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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 a...

Combining hybrid Electrical Storage Systems (ESS) is solving many electrical devices problems while using them separately. Batteries present limited charge/ discharge cycles which affect their lifetime and increase their cost. In fact, the lithium ion (li-ion) batteries are more and more studied and evolving in term of cycles. They provide high energy density while the supercapacitors (SCs) ensure long lifetime cycles and operate at large range temperatures. This paper presents a control strategy of battery/ SCs in Uninterruptible Power Supply (UPS) application in order to improve the efficiency, lifetime and reduce the cost. A comparison of using the hybridization with and without control system was established to highlight the power split between the two storage systems. A comparison of lead acid and li-ion battery was established. Finally, different ESS’ financial study was set.

International audience; Energy management of Battery/Supercapacitors (SCs) hybrid energy storage system (HESS) aims to reduce RMS battery current values and enhance the battery lifetime. This paper presents a reinforcement learning (RL) based energy management strategy for Electric Vehicles (EV). This approach allows for learning in real time the optimal power flow distribution between battery and supercapacitors starting from historic of the observation of RMS current of battery. The power management problem is presented with RL formulation verifying the electrical HESS constraints. The presented framework uses the RL technique to control the power flow distribution leading to the minimization of the RMS battery current. Particularly, we propose a methodology that generates optimal frequency sharing policy between battery and SCs taking into account the load variations of the EV dynamically in real time. Numerical simulations carried out on Matlab/Simulink confirmed the convergence of the RMS battery current to the optimal value without any prior knowledge of the driving conditions. The proposed framework aims to adapt automatically the power management policy to the optimal solution.

International audience; Battery/Supercapacitors combination offers superior performances for a hybrid electric energy storage system in Electric Vehicles. This paper, presents a frequency power sharing strategy to get the best use of complementarity between battery and supercapacitors. Storage devices are sized based on reduced scale specifications for the studied EV. Power and current waveform simulation results are shown for each storage device due to the use of a frequency power sharing policy. Various power split configurations are analyzed to study their effect on battery current waveforms. Optimal frequency sharing policy for the battery/SCs hybrid reducing RMS battery current is obtained. The best use of battery/SCs association provides significant improvements of Electric Vehicle performances in terms of battery lifetime and amortized cost.

International audience; The success of hybrid electrical storage systems which combines batteries and supercapacitors is related to the manner how these devices are managed. In this paper, optimal use of the complementarity between batteries and supercapacitors in electric vehicles is studied. First, storage devices are sized based on reduced size specifications of the electric vehicle. Then, power waveforms for each storage device obtained by simulation using the frequency sharing strategy are presented. Different values of filter constant are therefore analyzed to show the variation effect of power sharing strategy on battery current waveforms. The optimal filter constant is finally determined. It offers reduced values of RMS battery current and enhancement of battery service life.

International audience; Hybrid electrical energy storage systems (HESS) show promise for solving the problems and exploiting the benefits of heterogeneous electrical storage systems (ESS). This paper compares the performance of a lead-acid battery/supercapacitors hybrid to that of a battery alone under pulsed loads. Two types of aging protocols, using pulsed and smoothed power, were carried out on VRLA batteries at 40 °C. These protocols typically illustrate a single or hybrid battery’s use for an Uninterruptible Power Supply. In HESS, the supercapacitors smooth the power demand applied to the battery, and, when idle, the battery charges the supercapacitors. The same amount of energy is extracted from the battery during both protocols. The experiment indicated that the battery alone performs 150 ten-minute-cycles before reaching the end of its life. In the hybridized battery, the power dissipated was reduced to 36% of that used by the battery alone, and the number of cycles increased by 70%. The use of a hybrid also reduced the battery’s capacity fade by 60% and its increase of internal resistance by 83%. Finally, the amortized cost of the hybrid system was 17.6% less than that of the battery alone.

International audience; This paper proposes a comparative study of current-controlled 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.

