, Vicentini, Rafael, Nunes, Willian Gonçalves, Boas, Otávio Vilas, Alves, Thayane Almeida, Soares, Davi Marcelo, Zanin, Hudson
Controlled Manufacture of Porous Silicon CarbideTBMG-328619/1/2018
Extremely fine porous structures with tiny holes — resembling a kind of sponge at the nano level — can be generated in semiconductors. A method was developed for the controlled manufacture of porous silicon carbide (SiC), which has significant advantages over silicon. It possesses greater chemical resistance and can be used for biological applications, for example, without any additional coating required.
Near-Zero-Power Temperature SensorTBMG-296847/1/2018
A temperature sensor was developed that runs on 113 picowatts of power — about 10 billion times smaller than a Watt. The technology could enable devices that can be powered by harvesting energy from low-power sources, such as the body or the surrounding environment. Potentially, the system could run for years on a tiny battery.
Cryo-Fluid Capacitor (CFC)TBMG-290346/1/2018
NASA’s Kennedy Space Center (KSC) has created the Cryo-Fluid Capacitor (CFC) that capitalizes on the energy storage capacity of liquefied gases, and the relative simplicity of high-pressure gas bottles while limiting the downfalls associated with both methods. By exploiting a unique attribute of nanoporous materials — aerogel, in this case — fluid commodities such as oxygen, hydrogen, methane, etc. can be stored in a molecular surface adsorbed state at densities on par with liquid, at low to moderate pressure, and then supplied as a gas, on-demand, to a point of interest.
Modularized Simulation Tool to Evaluate Battery Solutions for 12 V Advanced Start Stop Vehicles2018-01-04464/3/2018
The 12 V advanced start stop systems can offer 5-8% fuel economy improvement over a conventional vehicle. Although the fuel economy is not as high as those of mild to full hybrids, its low implementation cost makes it an attractive electrification solutions for vehicles. As a result, the 12 V advanced start stop technology has been evolving fast in recent years. On one hand, battery suppliers are offering a variety of energy storage solutions such as stand-alone lead acid, stand-alone LFP/Graphite, dual batteries of lead acid parallel with NMC/LTO, LMO/LTO, NMC/Graphite, and capacitors, etc. For dual battery solutions, the architecture also varies from passive parallel connection to active switching. On the other hand, OEM are considering to leverage a lot more use out of traditional 12 V SLI (start, light, and ignition) for functions such as power steering, air conditioning, heater, etc. Depending on battery architecture and vehicle functioning design, the energy management strategy can easily become complicated. Since many variables are involved in the design of 12 V advanced start stop systems, an integrated simulation tool with a couple of modularized models including vehicle, batteries, and performance characterization have been developed. The modularized tool would help to evaluate many aspects of the design from motor size selection, power network management, battery evaluation, testing standardization. As a specific demonstration, in this work, we use the tool to compare three chemistries: stand-alone AGM, stand-alone LFP, and dual batteries of lead acid and LTO for different driving cycles including NEDC, WLTP, FTP72, and HWFET as function of motor size.
Zhang, Zhenli, Jin, Zhihong, Watson, Thomas
System-Level Investigation of Traction Inverter High-Temperature Operation2018-01-04644/3/2018
In this paper, the high-temperature capability of the traction inverter was investigated by applying coolant with temperature much higher than the typical allowed value until the system fails. The purpose of this study is to identify the weakest link of the traction inverter system in terms of temperature. This study was divided into two stages. In the first stage, a series of nondestructive tests were carried out to investigate temperature rise (ΔT) of the key component above coolant temperature as a function of the outside controllable parameters-i.e., dc link voltage, phase current, and switching frequency. The key components include power modules, gate driver board, gate driver power supply, current sensors and dc link capacitor. Their temperatures were monitored by thermocouples or on-die temperature sensors. The result showed that temperature rises of most key components were strongly affected by phase current, moderately affected by switching frequency, and slightly affected by dc link voltage. Therefore, the operating conditions used in the second stage (destructive test) were chosen to stress the phase current only rather than the dc link voltage and switching frequency for better effectiveness. In the second stage (the destructive test), the coolant temperature was controlled to increase every a few hours after the temperature stabilized while maintaining the controllable electrical parameters to be the same. Testing results showed that the traction inverter employed in this study can sustain coolant temperature > 105 °C for more than 10 hours, while the IGBT on-die temperatures were measured to be >200 °C. Under this specific condition, the IGBT module is the first component to fail after the coolant temperature was raised to a certain level (>120 °C). On the contrary, many other components are found to be functioning after the long-time operation at high temperatures. The measurement results were confirmed by the theoretical analysis.
