A novel architecture of a bidirectional bridgeless interleaved converter for EV battery chargers

This paper presents a novel architecture of a bidirectional bridgeless interleaved converter for battery chargers of electric vehicles (EVs). The proposed converter is composed by two power stages: an ac-dc converter that is used to interface the power grid and the dc-link, and a dc-dc converter that is used to interface the dc-link and the batteries. The ac-dc converter is an interleaved bridgeless bidirectional boost-type converter and the dc-dc converter is a bidirectional buck-boost-type converter. The proposed converter works with sinusoidal grid current and with high power factor for all operating power levels, and in both grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operation modes. In the paper is described in detail the proposed converter for EV battery chargers: the circuit topology, the principle of operation, the power control theory, and the current control strategy. Several simulation results for both G2V and V2G operation modes are presented.

A novel concept of unidirectional bridgeless combined boost-buck converter for EV battery chargers

This paper presents a novel concept of unidirectional bridgeless combined boost-buck converter for electric vehicles (EVs) battery chargers. The proposed converter is composed by two power stages: an ac-dc front-end converter used to interface the power grid and the dc-link, and a dc-dc back-end converter used to interface the dc-link and the batteries. The ac-dc converter is a bridgeless boost-type converter and the dc-dc converter is an interleaved buck-type converter. The proposed converter operates with sinusoidal grid current and unitary power factor for all operating power levels. Along the paper is described in detail the proposed converter for EV battery chargers: the circuit topology, the different stages describing the principle of operation, the power control theory, and the current control strategy, for both converters. Along the paper are presented several simulation results for a maximum power of 3.5 kW.

Bidirectional battery charger with grid-to-vehicle, vehicle-to-grid and vehicle-to-home technologies

This paper presents the development of na on-board bidirectional battery charger for Electric Vehicles (EVs) targeting Grid-to-Vehicle (G2V), Vehicle-to-Grid (V2G), and Vehicle-to-Home (V2H) technologies. During the G2V operation mode the batteries are charged from the power grid with sinusoidal current and unitary power factor. During the V2G operation mode the energy stored in the batteries can be delivered back to the power grid contributing to the power system stability. In the V2H operation mode the energy stored in the batteries can be used to supply home loads during power outages, or to supply loads in places without connection to the power grid. Along the paper the hardware topology of the bidirectional battery charger is presented and the control algorithms are explained. Some considerations about the sizing of the AC side passive filter are taken into account in order to improve the performance in the three operation modes. The adopted topology and control algorithms are accessed through computer simulations and validated by experimental results achieved with a developed laboratory prototype operating in the different scenarios.

Poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) lithium-ion battery separator membranes prepared by phase inversion

Separator membranes based on poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) were prepared by solvent casting technique based on its phase diagram in N,Ndimethylformamide (DMF) solvent. The microstructure of the PVDF-CTFE separator membranes depends on the initial position (temperature and concentration) of the solution in the phase diagram of the PVDF-CTFE/DMF system. A porous microstructure is achieved for PVDF-CTFE membranes with solvent evaporation temperature up to 50 ºC for a polymer/solvent relative concentration of 20 wt%. The ionic conductivity of the separator depends on the degree of porosity and electrolyte uptake, the highest room temperature value being 1.5 mS.cm-1 for the sample with 20 wt% of polymer concentration and solvent evaporation temperature at 25 ºC saturated with 1 mol L-1 lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) in propylene carbonate (PC). This PVDF-CTFE separator membrane in Li/C-LiFePO4 half-cell shows good cyclability and rate capability, showing a discharge value after 50 cycles of 92 mAh.g-1 at 2 C, which is still 55% of the theoretical value. PVDF-CTFE separators are thus excellent candidates for high-power and safety lithium-ion batteries applications.

Effect of the degree of porosity on the performance of poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide) blend membranes for lithium-ion battery separators

Porous polymer membranes based on poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide) copolymers, P(VDF-TrFE)/PEO, are prepared through the, from partial to total, elimination of PEO, leading to interconnected micropores in the polymer blends. Electrolyte uptake, thermal and mechanical properties depend on the amount of PEO present in the polymer blend. Further, the degree of crystallinity of PEO and the elastic modulus (E´) of the polymer blend decrease with increasing PEO removal. Electrical properties of the polymer blend membranes are influenced by the porosity and are dominated by diffusion. The temperature dependence of ionic conductivity follows the Arrhenius behavior. It is the highest for the membranes with a volume fraction of pores of 44% (i.e, 90% PEO removal), reaching a value of 0.54 mS.cm-1 at room temperature. Battery performance was determined by assembling Li/C-LiFePO4 swagelok cells. The polymer blends with 90% PEO removal exhibit rate (124 mAhg-1 at C/5 and 47 mAhg-1 at 2C) and cycling capabilities suitable for lithium ion battery applications.

