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Metallized polypropylene film capacitors are known to be one of the most common causes of failure in electronic systems. Predicting their lifetime to anticipate failures is a key issue in the assessment of these systems' reliability. In this paper, accelerated ageing tests applying voltage, temperature and humidity were conducted on 42 capacitors. The aim is to evaluate and sharpen the existing laws in literature thanks to the support of these data. Therefore, based on an analysis of failures and the understanding of this phenomenon, a new law is introduced modelling the capacitance degradation. The model has been assessed against the data, as compared to present laws in literature and other functions, describing the evolution of experimental curves. • Accelerated tests on metallized film capacitors on humidity, temperature, voltage • Analysis of failures on metallized film capacitor • Modelling corrosion impact based on moisture diffusion • Modelling corrosion impact with laws based on failure rate/Ageing laws based on corrosion impact • Comparison of ageing metallized film capacitors laws regarding data [ABSTRACT FROM AUTHOR]

In this paper, we present an innovative and precise way to calculate the available capacity in a battery. This quantity is essential to assess the ageing process during real use or ageing tests. Classical methods for measuring the available capacity in a battery are very dependent of impedance and relaxation state of the battery. Consequently, these methods are not suitable to quantify reversible and irreversible capacity losses occurring on batteries. We propose an indirect measure of available capacity that reduces the distortion caused by battery relaxation and impedance changes. This new method provides more accurate results allowing to distinguish reversible from irreversible part of capacity losses. The obtained results on calendar ageing tests are used in a second part to model both self-discharge and capacity fade in a global approach by using the generalized Eyring relationship. [ABSTRACT FROM PUBLISHER]

Due to its capacity to store or supply energy with high power, the supercapacitor is becoming an attractive component. Because of the electrostatic nature of energy storage, the endurance of this component toward repetitive charge and discharge cycles is relatively high. The goal of this paper is to demonstrate that cycling has an impact on the degradation of the supercapacitor and, as a result, on its lifetime. Based on accelerated cycling tests, some supercapacitors were studied using a dedicated test bench. Temperature, voltage, and current, which are the parameters that accelerate aging, are monitored. In fact, observations during the cycling tests show an important acceleration in the degradation compared with a similar static test having the same voltage and core temperature but without cycling. This paper proposes a method to quantify the acceleration of aging during a cycling phase. [ABSTRACT FROM PUBLISHER]

Like any electric energy storage system, supercapacitors have a limited lifetime. Indeed, they degrade with time because of parasitic reactions between electrodes and electrolyte. Porous electrodes are complex structures and pores have size dispersion because of manufacturing processes. This paper proposes to study the specific impact of supercapacitor floating ageing on different pore sizes using a multipore model. The multipore model is an equivalent electrical circuit model, capable of representing impedance behavior of supercapacitor in full range of its operating frequencies and classifying different sized pores by their impedance parameters. This paper first presents a link between pore sizes and impedance parameters of the modeling circuit. Then, floating ageing experiments are carried out using three samples from two different manufacturers. Multipore model impedance parameters evolution is monitored and discussed. Finally, a new representation of ageing processes is proposed by pore size and for different ageing phases. [ABSTRACT FROM AUTHOR]

This study presents a study of the reduction in battery stresses by using supercapacitors (SCs) in a 500-kVA rated UPS. We aim at investigating the optimal supercapacitors-battery combination versus the SCs cost. This investigation is threefold; first, supercapacitors and battery models developed using MATLAB/Simulink are presented and validated. Second, the architecture and the simulation of the designed system that combines the SCs and the battery are shown. The supercapacitors are used as high-power storage devices to smooth the peak power applied to the battery during backup time and to deliver full power during short grid outages. By charging the SCs through the battery at a suitable rate, all impulse power demands would be satisfied by the supercapacitors. Third, extensive simulations are carried out to determine the gain in battery RMS current, the gain in energy losses, the energy efficiency and the elimination rate of surge load power. These four performance parameters are determined by simulation and then analyzed. The influence of the SCs recharge on the performance indicators is highlighted. A thorough analysis involving optimal study proposes to draw the optimal SCs number and filter constant from the variation of the aforementioned parameters versus the cost of the SCs. [ABSTRACT FROM AUTHOR]

