[show abstract][hide abstract] ABSTRACT: Fuel cells are electrochemical energy converters which allow transformation of the chemical energy of a fuel to electricity through oxido-reduction reaction. The voltage of an elementary cell is usually near 1 V in open circuit and around 0.6 V in nominal conditions of power generation. Fuel cells are then by essence low voltage sources, so that for most practical applications, power management is carried out by electronic converters, allowing in particular to rise the voltage to usual application levels.In this paper, we propose to take advantage of this low voltage for a specific application stack such as superconducting coils power supply. At present, such applications are dealt with the use of specific electronic power supplies, exhibiting in most cases a huge volume and/or a low energy yield.
International Journal of Hydrogen Energy 05/2013; 38(16):6773–6779. · 3.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: Employing fuel cell as main source requires increasing and regulating its output voltage. In this paper, flatness based controllers for a hybrid source system, which contains fuel cell (FC) and supercapacitor (SC), are presented. Nonisolated DC/DC converters are used for achieving the hybrid power source and evaluating the performances of the flatness based controllers. The FC is used as the main power source. The SC is employed as auxiliary source to deal with the slow transient response of FC. The limitation of FC current changing rate is taken into account. The hybrid source including the proposed controller is validated by experimental results. Controls of the whole systems are realized by energetic trajectories planning based on flatness properties of the systems.
Power Plant and Power System Control Symposium, IFAC PPPSC 2012. 09/2012;
[show abstract][hide abstract] ABSTRACT: Fuel cells are complex systems which can be considered as low voltage electrical source. Preliminary investigations led with a single proton exchange membrane fuel cell, either short-circuited or hybridized by discharged supercapacitors, could evidence the behavior as a current source, in which the current is directly controlled by the hydrogen flow rate. This operation mode imposes the fuel cell voltage to be far below the threshold recommended by the fuel cell manufacturer. The paper deals with this unusual application of fuel cell and its benefits such as the high quality current, free of oscillations that might be upgraded for superconducting coil supply. To investigate this operation mode an appropriate single fuel cell model is established and then validated by means of a test bench equipped with a proton exchange membrane single fuel cell.
International Journal of Hydrogen Energy 09/2012; 37(17):12481–12488. · 3.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: This article deals with a PEMFC (proton exchange membrane fuel cell) electrical model based on a 1D analog representation of mass transport phenomena, and taking into account the influence of gas supply conditions on fuel cell voltage. By using an electrical analogy to describe transport of gaseous species in GDLs (gas diffusion layers), and water distribution in the membrane, the model can be directly imple-mented in standard simulation softwares used in electrical engineering (such as Saber, in our case), so that it can be easily employed for the simulation of fuel cell electrical systems. The paper explains how the analog model is obtained from mass transport equations, then it presents validation tests carried out in both steady-state and transient regimes on a PEM single cell bench.
Renewable Energy 08/2012; 44:128-140. · 2.99 Impact Factor
[show abstract][hide abstract] ABSTRACT: A renewable energy hybrid power plant, fed by photovoltaic (PV) and fuel cell (FC) sources with a supercapacitor (SC) storage device and suitable for distributed generation applications, is proposed herein. The PV is used as the primary source; the FC acts as a backup and a long-term storage system, feeding only the insufficiency power (steady-state) from the PV; and the SC functions as an auxiliary source and a short-term storage system for supplying the deficiency power (transient and steady-state) from the PV and the FC. A mathematical model (reduced-order model) of the FC, PV, and SC converters is described for the control of the power plant. Using the intelligent fuzzy logic controller based on the flatness property for dc grid voltage regulation, we propose a simple solution to the dynamic optimization and stabilization problems in the power system. This is the key innovative contribution of this research paper. The prototype small-scale power plant implemented was composed of a PEMFC system (1.2 kW, 46 A), a PV array (0.8 kW), and a SC module (100 F, 32 V). Experimental results validate the excellent control algorithm during load cycles.
[show abstract][hide abstract] ABSTRACT: This paper presents a new control strategy for dc-link stabilization in weak transportation networks that use supercapacitors as the energy storage unit. A two-port isolated converter based on a dual active bridge topology is presented, and a reduced-order mathematical model of the system is described for power plant control. Using a nonlinear control approach based on the flatness property, we propose a simple solution to dynamic and stabilization problems in the power electronics systems of transportation networks. The controller design parameters are independent of the operating point at which interactions between the dc main substation, loads and energy storage unit are taken into account by the controller. To validate the proposed method, a hardware system is modeled using digital estimation with a DS1103 dSPACE controller platform. We analyze a prototype small-scale network that uses a 1 kW six-pulse rectifier as a dc substation and a 250 F, 32 V supercapacitor bank as an energy storage substation. Finally, the utility of the control algorithm is validated using experimental results measured during motoring mode, ride-though, and braking mode drive cycles.