Lu, Xi, Xiao, Kewei, Lei, Guangyin, Chen, Chingchi
Transmission-Mounted Power Control Unit Including 12-Volt DC-DC Converter for Two-Motor Hybrid System2018-01-04574/3/2018
This research proposes a third-generation power control unit (PCU) for a two-motor hybrid system. To make a more compact intelligent power unit (IPU) to be located under the second seat, a PCU with a 12-volt DC-DC converter (DCDC) that mounts directly on the transmission was developed, whereas the DCDC was previously mounted within the IPU. Since this has a considerable impact on the engine room layout, the technology described below was used to make the PCU even more compact than the second-generation unit. The power module, a key component of the PCU, now uses Ag nanoparticles sintering bonding rather than conventional solder bonding. This helps lower thermal resistance and enables smaller power semiconductors. The voltage control unit (VCU) has a new circuit that uses a multi-stage switching circuit and electric power transfer capacitor instead of the conventional chopper circuit. This makes it possible to shrink the reactor to less than 65% of its usual volume without raising the carrier frequency, and enables a layout that efficiently uses both sides of the water jacket (W/J), so that no specially designed W/J needs to be added just for the DCDC. As for the W/J seal, friction stir welding (FSW) to increase rigidity was used to reduce seal width and to make the W/J itself more compact. The use of these compactness technologies enabled the PCU to maintain all the efficiency of a second-generation PCU and made it possible to build the DCDC in the PCU with its volume less than a second-generation one. Development of this PCU makes the IPU much more compact and provides a similar amount of trunk space as in a gasoline-powered vehicle.
Ozuchi, Yasuhiro, Tomokage, Ryoji
A Technical, Environmental and Financial Analysis of Hybrid Buses Used for Public Transport2018-01-04244/3/2018
This paper presents a technical, financial and environmental analysis of four different hybrid buses operated under Buenos Aires driving conditions. A conventional diesel bus is used as reference and three electric hybrids equipped with different energy storage technologies, Li-Ion, NiMH batteries and double layer capacitors (ultracapacitors), are evaluated, along with a hydraulic hybrid platform which uses high-pressure accumulators as its energy buffer. The operating conditions of the buses are set using real driving GPS data collected from various bus routes within the city. The different vehicle platforms are modeled on AUTONOMIE SA and validated by comparing the obtained fuel consumption results to those reported by local transport authorities and values found in the literature. The embedded energy and CO2 emissions of each platform are estimated using GREET and the total cost of ownership of each vehicle is calculated and compared to that of the conventional bus. Furthermore, aging models are proposed to evaluate the life duration of the batteries and ultracapacitors. Results show that, independent of the energy storage technology, the fuel economy performance of all hybrids is highly dependent on the size and configuration of the powertrain and energy storage components. When optimized, all hybrids achieve significant fuel consumption reductions compared to a conventional diesel bus, however, the ultracapacitor based system seems to outperform the other technologies. The battery based electric buses achieve similar fuel consumption reductions, but the NiMH based batteries shows a considerably shorter life expectancy. This has a significant impact on both the economic and environmental performance of this vehicle. The life cycle emission analysis shows that, given the high fuel consumption of a conventional bus, the additional embedded CO2 emissions of the hybrid vehicles are offseted by the achieved reduction of in-service CO2 emissions due to fuel consumption reductions. Regarding the economic performance of the different platforms, results show that the fuel savings achieved by all hybrids displace the higher capital costs required. Overall, all hybrid buses show a strong potential to reduce both CO2 emissions and costs, resulting in negative costs of CO2 abatement.
Orbaiz, Pedro, van Dijk, Nicolás, Cosentino, Santiago, Oxenford, Nicolas, Carignano, Mauro, Nigro, Norberto Marcelo
Near-Zero-Power Temperature SensorTBMG-285303/1/2018
A temperature sensor was developed that runs on 113 picowatts of power — about 10 billion times smaller than a Watt. The technology could enable devices that can be powered by harvesting energy from low-power sources, such as the body or the surrounding environment. Potentially, the system could run for years on a tiny battery.