Pulse charging and pulse discharging have been reported by many authors in the literature to improve the performance of various secondary electrochemical cells. Only a few authors mentioned the effects of such charge and discharge method on lithium-ion batteries. The overall objective of this work is to experimentally investigate the impact of certain current pulse profiles on the electrical performance of Li-ion batteries. The results highlight a detrimental impact of periodic pulses on the cell performance compared to profiles with constant current. [ABSTRACT FROM AUTHOR]

This paper presents a low-cost method to realize a real-time condition monitoring and a predictive-maintenance system of an electrolytic capacitor used in uninterruptible power supplies (UPSs). This method consists in detecting the changes in real time of the equivalent series resistance and the capacitance C values of the electrolytic capacitors. Simulation and experimental results are presented to illustrate the proposed monitoring technique. The proposed method can be used in UPS where waveforms are continuously varying in amplitude, frequency, and temperature. The proposed online failure prediction method has the merits of using only the existent resources in UPS and with the use of known algorithms. [ABSTRACT FROM AUTHOR]

The self-discharge of an electrochemical capacitor, also referred to as a supercapacitor, is an important factor in determining the duration of maintaining stored energy, especially in low-duty-cycle applications. The study of self-discharge is conducted as follows: first, the self-discharge is characterized by measuring the decline of open-circuit voltage of the electrochemical capacitor. Second, the mechanisms of self-discharge, leakage current, and diffusion of ions at the electrode-electrolyte interfaces are modeled by an electrical equivalent circuit. The equivalent circuit elements are experimentally determined according to the self-discharge time behavior. In addition, the dependence of the self-discharge parameters on both temperature and initial voltage across the electrochemical capacitor is described in detail. [ABSTRACT FROM AUTHOR]

Presents a study that used an analytic model to calculate the losses in the metallized polypropylene film capacitors. Information on polypropylene capacitors; Losses of capacitors of different geometric shape; Results of the thermal simulation for capacitors of different geometry.

Presents a study which focused on the failure prediction of electrolytic capacitors during operation of a switchmode power supply. Methods and materials used in the study; Description of a processing method for output-voltage ripple; Results of the study; Conclusions of the study.

At present, passive balancing methods dominate energy storage applications, however, they suffer from a long balancing duration. In this article, we took advantage of a modular architecture, where several modular power converters replace a central dc–dc converter for fast charging and balancing of a supercapacitor stack. A strategy has been proposed to control how power is shared among the converters during the charging period in order to balance the supercapacitors. However, some converters enter control saturation due to voltage differences between supercapacitors caused by their nonuniform conditions and characteristics. The originality of this article lies in taking into account the saturation by modifying an energy-based strategy to correct the power shares and make balancing the supercapacitors possible. Simulation and experimental case studies were used to demonstrate the strategy's performance and limitations. [ABSTRACT FROM AUTHOR]

Lifetime of energy storage systems is a key factor that is extremely influenced by the operating conditions. For this reason, lithium-ion batteries (LiBs) and supercapacitors (SCs) were subjected to accelerated aging tests in several previous research in order analyze their lifespan. Lithium-ion capacitors (LiCs), which fall in between LiBs and SCs, are still considered as a novel technology. Their behavior during accelerated aging tests is not yet well studied in the literature. This paper focuses on studying the degradation of their properties during floating aging. Eighteen samples were tested under three different voltage values and two different temperatures over 12 months. Cells that were discharged to the minimum voltage showed a severe capacitance decrease that was much higher than the one of fully charged cells. The best storage voltage of LiCs was found to be 3 V, which is equivalent to a half charging state. The hybrid structure of LiCs was found to be the major cause of this change in behavior during aging at different voltages. Mechanisms that affect the electrodes and the internal composition of the cells in the diverse conditions were analyzed and predicted. [ABSTRACT FROM AUTHOR]

