Nonlinear predictive control for durability enhancement and efficiency improvement in a fuel cell power system

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this work, a nonlinear model predictive control (NMPC) strategy is proposed to improve the efficiency and enhance the durability of a proton exchange membrane fuel cell (PEMFC) power system. The PEMFC controller is based on a distributed parameters model that describes the nonlinear dynamics of the system, considering spatial variations along the gas channels. Parasitic power from different system auxiliaries is considered, including the main parasitic losses which are those of the compressor. A nonlinear observer is implemented, based on the discretised model of the PEMFC, to estimate the internal states. This information is included in the cost function of the controller to enhance the durability of the system by means of avoiding local starvation and inappropriate water vapour concentrations. Simulation results are presented to show the performance of the proposed controller over a given case study in an automotive application (New European Driving Cycle). With the aim of representing the most relevant phenomena that affects the PEMFC voltage, the simulation model includes a two-phase water model and the effects of liquid water on the catalyst active area. The control model is a simplified version that does not consider two-phase water dynamics.Peer ReviewedPostprint (author's final draft

A DC-DC Converter-Based PEM Fuel Cell System Emulator

International audienceThe Proton Exchange Membrane Fuel Cell (PEMFC) is being investigated as an alternate power source for various applications as transportation and emergency power supplies. Fuel cell systems are characterized by high costs and complex auxiliary devices. For this reason, a fuel cell emulator can be used as a suitable and economic alternative to a real one for developing and testing a fuel cell power conditioning system. The fuel cell emulator must be able to reproduce the FC nonlinear output voltage-current characteristic. This paper proposes then a possible solution to emulate a PEMFC system by using a DC-DC converter. The fuel cell system, including all its auxiliaries and related control systems, is emulated by a full-bridge converter experimentally achieved and controlled in the DSP2812 environment. The converter-based system allows the behavior of any fuel cell to be easily emulated and can be used in laboratory as a low-cost system for design and experimental purposes since only a DC-DC control modification is necessary

Toward Holistic Energy Management Strategies for Fuel Cell Hybrid Electric Vehicles in Heavy-Duty Applications

The increasing need to slow down climate change for environmental protection demands further advancements toward regenerative energy and sustainable mobility. While individual mobility applications are assumed to be satisfied with improving battery electric vehicles (BEVs), the growing sector of freight transport and heavy-duty applications requires alternative solutions to meet the requirements of long ranges and high payloads. Fuel cell hybrid electric vehicles (FCHEVs) emerge as a capable technology for high-energy applications. This technology comprises a fuel cell system (FCS) for energy supply combined with buffering energy storages, such as batteries or ultracapacitors. In this article, recent successful developments regarding FCHEVs in various heavy-duty applications are presented. Subsequently, an overview of the FCHEV drivetrain, its main components, and different topologies with an emphasis on heavy-duty trucks is given. In order to enable system layout optimization and energy management strategy (EMS) design, functionality and modeling approaches for the FCS, battery, ultracapacitor, and further relevant subsystems are briefly described. Afterward, common methodologies for EMS are structured, presenting a new taxonomy for dynamic optimization-based EMS from a control engineering perspective. Finally, the findings lead to a guideline toward holistic EMS, encouraging the co-optimization of system design, and EMS development for FCHEVs. For the EMS, we propose a layered model predictive control (MPC) approach, which takes velocity planning, the mitigation of degradation effects, and the auxiliaries into account simultaneously