Inexpensive Method for Manufacturing Supercapacitor ElectrodesTBMG-283092/1/2018
Supercapacitors can store and deliver energy faster than conventional batteries. But to realize advanced applications, supercapacitors need better electrodes, which connect the supercapacitor to the devices that depend on their energy. These electrodes need to be both quicker and cheaper to make on a large scale, and also able to charge and discharge their electrical load faster.
Novel, Solid-State Hybrid Ultracapacitor BatteryTBMG-283232/1/2018
NASA's Marshall Space Flight Center has developed a solid-state ultracapacitor with a unique combination of high capacitance and battery-like discharge characteristics. The high capacitance in a solid-state form can enable a new type of ultracapacitor, and in combination with the ability to deliver sustained power like a battery, can perhaps enable an entirely new class of energy storage devices.
Process Turns Carbon Dioxide into 3D Graphene with Microporous SurfaceTBMG-281561/1/2018
The conversion of carbon dioxide to useful materials usually requires high energy input due to its ultrahigh stability. A heat-releasing reaction between carbon dioxide and sodium was developed to take carbon dioxide and turn it into 3D graphene with micropores across its surface.
High-Energy-Storage CapacitorTBMG-2781911/1/2017
A method was created for electroless deposition of conformal ultrathin (<20 nm) metal oxides on the high-surface-area walls of commercial carbon nanofoam papers, typically 0.1–0.3 mm thick. The resulting ultrathin metal oxides rapidly take up and release electrons and ions, thereby storing energy at 300–600 Farads per gram of oxide, while the carbon nanofoam paper serves as a three-dimensional current collector and defines a pre-selected porous electrode architecture.
Power Systems Infrastructure of Hybrid Electric Fuel Cell Competition Go Kart2017-01-245210/8/2017
This paper documents the electrical infrastructure design of a Hybrid Go Kart competition vehicle which includes a dual Fuel Cell power system, Ultra Capacitors for energy storage, and a dual AC induction motor capable of independent drive. The Kart was built primarily to compete in the 2009 Formula Zero international event. This paper emphasized the vehicle model and control strategy as a result of three (3) graduate student research projects. The vehicle was fabricated and tested but did not participate in the race competition since the race organization folded. The vehicle model was developed in Simulink to determine whether the fuel cell and ultra-capacitor combination will be sufficient for peak transient power requirement of 14 kW. The vehicle’s functional description and performance specifications are documented including the integration of the fuel cell power modules, energy storage system, power converters, and AC motor and motor controllers.
Berry, Kingsley Joel, Traore, Abdrahamane, Krishna, Aravind, Gangadhar, Pavankumar, Taylor, Allan
Tantalum Capacitors for Medical ApplicationsTBMG-274729/1/2017
DC-Link Capacitor Sizing Considerations for HEV/EV e-Drive Systems2017-01-12343/28/2017
Dc-link capacitor sizing considerations are discussed for HEV/EV e-Drive systems. The capacitance value of the dc-link in HEV/EV e-Drive systems affects numerous factors. Some of the most significant are the system stability and the maximum tolerable dc-bus transient voltage with operating point change or with worst-case energy dump into the capacitor. Also requiring attention is the equivalent series resistance and inductance of the capacitor module. The former affects thermal behavior of the capacitor module and the latter affects voltage spikes occurring at every turn-off of a power semiconductor switch. In addition, these factors are dependent on other power-stage component parameters, control structures and controller gains. Also such effects and cross-couplings are operating-point dependent. This makes the dc-link capacitor sizing for HEV/EV e-Drive systems a complex task and it looks as if the task is done primarily by empirical manner with possibly more than enough safety margin. It appears accordingly that no systematic step-by-step methodology for the capacitor sizing has been discussed in the public domain. This paper attempts to present a list of the items to be considered for such a systematic dc-link capacitor sizing, and a detailed description follows for each item. The above-mentioned cross-coupling matters and the resulting trade-offs are briefly discussed. Potential issues caused by the use of emerging wide-bandgap semiconductors are mentioned as well. The target system taken as an example is an HEV e-Drive system, consisting of two electric machine drive inverters and a dc-dc converter, which share a common dc-link.