The integration of energy storage systems (ESSs) in contemporary applications highly depends on the performance of these devices. Supplying high power for a reasonable period of time is one of their main targets in several applications like backup systems and transport technologies. For this purpose, lithium-ion capacitors (LICs) would demonstrate better suitability than conventional ESSs for applications requiring a small installation space and a long lifetime. They are known for their energy density greater than that of supercapacitors and their power density greater than that of lithium-ion batteries. This paper explains the electrochemical processes that interfere in the storage of energy inside an LIC. The analysis of these phenomena was the tool for assessing the nonlinear capacitance evolution of the LIC with respect to its voltage. Several measurement techniques in the frequency and time domains were elaborated and compared in order to assess this nonlinear behavior of the LIC. Some of the measurement protocols contained constant voltage phases that had a significant effect on the variation of the capacitance. The novelty of this study concerns the introduction of a new measurement protocol that takes into account the particular characteristics of LICs. Their unique behavior is explained for the first time based on a physicochemical analysis. [ABSTRACT FROM PUBLISHER]

Lithium-ion (Li-ion) batteries widely used in electric vehicles (EVs) and hybrid EVs (HEVs) are insufficient for vehicle use after they have degraded to 70% to 80% of their original capacity. Battery lifespan is a large consideration when designing battery packs for EVs/HEVs. Aging mechanisms, such as metal dissolution, growth of the passivated surface film layer on the electrodes, and loss of both recyclable lithium ions, affect the longevity of the Li-ion battery at high-temperature operations. Even vehicle maneuvers at low temperatures (T < \mbox0\ ^\circ\mboxC) contribute to battery lifetime degradation, owing to the anode electrode vulnerability to other degradation mechanisms such as lithium plating. Nowadays, only a few battery thermal management schemes have properly considered low-temperature degradation. This is due to the lack of studies on aging of Li-ion batteries at subzero temperature. This paper investigates how load cycle and calendar life properties affect the lifetime and aging processes of Li-ion cells at low temperatures. Accelerated aging tests were used to determine the effect of the ambient temperature on the performance of three 100-Ah LiFeMnP04 Li-ion cells. Two of them were aged through a normalized driving cycle at two temperature tests ( -\mbox20\ ^\circ\mboxC and 25 °C). The calendar test was carried out on one single battery at –20 °C and mid-range of state of charge (50%). Their capacities were continuously measured every two or three days. An aging model is developed and added to a preliminary single-cell electrothermal model to establish, in future works, a thermal strategy capable of predicting how the cell ages. This aging model was then validated by comparing its predictions with the aging data obtained from a cycling test at 0 °C. [ABSTRACT FROM PUBLISHER]

In hybrid vehicles, lithium-ion cells constituting a battery pack are frequently used to provide and recover high power to assist the vehicle's internal combustion engine (ICE) powertrain. This usage is more present in mild hybrid applications where the battery does not have long discharge time. Under such conditions, the pack's series resistance RS proved to be an important parameter to monitor since its evolution depends on the cell's characteristics (manufacturing tolerance, temperature, etc.). This resistance, which is monitored by the battery management system (BMS), reflecting the available power level in the cell can be used as an indicator to enhance the security of the battery pack. Its evolution can be used to quantify its aging (state of health: SoH). This paper presents an online approach to identify the cell's series resistance based on a direct estimation of RS. This parameter can be usually identified through the voltage drop occurring across the cell caused by a high current variation profile (mild hybrid conditions). These estimated values are then filtered with an “exponential moving average” method to limit the measurement noise effect. This approach provides good results for mild hybrid conditions, while minimizing the computing power required. [ABSTRACT FROM PUBLISHER]

Modular multilevel converters (MMCs) have been recognized as the most attractive technology for high voltage direct current (HVDC) applications during the last years. Their advantages include the ability to freely control the internally stored energy in the distributed submodules (SMs) and to independently control AC and DC powers. Recent studies showed that an MMC can take advantage of this degree of freedom to supply ancillary services with low energy requirements such as frequency response or power oscillation damping by connecting energy storage systems (ESSs) to its SM capacitors. This paper proposes a modular DC-DC converter as an interface between the energy storage element and the SM capacitor. As it can be built with switches allowing a high switching frequency, it is shown that the volume of the passive components can be reduced in comparison with interface converters known in the literature. The proposed control strategy avoids to transfer the harmonics of a SM to the ESS that prevents to drastically oversize the system. The proposed control method also provides an appropriate energy exchange without affecting the control philosophy of an MMC and it addresses balancing issues. Simulations and a downscaled prototype confirm the relevance of the proposed control. As the proposed interface converter is able to track the power reference with fast dynamics, it provides the same system-level advantages as other interface converters known in the literature but with a reduced volume. [ABSTRACT FROM AUTHOR]