STUDY OF STRATEGIES FOR AN OPTIMAL ENERGY MANAGEMENT ON ELECTRIC AND HYBRID VEHICLES

Questa tesi di dottorato è focalizzata sull’identificazione di strategie di gestione dell’energia a bordo di veicoli elettrici e ibridi, con l’obiettivo di ottimizzare la gestione dell’energia e, quindi, consentire un risparmio di risorse. Infatti, l’ottimizzazione della fase d’uso del veicolo, attraverso una più efficiente gestione dell’energia, consente di dimensionare in modo ridotto i principali componenti, come il pacco batterie. Innanzitutto, viene presentato un tool di simulazione denominato TEST (Target-speed EV Simulation Tool). Questo strumento consente di effettuare simulazioni di dinamica longitudinale per veicoli completamente elettrici o ibridi e, quindi, di monitorare tutti i dati rilevanti necessari per effettuare un corretto dimensionamento del gruppo propulsore, inclusi il/i motore/i elettrico/i ed il pacco batterie. Inoltre, è possibile testare anche diversi layout di propulsori, compresi quelli che utilizzano celle a combustibile, le cosiddette “fuel cell”. Viene poi presentata una strategia di frenata rigenerativa, adatta per veicoli FWD, RWD e AWD. L’obiettivo principale è quello di recuperare la massima energia frenante possibile, mantenendo il veicolo stabile, con buone prestazioni in frenata. La strategia è stata testata sia attraverso un consolidato software di simulazione della dinamica del veicolo (VI-CarRealTime), sia attraverso simulazioni “driver-in-the-loop” utilizzando un simulatore di guida. Inoltre, la strategia proposta è stata integrata nel tool TEST per valutarne l’influenza sull’autonomia e sui consumi del veicolo. Gli strumenti sopra menzionati sono stati utilizzati per studiare uno scenario di casi reali, per valutare la fattibilità dell’utilizzo di una flotta alimentata a fuel cell a metano per svolgere attività di raccolta rifiuti porta a porta. I risultati mostrano un’elevata fattibilità in termini di autonomia del veicolo rispetto alle missioni standard di raccolta dei rifiuti, a condizione che i componenti siano adeguatamente dimensionati. Il dimensionamento dei componenti è stato effettuato attraverso iterazioni, utilizzando diversi componenti nelle stesse missioni. Infine, è stata riportata un’analisi approfondita degli studi LCA (Life Cycle Assessment) relativi ai veicoli elettrici, con particolare attenzione al pacco batterie, evidenziando alcune criticità ambientali. Questo studio sull’LCA sottolinea quindi l’importanza di una corretta gestione dell’energia per ridurre al minimo l’impatto ambientale associato al consumo stesso di energia.This PhD thesis is focused on identifying energy management strategies on board electric and hybrid vehicles, to optimize energy management and thus allow for resource savings. In fact, vehicle’s operational phase optimisation through a more efficient energy management allows main components downsizing, such as battery pack. First of all, a simulation tool called TEST (Target-speed EV Simulation Tool), is presented. This tool allows to carry out longitudinal dynamics simulations on pure electric or hybrid-electric vehicles, and therefore monitoring all the relevant data needed to carry out a proper powertrain sizing, including the electric motor(s) and the battery pack. Furthermore, several powertrain layouts can be also tested, including those using fuel cells. Then a regenerative braking strategy, suitable for FWD, RWD and AWD vehicles, is presented. Its main target is to recover the maximum possible braking energy, while keeping the vehicle stable with good braking performance. The strategy has been tested both through a state-of-art vehicle dynamics simulation software (VI-CarRealTime) and through driver-in-the-loop simulations using a driving simulator. Furthermore, the proposed strategy has been integrated into TEST to evaluate its influence on vehicle range and consumptions. The above-mentioned tools have been used to evaluate a real-world case scenario to assess the feasibility of using a methane fuel cell powered fleet to carry out door to door waste collection activities. Results show high feasibility in terms of vehicle range compared to standard waste collection missions, provided that components are properly sized. Components sizing has been done through iterations using different components on the same missions. Finally, an in-depth analysis of the LCA (Life Cycle Assessment) studies related to electric vehicles has been reported, with particular focus to the battery pack, highlighting some environmental critical issues. This LCA study therefore emphasizes the importance of a correct energy management to minimize the environmental impact associated with energy consumption

APACHE: Integrated Hybrid Fuel Cell System for 2-Seat All Electric Aircraft Propulsion