Sridharan, Srikanthan, Kimmel, Joseph, Kikuchi, Jun
Modeling and Experiment Validation of the DC/DC Converter for Online AC Impedance Identification of the Lithium-Ion Battery2017-01-11983/28/2017
The lithium-ion battery plays an important role in saving energy and lowering emissions. Many parameters like temperature have an influence on the characteristic of the battery and this phenomenon becomes more serious in an electric vehicle. In this paper, the application of a boost DC/DC converter to the battery system of high power for online AC impedance identification is proposed. The function of the converter is to inject a current excitation signal into the battery at work and the normal output current is drawn by a load. Through analyzing the average state space equations and deriving the small signal model of the converter, the gain function is deduced of the fluctuated current signal against the fluctuated duty cycle which controls the converter. The control algorithm is designed and the system model is verified using Matlab/Simulink with respect to the disturbance current signal generation, the gain function and its variation with frequency range. Then the converter is designed and implemented to conduct the experiment on a power battery of 175Ah and the nominal voltage is 100V. The measured AC impedance of several single cells is presented and it demonstrates the feasibility of applying this DC/DC converter to the practical electric vehicle.
Hong, Po, Jiang, Hongliang, Li, Jian qiu, Xu, Liangfei, Ouyang, Minggao
Traction Inverter Design with a Direct Bypass to Boost Converter2017-01-12473/28/2017
Direct bypass to DC-DC boost converter in traction inverter increases converter's capability and efficiency significantly by providing a lower loss path for power flow between the battery and DC-link terminal. A bypass using diode is an excellent solution to achieve this capability at low cost and system complexity. Bypass diode operates in the linear operating region (DC Q-point) when the battery discharges through the bypass diode to drive the electric motors. Therefore, thermal stress on the DC-link capacitor is shared between the input and DC-link capacitors through the bypass diode. On the other hand, inverters introduce voltage oscillation in the DC-link terminal which results in unwanted energy oscillation through the bypass diode during battery charging. Both of these phenomena have been explained in details. It is possible to eliminate this power oscillation during battery charging using minimum voltage level boosting at a reduced frequency or using a bi-directional switch (i.e., IGBT/diode or MOSFET/diode pair). The control strategy to achieve minimum voltage level boosting has been described in details. Moreover, it is possible to further reduce power loss of the boost converter by completely bypassing the inductor using a bi-directional switch during high voltage battery charging.
Alam, Mohammed Khorshed, Chen, Lihua, Zhou, Yan, Xu, Fan, Yang, Shuitao
High Energy Ignition Strategies for Diluted Mixtures via a Three-Pole Igniter2016-01-217510/17/2016
A three-pole spark igniter, with the concept to broaden the ignition area, is employed in this paper to investigate the effect of spark discharge strategies on the early ignition burning process. The prototyped three-pole igniter has three independent spark gaps arranged in a triangular pattern with a circumradius of 2.3 mm. Direct-capacitor discharge techniques, utilizing close-coupled capacitors parallel to the spark gap, are applied on the three-pole igniter to enhance either the transient spark power or the overall energy. In particular, the simultaneous discharge of high energy plasma on three spark gaps can produce a surface-like ignition process which intensifies the plasma-flame interaction, thereby producing a rapid flame kernel development. The ignition strategies are evaluated in both constant volume combustion vessels and a modified single-cylinder metal engine. In the results, for both the lambda sweep and the CO2 dilution tests performed in the constant volume combustion vessels, three-pole ignition exhibits significantly faster burning, compared to the single-pole ignition, which is indicated by the shortened time to 5% mass fraction burnt (MFB) and the time to 50% MFB. The ignition improvement by the three-pole arrangement is consistently observed for various energy levels and sparking modes. A preliminary test on a modified single-cylinder research engine, with a relatively low spark energy level, shows that the three-pole ignition can noticeably improve the combustion phasing control for a lean burn operation.
Yu, Shui, Xie, Kelvin, Yu, Xiao, Wang, Meiping, Zheng, Ming, Han, Xiaoye, Tjong, Jimi
Finding Flaws in Medical ImplantsTBMG-246555/1/2016
Cracks in ceramic capacitors, devices that store electric charge in electronic circuits, can cause damage to such disparate objects as medical implants and spacecraft. The cracks, which are often hidden initially, can start conducting electricity, depleting batteries, or shorting out electronics. Detecting these cracks in capacitors before they evolve into electrically conducting pathways and cause failures is something that researchers at the National Institute of Standards and Technology (NIST), along with collaborators from the University of Maryland, NASA Goddard Space Flight Center, and Colorado State University have spent years investigating.