In view of their potential for high dielectric breakdown strengths, low dissipation factors, and good dielectric stability over a wide range of frequencies and temperature, metallized films capacitors are very used components for aeronautic applications. Nevertheless, capacitors remain unreliable components; a good acquaintance of their deterioration over time would enable us to perform a predictive maintenance on the component and thus improve the availability of the whole system. This operation requires the knowledge of the capacitor ageing law and their failure mechanisms associated with the application. In a standard six pulses rectifier-fed pulse width modulation inverter, dc-link capacitors are generally subjected to gradients of temperature due to the encountered electrical stresses. Since traditional floating ageing tests, which consist on applying constant voltages and temperature across the component, do not reflect the normal ageing of the component, we propose in this paper to study the degradation kinetics of metallized films capacitors under high ripple currents, alone or combined with a dc voltage across the devices terminals. It will therefore reproduce with a more representative way the ageing of the component in comparison with the traditional floating ageing tests. Based on the resonant circuit properties, the ageing test bench especially developed for our study provides high currents and voltages from a low power source. Through the study and analysis of the capacitors parameters evolution under high ripple currents, an original ageing law is proposed to model the capacitance decrease with time based on the electrochemical corrosion of the capacitors electrodes. The adequacy between the experimental points and the model proved the validity of the proposed law. [ABSTRACT FROM AUTHOR]

Metalized film capacitors are commonly used components in power electronics applications and their characteristics are drastically dependent on their operating frequency. Parasitic parameters could appear at low and high frequencies and disturb substantially the behavior of the component. Proper design of metalized film capacitors requires an understanding of all parasitic parameters' sources and their impacts on the circuit operation. This paper presents a modeling approach based on the complex form of the capacitor impedance to build its equivalent electrical circuit. This approach proved to be more accurate than the traditional modeling technique of identifying the electrical parameters using the modulus of the component impedance. Two different types of capacitors were tested; experimental results allowed to validate our model from 10 kHz to 35 MHz. [ABSTRACT FROM AUTHOR]

This paper proposes a comparative study of currentcontrolled hysteresis and pulsewidth modulation (PWM) techniques, and their influence upon power loss dissipation in a power-factor controller (PFC) output filtering capacitors. First, theoretical calculation of low-frequency and high-frequency components of the capacitor current is presented in the two cases, as well as the total harmonic distortion of the source current. Second, we prove that the methods already used to determine the capacitor power losses are not accurate because of the capacitor model chosen. In fact, a new electric equivalent scheme of electrolytic capacitors is determined using genetic algorithms. This model, characterized by frequency-independent parameters, redraws with accuracy the capacitor behavior for large frequency and temperature ranges. Thereby, the new capacitor model is integrated into the converter, and then, software simulation is carried out to determine the power losses for both control techniques. Due to this model, the equivalent series resistance (ESR) increase at high frequencies due to the skin effect is taken into account. Finally, for hysteresis and PWM controls, we suggest a method to determine the value of the series resistance and the remaining time to failure, based on the measurement of the output ripple voltage at steady-state and transient-state converter working. [ABSTRACT FROM AUTHOR]

