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Advanced control of renewable energy generation systems based on fuel cells\wind power

Final Report Summary - ACRES (Advanced control of renewable energy generation systems based on fuel cells\wind power)

The European Union (EU) is conscious about the fundamental problems arisen from the current energy system, based mainly on hydrocarbons and has a firm commitment to encourage renewable energy technologies research. Among experts in energy there is a growing trend to promote decentralised electrical generation systems (DEGS) with modular efficient non-polluting generation plants. DEGS that incorporate hydrogen as an energetic vector are of particular interest. Hydrogen can be easily produced, stored and efficiently converted into electricity by means of fuel cells, adding great flexibility to DEGS.

However, fuel cells based DEGS exhibit complex non-linear behaviour, have inaccessible variables and withstand severe disturbances, so special controllers are required. A wide range of linear controllers has been already proposed, but the validity of the results cannot be extrapolated. The development of advanced control systems for fuel cell based DEGS that incorporate renewable energy sources is then not merely a challenging area of research, but is also a field of great interest for environmental, social, economic and strategic reasons.

The key aim of project ACRES was the development of advanced controllers capable to improve the efficiency of fuel cells / wind power based DEGS. Controllers were being implemented and tested in the ACES labs in Barcelona. The results of these implementations were used to assess the theoretical developments and also provide technology demonstrators to aid technology transfer to industry.

The main objectives of the project ACRES were threefold:

1. Scientific: To develop advanced controllers to improve the efficiency and durability of fuel cell/renewable energy based electrical generation systems.
2. Knowledge transfer: To instruct and train the host group in new methodologies and techniques of non-linear control and their application to renewable based generation systems.
3. Strategic: To advise the host group in the new trends of renewable energies generation systems integration and control.

The work performed is in accordance with the objectives settled for the project. With respect to the development of controllers, particular attention was given to robustness, performance enhancement and efficiency optimisation. To attain such goals, advanced non-linear controllers were used with special emphasis on sliding mode techniques, including second order variable-gains algorithms. Several controllers, in different stages of development (design, implementation and testing) were proposed for manifold applications:

- power management strategies for different scenarios for a PEM fuel cell hybrid generation system;
- air supply control of PEM fuel cells based systems;
- active and reactive power control of wind turbines;
- controllers for two kind of power converters: an active rectifier and a double boost DC/DC converter;
- lean burn IC engine controller for a series hybrid vehicle.

With respect to the knowledge transfer and the assessment of Strategic Issues to the host group members, the visiting researcher, Prof. Puleston, performed many actions as, for instance, scientific / technical presentations to the whole research team, specific group discussion seminars and individual meetings with research members for concrete research projects. The topics that were the object of these activities refer to the analysis and design of advanced controllers for renewable energy systems, but also to the control oriented modelling of such specific systems. In addition, Prof. Puleston was very active in the weekly group's meeting where scientific and strategic decisions are taken.

Another important activity of Prof. Puleston that had great impact on the host group is the establishment of contacts and the diffusion of the host institution activities in relevant research centres in Europe, among others:

- School of Engineering and Digital Arts, University of Kent, Canterbury, United Kingdom (UK)
- Engineering Department, University of Leicester, UK
- Catalonia Institute for Energy Research (IREC), Barcelona, Catalonia
- Dip. di Ingegneria Elettrica ed Elettronica, Università degli Studi di Cagliari, Italy
- Department of Electric, Electronic and Automatic Control of the Univ. Rovira i Virgili, Tarragona, Catalonia.

In the framework of the project, Prof. Puleston has also boosted direct collaborations with relevant institutions:

- LEICI, Universidad Nacional de La Plata, Argentina
- Dep. de Automação e Sistemas, Univ, Federal de Santa Catarina, Florianópolis, Brasil
- Sliding Mode Control Laboratory, Facultad de Ingeniería. U.N.A.M Mexico
- LIFTEC, CSIC-University of Zaragoza, Spain.

The society in general is very conscious of the importance of giving support to renewable energy technologies research for both the imperative necessity of replacing the actual energy model and because the tremendous economic impact that the development of these new energies will have in the economies of our countries. The objectives and the results of this project are precisely in line with these society concerns. The experimental work done in the host laboratories has validated the different control strategies that have been designed in the project. Some of these implementations are in fact practical demonstrators that will be used in the short future in the foreseen presentations with some possible interested industrial companies.

The short duration of the project, only a year, limits the visibility reach of the work done. However the results already obtained during this project year are very good and can be summarised as follows:

- Obtaining relevant scientific achievements of the host control group in advanced control of fuel cells / wind power based DEGS. At this moment, two papers have been already published and one more has been accepted for publishing in JCI international Journals. Five papers have also been presented in specialised conferences reporting some of the results obtained. Two other achievements have already been submitted for reviewing in specialised forums. Ten other works are being still developed and will continue in the Return phase of the project.
- Increasing the international visibility of the host group with eight significant collaborations already accomplished with relevant groups in the automatic control area related with energy.
- Boosting the education of the hosting group in non-linear control, specifically in advanced sliding mode control techniques.
- Helping to find new scientific / technical trends and strategic planning advising for the host group.
The scientific impact of the project is being notable, as is seen from the acceptance of the articles already submitted and presented to experts. It is early to evaluate the socio-economic impact that will have the results of the project but the expectations to have the interest of some companies related with renewable energy equipment are high.

Having comprehensible experimental demonstrators able to show to industrial companies the advantages of the new generation of controllers for sustainable energy equipments.