The effect of lead-acid battery/supercapacitors combination on battery service life is addressed in this paper. With the help of a cycling bench, accelerated aging tests of VRLA batteries were carried out. Pulsed power and smoothed power profiles were applied to the battery under 40°C. These tests reproduce the battery operation with and without supercapacitors hybridization. For the hybrid system, the supercapacitors smooth the power applied to the battery which in turn charges the supercapacitors at a low load rate. So, the supercapacitors satisfy significant peak power demands of the application. After 150 of pulsed power cycles, a decrease of 20% of the initial battery capacity was observed indicating its end of life. On the other hand, smoothed power applied to the battery enhances with 1.7 times its lifetime compared to a stand-alone battery. The fade of the battery capacity and the increase of the internal resistance are shown to be slowing down. In our study, the improvement of battery service life was experimentally quantified, which represents the novelty of this work.

International audience; In this paper, a system for predictive maintenance of electrolytic capacitors in static converters is presented. The failure of these capacitors leads to an increase of their equivalent series resistance ESR and therefore the voltage ripple across the components rises. This waveform must be filtered to extract its fundamental component to get a good image of ESR. For power supply with variable switching frequency, electronic filter with controlled center frequency is realised. This center frequency is adjusted by the V.C.O. of converter's control circuit. The voltage ripple also depends on the converter parameters such as input voltage, output current and ambient temperature. A reference system taking into account all these parameters is determined for sound capacitors. A good interpretation of the increase of the ripple voltage allows then, the determination of ESR value. The remaining time to the failure of the capacitors is then deduced.

International audience; 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.

ISBN: 978-1-4673-1168-7; International audience; This work presents the study of the reduction in battery stresses by using supercapacitors (SC's) in a 500 kVA rated UPS. We aim at investigating the optimal SC-battery combination versus the SC's 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 combining the two types of storage devices are shown. The study emphasizes on UPS autonomous running for grid faults lasting few minutes, the supercapacitors supply the transient demand of power and the battery is responsible for the smoothness requirement of energy. 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. They reflect the potential decrease in battery stresses due to the SC's. A thorough analysis involving optimal study proposes to draw the optimal SC's number and filter constant from the variation of the aforementioned parameters versus the cost of the SC's.

International audience; In this paper we present a strategy to combine supercapacitors with the battery in a 500 kVA rated uninterruptible power supply. First the sizing of the supercapacitors and battery taking into account the UPS specifications is presented. The validation of the supercapacitor and the battery models is carried by using MATLAB/SIMULINK. Second, the power sharing system between the supercapacitors and the battery is presented. The supercapacitors are added as higher energy storage to overcome the full load power during short time grid failures and to boost peak power during backup time of few minutes. The UPS waveforms obtained by simulation are presented and analyzed.

Electrolytic filter capacitors are frequently responsible for static converter breakdowns. To predict these faults, a new method to set a predictive maintenance is presented and tested on two types of converters. The best indicator of fault of the output filter capacitors is the increase of ESR (equivalent series resistance). The output-voltage ripple /spl Delta/V/sub o/ of the converter increases with respect to ESR. In order to avoid errors due to load variations, /spl Delta/V/sub o/ is filtered at the switching frequency of the converter. The problem is that this filtered component is not only dependent on the aging of the capacitors, but also on the ambient temperature, output current, and input voltage of the converter. Thus, to predict the failure of the capacitors, this component is processed with these parameters and the remaining time before failure is deduced. Software was developed to establish predictive maintenance of the converter. The method developed is as follows. First, a reference system including all the converter parameters was built for the converter at its sound state, i.e., using sound electrolytic filter capacitors. Then, all these parameters were processed and compared on line to the reference system, thereby, the lifetime of these capacitors was computed.

International audience; The failure of electrolytic capacitors is the cause of most breakdowns of static converters. The function of these capacitors is to filter and to store electrical energy. Accelerated aging tests showed that the increase of the internal resistance ESR of the capacitors is a good indicator of their faulty state. The filter function is affected by the capacitors wearout on the one hand. At high frequency, the voltage ripple at the terminals of the capacitors increases according to ESR rise. On the other hand, the storage function is not much influenced by the capacitors aging. As static converters work most of the time at variable load, high transient values of the voltage ripple occur when output current changes that can induce false alarms. These transients are verified theoretically and experimentally. In order to avoid these transients effects, we suggest to monitor the fundamental component of the voltage ripple. This latter waveform is the best signature of the capacitors state. The ESR of the capacitors and the time before their failure are deduced from the processing of this waveform with other converter parameters such as input voltage, output current and ambient temperature.