Hybrid Vehicle Applications Research Articles

A Dead-Time-Controlled Gate Driver Using Current-Sense FET Integrated in SiC MOSFET

In comparison with silicon IGBT, silicon carbide (SiC) MOSFET is expected to reduce the switching loss and the conduction loss and to remove external freewheeling diodes (FWDs). However, its body diode has comparatively high forward voltage; therefore, the diode conduction loss generated during dead time increases. As a result, the loss reduction by the use of the SiC MOSFET can be weakened. This paper proposes a simple dead-time controller integrated in an isolated gate driver in order to reduce the diode conduction loss during the dead time. The proposed method has high speed and high robustness against switching noise by using of a current-sense FET with small parasitic capacitance. As a result, the diode conduction time can be shortened within 0.1 μs. In addition, the proposed dead-time control method can be achieved by existing components, including the current-sense FET, which is currently used for short-circuit current detection in hybrid vehicle applications. The proposed method was applied to a 10 kW boost converter with SiC MOSFET. The experimental results showed 1% higher efficiency of the converter with the proposed dead-time-controlled gate driver compared to that without dead-time control circuit, and the efficiency was the similar level as when a SiC Schottky barrier diode (SBD) was used as FWDs.

Separately Excited Synchronous Motor With Rotary Transformer for Hybrid Vehicle Application

The cost of rare earth (RE) permanent magnet along with the associated supply volatility have intensified the interests for machine topologies, which eliminate or reduce the RE magnets usage. This paper presents one such design solution, the separately excited synchronous motor (SESM) that eliminates RE magnets, but does not sacrifice the peak torque and power of the motor. The major drawback of such motors is the necessity of brushes to supply the field current. This is especially a challenge for hybrid or electric vehicle applications where the machine is actively cooled with oil inside the transmission. Sealing the brushes from the oil is challenging and would limit the application of such a motor inside a transmission. To overcome this problem, a contactless rotary transformer is designed and implemented for the rotor field excitation. The designed motor is built and tested. The test data show that the designed motor outperforms an equivalent interior permanent magnet (IPM) motor, which is optimized for a hybrid application for both peak torque and power. Better drive system efficiency is measured at high speed compared with the IPM machine, while the latter outperforms (for efficiency) the SESM at low- and medium-speed range.

Investigation of various input based on DC-DC converter in a hybrid vehicle application

Investigation of various input based on DC-DC converter in a hybrid vehicle application

From Chip to Converter: A Complete Cost Model for Power Electronics Converters

The unified knowledge on power converter design and manufacturing technology establishes a powerful tool, where the cost and topology realization can be analyzed simultaneously. This paper collects the design practice and cost estimation of various components in a power electronics converter and unites that to a choice of the assembling and manufacturing processes and resulting cost of the complete converter. The outcome of this work specifies the power converter at predefined power level and cooling condition and demonstrates the cost drivers of the complete unit depending on production volumes. As a case study, the cost of an inverter for a full electric or hybrid vehicle application is estimated and the results are compared with figures available in the literature, yielding the conclusion that the validity of such figures is highly dependent on production volumes and power levels. The essence of this paper is a set of general, reliable, and fast design models and production charts, in accordance with realistic cost estimates for the sake of system optimization and development of cost effective electric drives from small series to large volumes.

DC-Link Current and Torque Ripple Optimized Self-Sensing Control of Interior Permanent-Magnet Synchronous Machines for Hybrid and Electrical Vehicles

To minimize the ripple on the dc-link current and torque due to carrier signal injections, conventional saliency based self-sensing control schemes using voltage and current carrier signals for interior permanent magnet synchronous machines (IPMSMs) are optimized in this paper. Carrier signal oriented coordinates are introduced to model the high-frequency behavior of IPMSMs and are used for the analysis and signal processing of proposed methods. Moreover, stability issues are discussed in this paper. Experimental results on a commercial high voltage inverter for application in hybrid and electrical vehicles confirm the applicability of the proposed methods.

