Richard Lallemand

Study of Accelerated Aging of Supercapacitors for Transport Applications

One important part of the electrical transportation systems is the energy-storage system. This can be based, for example, on supercapacitors. In this paper, we propose to study its behavior under constraints similar to their uses in power and railway-traction systems. We define an adequate measurement protocol for accelerated aging which is applied to supercapacitors according to two accelerated factors: effective current and temperature. We model the supercapacitors for different states of health. The modeling gives a good estimation of the variation of electrical parameters of the supercapacitor at different states. We reveal general indicators of the supercapacitors aging, and we discuss about its life cycle.

Traction power converter for PEM fuel cell multi-stack generator used in urban transportation

This paper presents the study, based on technical specifications, of a power converter structure candidate to fuel cell multi-stack association for urban transport applications. This study is carried out in the frame of the French SPACT-80 research project. The converter topology is based on a DC-DC 3-phase IGBT interleaved boost converter which should meet the following relevant criteria: high efficiency, redundancy, minimisation of fuel cell current ripple, compactness, fault handling and strategies for degraded working modes. The degraded working modes which are considered are one fuel cell stack or converter phase out of work, and DC bus voltage fluctuation. The originality of this paper consists in the power converter design and the backup strategies. Converter operation and performances are studied by numerical simulation.

Power cycling issues and challenges of SiC-MOSFET power modules in high temperature conditions

Abstract Silicon carbide (SiC) MOSFETs power modules are very attractive devices and are already available in the market. Nevertheless, despite technological progress, reliability remains an issue and reliability tests must be conducted to introduce more widely these devices into power systems. Because of trapping/de-trapping phenomena at the SiC/SiO 2 interface that lead to the shift of threshold voltage, test protocols based on silicon components cannot be used as is, especially in high temperature conditions. Using high temperature SiC MOSFET power modules, we highlight the main experimental difficulties to perform power cycling tests. These reversible physical mechanisms preclude the use of temperature sensitive parameters (TSEP) for junction temperature measurements, so we set up fiber optic temperature sensors for this purpose. Moreover, these degradation phenomena lead to difficulties in both controlling the test conditions and seeking for reliable aging indicator parameters. Finally, a power cycling test protocol at high temperature conditions is proposed for such devices.

Description of supercapacitor performance degradation rate during thermal cycling under constant voltage ageing test

Great research effort is currently devoted towards enhancing performance and operating time of electrical vehicle (EV). Classic storage element in EV consists of accumulators, which allow a relatively high autonomy. However, the power capability of these devices can be considered as insufficient. Supercapacitors (SC) are a new promising storage system used in EV to minimize this lack thanks to their high power capability. One of the ageing cause for SCs for this application is the day/night cycling, that is why we study the impact of thermal cycling on SC performances in this paper. In this article, and in order to have a descriptive sample, impacts of three thermal cycling ageing test conditions are compared with obtained results coming from simple calendar ageing tests at constant temperature and voltage. The comparison is based on physics modelling parameters evolution in the Constant Phase Element (CPE) and Multi-Pore (MP) models. These parameters are calculated based on experimental measurements during calendar ageing tests up to 14,000 h and 6000 h, 10,000 h for thermal cycling tests. Finally, the study of modelling parameters highlights changes in the internal physical structure for both ageing tests.

Ageing quantification of supercapacitors during power cycling using online and periodic characterization tests

In this paper, a testing methodology for ageing quantification of supercapacitors (SC) for hybrid electric vehicles (HEV) applications is investigated. The accelerated ageing tests are based on power cycling and on the definition of a current profile that takes into account the high charge-discharge current levels of typical HEV functionalities. An online characterization method is used to follow the degradation of the cells performances in terms of evolution of capacitance and equivalent series resistance. The reproducibility of the measurements allows quantifying the impact of both the voltage and the temperature on the ageing for a significant number of cycles. Then, the regeneration phenomenon that appears during the power cycling stops is highlighted and its real impact on the cycle life is discussed. This database of experimental results will be used further to develop ageing laws that will be implemented in SC simulation models in order to optimize the sizing of the cells for a given HEV application.