[show abstract][hide abstract] ABSTRACT: This paper presents an energy management method in an electrical hybrid power source (EHPS) for electric vehicular applications. The method is based on the flatness control technique (FCT) and fuzzy logic control (FLC). This EHPS is composed of a fuel cell system as the main source and two energy storage sources (ESSs)-a bank of supercapacitors (SCs) and a bank of batteries (BATs)-as the auxiliary source. With this hybridization, the volume and mass of the EHPS can be reduced, because the high energy density of BAT and high power density of SC are utilized. In the proposed novel control strategy, the FCT is used to manage the energy between the main and the auxiliary sources, and the FLC is employed to share the power flow in the ESS between the SC and the BAT. The power sharing depends on the load power and the state of charge of the SC and the BAT. EHPS is controlled by the regulation of the stored electrostatic energy in the dc buses. The main property of this strategy is that the energy management in the power source is carried out with a single general control algorithm in different operating modes, consequently avoiding any algorithm commutation. An EHPS test bench has been assembled and equipped with a real-time system controller based on a dSPACE. The experimental results validate the efficiency of the proposed control strategy.
IEEE Transactions on Vehicular Technology 03/2011; · 2.06 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper presents a fuzzy control law based on differential flatness approach for distributed dc generation (nonlinear system) supplied by a fuel cell (FC) (main source) and supercapacitor (auxiliary source). The main technical feeble point of FCs is slow dynamics because the power slope is limited to prevent fuel starvation problems, improve performance and increase lifetime. The very fast power response and high specific power of a supercapacitor complements the slower power output of the main source to produce the compatibility and performance characteristics needed in a load. The energy in the system is balanced by dc bus energy regulation (or indirect voltage regulation). A supercapacitor module functions by supplying energy to regulate the dc bus energy. The FC, as a slow dynamic source in this system, supplies energy to the supercapacitor module in order to keep it charged. Using the intelligent fuzzy control law based on the flatness property, we propose straightforward solutions to hybrid energy management, dynamic and stabilization problems. To validate the proposed method, a hardware system is realized with analog circuits, and digital estimation is accomplished with a dSPACE controller. Experimental results with small-scale power plant (a polymer electrolyte membrane FC of 1200 W, 46 A and a supercapacitor module of 100 F, 500 A, and 32 V) in a laboratory corroborate the excellent control scheme during a load cycle.
[show abstract][hide abstract] ABSTRACT: A dysfunctioning of the heart of the fuel cell might affect the whole system, and thus the demand of electric power. To be able to estimate the damage of the fuel cell, the default has to be detected precisely. As it is well known, the physico-chemical processes involved in proton exchange membrane fuel cell (PEMFC) are strongly coupled, as such that putting apart a phenomenon by experimental measurement can be quite difficult. To this end, simulations of an online or offline diagnosis, for instance by electrochemical impedance spectroscopy (EIS) method are interesting. It can help also to analyze what happens locally in the heart of cell. The main aim of the presented work is to highlight the interest of using PEMFC dynamic model as a diagnosis tool. To illustrate this potential, EIS method has been implemented in 2D dynamic single cell in both simulated cases of defective and healthy cells.
Fuel and Energy Abstracts 01/2011; 36(17):10884-10890.
[show abstract][hide abstract] ABSTRACT: This paper presents a new steady state model which contains fewer polarisation curve fitting parameters compared to other semi-empirical models. The established model is also defined at no load operation and can be fitted perfectly to the static polarisation curve for a wide range of cell currents. The model links the fuel cell voltage to the current by a simple function to which various useful derivative laws can be applied. As a result, many analytical expressions, for example, polarisation resistance or power density, can be evaluated directly from the model.
The European Physical Journal Applied Physics 01/2011; 54. · 0.71 Impact Factor
[show abstract][hide abstract] ABSTRACT: Employing fuel cell (FC) as main source requires increasing and regulating its output voltage. In this paper, nonisolated dc-dc converter with high voltage ratio is proposed to interface between the FC and high-voltage dc bus. To take into account the low-voltage-high-density characteristics of power sources, a cascaded structure composed of two subconverters in cascade has been chosen and allows obtaining high voltage ratio. The choice of each subconverter is based on source requirements and its performances. Consequently, in this paper, a converter consisting of two-interleaved boost converter is chosen as first subconverter and a three-level boost converter is chosen as second subconverter. Control of the whole system is realized by energy trajectory planning based on flatness properties of the system. The design of trajectories is explained and allows respecting the fuel-cell constraints as main power source. To ensure correct design of the energy trajectories, a noninteger power-law function is used to model the static characteristic of the FC. This law allows investigating the effect of humidity and temperature on the dynamics of the proposed system. The control of both current and voltage balance across the output serial capacitors of the three-level boost converter is ensured by nonlinear controllers based on a new nonlinear model.