Electric recreational vehicles represent a new challenge in terms of power supply systems compared to the current light-duty electric vehicles, which achieve high performance and long-range. The recreational vehicles need to heed the limited dimension requirements while assuring the high requested power. This paper proposes an integration of Lithium-Ion Capacitor (LIC) with Fuel Cell (FC) without any power electronic device for a three-wheel electric motorcycle. Unlike other hybrid power supply systems, the proposed FC-LIC passive configuration is lighter, compact, more efficient, and simpler to implement. Due to the different impedance of the components the system is self-management, in which FC supplies the average power component and LIC operates as a low-pass filter. In this respect, a simulator is built based on experimental tests to study the system performance in terms of hydrogen consumption and FC degradation. Subsequently, the system is tested under three standard motorcycle driving cycles at three different FC system lifespan stages. The obtained results demonstrate that a passive topology can supply the requested power along different FC stages of life and reported just an increment of 12% of hydrogen consumption at the oldest condition compared to the new condition. [Display omitted] • Integration of LIC technology with a fuel cell system for a recreational vehicle. • Development of a hybrid FC-LIC vehicle simulator based on experimental data. • The system is tested under standard driving cycles at different FC lifespan stages. • The proposed passive design supplies the requested power under all the conditions. • The passive FC-LIC topology is lighter, simpler to implement and self-management. [ABSTRACT FROM AUTHOR]

The process of determination of batteries lifespan for a specific application generally contains some aging tests. Most of the time, these tests used simplified power or current profiles designed specially to be as representative as possible of the reality. The use of a real profile could improve the reliability of the approach but needs to know how to select the typical profile from an available database. This article shows the methodology used to analyze a database of 10 electric vehicles monitored during 2 years. Different mathematical methods (Pearson and Spearman coefficient of correlation, Shannon entropy, principal component analysis, K-means, …) were applied to sort the essential variables and classify the uses of the vehicle. Representative classes of uses were then gathered to constitute a profile used in aging tests. The aging results with this real-life type profile and with an adjusted WLTC (Worldwide Harmonized Light Vehicles Test Cycles) profile are presented and compared. The effectiveness of the use of the WLTC profile for aging tests in real life automotive application is shown. [ABSTRACT FROM AUTHOR]

The battery lifetime of Electric vehicles (EVs) is affected by hot temperatures and high charging and discharging effective battery current. Hybrid energy storage systems (HESS) coupling the best attributes of the battery with supercapacitors (SCs) help extend the battery lifetime and improve the EV storage performances. The key to a successful HESS at extending the battery lifetime is to adopt the appropriate Energy Management System (EMS) that ensures the best power sharing between battery and SCs. This paper proposes an innovative real-time optimization-based EMS with low computational costs and high adaptability to variable and commute driving profiles. The proposed EMS is organized in two levels. The lower level implements a rule-based frequency power sharing control. The upper level performs Reinforcement Learning (RL) optimizations to learn and adapt the best power sharing configuration considering real-time information and actual load conditions. An experimental test bench is developed and experimental measurements are conducted. The obtained results confirmed the effectiveness of the proposed EMS to provide the best trade-offs between simple implementation, computation time, solution optimality, real-time performance, and good adaption to variable driving conditions. [ABSTRACT FROM AUTHOR]

The driving range of electric vehicles is a complex issue. In simulation, this range is determined by coupling a battery model and a traction model of the vehicle. But most of the battery models used for such studies do not take into account the interaction between the temperature of the battery (impacting its electrical parameters) and the traction model of a studied EV. In this paper, a battery electro-thermal model (with all electrical parameters dependent upon the temperature) is dynamically coupled with the traction model of an electric vehicle. Simulation results are provided to show the impact of the temperature on the driving range. The initial battery model (without temperature dependence) leads to an overestimation of the driving range of 3.3% at −5 °C and an underestimation of 2.5% at 40 °C. [ABSTRACT FROM AUTHOR]

Energy storage elements such as supercapacitors are widely used in high-power applications. However, due to single cell voltage limitation, an energy storage system with a large number of supercapacitors is often employed. Energy management systems are associated to energy storage systems in order to assure user and equipment safety. Balancing circuits, which enable the equalization of the voltage of each element in series, are a part of the energy management system device. The work presented in this paper aims to enhance the lifetime of energy storage systems. It relies on better controlling balancing circuits on the terminals of the storage system elements. With the conventional function of balancing circuit, the energy storage system is limited by its weakest element that may fail prematurely. Thus, a new balancing approach is presented, discussed, and analyzed. It is based on the elements degradation level prediction. The model predictive control used with the new approach aims to equalize aging speed between elements of a module and ensures a maximum lifetime to the energy storage system. A comparison with the conventional control shows that adopting this new approach, with the same equipment, can enhance the storage system's lifetime by dozens percent. [ABSTRACT FROM AUTHOR]