Simple Impedance Matched Planar Microwave Blocking FilterTBMG-245245/1/2016
Thermal blocking filters find wide use in cryogenic applications ranging from quantum computing to ultra-low-noise detectors. They can be used to provide the environmental isolation between cooled devices and the warmer temperature supporting bias and readout circuitry. In particular, they are effective in rejecting thermal radiation, limiting radio frequency interference, and providing a convenient means of heat sinking or realizing a vacuum feedthrough for signal lines.
Model-Based Evaluation of Chemistry Selection for Dual Energy Storages for 12V Advanced Start-Stop Vehicles2016-01-12094/5/2016
Passively parallelizing two energy storage systems, one is energy type and the other is power type, requires minimal modifications of auto makers and thus a cost-effective method to enable advanced start stop technology. Traditional lead acid battery, lithium-ion battery, capacitor, are all candidate chemistries for dual energy storage solutions. However due to the dual nature of the technology the open circuit potential, resistance, and some other control variables should match in order to achieve optimal performance. In this work we use coupled equivalent circuit model and electrochemical model to study a few options of dual systems, namely the lead acid with NMC/LTO, lead acid with LFP-Graphite, and lead acid with capacitor. A few charging and discharging pulses are designed and simulated to evaluate the regen receiving capability and cranking capability of different chemistries. Also a driving cycle is simulated for different battery combinations to characterize their fuel economy, heat generation, SOC range.
Zhang, Zhenli, Jin, Zhihong, Wyatt, Perry
A Novel Equivalent Circuit Model for Lithium-ion Battery with Complex Electrical Element Parameters2016-01-11974/5/2016
An equivalent circuit model for lithium-ion battery including capacitor and inductor with complex parameters is proposed. The imaginary part of the complex-valued capacitor expresses diffusion processes instead of constant phase element, which leads to a higher computational efficiency by removing the exponential variant calculation. The inductor with the complex parameter, the imaginary part accounting for the frequency-dependent magnetic hysteresis loss of battery current collectors and cables, can accurately regenerate the impedance characteristics at high frequencies with various linear slope angles to the real axis in a Nyquist plot. The fitted electrochemical impedance spectrum of a lithium iron phosphate/graphite battery with this proposed model is compared to the measured data. The maximum relative error of the impedance magnitude is 4.94% at the frequencies between 0.01 Hz and 10 kHz. The electrical component parameters of the proposed equivalent circuit model are calculated and analyzed.
Wu, Zhengbin, Weng, Rongcheng, Zhang, Zhiqun, Li, Juan
Integrated Solar Array Power Management SystemTBMG-242634/1/2016
When solar cells are electrically connected to form solar arrays, they are organized into strings. Each string represents a specific number of cells connected in series to produce a specific voltage. The strings are then connected in parallel to add their currents to meet the array power requirement. This requires that the strings have the same voltage. Blocking diodes are used to take out strings with voltage that is too low, resulting in loss of power. When the arrays are mounted to a non-coplanar surface such as a spacecraft body or inflatable structure, many strings will have voltages lower than the rated voltage. This regulator manages the voltage of each string individually so that its power may be used, regardless of its voltage. It does this by converting each string’s energy into a series of high-voltage pulses that charges a reservoir capacitor to one of a set of common voltages used by the spacecraft bus. This allows for use of all of the illuminated strings in producing well-regulated power at pre-programmed voltages.
Calibration Requirements for Testing Coupling-Decoupling NetworksTBMG-244314/1/2016
Coupling-Decoupling Networks (CDNs) are the unglamorous workhorses that get “hitched up” to an impulse generator in order to perform impulse testing on powered equipment. As such, performance and calibration requirements for CDNs have not been specified to the same level of detail as the impulse generator. This is no longer the case with the Third Edition of IEC 61000-4-5, the international standard for surge immunity testing.
AC/DC Converter with DC Fault Suppression for Aircraft +/− 270 VDC Distribution Systems2015-01-24119/15/2015
The increasing electrical demand in commercial and military aircraft justifies a growing need for higher voltage DC primary distribution systems. A DC system offers reduced power losses and space savings, which is of major importance for aircraft manufacturers. At present, challenges associated with DC systems include reliable fast acting short circuit protection. Solid State Contactors (SSC) have gained wide acceptance in traditional 28 VDC secondary systems for DC fault interruption. However, the reliable operation at higher operating voltages and currents requires further technology maturation. This paper examines a supporting method to SSC for more reliable fault mitigation by investigating bidirectional AC/DC converter topology with DC fault current blocking capability. Replacement of semiconductor switches with full bridge cells allows instant reversal of voltage polarities to limit rapid capacitor discharge and machine inductive currents. Demonstration of this capability is realized by tracking DC fault currents in time-domain simulations of a ±270 VDC converter dynamic model built in MATLAB-Simulink. Simulation results have shown that the modified power converter topology provides a fast response to DC faults and it can be considered as a back-up to SSCs in clearing faults in ±270 VDC distribution systems.