High frequency power converter for PEFC generator architecture based on a multi stacks association for transportation applications

This paper presents the study and experimental validation of a high frequency (HF) power converter used in a powertrain composed of a polymer electrolyte fuel cell (PEFC) generator based on a multi-stack association and dedicated to transportation applications. As a first approach, the architecture of the system presented in this paper has been limited to two fuel cell stacks. An original power converter structure using a HF transformer (HFT) has been chosen. This structure has the main advantage of compactness and is well adapted to the testing of fuel cell generators either in normal or degraded mode (partial failure of one stack); which correspond to real transport operating conditions. Simulation results of the power system are presented and discussed. First experimental results for a normal PEFC working mode are presented and analyzed in this paper including the experimental determination of the power converter efficiency

Double resonant converter topology with fast switching semiconductors for lead-acid battery charger used in hybrid electric locomotive

This paper presents the study and experimental validation of a 9 kW lead-acid battery charger used to feed the 72V DC-Bus inside an hybrid electric locomotive demonstrator realized in the frame of the French research project PLATHEE (energy-efficient and environmentally friendly train platform). The proposed topology for the battery charger is a DC/AC/DC step-down converter structure using high frequency transformer and a double resonant series-parallel dipole. Main advantages of this topology are losses minimization due to soft switching operation, reduction of passive component weight and easy system integration. However, development and testing of the converter remain complex owing to high frequency constraints. Anti-parallel diodes of the DC/AC half-bridge dissipate losses in excess during switching sequences and their reverse recovery energy leads to constraining high current peaks. A solution consists in using fast Insulated Gate Bipolar Transistor (IGBT)/diode technology well suited to high frequency switching, and able to limit diode peak-current amplitude during switch-off. Electro-thermal endurance tests have been performed in order to characterize the thermal behavior of the semiconductor module and control its case temperature raise. The battery charger working has been first validated on laboratory test-bench using a battery emulator, and then implemented in the hybrid electric locomotive platform.

Assessment of electrothermal model of supercapacitors for railway applications

The aim of the SNCF research division program in collaboration with LTN-INRETS laboratory is to respond to the high demand to more environmentally friendly transportation. We have investigated general behaviours of supercapacitors for railway application with two powerful methods of analysis. The first is constant charge/discharge current at high level value (300, 500 A), the second is impedance spectroscopy method. An electrothermal circuit model of supercapacitors based on activated carbon and organic electrolyte is defined for a given railway application. Matlab/Simulink simulations are shown to assess the model under railway specifications

Power module thermal cycling tester for in-situ ageing detection

Abstract The success of the electric car depends heavily on battery technology and on compact, reliable and efficient power converters in which power modules are a key element. Power Module technology is evolving rapidly. New semiconductor chips are developed to improve electrical performance and reduce power losses. Innovative design architectures are introduced to improve thermal management. Before mass production launch, the performance and lifetime of these technological innovations needs to be evaluated to respect the longer warranty requirements. This is usually achieved by Accelerated Testing. In this case, the effect of thermal cycles on the lifetime of power modules is usually studied by placing unpowered power modules in a thermal chamber and checking that their performance matches the specification after a given number of thermal cycles. However this method provides no information on the power module performance degradation due to cyclic thermal stresses. The Thermal Cycling Tester presented in this paper reproduces the stresses created in use conditions by environmental thermal cycles. This approach makes it possible to monitor ageing by applying power cycles periodically and measuring thermal and electric parameters. These results are then combined with mechanical and acoustic microscopy characterizations and finite element modeling results to provide a better understanding of the failure mechanisms.

Influence of thermal cycling on supercapacitor performance fading during ageing test at constant voltage

In this paper, we focus on impacts of thermal cycling ageing on supercapacitors performances at a constant voltage. We compare obtained results with those coming from simple calendar ageing at constant temperature and voltage. The comparison is based on physics modeling parameters evolution based on results from experimental measurements during calendar ageing up to 10000 h and 6000 h, 8000 h for thermal cycling tests. Finally, the impacts of thermal cycling interval is highlighted and quantified.