L. Boulon

Characterization and Modeling of a Hybrid-Electric-Vehicle Lithium-Ion Battery Pack at Low Temperatures

Although lithium-ion batteries have penetrated hybrid electric vehicles (HEVs) and pure electric vehicles (EVs), they suffer from significant power capability losses and reduced energy at low temperatures. To evaluate those losses and to make an efficient design, good models are required for system simulation. Subzero battery operation involves nonclassical thermal behavior. Consequently, simple electrical models are not sufficient to predict bad performance or damage to systems involving batteries at subzero temperatures. This paper presents the development of an electrical and thermal model of an HEV lithium-ion battery pack. This model has been developed with MATLAB/Simulink to investigate the output characteristics of lithium-ion batteries over the selected operating range of currents and battery capacities. In addition, a thermal modeling method has been developed for this model so that it can predict the battery core and crust temperature by including the effect of internal resistance. First, various discharge tests on one cell are carried out, and then, cells parameters and thermal characteristics are obtained. The single-cell model proposed is shown to be accurate by analyzing the simulation data and test results. Next, real working conditions tests are performed, and simulation calculations on one cell are presented. In the end, the simulation results of a battery pack under HEV driving cycle conditions show that the characteristics of the proposed model allow a good comparison with data from an actual lithium-ion battery pack used in an HEV.

Two-Layer Energy-Management Architecture for a Fuel Cell HEV Using Road Trip Information

This paper investigates the design of a two-layer energy-management system for a fuel cell hybrid electric vehicle (HEV). The first layer (upper layer) deals with the vehicle energy consumption, whereas the second layer (lower layer) deals with the power splitting between the fuel cell and the battery. The upper layer aims at providing the globally optimal energy consumption profile by considering the road-trip information and the vehicle dynamics. This energy profile is independent of the number and type of power sources on the vehicle. Therefore, it can be used to assist the real-time power splitting algorithm implemented into the lower layer. This layer design goal is mainly to share the vehicle power demand between the fuel cell and the battery while minimizing the hydrogen consumption. In addition, the splitting method takes into account the fuel cell efficiency map and the hydrogen/electricity relative pricing while imposing a smooth behavior on the fuel cell. This smooth behavior is desirable to preserve the fuel cell life and reduce the oxygen starvation phenomenon. The proposed energy-management system has been successfully implemented and validated on an HEV test bench. The experiments and simulations using several standard driving cycles suggest that the approach can reduce the hydrogen consumption up to 10% compared to a rule-based method and a depleting-sustaining method while preserving at the same time the battery pack from overdischarging.

Hybrid electric vehicle power management strategy including battery lifecycle and degradation model

The following work is concerned with the inclusion of battery degradation mechanisms in power management strategies applied to current-generation hybrid electric vehicles (HEV). Using a real, physical electric vehicle as a basis for validation, a simulation model was realized to describe the behavior of the HEV and its components, including a lead-acid battery bank, an internal combustion engine (ICE) generator and a polymer electrolyte membrane fuel cell (PEMFC). This model is to be used in conjunction with a newly developed battery degradation model and included as part of a power management strategy aimed at reducing operating costs via an associated function, with the objective of studying the effects of battery lifecycle in such a strategy. As a first step towards the realization of this goal, this paper is aimed at describing the model of the HEV and its validation.

Simulation Model of a Military HEV With a Highly Redundant Architecture

The six-driven-wheel Electric Propulsion Demonstrator (DPE 6 × 6) is a military hybrid vehicle. Due to reliability demands, high redundancy is required, and the architecture is quite complex. A simulation model of this vehicle is proposed in this paper. The simulation model must allow the analysis of various power flows of the system. Moreover, this model has to be used to develop an efficient energy-management strategy. For these reasons, a graphical description [energetic macroscopic representation (EMR)] is used to develop the model in a systemic approach. The simulation model is, thus, described and validated from experimental results.

Energetic Macroscopic Representation of a Fuel Cell-Supercapacitor System

This paper presents a model of a fuel cell- supercapacitor system which represents the electric power supply device of a hybrid electric vehicle (HEV). The fuel cell and the supercapacitors are coupled with a DC bus and a common cooling system. The first part of this paper deals with the modeling of the elements of the system (fuel cell system (FCS), supercapacitors, power electronics, and temperature regulation system). The second part deals with the design of a control structure which regulates the DC bus voltage, the fuel cell power, and the power source temperature. Simulation and experimental results are provided and analyzed.

Design of an energy management strategy for PEM Fuel Cell Vehicles

This paper proposes a strategy management of Fuel Cell Vehicle. The objective is to design an energetic strategy for the Low Speed Vehicle (LSV) Nemo. The vehicle is equipped with Axane fuel cell and a battery pack. The modeling is based on the Energetic Macroscopic Representation (EMR). The model is validated on the vehicle test bench Nemo The strategy is based on the knowledge of the maximum and minimum power limits of the Proton Exchange Membrane Fuel Cell (PEMFC) Axane. The strategy gives two modes of running, the first one gives a maximum efficiency run of the PEMFC and the other one the maximum power of PEMFC.

Low Temperature Discharge Cycle Tests for a Lithium Ion Cell

As all drivers in cold countries know, operating HEV/EVs at cold temperature is rather difficult. Indeed, cold weather increases the internal resistance of the battery system creating a high opposing force while operating the battery: slowdown of Li+ diffusivity and decrease of ionic conductivity of electrolyte. Thereby, it limits the amount of energy extracted and reduces cell energy and power capability. Therefore, Li-Ion sensitivity to temperature remains one of the major obstacles to HEV/VEs market penetration. In fact, until now, investigations of low-temperature behaviors of Li-ion cells barely provide suitable information because they have only been extended to small battery capacities or non-currently used HEV/VEs batteries. Therefore, a complete thermal characterization of an actual HEV/VEs battery is missing. This characterization is described in this paper. Indeed; a 100 Ah lithium LiFePO4Mn HEV battery was tested under various operating conditions. The experimental process includes charging at ambient temperature, and discharging under extreme cold weather. The experimentations was conducted at four different temperatures to study the effect of seasonal changes in temperature.

Multi physics modelling and representation of power and energy sources for Hybrid Electric Vehicles

This paper presents power sources models for Hybrid Electric Vehicles (HEV). These models are designed in order to be integrated in a complete HEV simulation. Moreover, the final objective of this simulation is to study two control levels: the local control of each subsystems and the energy management of the entire system. Consequently, a multi-physics control oriented formalism is used: Energetic Macroscopic Representation (EMR).

Efficiency Map of the Traction System of an Electric Vehicle from an On-Road Test Drive

In this paper, the traction system modeling of a commercial electric car is studied. Experimental data acquired during an on-road test drive are used to determine an efficiency map of the traction system. Using the deduced model, simulation results are compared to experimental results. The simulation tool using the proposed efficiency map method yields less than 5 % error on energy consumption compared to experimental test drive results.

Inversion-Based Control of a Highly Redundant Military HEV

This paper deals with the control design of a military hybrid electric vehicle (HEV). The studied vehicle presents a highly redundant architecture to ensure high system reliability. As a consequence, the control scheme is complex to design. Energetic macroscopic representation (EMR) is used to describe the interaction between all subsystems of the powertrain. A control structure is deduced by an inversion of the EMR of the vehicle powertrain. Simulation results demonstrate the ability of this inversion-based control to achieve military missions.