Understanding the Effects of Cell Temperature Gradients on Battery Performance with Mathematical Modeling

With wide acceptance of lithium ion batteries for electric and hybrid vehicle applications, precise understanding of cell performance at different operating conditions is increasingly important. Cell temperature is often a critical variable determining the cell performance during the vehicle operation. For automotive applications, various cooling/heating strategies are used to keep the cell operating temperature within the predetermined limits. This ensures safety during cell operations as well as helps cells meet the cell warranty targets. Heat generation and heat rejection by a cell during the operation may result in non-uniform temperature distribution within a cell. These effects are pronounced in large format cells. The variation in local temperature affects the kinetic and transport rates and therefore, may result in non-uniformities in the current distribution across the length/breadth of the electrodes. Widely used, Pseudo 2D (P2D) porous electrode models may not be able to accurately predict cell performance with temperature distribution. Here a simple Pseudo 3D model is developed as an extension to the P2D model to understand the implications of the temperature gradient on the cell performance and eventually on the cell life. Differences in cell performance at uniform temperature operation and with cell temperature gradients are highlighted.

Hybrid Vehicle Battery Pack Useful Life Simulation

This paper describes the development of a computational model of a traction battery system for hybrid vehicle application. The battery model simulates the electrical and thermal performance of the entire battery system, including series and/or parallel cell design configuration in the pack, cell energy/power performance, thermal and electrical controls, and interfaces to the vehicle and external environment. The battery model is capable of estimating the battery performance and predicting the battery life under a variety of use cases in different environmental conditions. The model enables rapid optimization of battery pack size, electrical and thermal controls design to maximize battery usage and/or minimize battery cooling needs while still meeting the battery’s life targets. A systematic approach has been developed in which this vehicle-level information is quantified and ranked to be able to identify and simulate the battery usage for varieties of customer. Simulation results are verified with variety of laboratory and vehicle test data. The availability of this battery pack model enables minimizing of costly and time-consuming pack-level performance and life testing, allowing the majority of the life cycle analyses to be conducted before battery packs and vehicles are actually assembled. The model aims to ensure that when the battery pack model is utilized for life simulations, compliance with the battery pack warranty and fuel economy targets, as well as other vehicle standards, may be quickly and reliably assessed. The accuracy of the model predicted battery life performances is further validated with real field application vehicle data from customer return pack.

Real-time mass spectroscopy analysis of Li-ion battery electrolyte degradation under abusive thermal conditions

Abstract The lithium-ion batteries are widely used in rechargeable electronic devices. The current challenges are to improve the capacity and safety of these systems in view of their development to a larger scale, such as for their application in electric and hybrid vehicles. Lithium-ion batteries use organic solvents because of the wide operating voltage. The corresponding electrolytes are usually based on combinations of linear, cyclic alkyl carbonates and a lithium salt such as LiPF 6 . It has been reported that in abusive thermal conditions, a catalytic effect of the cathode materials lead to the formation fluoro-organics compounds. In order to understand the degradation phenomenon, the study at 240 °C of the interaction between positive electrode materials (LiCoO 2 , LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiMn 2 O 4 and LiFePO 4 ) and electrolyte in dry and wet conditions has been realized by an original method which consists in analyzing by mass spectrometry in real time the volatile molecules produced. The evolution of specific gases channels coupled to the NMR reveal the formation of rarely discussed species such as 2-fluoroethanol and 1,4-dioxane. Furthermore, it appears that the presence of water or other protic impurities greatly influence their formation.

