Melika Hinaje

Comparative Study of Fuel-Cell Vehicle Hybridization with Battery or Supercapacitor Storage Device

This paper studies the impact of fuel-cell (FC) performance and control strategies on the benefits of hybridization. One of the main weak points of the FC is slow dynamics dominated by a temperature and fuel-delivery system (pumps, valves, and, in some cases, a hydrogen reformer). As a result, fast load demand will cause a high voltage drop in a short time, which is recognized as a fuel-starvation phenomenon. Therefore, to employ an FC in vehicle applications, the electrical system must have at least an auxiliary power source to improve system performance when electrical loads demand high energy in a short time. The possibilities of using a supercapacitor or a battery bank as an auxiliary source with an FC main source are presented in detail. The studies of two hybrid power systems for vehicle applications, i.e., FC/battery and FC/supercapacitor hybrid power sources, are explained. Experimental results with small-scale devices (a polymer electrolyte membrane FC of 500 W, 40 A, and 13 V; a lead-acid battery module of 33 Ah and 48 V; and a supercapacitor module of 292 F, 500 A, and 30 V) in a laboratory authenticate that energy-storage devices can assist the FC to meet the vehicle power demand and help achieve better performance, as well as to substantiate the excellent control schemes during motor-drive cycles.

Modeling and Control of Fuel Cell/Supercapacitor Hybrid Source Based on Differential Flatness Control

Fuel-cell vehicles (FCVs) with energy storage (ES) device(s) could result in improved lifetime, performance, fuel economy, and reduced cost. This paper presents the utilization of an ES device consisting of a supercapacitor bank for future electric vehicles with a hydrogen fuel cell (FC) as the main power source. The study mainly focuses on the innovative control law based on the flatness properties for a FC/supercapacitor hybrid power source. Utilizing the flatness principle, we propose simple solutions to the hybrid energy-management and stabilization problems. A supercapacitor module, as a high dynamic and high-power density device, functions to supply energy to regulate the dc-bus energy. The FC, as a slower dynamic source in this system, functions by supplying energy to keep the supercapacitor module charged. To ensure energy-efficient operation of the FC stack, the output current ripple of the FC stack is minimized by parallel boost converters with an interleaving switching technique for a high-frequency ripple by the supercapacitor for a low-frequency ripple. To authenticate the proposed control laws, a test bench is realized in the laboratory. The control algorithm (energy and current control loops) is digitally implemented by dSPACE controller DS1103. Experimental results with small-scale devices (a proton exchange membrane FC (PEMFC) of 500 W, 50 A, and 10 V and a supercapacitor bank of 250 F, 32 V, and 500 A) substantiate the excellent performance during load cycles.

Control strategy of solar/wind energy power plant with supercapacitor energy storage for smart DC microgrid

This paper presents an original control algorithm for a hybrid energy system with a renewable energy source: a photovoltaic (PV) array and a wind turbine (WD). A single storage device, a supercapacitor (SC) module, is in the proposed structure. The very fast power response and high specific power of a SC complements the insufficient power output of the main sources to produce the compatibility and performance characteristics needed in a load. To verify the proposed principle, a hardware system is realized with analog circuits and with numerical calculation (dSPACE) for the energy control loops. Experimental results with small-scale devices, namely, a wind turbine generator (500 W), a photovoltaic array (800 W, 31 A) manufactured by the Ekarat Solar Company and a SC module (100 F, 32 V), illustrate the excellent energy-management scheme during load cycles.

Analytical modelling of a thin liquid metal layer submitted to an ac magnetic field

A cylindrical thin liquid metal layer is submitted to a uniform ac magnetic field. When the intensity of the electromagnetic field exceeds a critical value, an opening in the liquid is shaped from outside to inside. At a given intensity of the electromagnetic field, this opening is in a frozen state, that is, the liquid metal layer reaches a new equilibrium shape. In this paper, we show that this equilibrium corresponds to a minimum of the total energy of the system. This total energy is equal to the sum of the magnetic energy and the mechanical energy. The magnetic energy is computed by assuming that the induced eddy current flowing through the liquid metal layer is concentrated in the cross-section Sc equal to the product of the skin depth and the thickness of the layer. This assumption leads us to study an equivalent electrical circuit.The mechanical energy is composed of the potential energy and the surface energy.

A computation and a use of the magnetic energy in a thin liquid metal submitted to an AC magnetic field

A thin layer of liquid metal is submitted to a time-dependent, but uniform, magnetic field. The liquid gets an equilibrium shape that depends on the magnetic field intensity. A numeric model, that allows us to explain this behavior, is emphasized

Determination of stable shapes of a thin liquid metal layer using a boundary integral method

This paper deals with a thin liquid metal layer submitted to an ac magnetic field. Experimentally, we have noticed that even if the system (inductor+liquid metal) is axisymmetric, when an ac magnetic field is applied the symmetry is broken. The observed deformations of the liquid metal are in three dimensions. Therefore, our aim is to investigate this deformation using a numerical method as boundary element method in three dimensions.

Solar Electric Motor on Superconducting Bearings: Design and Tests in Liquid Nitrogen

The concept of the motor, described here, has been presented for the first time in 1959. It allows us to convert light energy into mechanical energy, without the need of any brushes or other power electronics. An original improvement that we have made to this structure concerns the superconducting suspension which tends to limit frictions and ensures natural stability of the rotor. The second major novelty is that we have designed the entire motor for operating in liquid nitrogen. The motor structure is detailed in this paper, including the electromagnetic design, the electrical and mechanical equations. Two different configurations of superconducting bearings are studied in order to make levitate the rotors. Finally, for the designed motors, only 10% of the installed onboard power is converted into mechanical power. All the experimental results, especially the speed of the motor, are consistent with the estimated values by the model.

Model based control of modified four-phase interleaved boost converter for fuel cell power source for mobile based station

This paper proposes a modified 4-phase interleaved converter for the FC power source for mobile based station applications. The ripple and harmonic content of the FC current is one of the various phenomena influencing FC lifetime. The main objective of this research is to minimize inductor size, capacitor, current/voltage ripples, and harmonic content. The main contribution is to presents a control law for a distributed dc generation supplied by a FC generator. Classically, to control the voltage, the current, or the power in the converter, a linearized technique is often used to study the stability and to select the controller parameters of the nonlinear converter. In this paper, a nonlinear-control algorithm based on the flatness property of the system is proposed. Utilizing the flatness property, we propose simple solutions to the system performance and stabilization problems. Design controller parameters are autonomous of the operating point. To authenticate the proposed control laws, a test bench is realized in the laboratory. The control algorithm is digitally implemented by dSPACE controller DS1104. Experimental results with small-scale device (a proton exchange membrane FC (PEMFC) of 1.2 kW, 26 V) substantiate the excellent performance during load cycles.

Nonintrusive Diagnosis of a PEMFC

Many reasons may cause malfunction of a proton exchange membrane fuel cell (FC) stack. Moreover, a single defect cell can affect the whole stack functioning; therefore, the localization of this cell is crucial as well as identifying the root causes for such malfunctioning. The diagnosis tool has to be nonintrusive and easy to replicate to a new FC system. This paper explores paths to achieve such monitoring based on the use of the magnetic field induced by the FC stack internal currents. Designing and using a 3-D simulation tool allows to establish a cause and effect relationship between FC defects and specific magnetic signatures. This preliminary work enables to determine the required magnetic sensor accuracy, the sensor orientation and location as well as the experimental precautions for relevant measurements.

Performance investigation of linear control and nonlinear control based-on flatness approach for a DC link stabilized fuel cell/supercapacitor hybrid power plant

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.