IEEE Transactions on Industrial Electronics 01/2011; · 5.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this paper, the control approaches of linear proportional-integral (PI) and nonlinear flatness-based estimation for dc link stabilization for fuel cell/supercapacitor hybrid power plants are compared. For high power applications, 4-phase parallel boost converters are implemented with a switching interleaving technique for a fuel cell (FC) converter, and 4-phase parallel bidirectional converters are implemented with a switching interleaving technique for a supercapacitor converter in the laboratory. As controls, mathematical models (reduced-order models) of the FC converter and the supercapacitor converter are given. The prototype small-scale power plant studied is composed of a PEMFC system (the Nexa Ballard FC power generator: 1.2 kW, 46 A) and a supercapacitor module (100 F, 32 V, based on Maxwell Technologies Company). Simulation (by Matlab/Simulink) and experimental results demonstrate that the nonlinear differential flatness-based control provides improved dc bus stabilization relative to a classical linear PI control method.
[show abstract][hide abstract] ABSTRACT: In this paper, a novel control strategy based on combination of the Flatness based Control Technique (FCT) and the Fuzzy Logic Control (FLC) is developed and investigated to control an Electrical Hybrid Power Source (EHPS). The main property of this strategy is that the system power flow in different operating modes is managed with the same control algorithm (without algorithm commutation). This EHPS is composed of a Fuel Cell system (FC) as the main source and two Energy Storage Devices (ESDs), a bank of SuperCapacitors (SC) and a bank of BATteries (BAT), as the auxiliary sources. Volume and mass of the EHPS can be reduced in this hybridization since the high energy density of the BAT and the high power density of the SC is used. The power flows between the fuel cell, the ESDs and the load is controlled by the FCT and the power sharing between the ESDs (a SC and a BAT) is carried out by the FLC. The power sharing depends on the load power, SOC of the SC and the BAT. To validate the proposed control of the EHPS, the implementation results are presented. The experimental results prove the validity of the proposed approach.
Energy Conversion Congress and Exposition (ECCE), 2010 IEEE; 10/2010
[show abstract][hide abstract] ABSTRACT: LIFEMIT project deals with Energy management, storage systems within the frame of hybrid and electric motorization. It deals more particularly with deployments of lithium-ion batteries in heavy vehicle application. It supports the development of tools and demonstrates how virtual prototyping and a system approach lower the risk for lithium-ion batteries development. The partnership includes: Nexter, military vehicles manufacturer; Saft, a world specialist in the design and manufacture of high-tech batteries for industry; Eigsi L3E , laboratory experts in electric and renewable energy; GREEN-ENSEM-INPL, laboratory experts in electronics and power electronics; and the IMS laboratory, more particularly for its expertise in electronics. The first result is obtained by the development and the experimental validation of an embedded algorithm which sharply increases practical lithium-ion battery power without accelerating its ageing. The second main result is the demonstration that virtual prototyping associated with system architecture analysis are powerful tools for battery design, especially for large lithium-ion battery systems.
Vehicle Power and Propulsion Conference (VPPC), 2010 IEEE; 10/2010
[show abstract][hide abstract] ABSTRACT: All electrochemical batteries are characterized by an electrical behavior that depends on temperature, state of charge, and current. In the case of lithium-ion accumulators, the energetical behavior is moreover deeply marked by line effects, due to the porosity of both electrodes. This paper deals with investigations on an accurate energetical modeling of lithium-ion battery. It is shown in particular that electrode porosity can be taken into account by means of a diffusion impedance represented by a capacitive transmission line. An energetical model, which couples this line with a current independent capacitance, is proposed and characterized at constant temperature (20°C) over different state-of-charge intervals (5%) and for different currents. Reactant diffusion within the electrolyte and relaxation period after discharge are investigated as well. Validation tests carried out on a 6.8-Ah lithium-ion element are conclusive.
IEEE Transactions on Energy Conversion 10/2010; · 2.43 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper presents an innovative control law for distributed dc generation supplied by a fuel cell (FC) (main source) and supercapacitor (auxiliary source). This kind of system is a multiconverter structure and exhibits nonlinear behavior. The operation of a multiconverter structure can lead to interactions between the controls of the converters if they are designed separately. Typically, interactions between converters are studied using impedance criteria to investigate the stability of cascaded systems. In this paper, a nonlinear control algorithm based on the flatness properties of the system is proposed. Flatness provides a convenient framework for meeting a number of performance specifications for the hybrid power source. Using the flatness property, we propose simple solutions to hybrid energy management and stabilization problems. The design controller parameters are autonomous of the operating point; moreover, interactions between converters are taken into account by the controllers, and high dynamics in disturbance rejection is achieved. To validate the proposed method, a hardware system is realized with analog circuits, and digital estimation is accomplished with a dSPACE controller. Experimental results with small-scale devices (a polymer electrolyte membrane FC of 1200 W, 46 A and a supercapacitor module of 100 F, 500 A, and 32 V) in a laboratory corroborate the excellent control scheme during a motor-drive cycle.
IEEE Transactions on Energy Conversion 10/2010; · 2.43 Impact Factor