Development of surface functionalized ZnO-doped LiFePO4/C composites as alternative cathode material for lithium ion batteries

Surface modified olivine-type LiFePO4/C-ZnO doped samples were synthesized using sol-gel assisted ball-milling route. In this work, the influence of ZnO-doping on the physiochemical, electrochemical and surface properties such as charge separation at solid-liquid interphase, surface force gradient, surface/ionic conductivity of pristine LiFePO4/C (LFP) has been investigated thoroughly. Synthesized samples were characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. All the synthesized samples were indexed to the orthorhombic phase with Pnma space group. Pristine LiFePO4 retain its structure for higher ZnO concentrations (i.e. 2.5 and 5.0wt.% of LFP). Surface topography and surface force gradient measurements by EFM revealed that the kinetics of charge carriers, e−/Li+ is more in ZnO-doped LFP samples, which may be attributed to diffusion or conduction process of the charges present at the surface. Among all the synthesized samples LFP/C with 2.5wt.% of ZnO (LFPZ2.5) displays the highest discharge capacity at all C-rates and exhibit excellent rate performance. LFPZ2.5 delivers a specific discharge capacity of 164 (±3) mAhg−1 at 0.1C rate. LFPZ2.5 shows best cycling performance as it provides a discharge capacity of 135 (±3) mAhg−1 at 1C rate and shows almost 95% capacity retention after 50 charge/discharge cycles. Energy density plot shows that LFPZ2.5 offers high energy and power density measured at high discharge rates (5C), proving its usability for hybrid vehicles application.

Rectifier Dynamic Electro-Thermal Simulation for Power Factor Correction in Electric Vehicles Application

This paper presents a PFCVF (Power Factor Correction) rectifier that uses a variable frequency source for alternators in electric and hybrid vehicles application. This technique allows to preserve a good THD (Total Harmonic Distortion) of the input source at any frequency and to decrease losses in semiconductors switches, thereby permitting more stability and decreasing the apparent power requirements. A comparative study between the standard and the new technique is made. A thermal network is used to calculate the junction temperatures in order to estimate the equivalent losses in the rectifier with respect of junction temperature modifications and power equilibrium. The relations of the proposed model are defined and simulation results as well as experimental results are discussed.

Fabrication of Tin-Plated Three-Dimensional Copper Nanostructure Using Electroless Plating and Its Anode Performance in Lithium-Ion Battery

Introduction Next-generation lithium-ion batteries with higher energy density are urgently needed for hybrid and electric vehicle applications, among others. Currently, graphite is typically used as the anode active material in lithium-ion batteries, but it is necessary to consider alternative, higher capacity materials. For example, tin has a larger theoretical capacity (991 mAh g-1) than that of graphite (372 mAh g-1). However, the volume of tin changes significantly during charging and discharging, causing it to slip down from the copper current collector, which deteriorates the cycling characteristics. Three-dimensional copper structures are effective at preventing such slippage.1) However, in general, the methods for fabricating such structures are very complicated. We have reported that a three-dimensional copper nanostructure (3DC-1) can be fabricated easily by one-step electrodeposition.2) In this study, a tin layer was formed on the 3DC-1 by electroless deposition, and its anode performance in a lithium-ion battery was evaluated. Experimental An acidic copper sulfate bath1) containing 0.85 M CuSO4∙5H2O + 0.55 M H2SO4 + 2.5×10-4 M polyacrylic acid (MW=5000) was used in the fabrication of the 3DC-1. Electrodeposition was conducted under galvanostatic conditions (1.2 A dm-2) at 25 °C without agitation. A bright Watts nickel plating bath (1 M NiSO4∙6H2O + 0.2 M NiCl2∙6H2O + 0.5 M H3BO3 + 0.01 M saccharin sodium dehydrate + 0.0025 M 1,4-butynediol) was prepared, and electrodeposition was conducted under galvanostatic conditions (3.0 A dm-2) at 25 °C without agitation. Tin was electrolessly plated onto the 3DC-1 at 80 °C for 15 s without agitation. An immersion plating bath containing 0.5 M K4P2O7 + 0.15 M Sn2P2O7+ 3 M thiourea was prepared. The pH was adjusted to 5 with hydrochloric acid. The microstructure of the tin anode was examined using field-emission scanning electron microscopy (FE-SEM). The phase structure of the deposits was analyzed by X-ray diffraction (XRD). A chemical composition analysis was carried out using X-ray fluorescence spectrometry (XRF) and energy-dispersive X-ray spectroscopy (EDX). Electrochemical studies of the tin anode were carried out with coin cells that were assembled in an Ar-filled glove box. Each coin cell consisted of a lithium foil as a counter electrode and a reference electrode. The plating film functioned as the working electrode. The electrolyte was 1 M LiPF6 in ethylene carbonate (EC) and diethyl carbonate (DEC) (1:1 vol%). Cycling tests were performed in the range of 0.02–1.5 V (vs. Li/Li+) at a constant temperature of 25 °C. Results and Discussion Fig. 1 shows a surface SEM image of the tin anode, which reveals that the tin film was plated homogeneously onto the three-dimensional copper nanostructure. Fig. 2 shows a cross-sectional SEM image of the tin anode and corresponding EDX mapping results for copper, nickel, and tin. The tin was distributed homogeneously on the 3DC-1. Fig. 3 compares the cycling characteristics of tin anodes fabricated using 3DC-1 (a) and a flat copper foil (b). For the former, the discharge capacity was about 900 mAh g-1 after the first cycle. Even after 100 cycles, the discharge capacity remained over 700 mAh g-1. In contrast, for the latter, the discharge capacity was 650 mAh g-1 after the first cycle and 250 mAh g-1after 100 cycles. References 1) Shichao Zhang, Yalan Xing, Tao Jiang, Zhijia Du, Feng Li, Lei He, Wenbo Liu; Journal of Power Sources,196, 6915-6919 (2011) 2) S.Arai and T.Kitamura, ECS Electrochemistry Letters, 3 (5), D7-D9 (2014) Figure 1