Sztykiel, Michal, Fletcher, Steven, Norman, Patrick, Galloway, Stuart, Burt, Graeme
Nanowire Yarn Boosts Supercapacitor EfficiencyTBMG-225017/9/2015
Researchers at the Massachusetts Institute of Technology discovered that yarn made of niobium nanowires enables more efficient supercapacitors. The new approach uses the yarns as the electrodes in tiny supercapacitors. Adding a coating of a conductive polymer to the yarn further increases the capacitor’s charge capacity.
Stacked Capacitor Special Lead AdapterTBMG-221866/1/2015
The current installation method for tall, stacked capacitors is very cumbersome because the lead form is very sharp and prone to solder cracking due to thermal cycling. An astringent installation process was developed to obtain the best chance of a successful solder joint with a proper heel fillet so the chance of cracking is minimized.
Carbon Nanotube Tower-Based SupercapacitorTBMG-216333/1/2015
A new technology to create electrochemical double-layer supercapacitors is provided using carbon nanotubes as electrodes of the storage medium. This invention allows efficient transport between the capacitor electrodes through the porous nature of the nanotubes, and has a low interface resistance between the electrode material and the collector. Carbon nanotubes directly grown on a metal surface are used to improve the supercapacitor performance. The nanotubes offer a high surface area and usable porosity for a given volume and mass, both of which are highly desirable for supercapacitor operation.
Negative Dielectric Constant Material Based on Ion-Conducting MaterialsTBMG-214082/1/2015
Metamaterials, or artificial negative index materials (NIMs), have generated great attention due to their unique and exotic electromagnetic properties. A negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI).
Power Loss and Data Integrity in Military SSDsTBMG-2117212/1/2014
For the defense industry, NAND Flash, with its lack of moving parts, has made it the common storage medium for a variety of field applications. With its small size, low power usage, high performance and robustness in extreme environments, choosing solid state storage has been a clear choice from the beginning.
Study of Two-Motor Hybrid Bulldozer2014-01-23769/30/2014
Hybrid bulldozers use less fuel by providing better efficiency and fewer emissions, which was confirmed by one Caterpillar application of D7E in the market in 2010. To take advantages of the series hybrid bulldozer system, Chinese government launched similar hybrid bulldozer with independent double motor design. The Hybrid Bulldozer Power-Train system includes 14 components including motor, motor control system, engine, super capacitor to BMS and etc. This specific hybrid architecture, compared with D7E, removes the complicated hydraulic steering system. Instead, the steering function was developed by running both traction motors, further simplifying the power-train system. A Diesel engine is used to propel the attached generator to produce AC power which is then converted to DC power and connected with the main power link (super capacitor). DC power is finally converted back to AC to propel those two independent traction motors. CAN network is applied for communication. Information could be displayed by the CAN connected instruments while components' status can be detected and diagnosed. By using remote wireless system (GPRS), the bulldozer could realize remote monitoring and remote driving functions. The energy-saving principles with the corresponding power flow control algorithm of hybrid bulldozer are discussed. The power-train controller, based on driver's demand and vehicle situation, send torque or speed commands to the traction motors. A super capacitor was used as energy storage device. The vehicle control algorithms control the engine in the highly efficient load conditions, while the super capacitor works as a buffer to prevent the voltage from fluctuating. The results of vehicle tests show that the power follow control strategy can achieve the performances of 24% fuel efficiency.