Modeling separator membranes physical characteristics for optimized lithium ion battery performance

The effect of varying separator membrane physical parameters such as degree of porosity, tortuosity and thickness, on battery delivered capacity was studied in order to optimize performance of lithium-ion batteries. This was achieved by a theoretical mathematical model relating the Bruggeman coefficient with the degree of porosity and tortuosity. The inclusion of the separator membrane in the simulation model of the battery system does not affect the delivered capacity of the battery. The ionic conductivity of the separator and consequently the delivered capacity values obtained at different discharge rates depends on the value of the Bruggeman coefficient, which is related with the degree of porosity and tortuosity of the membrane. Independently of scan rate, the optimal value of the degree of porosity is above 50% and the separator thickness should range between 1 μm at 32 μm for improved battery performance.

Polymer composites and blends for battery separators: State of the art, challenges and future trends

In lithium ion battery systems, the separator plays a key role with respect to device performance. Polymer composites and polymer blends have been frequently used as battery separators due to their suitable properties. This review presents the main issues, developments and characteristics of these polymer composites and blends for battery separator membrane applications. This review is divided into two sections regarding the composition of the materials: polymer composite materials, subdivided according to filler type, and polymer blend materials. For each category the electrolyte solutions, ionic conductivity and other relevant physical-chemical characteristics are described. This review shows the recent advances and opportunities in this area and identifies future trends and challenges.

OnBoard reconfigurable battery charger for electric vehicles with traction-to-auxiliary mode

This paper proposes a single-phase reconfigurable battery charger for Electric Vehicle (EV) that operates in three different modes: Grid-to-Vehicle (G2V) mode, in which the traction batteries are charged from the power grid; Vehicle-to-Grid (V2G) mode, in which the traction batteries deliver part of the stored energy back to the power grid; and in Traction-to-Auxiliary (T2A) mode, in which the auxiliary battery is charged from the traction batteries. When connected to the power grid, the battery charger works with sinusoidal current in the AC side, for both G2V and V2G modes, and also regulates the reactive power. When the EV is disconnected from the power grid, the control algorithms are modified and the full-bridge AC-DC bidirectional converter works as a full-bridge isolated DC-DC converter that is used to charge the auxiliary battery of the EV, avoiding the use of an additional charger to accomplish this task. To assess the behavior of the proposed reconfigurable battery charger under different operation scenarios, a 3.6 kW laboratory prototype has been developed and experimental results are presented.

Titanium oxide adhesion layer for high temperature annealed Si/Si3N4/TiOx/Pt/LiCoO2 battery structures

This work describes the influence of a high annealing temperature of about 700C on the Si(substrate)/Si3N4/TiOx/Pt/LiCoO2 multilayer system for the fabrication of all-solid-state lithium ion thin film microbatteries. Such microbatteries typically utilize lithium cobalt oxide (LiCoO2) as cathode material with a platinum (Pt) current collector. Silicon nitride (Si3N4) is used to act as a barrier against Li diffusion into the substrate. For a good adherence between Si3N4 and Pt, commonly titanium (Ti) is used as intermediate layer. However, to achieve crystalline LiCoO2 the multilayer system has to be annealed at high temperature. This post-treatment initiates Ti diffusion into the Pt-collector and an oxidation to TiOx, leading to volume expansion and adhesion failures. To solve this adhesion problem, we introduce titanium oxide (TiOx) as an adhesion layer, avoiding the diffusion during the annealing process. LiCoO2, Pt and Si3N4 layers were deposited by magnetron sputtering and the TiOx layer by thermal oxidation of Ti layers deposited by e-beam technique. Asdeposited and annealed multilayer systems using various TiOx layer thicknesses were studied by scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS). The results revealed that an annealing process at temperature of 700C leads to different interactions of Ti atoms between the layers, for various TiOx layer thicknesses (25–45 nm).

Flexible thin-film lithium battery

Tese de Doutoramento Programa Doutoral em Engenharia Electrónica e Computadores.

High performance screen printable lithium-ion battery cathode ink based on C-LiFePO4

Lithium-ion battery cathodes have been fabricated by screen-printing through the development of CLiFePO4 inks. It is shown that shear thinning polymer solutions in N-methyl-2-pyrrolidone (NMP) with Newtonian viscosity above 0.4 Pa s are the best binders for formulating a cathode paste with satisfactory film forming properties. The paste shows an elasticity of the order of 500 Pa and, after shear yielding, shows an apparent viscosity of the order of 3 Pa s for shear rates corresponding to those used during screen-printing. The screen-printed cathode produced with a thickness of 26 mm shows a homogeneous distribution of the active material, conductive additive and polymer binder. The total resistance and diffusion coefficient of the cathode are 450 V and 2.5 10 16cm2 s 1, respectively. The developed cathodes show an initial discharge capacity of 48.2 mAh g 1 at 5C and a discharge value of 39.8 mAh g 1 after 50 cycles. The capacity retention of 83% represents 23% of the theoretical value (charge and/or discharge process in twenty minutes), demonstrating the good performance of the battery. Thus, the developed C-LiFePO4 based inks allow to fabricate screen-printed cathodes suitable for printed lithium-ion batteries

