DC/DC Converters for Electric Vehicles

International audienceThe large number of automobiles in use around the world has caused and continues to cause serious problems of environment and human life. Air pollution, global warming, and the rapid depletion of the earth’s petroleum resources are now serious problems. Electric Vehicles (EVs), Hybrid Electric Vehicles (HEVs) and Fuel Cell Electric Vehicles (FCEVs) have been typically proposed to replace conventional vehicles in the near future. Most electric and hybrid electric configurations use two energy storage devices, one with high energy storage capability, called the “main energy system” (MES), and the other with high power capability and reversibility, called the “rechargeable energy storage system” (RESS). MES provides extended driving range, and RESS provides good acceleration and regenerative braking. Energy storage or supply devices vary their output voltage with load or state of charge and the high voltage of the DC-link create major challenges for vehicle designers when integrating energy storage / supply devices with a traction drive. DC-DC converters can be used to interface the elements in the electric power train by boosting or chopping the voltage levels. Due to the automotive constraints, the power converter structure has to be reliable, lightweight, small volume, with high efficiency, low electromagnetic interference and low current/voltage ripple. Thus, in this chapter, a comparative study on three DC/DC converters topologies (Conventional step-up dc-dc converter, interleaved 4-channels step-up dc-dc converter with independent inductors and Full-Bridge step-up dc-dc converter) is carried out. The modeling and the control of each topology are presented. Simulations of 30KW DC/DC converter are carried out for each topology. This study takes into account the weight, volume, current and voltage ripples, Electromagnetic Interference (EMI) and the efficiency of each converter topology

Batteries and Supercapacitors for Electric Vehicles

International audienceDue to increasing gas prices and environmental concerns, battery propelled electric vehicles (BEVs) and hybrid electric vehicles (HEVs) have recently drawn more attention. In BEV and HEV configurations, the rechargeable energy storage system (RESS) is a key design issue [1–3]. Thus, the system should be able to have good performances in terms of energy density and power capabilities during acceleration and braking phases. However, the thermal stability, charge capabilities, life cycle and cost can be considered also as essential assessment parameters for RESS systems.Presently batteries are used as energy storage devices in most applications. These batteries should be sized to meet the energy and power requirements of the vehicle. Furthermore, the battery should have good life cycle performances. However, in many BEV applications the required power is the key factor for battery sizing, resulting in an over-dimensioned battery pack [4,5] and less optimal use of energy [4]. These shortcomings could be solved by combination of battery system with supercapacitors [6–8]. In [9], it is documented that such hybridization topologies can result into enhancing the battery performances by increasing its life cycle, rated capacity, reducing the energy losses and limiting the temperature rising inside the battery. Omar et al. concluded that these beneficial properties are due to the averaging of the power provided by the battery system [4,6,9]. However, the implementation of supercapacitors requires a bidirectional DC–DC converter, which is still expensive. Furthermore, such topologies need a well-defined energy flow controller (EFC). Price, volume and low rated voltage (2.5–3 V) hamper the combination of battery with supercapacitors [6,10]. In order to overcome these difficulties, Cooper et al. introduced the Ultra-Battery, which is a combination of lead-acid and supercapacitor in the same cell [11]. The new system encompasses a part asymmetric and part conventional negative plate. The proposed system allows to deliver and to absorb energy at very high current rates. The Ultra-Batteries have been tested successfully in the Honda Insight. However, this technology is still under development. In the last decade, a number of new lithium-ion battery chemistries have been proposed for vehicular applications. In [12–15], it is reported that the most relevant lithium-ion chemistries in vehicle applications are limited to lithium iron phosphate (LFP), lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium manganese spinel in the positive electrode and lithium titanate oxide (LTO) in the negative electrode. In this chapter, the performance and characteristics of various lithium-ion based batteries and supercapacitor will be evaluated and discussed. The evaluation will be mainly based on the electrical behavior. Then the characteristics of these RESS systems will be investigated based on the electrical and thermal models

Extension of the Stray Voltage Capture Short-Circuit Detection Method to a 6-Phase Fault-Tolerant Dual-Motor Drive

This article investigates and validates the applicability of the recently developed stray voltage capture (SVC) ultra-fast short-circuit (SC) detection method and its extended version (ESVC) to fault-tolerant multi-motor drives. As these methods are system-based, a fault localization algorithm is also developed. Simulation analysis of the inverter stray inductances shows additional challenges for the SVC method making it hard to achieve ultra-fast SC detection. The ESVC method is slower but overcomes these challenges. The methods are adapted for a 400 V 6-phase Silicon Carbide based inverter equipped with a 2-level turn-Off hardware protection scheme. Fault under load and hard switching fault tests are performed showing the effectiveness of the ESVC in fast (smaller than 330 ns) and reliable SC detection and protection for SiC MOSFETs. The fault localization algorithm is also validated showing a localization speed smaller than 20 μs