Compared to Li-ion batteries, supercapacitors (SCs) boast longer lifespan, higher power density, and wider operational temperature range. Nevertheless, SCs are expensive (almost 40 times more expensive per watthour than Li-ion batteries). SCs aging is critical. Two types of aging tests are usually performed. Floating aging tests apply constant constraints (voltage and temperature), and cycling aging tests apply multiple charges and discharges. We focus our study on floating aging [corresponding for instance to parking mode for electrical vehicles (95% of the time) or uninterruptible power supplies (UPSs) when they are not solicited (quite all the time)]. All results in the literature conclude that voltage level is an acceleration factor for SC aging. According to the literature, it would be interesting to totally discharge the SCs when they are not in active use (i.e., when the UPSs or vehicles are turned off) to improve their lifespan. Contrary to the literature forecasts (i.e., lower voltage increases lifespan of SC), the results obtained in this paper by alternating voltage resets (0 V, 60 °C) and floating aging (2.8 V, 60 °C) show that discharging even very few times the SCs shortens their lifespan drastically. Physical interpretations are presented to explain aging increase with voltage resets. [ABSTRACT FROM AUTHOR]

Supercapacitors (SCs) impedance modeling represents one important key to get information for SCs health monitoring and simulation. As a matter of fact, SCs behavior is dependent on various parameters such as pore size distribution of electrodes, electrolyte state, temperature, aging, etc. We propose in this study to model SC taking into account physical considerations. Basing on the theory on homogenous structure impedance, we first define the single pore model using the uniform size of pores distribution. In the second step, we attempt to generalize this circuit model considering an electrode with different pores sizes or different penetrabilities of the pores. This model called multipore (MP) model (or multipenetrability model) has been developed by our laboratories. This model allows analyzing the behavior of SC by modeling each group of electrode pores as a branch of an electrical equivalent circuit. This paper is the first in the literature to give a simple and reproducible method for MP model parameters identification. The validity of the identification method will also be verified at different SC aging rates thanks to experimental aging tests. [ABSTRACT FROM AUTHOR]

This paper proposes an original model for supercapacitors that takes into account both calendar aging and cycling aging. A state variable is used to quantify the state of aging. This model is based on a series of recent experiments conducted in various research laboratories on the same technology (Maxwell Technology) and serves to represent the degradation of equivalent series resistance and capacitance. This model is particularly useful in an aging-aware life-cycle cost analysis. We show that an accurate aging model is critical to the design of an energy storage system that optimizes the economic life-cycle cost. Such an optimization is particularly applicable for smoothing in offshore systems such as direct wave energy converters, which require both cost reduction and high reliability. The influence of an aging model in the sizing process is investigated toward the end of this paper. [ABSTRACT FROM AUTHOR]

Abstract: The study of traction batteries real-world usage in vehicular applications faces a handful of serious challenges. To date, we are unable to accurately predict the cycle life of a battery under real-world operating conditions. There are a couple of reasons for that; on the one hand, the battery technology evolves rapidly whereas the battery cycle life testing requires large amounts of time and on the second hand, we know little about real-world duty profile of batteries. The work presented here intends to tackle this latter issue. In this paper, we evaluate real-world collected data of battery usage in an instrumented neighbourhood electric vehicle, using a new approach based on the concept of duty pulses. This automated method relies on the K-means clustering algorithm and aims at classifying duty pulses according to their current and energy distributions. We present the way data must be prepared and we discuss the results of the clustering. We report on the duty profiles of this vehicle’s battery under various driving conditions. [Copyright &y& Elsevier]

In the field of urban transport, supercapacitors are submitted to relative high charge and discharge currents and therefore significant heat generation occurs. It has been shown that the temperature has a great influence on the aging mechanism of supercapacitors and, by consequence, on the lifetime of the system. That is why the thermal management becomes a key issue in the study of the performance of a supercapacitors stack. In this paper, thermal modeling of a supercapacitors stack is presented and a matrix representation of the model is deduced. Validation of the model has been carried out using measurement on a developed test bench. Sensitivity of the model according to input uncertainties is finally discussed. [ABSTRACT FROM PUBLISHER]