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Über dieses Buch

Sliding-mode Control of PEM Fuel Cells demonstrates the application of higher-order sliding-mode control to PEMFC dynamics showing the advantages of sliding modes.

The book introduces the theory of fuel cells and sliding-mode control. It contextualises PEMFCs both in terms of their development and within the hydrogen economy and today’s energy production situation as a whole. It then discusses fuel-cell operation principles, the mathematical background of high-order sliding-mode control and to a feasibility study for the use of sliding modes in the control of an automotive fuel stack.

Part II presents experimental results of sliding-mode-control application to laboratory fuel cells and deals with subsystem-based modelling, detailed design, and observability and controllability. Simulation results are contrasted with empirical data and performance, robustness and implementation issues are treated in depth. Possibilities for future research are also laid out.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introducing Fuel Cells

Abstract
Increasing demands on pollution reduction is driving innovation on clean energy sources. Among these, fuel cells are regarded as one of the most promising technologies, due to their high efficiency, compactness, and reliability. Fuel cells are electrochemical devices that generate electrical current from hydrogen and oxygen. In this chapter, the basic operation of a fuel-cell-based generation system is analysed, and the main technologies used at each of its subsystems are reviewed. A brief history of fuel cell development is summarised, from early experiences in the 19th century to the space shuttle and automotive applications. Closed-loop operation of fuel cell (FC) systems arises as a way to improve performance and reliability. In particular, robust control techniques based on sliding modes are proposed as suitable alternatives to provide performance under model uncertainty and external disturbances, usually present in these complex systems. Finally, the general organisation of the book is briefly outlined.
Cristian Kunusch, Paul Puleston, Miguel Mayosky

Chapter 2. PEM Fuel Cell Systems

Abstract
Proton Exchange Membrane (PEM) fuel cells are extensively used for mobile and portable applications. This is due to their compactness, low weight, high power density, and clean, pollutant-free operation. Besides, their low temperature of operation (typically 60–80 degrees Celsius) allows fast starting times, a key feature for automotive applications, for instance. In a PEM Fuel Cell, a hydrogen-rich fuel is injected by the anode, and an oxidant (usually pure oxygen or air) is fed through the cathode. Both electrodes are separated by a solid electrolyte that allows ionic conduction and avoids electrons circulation. The output of a PEM Fuel Cell is electric energy, with water and heat as the only by-products. In this chapter, the basics of PEM fuel cells operation are reviewed, including electrochemical equations, losses, and efficiency issues. The state-of-the-art in PEM fuel cells technology is summarised, including membranes, electrodes, catalysts, line heaters, water, and heat management devices. Control-oriented models in the literature are discussed, and typical control objectives are analysed.
Cristian Kunusch, Paul Puleston, Miguel Mayosky

Chapter 3. Fundamentals of Sliding-Mode Control Design

Abstract
This chapter provides an introduction to Variable Structure Control theory and its extension to the so-called Sliding-Mode (SM) control. The presentation is not intended as a comprehensive survey of the state-of-the-art in the field, but to supply the basic concepts on SM control required to understand the developments to come in this book. The readers can use this material as a straightforward introduction to the field of SM control.
The chapter is divided into two parts. In the first one, a general analysis of the classic or first-order SM control is formulated, which is the natural background to the subsequent generalisation known as Higher-Order Sliding-Mode control.
In the second part, a general study of systems operating in sets of arbitrary sliding-mode order is presented, outlining the fundamentals of Higher-Order Sliding-Mode control theory. It focuses on Second-Order Sliding-Mode (SOSM) controllers design, particularly on three of the most widely used SOSM algorithms, namelyTwisting,Super-Twisting, andSub-Optimal.
Cristian Kunusch, Paul Puleston, Miguel Mayosky

Chapter 4. Assessment of SOSM Techniques Applied to Fuel Cells. Case Study: Electric Vehicle Stoichiometry Control