International audienceThe French APACHE project aims at demonstrating the feasibility of using a Hybrid Fuel Cell System (HFCS) as the power generator for all electric 2-seat aircrafts. This study focuses on three main topics: airworthiness of Proton Exchange Membrane Fuel Cells (PEMFC), their hybridization with Lithium Ion (Li-Ion) batteries and systems' integration into light aircrafts. Altitude and inclination tests have been led and allow to conclude on the ability of PEMFC to operate in aeronautical conditions. A comparison of aerobic and anaerobic fuel cells is realised and reveals the superiority of anaerobic fuel cells for high altitude applications. Innovative architectures of hybridization are proposed and tested numerically and experimentally. Finally, examples of integration to two light aircrafts of a HFCS composed of an anaerobic FC, hydrogen and oxygen storages and a Li-Ion battery pack are presented

An Efficient and Robust Current Control for Polymer Electrolyte Membrane Fuel Cell Power System

Taking into account the restricted ability of polymer electrolyte membrane fuel cell (PEMFC) to generate energy, it is compulsory to present techniques, in which an efficient operating power can be achieved. In many applications, the PEMFC is usually coupled with a high step-up DC-DC power converter which not only provides efficient power conversion, but also offers highly regulated output voltage. Due to the no-linearity of the PEMFC power systems, the application of conventional linear controllers such as proportional-integral (PI) did not succeed to drive the system to operate precisely in an adequate power point. Therefore, this paper proposes a robust non-linear integral fast terminal sliding mode control (IFTSMC) aiming to improve the power quality generated by the PEMFC; besides, a digital filter is designed and implemented to smooth the signals from the chattering effect of the IFTSMC. The stability proof of the IFTSMC is demonstrated via Lyapunov analysis. The proposed control scheme is designed for an experimental closed-loop system which consisted of a Heliocentric hy-Expert™ FC-50W, MicroLabBox dSPACE DS1202, step-up DC-DC power converter and programmable DC power supplies. Comparative results with the PI controller indicate that a reduction of 96% in the response time could be achieved using the suggested algorithm; where, up to more than 91% of the chattering phenomenon could be eliminated via the application of the digital filter.The authors wish to express their gratitude to the Basque Government through the project SMAR3NAK (ELKARTEK KK-2019/00051), to the Diputación Foral de Álava (DFA) through the project CONAVAUTIN 2 and to the UPV/EHU for supporting this work

Hydrogen-powered refrigeration system for environmentally friendly transport and delivery in the food supply chain

Urban population and the trend towards online commerce leads to an increase in delivery solution in cities. The growth of the transport sector is very harmful to the environment, being responsible for approximately 40% of greenhouse gas emissions in the European Union. The problem is aggravated when transporting perishable foodstuffs, as the vehicle propulsion engine (VPE) must power not only the vehicle but also the refrigeration unit. This means that the VPE must be running continuously, both on the road and stationary (during delivery), as the cold chain must be preserved. The result is costly (high fuel consumption) and harmful to the environment. At present, refrigerated transport does not support full-electric solutions, due to the high energy consumption required, which motivates the work presented in this article. It presents a turnkey solution of a hydrogenpowered refrigeration system (HPRS) to be integrated into standard light trucks and vans for short-distance food transport and delivery. The proposed solution combines an air-cooled polymer electrolyte membrane fuel cell (PEMFC), a lithium-ion battery and low-weight pressurised hydrogen cylinders to minimise cost and increase autonomy and energy density. In addition, for its implementation and integration, all the acquisition, power and control electronics necessary for its correct management have been developed. Similarly, an energy management system (EMS) has been developed to ensure continuity and safety in the operation of the electrical system during the working day, while maximizing both the available output power and lifetime of the PEMFC. Experimental results on a real refrigerated light truck provide more than 4 h of autonomy in intensive intercity driving profiles, which can be increased, if necessary, by simply increasing the pressure of the stored hydrogen from the current 200 bar to whatever is required. The correct operation of the entire HPRS has been experimentally validated in terms of functionality, autonomy and safety; with fuel savings of more than 10% and more than 3650 kg of CO2/ year avoided.This work is a contribution of the two following Projects: “H2Integration& Control. Integration and Control of a hydrogen-based pilot plant in residential applications for energy supply”, Ref. PID2020-116616RB-C31 supported by the Spanish State Program of R + D + I Oriented to the Challenges of Society; and “SALTES: Smartgrid with reconfigurable Architecture for testing controL Techniques and Energy Storage priority contaminant waste”, Ref. P20-00730 supported by Andalusian Regional Program of R + D + I. Funding for open access charge: Universidad de Huelva/CBUA