Mathematical Model to Understand Effects of Cell Temperature Gradients on Lithium Ion Battery Performance

With wide acceptability of lithium ion batteries for electric and hybrid vehicle applications, precise understanding of cell performance at different operating conditions is increasingly important. Cell temperature is often a critical variable determining the cell performance during the vehicle operation. For automotive applications, difference cooling/heating strategies are used to keep the cell operating temperature within the predetermined limits. This ensures safety during cell operations as well as helps cells meet the cell warranty targets. Heat generation and heat rejection by a cell during the operation may result in non-uniform temperature distribution with a cell. These effects are pronounces in large format cells. The variation in local temperature affects the kinetic and transport rates and thus may result in inhomogeneities in the current distribution across the length/breadth of the electrodes. Widely used, Pseudo 2D (P2D) porous electrode models may not be able to accurately predict cell performance with temperature distribution. Here a simple Pseudo 3D model is developed as an extension to the P2D model to understand the implications of the temperature gradient on the cell performance and eventually on the cell life. Differences in cell performance at uniform temperature operation and with cell temperature gradients are highlighted.

Detecting, Diagnosing and Controlling Degradation in Lithium Ion Battery Packs

One of the biggest causes of degradation in lithium-ion batteries is elevated temperature. In electric vehicle, particularly hybrid vehicle applications this can be very difficult to manage, and without fundamentally redesigning the cell is the province of the battery pack engineer. Yet how battery pack design affects both cell performance and degradation has been very poorly studied in the past. The latest work of the electrochemical science & engineering group at Imperial College London on understanding how thermal gradients affect performance and degradation, and how thermal techniques can be used to detect and diagnose path dependent degradation will be presented. State-of-the-art models that can reproduce the diagnostic outputs and can be embedded in battery management systems and could therefore be used for diagnostic and even prognostic purposes in real world battery packs will also be presented. Recent work exploring the effect of cell surface cooling and cell tab cooling is shown, reproducing two typical cooling systems that are used in real-world battery packs. It is shown that cooling method alone can significantly affect useable capacity. For new cells at C/20 discharge, very little difference in capacity was seen, however, at 6C discharge surface cooling led to a loss of useable capacity of 9.2% compared to 1.2% for cell tab cooling. Furthermore, after cycling the cells for a 1,000 times at 6C discharge and 2C charge, surface cooling resulted in a degradation rate three times higher than cell tab cooling. Using incremental capacity analysis, electrochemical impedance analysis and thermal models of cells, it is shown that this is due to thermal gradients being perpendicular to the layers for surface cooling leading to higher local currents and faster degradation, but in-plane with the layers for tab cooling leading to more homogenous behaviour. Aged cells were put with new cells in a parallel pack configuration with cooling where measuring the current flowing through each individual cell is often impractical. Using a novel diagnostic method based on simple cell surface temperature measurements developed by our group, a diagnosis method capable of quantitatively determining the state-of-health of individual cells simultaneously during both charge and discharge by only using temperature and voltage readings, and whilst cells are being thermally managed, will be shown. Our latest models account for complex electrochemical phenomena that are usually omitted in battery models such as variable double layer capacitance, the full current-overpotential relation and overpotentials due to mass transport limitations in the double layer. The coupled electrochemical and thermal model accounts for capacity fade via a loss in active species and for power fade via an increase in resistive solid electrolyte passivation layers at both electrodes. The model's capability to simulate cell behaviour under dynamic events is validated against test procedures, such as standard battery testing load cycles for current rates up to 20 C, as well as realistic automotive drive cycle loads, and ageing up to 1,000 cycles including reproducing incremental capacity analysis results.