Thermal modeling and heat management of supercapacitor modules for vehicle applications

International audienceTemperature has a huge influence on supercapacitor cells and modules ageing. Consequently, thermal management is a key issue concerning lifetime and performance of supercapacitor modules. This paper presents thermal modeling and heat management of supercapacitor modules for vehicle applications. The thermal model developed is based on thermal-electric analogy and allows the determination of supercapacitor temperature. Relying on this model, heat management in supercapacitor modules was studied for vehicle applications. Thus, the modules were submitted to real life driving cycles and the evolution of temperatures of supercapacitors was estimated according to electrical demands. The simulation results show that the hotspot is located in the middle of supercapacitors module and that a forced airflow cooling system is necessary

Modeling of an active torsion bar automotive suspension for ride comfort and energy analysis in standard road profiles

Author's accepted manuscript (postprint).publishedVersio

Modeling of an active torsion bar automotive suspension for ride comfort and energy analysis in standard road profiles

Author's accepted manuscript (postprint).publishedVersio

Electric and thermal characterization of advanced hybrid Li-Ion capacitor rechargeable energy storage system

International audienceThe Lithium-Ion Capacitor (LIC) is a new hybrid energy storage device. Its structure combines the electrical double-layer capacitor (EDLCs) and lithium-ion technology. Its elementary structure is composed of a positive electrode with activated carbon as in double-layer capacitor and a negative electrode based on Li doped carbon similar to the Li-Ion battery. The advantage of the LIC technology compared to the conventional storage device lies in the fact that the power density and the nominal voltage are higher and the energy density is much higher than EDLCs. This paper deals with the electrical and thermal characterization of this new energy storage device. The LIC equivalent series resistance and capacitance are determined based on extended electrical characterization tests. The LIC parameters variations according to the frequency and to the temperature are presented. Finally, the LIC temperature parameters and distribution over the surface area as a function of time is presented and analyzed

The Challenge of PHEV Battery Design and the Opportunities of Electrothermal Modeling

International audienceThis chapter proposes an advanced thermal model for lithium-ion battery technology. The model is able to predict the surface temperature of lithium-ion battery cell accurately. The model exists of electrical components such as thermal capacitance, inside thermal resistance and convective thermal resistance.In this chapter, a new methodology is presented that allows to determine the parameters of the thermal model. Then, the model has been calibrated and validated at different environmental conditions. According to the validations results, the error of the simulation compared to experimental results is less than 1 °C. Furthermore, the model has been extended to a novel electrothermal model for enhancing of the model performances. Particularly, the association of the electrical model with the thermal model is of high importance due to the change of the battery parameters such as internal resistance in function of state of charge, temperature and current rates

Curve Tilting With Nonlinear Model Predictive Control for Enhancing Motion Comfort

The benefits of automated driving can only be fully realized if the occupants are protected from motion sickness. Active suspensions hold the potential to raise the comfort level in automated passenger vehicles by enabling new functionalities in chassis control. One example is to actively lean the vehicle body toward the center of the corner to counteract the inertial lateral acceleration. Commonly known as curve tilting, the concept is deemed effective in reducing postural disturbance on the occupants and the visual-vestibular conflict when the occupants do not have an external view. We present in this article a nonlinear model predictive control (NMPC) method for the curve tilting functionality. The controller incorporates the nonlinear suspension forces in the prediction model to help achieve high tracking accuracy near the physical limit of the suspension system. The optimization process is accelerated with an explicit initialization method that is based on piecewise-affine (PWA) modeling and offline solution to an alternative optimal control problem (OCP). The controller is able to operate at 20 Hz in a hardware-in-the-loop (HIL) setup. Given sufficient computational resources, we observe a significant reduction in the lateral acceleration sensed by the passenger over a vehicle with passive suspensions, namely, by 46.5%, 25.4%, and 25.4% in the highway, rural, and urban driving scenarios, respectively. The NMPC also outperforms the baseline proportional-integral-derivative (PID) controller by achieving lower tracking error, namely, by 12.9%, 16.4%, and 38.0% in the aforementioned scenarios.Intelligent VehiclesTeam Tamas Keviczk