Wang, Hongyu, Liu, Lin, Zheng, Guanyu, Liu, Xiaohui, Zhao, Xiumin
Experimental Investigation of Asymmetrical Capacitors for Electric Propulsion2014-01-22219/16/2014
Investigation into electric propulsion continues to be an area of hopeful research since the pioneering age of aviation. However, more recent global awareness of carbon emissions on the planet and the desire to create more efficient systems has reinvigorated new life into the field. Experimental studies on electric propulsion by virtue of asymmetrical electrodes, on a micro scale, have yielded potentially superior efficiency ratings when compared to currently adopted methods. The observed effect is that asymmetrical electrodes which are subjected to high voltage and are separated by a fluid dielectric medium experience thrust towards the smaller electrode. This method of propulsion is unique and possesses several features that differentiate it from conventional methods of propulsion. One major benefit of this phenomenon is that the electrical energy is directly converted into a mechanical force without the requirement of any moving components. Such a method of would only require a high voltage power supply unit drawing relatively low current. The implications of this include increased travel time, improved maneuverability and improved stealth characteristics. Craft of this essence would eliminate both acoustic and heat signatures due to the absence of exhaust heat and noise like conventional propulsion systems. To date, the characteristics of the thrust produced on the asymmetrical electrodes are not entirely understood. In the context of increasing the ability of this technology, an experimental program at the University of New South Wales Aerodynamics Laboratory is under-way which investigates model asymmetrical electrodes charged with voltages ranging from 0-30 kV. A series of characteristic experiments are conducted aiming to gain a deeper understanding of the phenomenon which include varying emitter electrode diameter, the inter-electrode separation and collector electrode radius of curvature. In addition, the electrodes were influenced by a permanent magnetic field placed in various positions aiming to increase the thrust performance of the system. As a result, it is found that both the geometry of the electrodes and magnetic fields greatly affect the thrust on the asymmetrical capacitor.
Matsoukas, George, Ahmed, Noor
Thin-Film High Voltage Capacitors on Ultra-Thin Glass for Electric Drive Vehicle Inverter Applications2014-01-04174/1/2014
The propulsion system in most Electric Drive Vehicles (EDVs) requires an internal combustion engine in combination with an alternating current (AC) electric motor. An electronic device called a power inverter converts battery DC voltage into AC power for the motor. The inverter must be decoupled from the DC source, so a large DC-link capacitor is placed between the battery and the inverter. The DC-link capacitors in these inverters negatively affect the inverters size, weight and assembly cost. To reduce the design/cost impact of the DC-link capacitors, low loss, high dielectric constant (κ) ferroelectric materials are being developed. Ceramic ferroelectrics, such as (Pb,La)(Zr,Ti)O3 [PLZT], offer high dielectric constants and high breakdown strength. Argonne National Laboratory and Delphi Electronics & Safety have been developing thin-film capacitors utilizing PLZT. Capacitors made with PLZT are well suited for power applications due to its high dielectric constant, low loss, high temperature capability, low equivalent series resistance, high breakdown strength and benign failure. Previously published papers described PLZT capacitors created by depositing PLZT onto metal foils; this paper describes an ultra-thin flexible glass as the substrate with a thin metal (platinum- Pt) vapor deposited as an electrode. PLZT is deposited onto the metal to create the dielectric. A top electrode metal is then applied by electron beam evaporation to create the capacitor [1] [2]. This project involved the fabrication and electrical evaluation of thin-film capacitors built on flexible glass for Electric Drive Vehicle inverters. The capacitors were tested for dielectric integrity, capacitance, dielectric constant and voltage breakdown. Results from these tests, processing challenges, and implementation methods will be described.
Fairchild, M. Ray, Taylor, Ralph, Berlin, Carl, Wong, Celine, Ma, Beihai, Balachandran, U. (Balu)
Switched-Capacitor Cell Balancing: A Fresh Perspective2014-01-18464/1/2014
No two battery cells can be identical. Charging/discharging a battery pack without monitoring cell voltages or SoC (State-of-Charge) will cause cell voltages to deviate over time and the packs useable capacity to decrease quickly. To redistribute charge uniformly among cells, various cell balancing methods have been proposed in the literature. In this paper, a cell balancing method based on a single switched-capacitor is presented from a brand new perspective. Unlike the traditional balancing methods that rely on the voltage divergence criterion, this paper uses the SoC divergence criterion to shuttle charge from a highly charged cell to a poorly charged cell. Moreover, an equivalent resistance of the single-switched capacitor topology is derived in steady state. For fast cell balancing, design guidelines are provided for selecting a proper switching-time period and the capacitor parameters. Ultracapacitors are recommended to achieve this goal. To demonstrate the effectiveness of the proposed method, numerous simulations are performed on a string of five series connected Lithium-ion cells that have different initial SoCs and electrochemical parameters. Finally, the simulation results are compared with that of a traditional balancing method.
Arasaratnam, Ienkaran, Tjong, Jimi, Habibi, Saeid
Items per page:
1 – 50 of 248