APPLICATIONS OF MULTI BOOST AND FULL BRIDGE CONVERTERS FOR SUPER CAPACITORS AND BATTERY POWER MANAGEMENT FOR ECCE HYBRID VEHICLE

This paper presents Methodology based on super capacitors and battery power management for applications of the ECCE Hybrid Vehicle using the principle of multi boost and full bridge rectifiers. In collaboration with the Electrical and Electronics Research center in Belfort (CREEBEL) and French innovators ECCE for Hybrid vehicle system was developed as an experiment at L2ES Laboratory. An experiment ECCE for the Hybrid Vehicle incorporates the dc motors coupled with the alternator with the rated voltage of 540V. Energy source to the system is by using two super capacitors bank, each bank consists of the 108 cells with provision of maximum voltage of 270V.To embarked the best power management topology for the Hybrid vehicle application, author proposed the multi boost and full bridge converter topologies for it. In this paper the two converter topologies are presented with experimental and the simulation results

Dynamical modeling of Li-ion batteries for electric vehicle applications based on hybrid Particle Swarm–Nelder–Mead (PSO–NM) optimization algorithm

In recent years, Li-ion batteries are widely used in various applications, such as electric and hybrid vehicles application. Their higher specific power and energy density, high cycle lifetime and decreasing costs have made them an attractive and alternative energy storage technology to lead-acid or nickel-metal hydride batteries in embedded power supplies. In the present work, the electric modeling of a Li-ion battery cell in real operation conditions imposed by an electric vehicle application is carried out. A dynamic equivalent circuit model has been used to simulate several electrochemical processes occurring in a commercially available 40 Ah Li-ion battery cell with NMC cathode material and graphitic anode. The model is parameterized with measurement data in time-domain using a hybrid Particle Swarm–Nelder–Mead (PSO–NM) optimization algorithm. This last one is used to solve the parameters identification problem of Li-ion battery model.The developed model of Li-ion battery cell has been validated on real driving cycle provided by an urban electric vehicle. Obtained results show that there is a good match between experiment and simulation results with a maximum modeling error less than 0.5%, which proves the well performance of our model and confirms the interest of a hybrid (PSO–NM) optimization algorithm for battery identification parameters.

Inductance Surface Learning for Model Predictive Current Control of Switched Reluctance Motors

In this paper, an inductance surface estimation and learning for utilization with a stochastic model predictive control (MPC) scheme for the current control of switched reluctance motors (SRMs) is introduced. This MPC is equipped with state estimators and is implemented as a recursive linear quadratic regulator for practical deployments in hybrid vehicle applications. Additionally, a learning mechanism is developed to dynamically adapt to the inductance profile of the machine and update the MPC and Kalman filter parameters. The introduced control scheme can cope with noise as well as uncertainties within the machine nonlinear inductance surface. The introduced system will benefit from a fixed switching frequency and will offer low current ripples by calculating the optimal duty cycles using the SRM model. Finally, simulations and experimental results are provided to evaluate the proposed method.

