Abstract: This paper presents a general formulation of the energy management in a hybrid vehicle with fuel cell and
supercapacitors. The approach proposed in this paper consists in keeping the sum of the energy stored in
the supercapacitors and the vehicle kinetic energy constant. The goal of the strategy is to minimize the
fuel cell system maximum power and its fuel consumption as well as keeping a smooth dynamical
behaviour.
A comparison with a stand-alone fuel cell powered vehicle taken as a reference case study is carried out.
Results show that the fuel cell power can be reduced to 30 % and the fuel economy improved by 15 %.
Abstract: AbstractâThis paper presents a hardware-in-the-loop experimental rig for testing a proton exchange membrane fuel cell (PEMFC) driving an electrical vehicle. The PEMFC includes an air-management system with a scroll compressor driven by a highperformance sensorless induction motor drive. The sensorless technique is based on a neural-network-based speed observer, i.e., the total least-squares EXIN full-order observer. The whole system is driven by a classic European Driving Cycle (EEC Directive 90/C81/01). An experimental rig has been built to test the system. The torqueâspeed characteristics of a real scroll compressor have first been measured. Then, these characteristics have been emulated by a brushless interior-mounted permanent-magnet machine controlled in torque. This emulated scroll compressor has been driven by a sensorless field-oriented controlled induction motor drive. The experimental results show that the system attains a global efficiency of about 50% and that the speed estimation accuracy is high at both very low and very high speeds with a stable behavior at zero speed at no load, which is particularly difficult to achieve for model-based sensorless techniques.
Abstract: This paper proposes a technological solution with a scroll compressor driven by a high performance induction machine drive for the air management of PEMFC (Proton Exchange Membrane Fuel Cells) for automotive applications. The torque-speed characteristics of a real scroll compressor have been measured and then emulated by a brushless IMPM (internal Mounted Permanent Magnets) machine controlled in torque. This emulated scroll compressor has been driven by a field oriented controlled (FOC) induction motor drive. The whole car model as well as the PEMFC have been implemented by software on the same DSP which implements the drive control algorithm; in this way the hardware-in-the-loop structure has been employed for emulating the behaviour of a real car including the electrical supply of the PEMFC. The whole system has been tested with a classic European driving cycle. Two experimental rigs have been setup, one for characterizing the scroll compressor and the other for emulating the entire vehicle. The experimental results have shown that the speed reference profile, obtained during a urban driving cycle, is followed correctly and that the tank-to-wheel efficiency remains at quite high values confirming the goodness of the proposed technological solution. The hardware-in-the-loop approach of the experimental rig allows tests to be performed to verify the operation in steady and transient states with low cost and reduced employment of the Fuel Cell stack, with resulting increased durability.
Abstract: This paper deals with the scroll compressor, which is a machine used for compressing air or refrigerant. By using a novel reference frame, it proposes an original way of describing the geometry of the scroll wraps (represented as circle involutes) in which the symmetries are exploited in order to establish a thermodynamic model of the scroll compressor. This approach allows the chamber volumes to be analytically described without any special assumption and takes into account the discharge as a non-symmetrical process. The proposed geometric model is aimed to be coupled with the thermodynamic model by using the standardized VHDL-AMS language and should be then considered as preliminary to the scroll overall simulation and design of a functional virtual prototype. Simulations and experiments have shown good agreement.
Abstract: Component hybrid dynamic nets (CHDNs) are a graphic model for hybrid dynamic systems, which allow every component of the hybrid system to be individually represented. On the basis of this methodology, a software tool dedicated to electrical engineering simulations has been developed. Thus, the aim of this paper is to present a brief review of the model structure and to describe the developed software called SimRDH. In order to show the applications of this software tool, a hydraulic system, a mechanical system, and finally, an elevator system powered by supercapacitors have been studied.
Abstract: This study presents a VHDL-AMS modelling of a complex multi-domain energy conversion system: a fuel cell stack. A comparative study between the different modelling approaches (bond-graphs, electrical equivalent circuits) is given to show the great advantages of the VHDL-AMS language in the design process of fuel cell systems. The modelling approach allows the design team to split the work into several parts (concurrent engineering) and validate each part independently. The fuel cell stack model fits the experimental results. It is able to predict the voltage and the power of the fuel cell with a good accuracy taking into account the water content of the membrane. This last point is really important to design the air supply system (compressor and humidifier) and its associated control.