Design and Modelling of the Powertrain of a Hybrid Fuel Cell Electric Vehicle

This paper presents a Fuel Cell Electric Vehicle (FCEV) powertrain development and optimization, aiming to minimize hydrogen consumption. The vehicle is a prototype that run at the Shell Eco-marathon race and its powertrain is composed by a PEM fuel cell, supercapacitors and a DC electric motor. The supercapacitors serve as an energy buffer to satisfy the load peaks requested by the electric motor, allowing a smoother (and closer to a stationary application) working condition for the fuel cell. Thus, the fuel cell can achieve higher efficiency rates and the fuel consumption is minimized. Several models of the powertrain were developed using MATLAB-Simulink and then experimentally validated in laboratory and on the track. The proposed models allow to evaluate two main arrangements between fuel cell and supercapacitors: 1) through a DC/DC converter that sets the FC current to a desired value; 2) using a direct parallel connection between fuel cell and supercapacitors. The results obtained with the direct parallel connection (with the appropriate sizing of the overall capacity) have highlighted a significant efficiency advantage, while the DC/DC converter insertion enables an improved control of the fuel cell current and requires a smaller capacitance. Furthermore, a sizing methodology for the supercapacitors capacitance is proposed for both layouts: with the DC/DC converter it mainly depends on the energy range provided by supercapacitors to the electric motor, while in the direct parallel connection the supercapacitors sizing is outlined by concurrently evaluating the circuit's predicted hydrogen consumption and granting the most suitable conditions to increase the fuel cell performance. Finally, the results obtained from the model were validated by comparing them with experimental data obtained in the laboratory and on the track

Modeling and Control of a Proton Exchange Membrane Fuel Cell-Battery Power System

A general methodology of modeling, control and building a proton exchange membrane fuel cell-battery system is introduced in this thesis. A set of fuel cell-battery power system model has been developed and implemented into Simulink environment. The model is able to address the dynamic behaviours of PEM fuel cell stack, boost DC/DC converter and lithium-ion battery. In order to control the power system to achieve a proper performance, a set of system controller including a PEM fuel cell reactant supply control, a humidification controller, and a power management controller was developed based on the system model. A physical 100W PEM fuel cell-battery power system using microcontroller as embedded controller is built to validate the simulation results as well as demonstrate this new environment-friendly power source. Experimental results show that the 100W PEM fuel cell-battery power system can operates automatically with the varying load condition as a stable power supply. The experiment results follow the basic trend of the simulation results

A standalone proton exchange membrane fuel cell generation system with different tracking techniques

The proton exchange membrane fuel cell (PEMFC) may be operated at the maximum power point (MPP) or maximum efficiency point (MEP). In this thesis, a complete user-friendly Simulink model of the PEMFC is developed to implement the maximum power point tracking (MPPT) technique and maximum efficiency point tracking (MEPT) technique. A new tracking technique referred to as the midpoint tracking (MDT) technique, is proposed to overcome the limitations of the MPPT and MEPT techniques. A detailed analysis of the tracking techniques based on simulation results using the Ballard MK5-E PEMFC as reference is presented. Simulation results indicate that the midpoint tracking technique provides a trade-off operation with acceptable efficiency derating of 15%, high output power, and small size of the fuel cell when compared with the maximum efficiency point tracking technique. In order to analyse the effects of the tracking techniques on the PEMFC system economics, a detailed economic analysis for ten different cases of standalone PEMFC system is carried out. From the point of view of the economics of a standalone fuel cell generation system, it is found that the MPPT technique is suitable for low power applications (<50kW) and MDT technique is suitable for medium to high power applications. Finally, based on the particular requirements of stationary PEMFC application, suitable tracking techniques are suggested