Hazard assessment of storm events for the battery, New York

The environmental and socio-economic importance of coastal areas is widely recognized, but at present these areas face severe weaknesses and high-risk situations. The increased demand and growing human occupation of coastal zones have greatly contributed to exacerbating such weaknesses. Today, throughout the world, in all countries with coastal regions, episodes of waves overtopping and coastal flooding are frequent. These episodes are usually responsible for property losses and often put human lives at risk. The floods are caused by coastal storms primarily due to the action of very strong winds. The propagation of these storms towards the coast induces high water levels. It is expected that climate change phenomena will contribute to the intensification of coastal storms. In this context, an estimation of coastal flooding hazards is of paramount importance for the planning and management of coastal zones. Consequently, carrying out a series of storm scenarios and analyzing their impacts through numerical modeling is of prime interest to coastal decision-makers. Firstly, throughout this work, historical storm tracks and intensities are characterized for the northeastern region of United States coast, in terms of probability of occurrence. Secondly, several storm events with high potential of occurrence are generated using a specific tool of DelftDashboard interface for Delft3D software. Hydrodynamic models are then used to generate ensemble simulations to assess storms' effects on coastal water levels. For the United States’ northeastern coast, a highly refined regional domain is considered surrounding the area of The Battery, New York, situated in New York Harbor. Based on statistical data of numerical modeling results, a review of the impact of coastal storms to different locations within the study area is performed.

Direct electrical stimulation using a battery-operated device for induction and modulation of colonic contractions in pigs.

Direct electrical stimulation of the colon offers a promising approach for the induction of propulsive colonic contractions by using an implantable device. The objective of this study was to assess the feasibility to induce colonic contractions using a commercially available battery-operated stimulator (maximum pulse width of 1 ms and maximum amplitude of 10 V). Three pairs of pacing electrodes were inserted into the cecal seromuscular layer of anesthetized pigs. During a first set of in vivo experiments conducted on six animals, a pacing protocol leading to cecum contractions was determined: stimulation bursts with 1 ms pulse width, 10 V amplitude (7-15 mA), 120 Hz frequency, and 30-s burst duration, repeated every 2-5 min. In a second testing phase, an evaluation of the pacing protocol was performed in four animals (120 stimulation bursts in total). By using the battery-operated stimulator, contractions of the cecum and movement of contents could be induced in 92% of all stimulations. A cecal shortening of about 30% and an average intraluminal pressure increase of 10.0 +/- 6.0 mmHg were observed.

Detection of cognitive impairment with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) in adolescents with psychotic symptomatology.

Cognitive impairment has been identified in the early phase of schizophrenia spectrum disorders, and is a major contributor to disease-related disability. While screening tools assessing cognitive impairment have been validated for adult schizophrenic populations, there is a need for brief, easily administered, standardized instruments that provide clinically relevant information for adolescents. This study examines the utility of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) in identifying and quantifying neurocognitive impairment in adolescents with schizophrenia spectrum disorders and other serious psychiatric illnesses. 112 adolescents, including 32 healthy subjects and 80 patients, were administered the RBANS. Patients with psychotic disorders demonstrated significant impairment on the RBANS total score compared to patients with other disorders and healthy controls, but this impairment appeared somewhat less severe than is typically reported for in adult patients with schizophrenia on this measure. The RBANS appears to be sensitive in the detection of neurocognitive impairment in a psychiatric population of adolescents with psychotic symptomatology, and may therefore have utility as a clinical screening instrument and/or neurocognitive outcome measure in this population.

Validation d'une nouvelle grille de codage de la régulation émotionnelle avec le Laboratory Temperament Assessment Battery (Lab-TAB)

L'objectif de cette étude est de valider une nouvelle grille de codage pour le Lab-TAB (Goldsmith et Rothbart, 1999). Cette grille mesure l'intensité émotionnelle et les comportements de régulation chez l'enfant âgé de six mois. L'accord interjuge se révèle satisfaisant. Les analyses factorielles ont mis en évidence trois facteurs - attention, niveau d'activité et détournement actif - retrouvés dans la littérature comme stratégies de régulation émotionnelle. Les analyses de consistance interne démontrent une bonne homogénéité de ces facteurs. La validité externe se révèle satisfaisante aux niveaux concourant et prédictif. Enfin, cet outil de codage permet de distinguer les prématurés et les nés à terme. L'ensemble de ces résultats indiquent que l'outil élaboré présente de bonnes qualités psychométriques.