Abstract
The feasibility of SOSM techniques to control PEM fuel cells is evaluated in this chapter. Assessment is accomplished through simulations, using a benchmark model of a fuel cell system for an electric vehicle. The viability of SOSM techniques for oxygen stoichiometry control, with the prime objective of improving the overall energy efficiency, is established.
Taking into account several features, such as the controlled system performance, robustness and implementation simplicity, the SOSM controllers prove to be a highly efficient solution for this challenging problem. Among them, theSuper-Twisting emerges as a very suitable algorithm for the fuel cell stack, given that it is specially intended for relative degree one systems and only requires real-time knowledge of the sliding variable.
Comparisons with standard LQR control are conducted. SOSM controllers demonstrate better robustness features in a wide range of operation. Additionally, no state observers are required, resulting in a simple and low computational cost control solution for this type of applications.
Cristian Kunusch, Paul Puleston, Miguel Mayosky

Chapter 5. Control-Oriented Modelling and Experimental Validation of a PEMFC Generation System

Abstract
he control-oriented modelling of an actual PEM fuel cell stack is approached. The proposed procedure tackles the modular modelling of an experimental complex system that combines mechanical, electrical, pneumatic and electrochemical subsystems. It provides a nonlinear characterisation that satisfactorily describes the steady state and dynamical behaviour, successfully covering the entire operation range of the fuel-cell-based system under study.
The semi-empirical methodology followed in this chapter is not an example on identification nor a theoretical exercise. Guided by the knowledge of the processes and reactions that take place in the real fuel cell, the different components were modelled using available general information and particular experimental data, gathered from simple tests. Therefore, the proposed procedure can be used as a guide for control-oriented modelling of PEM fuel cell systems with similar features.
Important control problems found in PEM fuel cells (such as H2/O2 stoichiometry regulation, total and partial pressures control, nonlinear observers for anode and cathode lines, H2 consumption minimisation, etc.) can be approached using the developed control model.
Cristian Kunusch, Paul Puleston, Miguel Mayosky

Chapter 6. SOSM Controller for the PEMFC-Based Generation System. Design and Implementation

Abstract
The main purpose is to present the actual development and experimental validation of SOSM controllers, previously reviewed and analysed in this book. As anticipated, the controllers are designed and implemented in the real FC-based generation workbench introduced and modelled in the previous chapter. Three control set-ups based onSuper-Twisting,Twisting andSub-Optimal algorithms are developed. Power conversion optimisation of the laboratory PEM fuel cell system is sought via oxygen stoichiometry regulation. In the implementation, the effect of practical problems such as saturation and possible wind-up are taken into account.
There is also a second intention for this chapter. Taking advantage of the consecutive steps required to present the development of the aforementioned actual FC controllers, it is aimed to provide a condensed recapitulation of the concepts and design procedures reviewed and elaborated along the previous chapters. The objective is twofold. On the one hand, this endows the chapter with a certain degree of self-containment, improving its readability by sparing the reader from awkward goings and comings. On the other hand, the goal is to summarise the successive stages of the FC-SOSM control design process presented in this book, into one concise format. This would offer a unified abridged design guideline to develop proficient practical SOSM controllers for efficiency optimisation of FC generation systems.
Cristian Kunusch, Paul Puleston, Miguel Mayosky

Chapter 7. Conclusions, Open Lines and Further Reading

Abstract
This chapter summarises the main results presented in the book, regarding the application of Second-Order Sliding-Mode algorithms for robust control of autonomous PEM fuel cells. Several improvements to the existing control schemes and many open directions of research are proposed. Most promising issues are related to Adaptive Super-Twisting algorithms, Higher-Order Sliding-Mode MIMO Control, Model Predictive Control, and Sliding-Mode Observers for internal Fuel cell variables. As further issues related to fuel-cell-based systems, hybrid standalone systems and distributed generation systems are regarded as appealing fields for future improvements.
Cristian Kunusch, Paul Puleston, Miguel Mayosky

Backmatter

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