Study on specific effects of high frequency ripple currents and temperature on supercapacitors ageing

Although supercapacitors can store less energy than batteries, they are particularly appealing for hybrid vehicle applications (for example, for braking energy recovery, or stop and start systems supply…). As power networks in hybrid vehicle experience high frequency ripple currents due to power electronics components such as static converters, experiments are done to study the impact of high frequency ripple currents on supercapacitor ageing. The results suggest that high frequency ripple currents do not create new ageing mechanisms. A complementary ageing test is also carried out to study the effect of temperature on supercapacitor ageing at very low voltage. It clearly shows that a significant part of increase in supercapacitor resistance is only linked to temperature, instead of the combined effect of temperature and voltage as assumed by literature for supercapacitor ageing. Whereas tests demonstrate that capacitance loss through time is linked (for the most part) to the combined effect of voltage and temperature. Hence, this paper shows that resistance increase is only partially linked to capacitance loss.

Investigation of Automotive Power Semiconductor Module Operates at Elevated Cooling Temperature

The degradation of performance and reliability of power semiconductor module with increment of temperature is an important issue to deal with in Hybrid and Electric Vehicles (HEV/EV) application. The high ambient and cooling temperatures are challenges to HEV/EV modules as the automotive industry is interested in cooling power electric system by sharing with engine's high temperature coolant. The elimination of low temperature cooling circuit has significant benefits to cost and volume/weight. However, the performance and reliability will be worsened to a large degree which may affect the feasibility of module application. In this work, an investigation is done to evaluate the electrical, thermal performance and reliability of a standard direct liquid cooled automotive IGBT module operates at 105°C coolant.

Simulation and Optimization of Air-Cooled PEMFC Stack for Lightweight Hybrid Vehicle Application

A model of 2 kW air-cooled proton exchange membrane fuel cell (PEMFC) stack has been built based upon the application of lightweight hybrid vehicle after analyzing the characteristics of heat transfer of the air-cooled stack. Different dissipating models of the air-cooled stack have been simulated and an optimal simulation model for air-cooled stack called convection heat transfer (CHT) model has been figured out by applying the computational fluid dynamics (CFD) software, based on which, the structure of the air-cooled stack has been optimized by adding irregular cooling fins at the end of the stack. According to the simulation result, the temperature of the stack has been equally distributed, reducing the cooling density and saving energy. Finally, the 2 kW hydrogen-air air-cooled PEMFC stack is manufactured and tested by comparing the simulation data which is to find out its operating regulations in order to further optimize its structure.

Sampling based State of Health estimation methodology for Li-ion batteries

Storage and management of energy is becoming a more and more important problem every day, especially for electric and hybrid vehicle applications. Li-ion battery is one of the most important technological alternatives for high capacity energy storage and related industrial applications. State of Health (SoH) of Li-ion batteries plays a critical role in their deployment from economic, safety, and availability aspects. Most, if not all, of the studies related to SoH estimation focus on the measurement of a new parameter/physical phenomena related to SoH, or development of new statistical/computational methods using several parameters. This paper presents a new approach for SoH estimation for Li-ion battery systems with multiple battery cells: The main idea is a new circuit topology which enables separation of battery cells into two groups, main and test batteries, whenever a SoH related measurement is to be conducted. All battery cells will be connected to the main battery during the normal mode of operation. When a measurement is needed for SoH estimation, some of the cells will be separated from the main battery, and SoH estimation related measurements will be performed on these units. Compared to classical SoH measurement methods which deal with whole battery system, the proposed method estimates the SoH of the system by separating a small but representative set of cells. While SoH measurements are conducted on these isolated cells, remaining cells in the main battery continue to function in normal mode, albeit in slightly reduced performance levels. Preliminary experimental results are quite promising, and validate the feasibility of the proposed approach. Technical details of the proposed circuit architecture are also summarized in the paper.