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

Optimal cost minimization strategy for fuel cell hybrid electric vehicles based on decision making framework

The low economy of fuel cell hybrid electric vehicles is a big challenge to their wide usage. A road, health, and price-conscious optimal cost minimization strategy based on decision making framework was developed to decrease their overall cost. First, an online applicable cost minimization strategy was developed to minimize the overall operating costs of vehicles including the hydrogen cost and degradation costs of fuel cell and battery. Second, a decision making framework composed of the driving pattern recognition-enabled, prognostics-enabled, and price prediction-enabled decision makings, for the first time, was built to recognize the driving pattern, estimate health states of power sources and project future prices of hydrogen and power sources. Based on these estimations, optimal equivalent cost factors were updated to reach optimal results on the overall cost and charge sustaining of battery. The effects of driving cycles, degradation states, and pricing scenarios were analyzed

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

Efficient power-electronic converters for electric vehicle applications

This paper introduces advanced power-electronic converter topologies for Electric Vehicles (EVs) using a four-phase DC/DC interleaved boost converter (FP-IBC) and a five-level T-type DC/AC multilevel converter. A comparison between the proposed topologies and other converter topologies is performed and discussed. The simulation results are analysed to evaluate the converters based on power loss calculations and harmonic analysis. The converters are studied at different switching frequencies and various loading conditions to reflect their effects on the converter losses. The results highlight the proposed converters' higher efficiency compared to other studied converter topologies in electric vehicle applications

Optimisation et gestion d'énergie pour un système hybride (association pile à combustible et supercondensateurs)

BELFORT-BU L. FEBVRE (900102102) / SudocBELFORT-UTBM-SEVENANS (900942101) / SudocSudocFranceF

Online parameter and state estimation of lithium-ion batteries under temperature effects

International audienceIn this paper, a hybrid estimation technique is proposed for lithium-ion batteries. This strategy makes use of state-space observer theory to reduce the complexity of the design and the stability analysis. However, the battery's parameters knowledge is required for the state-space model, which limits the performance as the battery's parameters vary. Therefore, an online parameter identification strategy is proposed to track the parameters deviation. The stability of the closed-loop estimation scheme is guaranteed by Lyapunov's direct method. Unlike other estimation techniques where temperature effects are ignored, this paper proposes a universal compensation strategy which can be used with many estimation algorithms available in the literature. The performance of the proposed scheme is validated through a set of experiments under different currents and temperatures along with comparison against an adaptive observer

Online Lifetime Estimation of Supercapacitors

International audienceThis paper proposes an online lifetime estimation methodology for supercapacitors. The online technique uses a Lyapunov-based adaptation law to estimate online the supercapacitor's parameters. Unlike offline time- or frequency-domain characterization techniques that require discontinuation of the system's normal operation, the proposed approach is more suitable for real-time applications, such as electric/hybrid vehicles, as it provides online lifetime estimation. Furthermore, convergence and stability analysis is provided by Lyapunov's stability theory as opposed to many online estimators available in the literature. The effectiveness of the proposed strategy is validated through experiments along with comparison against two different methods

Supercapacitor Thermal Modeling and Characterization in Transient State for Industrial Applications

International audienceA new thermal model, which allows temperature distribution determination inside a supercapacitor cell, is developed. The model is tested for a supercapacitor based on the activated carbon and organic electrolyte technology. In hybrid vehicle applications, supercapacitors are used as energy-storage devices, offering the possibility of providing the peak-power requirement. They are charged and discharged at a high current rate. The problem with this operating mode is the large amount of heat produced in the device which can lead to its destruction. An accurate thermal modeling of the internal temperature is required to design a cooling system for supercapacitor module, meeting the safety and reliability of the power systems. The purpose of this paper is to study the supercapacitor temperature distribution in steady and transient states. A thermal model is developed; it is based on the finite-differential method which allows for the supercapacitor thermal resistance determination. The originality of this paper is in the fact that a thermocouple (type K) was placed inside the supercapacitor from Maxwell Technologies. A test bench is realized. The cases of supercapacitor thermal distribution using natural and forced convection are studied. Simulations and experimental results are reported to validate the proposed model. The results obtained with this model may be used to determine the cooling system required for actual supercapacitor applications

Supercapacitor Module Sizing and Heat Management under Electric, Thermal, and Aging Constraints

International audienceSupercapacitors have an important role to play in the development of electric power applications, mostly in the transport domain. Acceleration and braking of cars or trains generate or require a large amount of power during a few seconds. These conditions are particularly suitable for using supercapacitors, which have a very high‐power density and a long lifetime compared to batteries. In these applications, the energetic performance depends mainly on the design of the supercapacitor modules.In automotive and rail applications, the supercapacitor modules are designed according to customer mission profiles of the vehicle. The design methods must also incorporate the constraints and the operating environment of the system (electrical stress, thermal constraints, vibration, etc.). Thus, supercapacitor modules must also work correctly and always provide the required power to the system during their lifetime. Therefore, it is vital to take into account the aging of these components in the phase of system designing.This chapter is devoted to the sizing of supercapacitor modules, taking into account the different constraints mentioned. Several designing methods are discussed and validated by simulation of some real applications. It is important to model the electrical and thermal behavior and the aging of the supercapacitor modules before the sizing. Temperature accelerates supercapacitor and module aging. A decrease in the capacitance and an increase in the series resistance are observed. Consequently, thermal management is a key issue concerning lifetime and performance of supercapacitor modules. We propose to begin this chapter by presenting the characterization, the electrical and thermal modeling and the aging of supercapacitors and finish by the sizing of supercapacitor modules

Supercapacitor Module Sizing and Heat Management under Electric, Thermal, and Aging Constraints

International audienceSupercapacitors have an important role to play in the development of electric power applications, mostly in the transport domain. Acceleration and braking of cars or trains generate or require a large amount of power during a few seconds. These conditions are particularly suitable for using supercapacitors, which have a very high‐power density and a long lifetime compared to batteries. In these applications, the energetic performance depends mainly on the design of the supercapacitor modules.In automotive and rail applications, the supercapacitor modules are designed according to customer mission profiles of the vehicle. The design methods must also incorporate the constraints and the operating environment of the system (electrical stress, thermal constraints, vibration, etc.). Thus, supercapacitor modules must also work correctly and always provide the required power to the system during their lifetime. Therefore, it is vital to take into account the aging of these components in the phase of system designing.This chapter is devoted to the sizing of supercapacitor modules, taking into account the different constraints mentioned. Several designing methods are discussed and validated by simulation of some real applications. It is important to model the electrical and thermal behavior and the aging of the supercapacitor modules before the sizing. Temperature accelerates supercapacitor and module aging. A decrease in the capacitance and an increase in the series resistance are observed. Consequently, thermal management is a key issue concerning lifetime and performance of supercapacitor modules. We propose to begin this chapter by presenting the characterization, the electrical and thermal modeling and the aging of supercapacitors and finish by the sizing of supercapacitor modules