Abstract: This paper presents a hybrid fuel cell/battery wheelchair modeling and design. In this system, the fuel cell acts as a range extender allowing this component to have a low dynamic. The peaks of power are given by a battery. The control of the fuel cell system and the control of the overall system is presented together with an experimental validation.
Abstract: This paper proposes a technological solution with a scroll compressor driven by a high performance induction machine drive for the air management of PEMFC (Proton Exchange Membrane Fuel Cells) for automotive applications. The torque-speed characteristics of a real scroll compressor have been measured and then emulated by a brushless IMPM (internal Mounted Permanent Magnets) machine controlled in torque. This emulated scroll compressor has been driven by a field oriented controlled (FOC) induction motor drive. The whole car model as well as the PEMFC have been implemented by software on the same DSP which implements the drive control algorithm; in this way the hardware-in-the-loop structure has been employed for emulating the behaviour of a real car including the electrical supply of the PEMFC. The whole system has been tested with a classic European driving cycle. Two experimental rigs have been setup, one for characterizing the scroll compressor and the other for emulating the entire vehicle. The experimental results have shown that the speed reference profile, obtained during a urban driving cycle, is followed correctly and that the tank-to-wheel efficiency remains at quite high values confirming the goodness of the proposed technological solution. The hardware-in-the-loop approach of the experimental rig allows tests to be performed to verify the operation in steady and transient states with low cost and reduced employment of the Fuel Cell stack, with resulting increased durability.
Abstract: This paper deals with the state-of-the-art of air management in PEM fuel cell which is a challenge because commercial compressors and humidification systems are not suitable
for automotive applications. Major tasks and requirements for compression and humidification subsystems have been introduced showing that compression and humidification subsytems cannot be decoupled. A higher working pressure around 2.5 bar is recommended, because it permits the PEMFC to have a higher efficiency, as well as a lighter stack and a lower volume than an equivalent PEMFC working at a lower pressure, moreover the water necessary for humidifying the membrane decreases, resulting in a simple management. For high pressure fuel cells, centrifugal compressors or positive displacement compressors with internal compression have to be preferred to those with external compression, because they offer a better efficiency. The built-in compression ratio has to be as close as possible to the fuel cell working pressure to ensure maximum efficiency.
Downstream or integrated direct water injection, has shown many advantages for air humidication compared to other methods, because of its controllability, low power consumption and compactness.
Abstract: Most scroll compressor models are based on a geometrical description of the scroll wraps. Since geometry is one of the main factors affecting the efï¬Âciency of the compressor, a complete description of the geometry of scroll wraps has to be known in order to establish an accurate thermodynamic model. Most authors do not yield an analytical expression of the discharge chamber, also because their assumptions are questionable. This paper gives a novel description of the geometry based on the parametric equations for the circle involutes in a novel reference system, in order to exploit the symmetry of the compressor. This approach simpliï¬Âes the scroll model and yields an exact analytical expression of the compression and discharge chamber volumes, together with all the geometrical parameters and constraints, thus allowing the compressor to be optimized geometrically. The existence conditions of the conjugacy points, as well as the manufacturing constraints are also considered.
Abstract: A mathematical model of the Polymer electrolyte fuel cell (PEFC), including air compression process and humidification has been developed to study the performances of the fuel cell. The study is focused on the air supply management with the objective to optimize the inlet air pressure and stoechiometry given by the compression system. A simple optimization method is given to maximize the voltage gain including the voltage drop due to the compression process. The optimization has to take into account the outlet relative air humidity (optimization constraint) leaving the fuel cell to avoid drying or flooding problems. The optimization results show that working at fully humidified air at the inlet is not always a good solution especialy for low air mass flow rates because of the high level of air stoechiometry to avoid flooding of the polymer membrane. On the other hand, it is better to work at fully humidified air at the inlet at high air mass flow rates. In all the cases, the optimal pressure is less than 2.5 bar which gives an indication for the design of air compressor for fuel cells.
